technical committee on handling and conveying of … · cv technology, inc. 15852 mercantile court...

TECHNICAL COMMITTEE ON HANDLING AND CONVEYING OF DUSTS, VAPORS,

AND GASES

NFPA 655 CMD-HAP – F2016

First Draft Web/Teleconference Meeting

February 23, 2015

10 AM – 4 PM ET

AGENDA

1.0 Meeting is called to order at 10 AM ET

2.0 Welcome and Self-Introduction of Committee Members and Guests

3.0 Chair and Staff Liaison Remarks

4.0 Approve minutes from last meeting of TC (first draft for 654)

5.0 Review of F2016 Revision Cycle and new NFPA process (staff liaison presentation on new

process and procedures, will include membership review and review of schedule)

6.0 Committee Correspondence

7.0 Review of public input to NFPA 655

8.0 Review of correlating notes for other dust documents

9.0 Old Business

10.0 New Business and determination of next meeting date and location

11.0 Adjournment – Meeting will adjourn at 4 PM ET

TECHNICAL COMMITTEE ON HANDLING AND CONVEYING OF DUSTS, VAPORS,

AND GASES

Minutes of Meeting – NFPA 654 First Draft Meeting Atlanta, GA

July 30 – August 1, 2014

Member Attending

Mark Runyon – chair Yes Principal

Brice Chastain Yes Principal

John Cholin Yes Principal

Burke Desautels No Principal

Tony DiLucido No Principal

Vahid Ebadat No Principal

Henry Febo Yes Principal

Larry Floyd Yes Principal

Walter Frank Yes Principal

Stephen Greeson Yes Principal

Mark Holcomb Yes Principal

Jerry Jennett No Principal

David Kirby Yes Principal

James Koch Yes – by phone Principal

Bruce McLelland Yes Principal

Jack Osborn Yes Principal

Richard Pehrson No Principal

Jason Reason Yes – by phone Principal

Ali Reza Yes Principal

James Roberts No Principal

Samuel Rodgers Yes- by phone Principal

Thomas Scherpa Yes Principal

Bill Stevenson Yes Principal

Jeffrey Sutton Yes Principal

Robert Taylor Yes Principal

Tony Thomas Yes Principal

Erdem Ural Yes – by phone Principal

Harold Weber No Principal

Glenn Baldwin Yes – by phone Alternate

Amy Brown Yes Alternate

David Clayton No Alternate

James Dahn No Alternate

Randal Davis Yes Alternate

Randall Dunlap Yes Alternate

Robert Gravell No Alternate

William Hilton No Alternate

Jason Krbec No Alternate

Philip Parson Yes Alternate

Robert Shafto No Alternate

Jerome Taveau No Alternate

Matthew Chibbaro No Alternate

Harry Verakis No Alternate

William Hamilton No Alternate

Jay Juvenal Yes Guest

Niels Petersen Yes Guest

Susan Bershad Yes NFPA staff

Guy Colonna Yes NFPA staff

1.0 The meeting was called to order at 8 am by Mark Runyon, chair. The attendees,

guests, and those attending via the web conference made self-introductions. 2.0 Guy Colonna, NFPA staff, introduced the new staff liaison, Susan Bershad, and gave a

presentation on the new process, the schedule for the A2016 cycle, and the committee membership. There are currently 28 voting members on the technical committee.

3.0 The committee reviewed and approved the minutes from the July 23, 2014 Second Draft Meeting for NFPA 91.

4.0 The committee reviewed and acted on the public input received for NFPA 654. The committee reviewed and acted on 109 of the 112 public input received on the document. The last three public input will be discussed in a web meeting scheduled for Friday, August 15, 2014 from 10 AM to 3 PM ET.

5.0 The meeting adjourned at 5 PM on July 30 and 31, and at 1 PM on August 1, 2014. 6.0 The committee discussed the timing and location of the Second Draft Meeting. A

decision was made to hold the Second Draft Meeting after the NFPA annual meeting next June in Chicago. If there are any NITMAMs received on NFPA 652, they will be heard at the June, 2015 annual meeting, which will be held in Chicago June 22 to the 25, 2015. The committee decided to hold the Second Draft Meeting July 7, 8, and 9, 2015 in Seattle, WA.

TECHNICAL COMMITTEE ON HANDLING AND CONVEYING OF DUSTS, VAPORS, AND GASES

Minutes of Meeting – NFPA 654 First Draft Meeting - Continuation

Web Meeting August 15, 2014, 10 AM – 1 PM ET

Member Attending

Mark Runyon – chair Yes Principal

Brice Chastain Yes Principal

John Cholin Yes Principal

Burke Desautels Yes Principal

Tony DiLucido Yes Principal

Vahid Ebadat No Principal

Henry Febo Yes Principal

Larry Floyd No Principal

Walter Frank No Principal

Stephen Greeson Yes Principal

Mark Holcomb No Principal

Jerry Jennett No Principal

David Kirby No Principal

James Koch No Principal

Bruce McLelland No Principal

Jack Osborn No Principal

Richard Pehrson Yes Principal

Jason Reason Yes Principal

Ali Reza No Principal

James Roberts No Principal

Samuel Rodgers Yes Principal

Thomas Scherpa No Principal

Bill Stevenson Yes Principal

Jeffrey Sutton No Principal

Robert Taylor No Principal

Tony Thomas Yes Principal

Erdem Ural Yes Principal

Harold Weber No Principal

Glenn Baldwin Yes Alternate

Amy Brown No Alternate

David Clayton Yes Alternate

James Dahn No Alternate

Randal Davis No Alternate

Randall Dunlap No Alternate

Robert Gravell No Alternate

William Hilton No Alternate

Jason Krbec No Alternate

Philip Parson Yes Alternate

Robert Shafto No Alternate

Jerome Taveau No Alternate

Matthew Chibbaro No Alternate

Harry Verakis No Alternate

William Hamilton No Alternate

Niels Pedersen Yes Guest

Susan Bershad Yes NFPA

Tony Supine Yes Guest

Mike Walters Yes Guest

Guy Colonna Yes NFPA

1.0 The meeting was called to order at 10 am by Mark Runyon, chair. Staff did a roll call

and noted attendance. 2.0 Prior to consideration of the remaining three public input from the Atlanta meeting,

Niels Pedersen made a presentation providing background information for the three public input, which he submitted to the technical committee. This presentation is a rather large file, and the link to it was forwarded to the committee via e-mail subsequent to the meeting.

3.0 The committee considered the three remaining public input for 654, all of which were for annex material. These were PI-43, 44, and 45.

4.0 Camfil made a presentation on its position on PI-42. PI-42 was considered at the meeting in Atlanta. The committee response to PI -42 is FR-44. The committee did not vote to reconsider its response to PI-42 and invites Camfil and any other interested parties to submit public comment on the material. A copy of this presentation was transmitted to the committee via e-mail after the meeting.

5.0 The committee reviewed the membership and scope of task groups going forward. These are as listed below. If there are any committee members that would like to join one of the task groups, please let the chair or the staff know. Note that the task group leaders are designated in bold:

Task group to develop public comment on FR-44. o Bill Stevenson, Erdem Ural

Task group to review PI 101 – compare housekeeping requirements to 652. o Tom Scherpa, Sam Rodgers, Bill Stevenson, Erdem Ural

Task group to develop annex material for material in 10.2 o Tony Thomas and John Cholin, Sam Rodgers.

Scope of task group work – Develop annex material to explain the material in 10.2 and to develop public comment on the first revisions in 10.2 that are consistent with the annex material. This will be presented to the TC at the second draft.

Task group to develop public comment for FR-37 – reach out to the 69 TC for participation

o Erdem Ural, Sam Rodgers, Bill Stevenson, John Cholin, and Henry Febo.

Task group to develop public comment to annex material on abort gates (committee input response to PI- 43, 44, and 45.

o Bill Stevenson, Erdem Ural, Tony Thomas, Niels Pedersen, and John Cholin

6.0 The meeting was adjourned at 1 PM ET. The next meeting of the committee will be the second draft meeting currently scheduled for July 7, 8, and 9, 2015 in Seattle, WA.

Address List No PhoneHandling and Conveying of Dusts, Vapors, and Gases CMD-HAP

Combustible Dusts

Susan Bershad02/04/2015

CMD-HAP

Mark L. Runyon

ChairMarsh Risk Consulting111 SW Columbia, Suite 500Portland, OR 97201

I 1/10/2008CMD-HAP

Brice Chastain

PrincipalGeorgia-Pacific LLC133 Peachtree Street NE, 9th FloorAtlanta, GA 30303Alternate: William C. Hilton

U 10/28/2008

CMD-HAP

John M. Cholin

PrincipalJ. M. Cholin Consultants Inc.101 Roosevelt DriveOakland, NJ 07436

SE 1/1/1992CMD-HAP

Ashok Ghose Dastidar

PrincipalFauske & Associates, LLC16W070 83rd StreetBurr Ridge, IL 60527-5802

SE 10/28/2014

CMD-HAP

Burke Desautels

PrincipalFenwal/IEP Technologies400 Main StreetAshland, MA 01721-2150Alternate: Randal R. Davis

M 03/07/2013CMD-HAP

Tony DiLucido

PrincipalZurich Risk Engineering Services720 Ash AvenueCollingdale, PA 19023Alternate: Robert D. Shafto

I 8/5/2009

CMD-HAP

Vahid Ebadat

PrincipalChilworth Technology Inc.113 Campus DrivePrinceton, NJ 08540Alternate: C. James Dahn

SE 7/1/1996CMD-HAP

Henry L. Febo, Jr.

PrincipalFM GlobalEngineering Standards1151 Boston-Providence TurnpikePO Box 9102Norwood, MA 02062-9102Alternate: Amy Brown

I 4/1/1996

CMD-HAP

Larry D. Floyd

PrincipalBASF1379 Ciba RoadMcIntosh, AL 36553

U 8/5/2009CMD-HAP

Walter L. Frank

PrincipalFrank Risk Solutions, Inc.1110 Shallcross AvenueWilmington, DE 19806

SE 7/1/1994

CMD-HAP

Stephen T. Greeson

PrincipalHSB Professional Loss Control3410 Navasota CircleSan Antonio, TX 78259

I 8/5/2009CMD-HAP

Mark L. Holcomb

PrincipalKimberly-Clark Corporation2001 Marathon AvenueNeenah, WI 54956

U 7/23/2008

CMD-HAP

Jerry J. Jennett

PrincipalGeorgia Gulf Sulfur CorporationPO Box 1165Valdosta, GA 31603-1165Alternate: Randall Dunlap

U 1/15/1999CMD-HAP

David C. Kirby

PrincipalBaker Engineering & Risk Consultants, Inc.1560 Clearview HeightsCharleston, WV 25312Alternate: Philip J. Parsons

SE 1/1/1983

1



CMD-HAP

James F. Koch

PrincipalThe Dow Chemical Company1400 BuildingMidland, MI 48667American Chemistry CouncilAlternate: Glenn W. Baldwin

U 10/28/2008CMD-HAP

Bruce McLelland

PrincipalFike Corporation704 SW 10th StreetBlue Springs, MO 64015-4263Alternate: Jérôme R. Taveau

M 3/2/2010

CMD-HAP

Jack E. Osborn

PrincipalAirdusco, Inc.4739 Mendenhall Road SouthMemphis, TN 38141

M 1/10/2008CMD-HAP

Richard Pehrson

PrincipalPehrson Fire PC7455 France Avenue South, Suite 271Edina, MN 55435International Fire Marshals Association

E 3/1/2011

CMD-HAP

Jason P. Reason

PrincipalLewellyn Technology321 North 18th AvenueBeech Grove, IN 46107-1171

SE 3/2/2010CMD-HAP

Ali Reza

PrincipalExponent, Inc.5401 McConnell AvenueLos Angeles, CA 90066-7027Alternate: David B. Clayton

SE 03/05/2012

CMD-HAP

James L. Roberts

PrincipalFluor Enterprises, Inc.100 Fluor Daniel DriveGreenville, SC 29607-2762

SE 1/1/1989CMD-HAP

Samuel A. Rodgers

PrincipalHoneywell, Inc.15801 Woods Edge RoadColonial Heights, VA 23834-6059

U 7/20/2000

CMD-HAP

Thomas C. Scherpa

PrincipalThe DuPont Company, Inc.71 Valley RoadSullivan, NH 03445Alternate: Robert L. Gravell

U 3/21/2006CMD-HAP

Bill Stevenson

PrincipalCV Technology, Inc.15852 Mercantile CourtJupiter, FL 33478Alternate: Jason Krbec

M 1/15/1999

CMD-HAP

Jeffery W. Sutton

PrincipalGlobal Risk Consultants Corporation350 Highway 7, Suite 220Excelsior, MN 55331-3170

SE 3/4/2008CMD-HAP

Robert D. Taylor

PrincipalPRB Coal Users Group4377 Sandra Kay LaneNewburgh, IN 47630-8596

U 8/9/2011

CMD-HAP

Tony L. Thomas

PrincipalFlamex, Inc.4365 Federal DriveGreensboro, NC 27313

M 10/27/2009CMD-HAP

Erdem A. Ural

PrincipalLoss Prevention Science & Technologies, Inc.2 Canton Street, Suite A2Stoughton, MA 02072

SE 7/23/2008

2


Combustible Dusts


CMD-HAP

Michael Walters

PrincipalCamfil Farr Air Pollution Control3501 South Airport RoadJonesboro, AR 72401

M 10/27/2009CMD-HAP

Harold H. Weber, Jr.

PrincipalThe Sulphur Institute1020 19th Street, NW, Suite 520Washington, DC 20036

VL to Document: 655

U 1/1/1986

CMD-HAP

Glenn W. Baldwin

AlternateThe Dow Chemical CompanyPO Box 8361South Charleston, WV 25303American Chemistry CouncilPrincipal: James F. Koch

U 03/07/2013CMD-HAP

Amy Brown

AlternateFM Global1151 Boston-Providence TurnpikePO Box 9102Norwood, MA 02062-9102Principal: Henry L. Febo, Jr.

I 03/03/2014

CMD-HAP

David B. Clayton

AlternateExponent, Inc.5401 McConnell AvenueLos Angeles, CA 90066-7027Principal: Ali Reza

SE 10/29/2012CMD-HAP

C. James Dahn

AlternateSafety Consulting Engineers Inc.2131 Hammond DriveSchaumburg, IL 60173Principal: Vahid Ebadat

SE 1/1/1989

CMD-HAP

Randal R. Davis

AlternateIEP Technologies417-1 South StreetMarlborough, MA 01752-3149Principal: Burke Desautels

M 10/29/2012CMD-HAP

Randall Dunlap

AlternateGeorgia Gulf Sulfur CorporationPO Box 67Bainbridge, GA 39818Principal: Jerry J. Jennett

U 3/2/2010

CMD-HAP

Robert L. Gravell

AlternateThe DuPont Company, Inc.Chambers Works SiteExplosion Hazards LaboratoryMail Spot WWTP ‘O’Deepwater, NJ 08023Principal: Thomas C. Scherpa

U 3/4/2009CMD-HAP

William C. Hilton

AlternateGeorgia-Pacific133 Peachtree Street, NEAtlanta, GA 30303Principal: Brice Chastain

U 7/23/2008

CMD-HAP

Jason Krbec

AlternateCV Technology, Inc.15852 Mercantile CourtJupiter, FL 33478Principal: Bill Stevenson

M 3/1/2011CMD-HAP

Philip J. Parsons

AlternateBaker Engineering & Risk Consultants, Inc.1406 West Lynnwood AvenueSan Antonio, TX 78201Principal: David C. Kirby

SE 8/9/2011

3



CMD-HAP

Robert D. Shafto

AlternateZurich Insurance1093 Tall Pines TrailHighland, MI 48356Principal: Tony DiLucido

I 8/5/2009CMD-HAP

Jérôme R. Taveau

AlternateFike Corporation704 SW 10th StreetBlue Springs, MO 64015-4263Principal: Bruce McLelland

M 03/07/2013

CMD-HAP

Matthew I. Chibbaro

Nonvoting MemberUS Department of LaborOccupational Safety & Health Administration200 Constitution Ave. NW, Room N3609Washington, DC 20210Alternate: William R. Hamilton

E 3/4/2009CMD-HAP

William R. Hamilton

Alt. to Nonvoting MemberUS Department of LaborOccupational Safety & Health Administration200 Constitution Ave. NW, Room N3609Washington, DC 20210Principal: Matthew I. Chibbaro

E 3/4/2009

CMD-HAP

Susan Bershad

Staff LiaisonNational Fire Protection Association1 Batterymarch ParkQuincy, MA 02169-7471

04/16/2014

4

2016 FALL REVISION CYCLE *Public Input Dates may vary according to standards and schedules for Revision Cycles may change. Please check the NFPA Website for the most up‐to‐date information on Public Input Closing Dates and schedules at

www.nfpa.org/document # (i.e. www.nfpa.org/101) and click on the Next Edition tab.

Process Stage

Process Step

Dates for TC

Dates forTC with

CC Public Input Closing Date* 1/5/15 1/5/15

Final Date for TC First Draft Meeting 6/15/15 3/16/15

Public Input Posting of First Draft and TC Ballot 8/3/15 4/27/15

Stage Final date for Receipt of TC First Draft ballot 8/24/15 5/18/15

(First Draft) Final date for Receipt of TC First Draft ballot ‐ recirc 8/31/15 5/25/15

Posting of First Draft for CC Meeting 6/1/15

Final date for CC First Draft Meeting 7/13/15

Posting of First Draft and CC Ballot 8/3/15

Final date for Receipt of CC First Draft ballot 8/24/15

Final date for Receipt of CC First Draft ballot ‐ recirc 8/31/15

Post First Draft Report for Public Comment 9/7/15 9/7/15

Public Comment closing date 11/16/15 11/16/15

Final Date to Publish Notice of Consent Standards (Standards that received no Comments)

11/30/15 11/30/15

Appeal Closing Date for Consent Standards (Standards that received no Comments)

12/14/15 12/14/15

Final date for TC Second Draft Meeting 5/2/16 1/25/16

Comment Posting of Second Draft and TC Ballot 6/13/16 3/7/16

Stage Final date for Receipt of TC Second Draft ballot 7/5/16 3/28/16

(Second Final date for receipt of TC Second Draft ballot ‐ recirc 7/11/16 4/4/16

Draft) Posting of Second Draft for CC Meeting 4/11/16

Final date for CC Second Draft Meeting 5/23/16

Posting of Second Draft for CC Ballot 6/13/16

Final date for Receipt of CC Second Draft ballot 7/5/16

Final date for Receipt of CC Second Draft ballot ‐ recirc 7/11/16

Post Second Draft Report for NITMAM Review 7/18/16 7/18/16

Tech Session Notice of Intent to Make a Motion (NITMAM) Closing Date 8/22/16 8/22/16

Preparation Posting of Certified Amending Motions (CAMs) and Consent Standards

10/17/16 10/17/16

(& Issuance) Appeal Closing Date for Consent Standards 11/1/16 11/1/16

SC Issuance Date for Consent Standards 11/11/16 11/11/16

Tech Session Association Meeting for Standards with CAMs 6/4‐7/17 6/4‐7/17

Appeals and Appeal Closing Date for Standards with CAMs 6/27/17 6/27/17

Issuance SC Issuance Date for Standards with CAMs 8/10/17 8/10/17

Approved___ October 30, 2012 Revised________________________

Public Input No. 3-NFPA 655-2014 [ Chapter 2 ]

Chapter 2 Referenced Publications

2.1 General.

The documents or portions thereof listed in this chapter are referenced within this standard and shall beconsidered part of the requirements of this document.

2.2 NFPA Publications.

National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02169-7471.

NFPA 17, Standard for Dry Chemical Extinguishing Systems, 2009 edition 2013 .

NFPA 51B, Standard for Fire Prevention During Welding, Cutting, and Other Hot Work,2009 edition 2014 .

NFPA 68, Standard on Explosion Protection by Deflagration Venting, 2007 edition 2013 .

NFPA 69, Standard on Explosion Prevention Systems, 2008 edition 2014 .

NFPA 70® , National Electrical Code®, 2011 edition 2014 .

NFPA 72® , National Fire Alarm and Signaling Code, 2010 edition 2016 .

NFPA 80, Standard for Fire Doors and Other Opening Protectives, 2010 edition 2016 .

NFPA 101® , Life Safety Code®, 2012 edition 2015 .

NFPA 220, Standard on Types of Building Construction, 2012 edition 2015 .

NFPA 221, Standard for High Challenge Fire Walls, Fire Walls, and Fire Barrier Walls, 2012 edition 2015 .

NFPA 496, Standard for Purged and Pressurized Enclosures for Electrical Equipment, 2008 edition 2013 .

NFPA 600, Standard on Industrial Fire Brigades, 2010 edition 2015 .

NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing,and Handling of Combustible Particulate Solids, 2006 edition 2013 .

NFPA 780, Standard for the Installation of Lightning Protection Systems, 2011 edition 2014 .

NFPA 2113, Standard on Selection, Care, Use, and Maintenance of Flame-Resistant Garments forProtection of Industrial Personnel Against Flash Fire, 2012 edition 2015 .

2.3 Other Publications.

2.3.1 ISA Publications.

The Instrumentation, Systems, and Automation Society, 67 Alexander Drive, Research Triangle Park, NC27709.

ANSI/ISA 84.00.01, Functional Safety: Safety Instrumental Systems for the Process Industry Sector, 2004edition.

2.3.2 U.S. Government Publications.

U.S. Government Printing Office, Washington, DC 20402.

Title 29, Code of Federal Regulations, 1910. 242(b).

2.3.3 Other Publications.

Merriam-Webster's Collegiate Dictionary, 11th edition, Merriam-Webster, Inc., Springfield, MA, 2003.

2.4 References for Extracts in Mandatory Sections.


NFPA 2113, Standard on Selection, Care, Use, and Maintenance of Flame-Resistant Garments forProtection of Industrial Personnel Against Flash Fire, 2012 edition 2015 .

Statement of Problem and Substantiation for Public Input

National Fire Protection Association Report http://submittals.nfpa.org/TerraViewWeb/ContentFetcher?commentPara...

1 of 11 2/4/2015 1:08 PM

Referenced current editions.

Related Public Inputs for This Document

Related Input Relationship

Public Input No. 4-NFPA 655-2014 [Chapter C]

Submitter Information Verification

Submitter Full Name: Aaron Adamczyk

Organization: [ Not Specified ]

Street Address:

City:

State:

Zip:

Submittal Date: Fri Jun 20 00:30:29 EDT 2014


2 of 11 2/4/2015 1:08 PM

Public Input No. 9-NFPA 655-2014 [ Section No. 4.6.8.1.5 ]

4.6.8.1.5 *

Where lightning protection is provided, it shall be installed in accordance with NFPA 780, Standard for theInstallation of Lightning Protection Systems.


The proposed annex text provides the user of the standard with information on the source of risk assessment procedures which may be used to determine when lightning protection should be provided.


Submitter Full Name: Mark Morgan

Organization: East Coast Lightning Equipment

Affilliation: On behalf of NFPA 780 References Task Group

Street Address:

City:

State:

Zip:

Submittal Date: Tue Dec 30 17:24:56 EST 2014


3 of 11 2/4/2015 1:08 PM

Public Input No. 6-NFPA 655-2014 [ Section No. 5.5 ]

5.5 Fire Fighting.

5.5.1

Protection for covered liquid sulfur storage tanks, pits, and trenches shall be by one of the following means:

(1) Inert gas system in accordance with NFPA 69, Standard on Explosion Prevention Systems

(2)

Rapid

(3.)* Rapid sealing of the enclosure to exclude air . For sulfur tanks and sulfur pits the use of a steam

rate of 1.0 lb/min (0.45 kg/min) of steam per 100 ft 3 (2.83 m 3 ) of total tank or pit volume is expected todevelop a positive pressure in the enclosure thereby sealing the sulfur tank or sulfur pit preventing airingress and extinguishing the fire.

5.5.2 Snuffing Steam and Sealing Steam Precautions

5.5.2.1 The vent systems on enclosed sulfur tanks and sulfur pits must be designed to allow the requiredsnuffing steam rate or sealing steam rate to vent without over pressuring the enclosure. The vent systemsmust also be designed for proper operation during normal operation.

5.5.3 Water Extinguishing Precautions.

5.5. 2 3 .1

Liquid sulfur stored in open containers shall be permitted to be extinguished with a fine water spray.

5.5. 2 3 .2

Use of high-pressure hose streams shall be avoided.

5.5. 2 3 .3

The quantity of water used shall be kept to a minimum.

5.5. 3 4 Dry Chemical Extinguishers.

Where sulfur is being heated by a combustible heat transfer fluid, dry chemical extinguishers complyingwith NFPA 17, Standard for Dry Chemical Extinguishing Systems, shall be provided.


The NFPA 655 snuffing steam rate is so large that it creates issues with overpressureing sulfur tanks and sulfur pits. We have written a paper called M olten Sulfur Fire Sealing Steam Requirements to address the problemsfound, present our analysis of the issues and propose a sealing steam rate that we want NFPA 655 to consider


Submitter Full Name: ALAN MOSHER

Organization: Black & Veatch

Street Address:

City:

State:

Zip:

Submittal Date: Fri Dec 19 18:07:32 EST 2014

* Steam extinguishing system capable of delivering a minimum of 2.5 lb/min (1.13 kg/min) of steam

per 100 ft3 (2.83 m3) of volume


4 of 11 2/4/2015 1:08 PM

Public Input No. 5-NFPA 655-2014 [ Section No. 5.5.3 ]

5.5.3 Dry Chemical Portable Fire Extinguishers.

Where sulfur is being heated by a combustible heat transfer fluid, dry chemical extinguishers complyingwith NFPA 17, Standard for Dry Chemical Extinguishing Systems , water mist extinguishers rated 2-A:C,shall be provided.


Dry chemical extinguishers can disrupt a sulfur pile and cause the dust to become airborne, which can explode on contact with an ignition source such as a spark or flame. Water mist extinguishers deliver a fine spray which ensures that sulfur dust clouds are not created. Water mist is also the most satisfactory extinguishing agent for bulk stores.


Submitter Full Name: Jennifer Boyle

Organization: Mark Conroy, Brooks Equipment

Affilliation: Fire Equipment Manufacturers Association (FEMA)

Street Address:

City:

State:

Zip:

Submittal Date: Wed Dec 10 10:05:04 EST 2014


5 of 11 2/4/2015 1:08 PM

Public Input No. 10-NFPA 655-2014 [ New Section after A.4.6.8.1.4 ]

A. 4.6.8.1.5 NFPA 780, Annex L.6 and IEC 62305-2 provide methods for assessments todetermine the need for lightning protection.


The proposed annex text provides the user of the standard with information on the source of risk assessment procedures which may be used to determine when lightning protection should be provided


Submitter Full Name: Mark Morgan

Organization: East Coast Lightning Equipment

Affilliation: On behalf of NFPA 780 References Task Group

Street Address:

City:

State:

Zip:



6 of 11 2/4/2015 1:08 PM

Public Input No. 7-NFPA 655-2014 [ Section No. A.5.5.1(2) ]

A.5.5.1(2)

The steam should preferably be introduced near the surface of the molten sulfur. See NFPA 86, Standardfor Ovens and Furnaces, Section F.3.

A.5.5.1(3)

For enclosed sulfur tanks or sulfur pits with air sweep systems, the sealing steam should be fed into theenclosure very near the air inlets. As the sealing steam vents backwards through the air inlets the sealingsteam will quickly stop air ingress to the fire. Sealing steam should be fed into the sulfur tank or sulfur pitfor a minimum of 15 minutes or until the temperature has returned to near normal. For further informationand good engineering practice regarding sealing steam see Molten Sulfur Fire Sealing SteamRequirements.


This is additional information for 6-NFPA 655-2014. System is not letting me link the input forms together.




Street Address:

City:

State:

Zip:



7 of 11 2/4/2015 1:08 PM

Public Input No. 4-NFPA 655-2014 [ Chapter C ]

Annex C Informational References

C.1 Referenced Publications.

The documents or portions thereof listed in this annex are referenced within the informational sections ofthis standard and are not part of the requirements of this document unless also listed in Chapter 2 for otherreasons.

C.1.1 NFPA Publications.


NFPA 68, Standard on Explosion Protection by Deflagration Venting, 2007 edition.

NFPA 69, Standard on Explosion Prevention Systems, 2008 edition.

NFPA 77, Recommended Practice on Static Electricity, 2007 edition.

NFPA 86, Standard for Ovens and Furnaces, 2011 edition.

NFPA 499, Recommended Practice for the Classification of Combustible Dusts and of Hazardous(Classified) Locations for Electrical Installations in Chemical Process Areas, 2008 edition.

NFPA 5000 ®, Building Construction and Safety Code ®, 2012 edition.

C.1.2 Other Publications.

C.1.2.1 AIChE Publications.

American Institute of Chemical Engineers, Three Park Avenue, 120 Wall Street, Floor 23 , New York, NY10016 10005 - 5991 4020 .

Guidelines for Safe Automation of Chemical Processes, 1993.

C.1.2.2 ASTM Publications.

ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959.

ASTM D 257, Standard Test Methods for DC Resistance or Conductance of Insulating Materials, 20072014 .

ASTM E 1515, Standard Test Method for Minimum Explosible Concentration of Combustible Dusts, 2007.

ASTM E 2019, Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air, 2007,reapproved 2013 .


8 of 11 2/4/2015 1:08 PM

C.1.2.3 Other Publications.

Britton, L., Avoiding Static Ignition Hazards in Chemical Operations, CCPS, New York, NY, 1999, pp.199–204.

Ebadat, V., and Mulligan, J. C., “Testing the Suitability of FIBCs for Use in Flammable Atmospheres,”Process Safety Progress, Vol. 15, No. 3, 1996.

Eckhoff, R. K., Dust Explosions in the Process Industries, Oxford, UK: Butterworth-Heinemann Ltd., 3rdedition, 2003.

Hawley's Condensed Chemical Dictionary, 15th edition, ed. R. J. Lewis, John Wiley & Sons Inc., Hoboken,NJ, 2007.

C.2 Informational References.

The following documents or portions thereof are listed here as informational resources only. They are not apart of the requirements of this document.

C.2.1 NFPA Publications.


NFPA 51, Standard for the Design and Installation of Oxygen–Fuel Gas Systems for Welding, Cutting, andAllied Processes, 2007 edition.

NFPA 91, Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and NoncombustibleParticulate Solids, 2010 edition.

NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing,and Handling of Combustible Particulate Solids, 2006 edition.

C.2.2 Additional Publications.

Furno, A. L., G. H. Martindill, and M. G. Zebetakis, “Gas Explosion Hazards Associated with the BulkStorage of Molten Sulfur,” U.S. Department of the Interior, Bureau of Mines RI 6185 (1963).

Handling and Storage of Solid Sulfur, National Safety Council, Data Sheet I-612, revised 1991.

Handling Liquid Sulfur, National Safety Council, Data Sheet 592, revised 1993.

Lagas, J. A., et al., “Understanding the Formation of and Handling of H2S and SO2 Emissions from Liquid

Sulphur During Storage and Transportation.”

Schicho, C. M., W. A. Watson, K. R. Clem, and D. Hartley, “A New Safer Method of Sulfur Degassing,”Chemical Engineering Progress, October 1985, pp. 42–44.

Wiewiorwski, T. K., and F. J. Touro, “The Sulfur-Hydrogen Sulfide System,” Journal of Physical Chemistry,vol. 70, pp. 234–239 (January No. 1) (1966).

The Sulphur Data Book, Library of Congress ISBN 54-7368.

C.3 References for Extracts in Informational Sections.



Referenced current addresses, and editions.

Related Public Inputs for This Document

Related Input Relationship

Public Input No. 3-NFPA 655-2014 [Chapter 2] Referenced current editions.


Submitter Full Name: Aaron Adamczyk


Street Address:


9 of 11 2/4/2015 1:08 PM

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Submittal Date: Fri Jun 20 01:03:02 EDT 2014


10 of 11 2/4/2015 1:08 PM

Public Input No. 8-NFPA 655-2014 [ Section No. C.1.2.3 ]


Britton, L., Avoiding Static Ignition Hazards in Chemical Operations, CCPS, New York, NY, 1999, pp.199–204.

Ebadat, V., and Mulligan, J. C., “Testing the Suitability of FIBCs for Use in Flammable Atmospheres,”Process Safety Progress, Vol. 15, No. 3, 1996.

Eckhoff, R. K., Dust Explosions in the Process Industries, Oxford, UK: Butterworth-Heinemann Ltd., 3rdedition, 2003.

Hawley's Condensed Chemical Dictionary, 15th edition, ed. R. J. Lewis, John Wiley & Sons Inc., Hoboken,NJ, 2007.

Mosher, A. D., McGuffie, S. M., and Martens, D.H., Molten Sulfur Fire Sealing Steam Requirements ,Brimstone Sulfur Symposium, Vail CO., September 2015.


This is additional information for 6-NFPA 655-2014 and 7-NFPA 655-2014. The system is not letting me link the public inputs.




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Correlating Committee Note No. 1-NFPA 61-2014 [ Global Input ]


Submitter Full Name: Susan Bershad

Organization: National Fire Protection Assoc

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Committee Statement

CommitteeStatement:

The Correlating Committee recommends that the 61 technical committee reconsider FR-52. Thestatement is considered to be broad and overreaching. The 61 committee is encouraged to review61 in more detail to determine how it aligns with NFPA 652. Please refer to CN # 3 for direction onaligning the layout and content of 61 with NFPA 652. It is understood by the correlating committeethat this alignment will be a process that may need to take place over several revision cycles.


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Submittal Date: Thu Jan 08 20:24:54 EST 2015

Committee Statement

CommitteeStatement:

The Correlating Committee recommends that the 61 TC consider pointing the user in thedirection of NFPA 87 and NFPA 30 for guidance on heat transfer systems. This may be bestaccomplished through the addition of annex material.


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Submittal Date: Fri Jan 09 09:35:23 EST 2015

Committee Statement

CommitteeStatement:

The Correlating Committee recognizes the 61 technical committee for the significant progressthey have made in this first draft.


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Committee Statement

CommitteeStatement:

The 61 technical committee should consider including the language in Section 1.4.1 ofNFPA 654 -

1.4.1

This standard shall be used to supplement the requirements established by NFPA 652.

This clarifies the relationship between 652 and the commodity-specific standards.


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Committee Statement

CommitteeStatement:

The Correlating Committee recommends that the 61 technical committee consider adding thefollowing material to the proposed new chapter on general requirements. This material was addedto the first draft of 654 as well as 664. This recommendation is also being made to 484 and 655 asthey enter their revision cycles.

4.1.3 Owner's Obligation.

The facility owner/operator shall be responsible for ensuring that the facility and the systemshandling combustible particulate solids are designed, installed, and maintained in accordance withthe requirements of this standard and NFPA 652


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Committee Statement

CommitteeStatement:

The 61 technical committee should review the definitions in Chapter 3 for consistency with 652. Thedefinitions in Chapter 3 of 652 should be considered a baseline for those in the other dustdocuments. In some cases, the occupancy specific document may elect to define a term differently.In those cases, the rationale for the differences should be documented. Note that this comment isalso being made to the 654 and the 664 technical committees, and will be made to the 655 and 484committees as they go through their next revision cycle.


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Supplemental Information

File Name Description

652_outline.docx




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Committee Statement

CommitteeStatement:

The 61 technical committee should review the layout of the document for consistency with NFPA652. The chapter layout for the commodity specific standards should align with the layout of NFPA652 in order to facilitate their use with NFPA 652 in accordance with section 1.4.2 of NFPA 652. Thiscomment is also being made to the 654 and 664 technical committees, and will be made to the 655and 484 technical committees as they go through the next revision cycle.

The Correlating Committee is providing an outline taken from 652 to assist the commodity specificcommittees with their expected alignment to 652 over the next revision cycles. In addition the outlineincludes the level of subsection that a user would use to compare 652 to an industry specificstandard. This is the minimum level of alignment expected, the committee is free to go beyond thislevel. Note that the unhighlighted sections are those that should be used. It is expected that this maynot be able to be completed in the current revision cycle, but this a goal that committees should worktoward.


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652 Chapter 1 Administration

1.1 Scope

1.2 Purpose

1.3 Application

1.4 Conflicts

1.5 Retroactivity

1.6 Equivalency

1.7 Units and Formulas


2.1 General


2.3 Other Publications

2.4 References for Extracts in Mandatory Sections

Chapter 3 Definitions

Committees should align with 652 definitons

Chapter 4 General Requirements

4.1* General

4.2 Objectives

4.2.1 Life Safety

4.2.2* Mission Continuity

4.2.3 Mitigation of Fire Spread and Explosions

Chapter 5 Hazard Identification

5.1* Responsibility

5.2 Overview Screening for Combustibility and Explosibility

5.3* Self-Heating and Reactivity Hazards (Reserved)

5.4 Combustibility and Explosibility Tests

5.4.1* Determination of Combustibility

5.4.2 Determination of Flash Fire Hazard (Reserved)

5.4.3 Determination of Explosibility

5.4.4 Quantification of Combustibility and Explosibility Characteristics

5.5 Sampling

5.5.1 Sampling Plan

5.5.2 Mixtures

5.5.3 Representative Samples

Chapter 6 Performance-Based Design Option

6.1* General Requirements

6.1.12 Approved Qualifications

6.1.2* Document Requirements

6.1.4 Sources of Data

6.1.5* Maintenance of the Design Features

6.2 Risk Component and Acceptability (Reserved)

6.3 Performance Criteria

6.3.1 Life Safety

6.3.2 Structural Integrity

6.3.3 Mission Continuity


6.3.5 Effects of Explosions

6.4* Design Scenarios

6.4.1 Fire Scenarios

6.4.2 Explosion Scenarios

6.5 Evaluation of Proposed Design

Chapter 7 Dust Hazard Analysis


7.1.1 Responsibility

7.2 Criteria

7.2.1* Overview

7.2.2* Qualifications

7.2.4 Documentation

7.3 Methodology

7.3.1 General

7.3.2 Material Evaluation

7.3.3 Process Systems

7.3.4 Facility Compartments

Chapter 8 Hazard Management: Mitigation and Prevention

8.1 Inherently Safe Designs (Reserved)

8.2 Building Design

8.2.1* Construction

8.2.2 Building/Room Protection

8.2.3 Life Safety

8.2.5 Separation of Hazard Areas from Other Hazard Areas and from Other Occupancies

8.3 Equipment Design

8.3.1* Risk Assessment

8.3.2* Design for Dust Containment

8.3.3* Pneumatic Conveying, Dust Collection, and Centralized Vacuum Cleaning Systems

8.3.4 AMS Locations

8.3.5 Recycle of AMS Clean Air Exhaust AMS

8.3.6 Transfer Points (Reserved)

8.4 Housekeeping

8.4.1 General

8.4.2* Methodology

8.4.3 Training

8.4.4 Equipment (Reserved)

8.4.5 Vacuum Trucks

8.4.6 Frequency and Goal

8.4.7 Auditing and Documentation

8.5 Ignition Source Control

8.5.1* General


8.5.3 Hot Work

8.5.5 Bearings

8.5.6 Electrical Equipment and Wiring

8.5.7 Electrostatic Discharges

8.5.8 Open Flames and Fuel Fired Equipment

8.5.9 Industrial Trucks

8.5.10 Process Air and Media Temperatures

8.5.11 Self-Heating

8.5.12 Friction and Impact Sparks

8.6 Personal Protective Equipment

8.6.1 Workplace Hazard Assessment

8.6.2 Limitations of PPE Application (Flame-Resistant Garments)

8.6.3 Limitations of PPE to Combustible Dust Flash-Fires (Reserved)

8.6.4 Face, Hands, and Footwear Protection (Reserved)

8.x Pyrophoric Dusts (Reserved)

8.7 Dust Control

8.7.2* Liquid Dust Suppression Methods for Dust Control

8.7.3 Fans to Limit Accumulation (Reserved)

8.8 Explosion Prevention/Protection

8.8.1 General

8.8.2 Risk Assessment

8.8.3 Equipment Protection

8.8.4 Equipment Isolation

8.9 Fire Protection

8.9.1 General

8.9.3 Fire Extinguishers

8.9.4 Hose, Standpipes, Hydrants, and Water Supply

8.9.5 Automatic Sprinklers

8.9.6 Spark/Ember Detection and Extinguishing Systems

8.9.7 Special Fire Protection Systems

Chapter 9 Management Systems

9.1 Retroactivity

9.2* General

9.3 Operating Procedures and Practices

9.4 Inspection, Testing, and Maintenance

9.5 Training and Hazard Awareness

9.6 Contractors

9.6.3* Contractor Training

9.7 Emergency Planning and Response

9.8* Incident Investigation

9.9 Management of Change

9.10* Documentation Retention

9.11 Management Systems Review

9.12* Employee Participation





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Committee Statement

CommitteeStatement:

The 61 technical committee should review the document to ensure that retroactivity is handledconsistently with the other combustible dust documents. Those sections that are to be appliedretroactively should be explicitly designated in the document section. Typically, management systemelements that do not require capital improvements, such as training and housekeeping, areretroactive. This comment is also being made to the 654 and 664 technical committees and will bemade to the 655 and the 484 technical committees as they go through their next revision cycle.


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Draft_Objectives_for_CC_review.docx




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Committee Statement

CommitteeStatement:

The 61 committee should consider aligning their objectives with those presented in attacheddocument developed by the correlating committee task group on objectives. The correlatingcommittee would like to work towards having all of the dust documents have similar objectives. Thisdocument is a product of a task group with representation from all of the combustible dustcommittees and represents the direction the correlating committee would like to head in. Thisrecommendation is also being made to the 654 and the 664 technical committees, and will be madeto the 484, 655, and 652 technical committees as they enter the next revision cycle.


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NFPA 652 – Draft Objectives for CC review (product of the objectives task group) 4.2 Objectives. 4.2.1 The design of the facility, processes and equipment shall be based upon the goal of providing a reasonable level of safety and property protection by meeting the following objectives:

1.) Life Safety 2.) Mission Continuity 3.) Mitigation of Fire Spread and Explosions

4.2.1.1 The objectives stated in Section 4.2 shall be interpreted as intended outcomes of this standard and not as prescriptive requirements.

4.2.1.2 The objectives stated in Section 4.2 shall be deemed to be met when, consistent with the goal in Section 4.2.1 and the provisions in Sections 1.4 and 1.6,

1.) the facility, processes and equipment are designed, constructed and maintained in accordance with the prescriptive criteria set forth in this standard, and

2.) The management systems set forth in this standard are implemented.

4.2.1.3 Where a performance-based alternative design is used, it shall be documented to meet the same objectives as the prescriptive design it replaces, in accordance with Chapter 6 of this standard.

4.2.2 Life Safety. The life safety objective shall be deemed to have been met when, consistent with the goal in Section 4.2.1 and the provisions in Sections 1.4 and 1.6, the occupants not in the immediate proximity of the ignition are protected from the effects of fires, flash-fires, and explosions for the time needed to evacuate, relocate, or take refuge in order to prevent serious injury. 4.2.3* Mission Continuity. The mission continuity objective shall be deemed to have been met when, consistent with the goal in Section 4.2.1 and the provisions in Sections 1.4 and 1.6, the protection features for the facility, processes and equipment limit damage to levels that ensure the ongoing mission, production, or operating capability of the facility to a degree acceptable to the owner/operator. A.4.2.3 Other stakeholders could also have mission continuity goals that will necessitate more stringent objectives as well as more specific and demanding performance criteria. The protection of property beyond maintaining structural integrity long enough to escape is actually a mission continuity objective.

The mission continuity objective encompasses the survival of both real property, such as the building, and the production equipment and inventory beyond the extinguishment of the fire. Traditionally, property protection objectives have addressed the impact of the fire on structural elements of a building as well as the equipment and contents inside a building. Mission continuity is concerned with the ability of a structure to perform its intended functions and with how that affects the structure's tenants. It often addresses post-fire smoke contamination, cleanup, and replacement of damaged equipment or raw materials. 4.2.4* Mitigation of Fire Spread and Explosions. The mitigation of fire spread and explosions shall be deemed to have been met when, consistent with the goal in Section 4.2.1 and the provisions in Sections 1.4 and 1.6, the prescribed or performance based alternative design features are incorporated into the facility and processes to prevent or mitigate fires and explosions that can cause failure of adjacent buildings or building compartments, or other enclosures, emergency life safety systems, adjacent properties, adjacent storage, or the facility's structural elements. A.4.2.4 Adjacent compartments share a common enclosure surface (wall, ceiling, floor) with the compartment of fire or explosion origin. The intent is to prevent the collapse of the structure during the fire or explosion. 4.2.5 Where a dust fire, deflagration, or explosion hazard exists within a process system, the hazards shall be managed in accordance with this standard. 4.2.6 Where a dust fire, deflagration, or explosion hazard exists with a facility compartment, the effects of the fire, deflagration, or explosion shall be managed in accordance with this standard. 4.2.7* Compliance Options. The objectives in Section 4.2 shall be achieved by either of the following means:

1. A prescriptive approach in accordance with Chapters 5, 7, 8, and 9 in conjunction with any additional prescriptive provisions of applicable commodity-specific NFPA standards.

2. A performance-based approach in accordance with Chapter 6.

A.4.2.7

Usually a facility or process system is designed using the prescriptive criteria until a prescribed solution is found to be infeasible or impracticable. Then the designer can use the performance-based option to develop a design, addressing the full range of fire and explosion scenarios and the impact on other prescribed design features. Consequently, facilities are usually designed not by using performance-based design methods for all facets of the facility but rather by using a mixture of both design approaches as needed.





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Committee Statement

CommitteeStatement:

The correlating committee recommends that the 61 technical committee review the exceptions forbucket elevators with capacities less than 106 m3/hr (3750 ft3/hr) found in sections 7.5.1.10.4,7.5.2.1, and 7.5.3.3.1. The 61 committee should provide technical justification for these exceptionsor remove them. Note that these exceptions have been removed from NFPA 654.


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Correlating Committee Note No. 11-NFPA 61-2015 [ New Section after 4.1.3 ]




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Committee Statement

CommitteeStatement:

The Correlating Committee recommends that the 61 technical committee consider includingsegregation and detachment as management strategies for consistency with the other combustibledust documents. In addition to including the other two management strategies, the 61 technicalcommittee should include the definitions for these terms, as extracted from NFPA 652, in Chapter 3of NFPA 61.


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Correlating Committee Note No. 9-NFPA 61-2015 [ Section No. 4.4.3.1 ]




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Committee Statement

CommitteeStatement:

The correlating committee recommends that the 61 technical committee review the use of the termfire-resistance in this section. 654 made several first revisions changing the term fire-resistancerating to fire-protection rating for doors. The 61 committee should review the changes in 654 andensure that it used the proper term throughout the document. This is a correlating issue between thedocuments.


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Correlating Committee Note No. 10-NFPA 61-2015 [ Section No. 6.2 ]




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Committee Statement

CommitteeStatement:

The Correlating Committee recommends that the 61 technical committee review the use of theterm "combustion explosion" in this section. This terminology is not consistent with those usedthroughout the other combustible dust standards.


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Correlating Committee Note No. 7-NFPA 61-2015 [ Section No. 7.4.2 ]




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Committee Statement

CommitteeStatement:

The 61 technical committee should review FR-18 in light of the negative comments, specificallythose that suggest that the provisions conflict with those in NFPA 68.

First Revision No. 18-NFPA 61-2014 [Section No. 7.4.2]


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Correlating Committee Note No. 8-NFPA 61-2015 [ New Section after 13.11 ]




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Committee Statement

CommitteeStatement:

The Correlating Committee recommends that the 61 technical committee review its action relatingto FR-50. The proposed text does not meet the standard of care established by the othercombustible dust documents such as NFPA 652 and 654 with regards to dust hazard analysis(DHA).

The Correlating Committee recognizes the work of the 61 technical committee. It is aware that thecommittee has a task group that is working on this issue for the second draft. The CorrelatingCommittee encourages the 61 technical committee to review the material in NFPA 652 and strive towork towards the goals and objectives addressed in chapters 5 and 7 of NFPA 652.

First Revision No. 50-NFPA 61-2014 [New Section after 13.11]


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Submittal Date: Wed Jan 07 16:55:15 EST 2015

Committee Statement

CommitteeStatement:

The 654 committee should consider aligning their objectives with those presented in attacheddocument developed by the correlating committee task group on objectives. The correlatingcommittee would like to work towards having all of the dust documents have similar objectives. Thisdocument is a product of a task group with representation from all of the combustible dustcommittees and represents the direction the correlating committee would like to head in. Thisrecommendation is also being made to the 61 and the 664 technical committees, and will be made tothe 484, 655, and 652 technical committees as they enter the next revision cycle.


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A.4.2.7






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Committee Statement

CommitteeStatement:

The correlating committee recommends that the 654 technical committee review and update ifnecessary, Annex B and C of the document. Both are extracted into 664 and neither has beenupdated over the past several revision cycles. They may be more recent material that could beincorporated into both annexes. It is understood that this may not take place until the next revisioncycle for 654.


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Committee Statement

CommitteeStatement:

The 654 technical committee should consider adding the language in the first draft of NFPA 61 onconflicts, section 1.4.1 and section 1.4.2.

1.4.1

Where a requirement specified in this industry-specific standard differs from a requirementspecified in NFPA 652, the requirement in this standard shall be permitted to be used instead.

1.4.2

Where a requirement specified in this standard specifically prohibits a requirement specified inNFPA 652, the prohibition in this standard shall be permitted.

The Correlating Committee believes that adding this to 654 would provide clarity to the user of thedocument. This recommendation is also being made to the 664 technical committee and will bemade to the 484 and the 655 technical committees as they enter their revisions cycles.


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Submittal Date: Mon Jan 12 10:20:15 EST 2015

Committee Statement

CommitteeStatement:

The correlating committee recommends that the 654 technical committee revise the scope of thedocument to be consistent with the structure of the scope statement in NFPA 61. This scope statesthe "standard provides requirements...". The correlating committee is working towards aligning thescope statements in all of the dust document to be consistent. This recommendation is also beingmade to the 664 TC and the 484 and 655 technical committees as they enter their revision cycles.


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Submittal Date: Tue Jan 06 18:28:34 EST 2015

Committee Statement

CommitteeStatement:

The 654 technical committee should review the responses to PI - 72, 73, 74, 75, 78, and 81. Theterms defined in some of these public inputs are used in 654. Even if the terms are defined in 652,the 654 technical committee should reconsider whether or not these definitions should be includedin 654. It may be easier for the user if the terms are also defined in 654.


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Committee Statement

CommitteeStatement:

The 654 technical committee should review the definitions in Chapter 3 for consistency with 652.The definitions in Chapter 3 of 652 should be considered a baseline for those in the other dustdocuments. In some cases, the occupancy specific document may elect to define a term differently.In those cases, the rationale for the differences should be documented. Note that this comment isalso being made to the 61 and the 664 technical committees, and will be made to the 655 and 484committees as they go through their next revision cycle.


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652_outline_CC_meeting.docx




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Committee Statement

CommitteeStatement:


The Correlating Committee is providing an outline taken from 652 to assist the commodity specificcommittees with their expected alignment to 652 over the next revision cycles. In addition the outlineincludes the level of subsection that a user would use to compare 652 to an industry specificstandard. This is the minimum level of alignment expected, the committee is free to go beyond thislevel. Note that the highlighted sections are those that should be used. It is expected that this maynot be able to be completed in the current revision cycle, but this a goal that committees should worktoward.


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1.1 Scope

1.2 Purpose

1.3 Application

1.4 Conflicts

1.5 Retroactivity

1.6 Equivalency



2.1 General





Committees should align with 652 definitions


4.1* General

4.2 Objectives

4.2.1 Life Safety




5.1* Responsibility








5.5 Sampling

5.5.1 Sampling Plan

5.5.2 Mixtures










6.3.1 Life Safety












7.2 Criteria

7.2.1* Overview


7.2.4 Documentation

7.3 Methodology

7.3.1 General






8.2 Building Design

8.2.1* Construction


8.2.3 Life Safety






8.3.4 AMS Locations



8.4 Housekeeping

8.4.1 General

8.4.2* Methodology

8.4.3 Training


8.4.5 Vacuum Trucks




8.5.1* General


8.5.3 Hot Work

8.5.5 Bearings






8.5.11 Self-Heating








8.7 Dust Control




8.8.1 General




8.9 Fire Protection

8.9.1 General







9.1 Retroactivity

9.2* General




9.6 Contractors












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Committee Statement

CommitteeStatement:

The 654 technical committee should consider referring to Chapter 5 of 652 for testingrequirements for combustible dusts. This could be done by a reference to 652 or by extracting thematerial in Chapter 5 of 652 into 654.


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Committee Statement

CommitteeStatement:

The 654 technical committee should review the document to ensure that retroactivity is handledconsistently. Those sections that are to be applied retroactively should be explicitly designated in thedocument section. Typically, management system elements that do not require capitalimprovements, such as training and housekeeping, are retroactive. This comment is also beingmade to the 61 and 664 technical committees and will be made to the 655 and the 484 technicalcommittees as they go through their next revision cycle.


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Committee Statement

CommitteeStatement:

The 654 technical committee should consider adding the term "flash fire" to fire and explosionhazard in this section. This would make the scope, section 1.1.1, consistent with the purpose,section 1.1.2. The 654 technical committee should also review the rest of the document to ensurethat these terms are used consistently.


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Committee Statement

CommitteeStatement:

The 654 technical committee should consider whether or not the annex material that was addedas part of FR-2 is relevant to this section. It appears to be more appropriate to 652.


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Correlating Committee Note No. 9-NFPA 654-2015 [ Sections 4.3, 4.4 ]




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Committee Statement

CommitteeStatement:

The 654 technical committee should compare Sections 4.3 and 4.4, Management of Change andIncident Investigation, to the analogous sections in 652. The committee should determine if anyadditions or omissions between the two documents are intentional or an oversight. An effort shouldbe made to more closely align the two documents.


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Committee Statement

CommitteeStatement:

The 654 committee should review FR-27 as to whether or not other additional test methods shouldbe included as part of this requirement. As a minimum, ASTM E 152, Standard Method of Fire TestsFor Door Assemblies and FM Approvals Class 4100, Approval Standard for Fire Doors, as noted inthe negative comments on the ballot, should be considered.


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Committee Statement

CommitteeStatement:

The 654 technical committee should consider revising 7.1.6.2 (5) in FR-37 to include enforceablelanguage as per the NFPA manual of style. Note that this comment was made by severalcommittee members on the ballot.


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Committee Statement

CommitteeStatement:

The 654 technical committee should review this section in light of the response by the NFPAtechnical committee to PI-52 submitted to NFPA 61. PI-52 proposed to extract this requirement from654 into 61. The NFPA 61 committee stated that: "The committee is not sure that a design thatmeets this requirement exists. The committee does not want to leave this as a potential requirementwithout additional information."


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Committee Statement

CommitteeStatement:

The 664 technical committee should review the definitions in Chapter 3 for consistency with 652.The definitions in Chapter 3 of 652 should be considered a baseline for those in the other dustdocuments. In some cases, the occupancy specific document may elect to define a term differently.In those cases, the rationale for the differences should be documented. Note that this comment isalso being made to the 61 and the 654 technical committees, and will be made to the 655 and 484committees as they go through their next revision cycle.


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Committee Statement

CommitteeStatement:

The 664 technical committee should consider adding the language in the first draft of NFPA 61 onconflicts, section 1.4.1 and section 1.4.2.

1.4.1

Where a requirement specified in this industry-specific standard differs from a requirementspecified in NFPA 652, the requirement in this standard shall be permitted to be used instead.

1.4.2

Where a requirement specified in this standard specifically prohibits a requirement specified inNFPA 652, the prohibition in this standard shall be permitted.

The Correlating Committee believes that adding this to 664 would provide clarity to the user of thedocument. This recommendation is also being made to the 654 technical committee and will bemade to the 484 and the 655 technical committees as they enter their revisions cycles.


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Street Address:

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Committee Statement

CommitteeStatement:

The Correlating Committee recommends that the 664 TC consider pointing the user in thedirection of NFPA 87 for guidance on heat transfer systems. This may be best accomplishedthrough the addition of annex material


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Committee Statement

CommitteeStatement:

The 664 technical committee should consider including the language in Section 1.4.1 ofNFPA 654 -

1.4.1

This standard shall be used to supplement the requirements established by NFPA 652.

This clarifies the relationship between 652 and the commodity-specific standards.


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652_outline_CC_meeting.docx




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The Correlating Committee is providing an outline taken from 652 to assist the commodity specificcommittees with their expected alignment to 652 over the next revision cycles. In addition the outlineincludes the level of subsection that a user would use to compare 652 to an industry specificstandard. This is the minimum level of alignment expected, the committee is free to go beyond thislevel. Note that the highlighted sections are those that should be used. It is expected that this maynot be able to be completed in the current revision cycle, but this a goal that committees should worktoward.


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1.1 Scope

1.2 Purpose

1.3 Application

1.4 Conflicts

1.5 Retroactivity

1.6 Equivalency



2.1 General





Committees should align with 652 definitions


4.1* General

4.2 Objectives

4.2.1 Life Safety




5.1* Responsibility








5.5 Sampling

5.5.1 Sampling Plan

5.5.2 Mixtures










6.3.1 Life Safety












7.2 Criteria

7.2.1* Overview


7.2.4 Documentation

7.3 Methodology

7.3.1 General






8.2 Building Design

8.2.1* Construction


8.2.3 Life Safety






8.3.4 AMS Locations



8.4 Housekeeping

8.4.1 General

8.4.2* Methodology

8.4.3 Training


8.4.5 Vacuum Trucks




8.5.1* General


8.5.3 Hot Work

8.5.5 Bearings






8.5.11 Self-Heating








8.7 Dust Control




8.8.1 General




8.9 Fire Protection

8.9.1 General







9.1 Retroactivity

9.2* General




9.6 Contractors












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The 664 technical committee should review the document to ensure that retroactivity is handledconsistently. Those sections that are to be applied retroactively should be explicitly designated in thedocument section. Typically, management system elements that do not require capitalimprovements, such as training and housekeeping, are retroactive. This comment is also beingmade to the 61 and 654 technical committees and will be made to the 655 and the 484 technicalcommittees as they go through their next revision cycle


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Committee Statement

CommitteeStatement:

The 664 committee should consider aligning their objectives with those presented in attacheddocument developed by the correlating committee task group on objectives. The correlatingcommittee would like to work towards having all of the dust documents have similar objectives. Thisdocument is a product of a task group with representation from all of the combustible dustcommittees and represents the direction the correlating committee would like to head in. Thisrecommendation is also being made to the 61 and the 654 technical committees, and will be made tothe 484, 655, and 652 technical committees as they enter the next revision cycle.


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A.4.2.7






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The correlating committee recommends that the 664 TC review their response to PI -2 andPI-24 based on CN #4


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Committee Statement

CommitteeStatement:

The correlating committee recommends that the 664 technical committee review its response toPI-32. 654 made several first revisions changing the term fire-resistance rating to fire-protectionrating for doors. The 664 committee should review the changes in 654 and ensure that it used theproper term throughout the document. This is a correlating issue between the documents.


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Correlating Committee Note No. 14-NFPA 664-2015 [ Section No. 1.1 [Excluding any

Sub-Sections] ]




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Committee Statement

CommitteeStatement:

The correlating committee recommends that the 664 technical committee revise the scope of thedocument to be consistent with the structure of the scope statement in NFPA 61. This scope statesthe "standard provides requirements...". The correlating committee is working towards aligning thescope statements in all of the dust document to be consistent. This recommendation is also beingmade to the 654 TC and the 484 and 655 technical committees as they enter their revision cycles.


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The correlating committee recommends that the 664 committee review this first revision in light ofthe negative comments received on the ballot. This criteria is not consistent with material in 652for triggering a dust hazard analysis.

First Revision No. 2-NFPA 664-2014 [New Section after 1.4.3]


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CommitteeStatement:

The correlating committee recommends the 664 technical committee reconsider this FR based onthe negative comments received on the ballot. This term is used throughout this document as wellas the other dust documents and should be defined consistently, if it needs to be defined at all.

First Revision No. 35-NFPA 664-2014 [New Section after 3.3.20]


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The 664 technical committee should review this section and correlate it with the material in 652on dust hazard analysis. This would ensure consistency between the two documents.


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Correlating Committee Note No. 11-NFPA 664-2015 [ New Section after 6.3 ]




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Committee Statement

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The 664 technical committee should consider extracting the definitions for separation,segregation, and detachment from 652 into this document. The material is extracted from 652, butthe terms are not defined. This will ensure consistency with 652.

First Revision No. 32-NFPA 664-2014 [New Section after 6.3]


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Committee Statement

CommitteeStatement:

The correlating committee recommends that the 664 technical committee review this FR inlight of the negative comments received on the ballot.

First Revision No. 16-NFPA 664-2014 [Section No. 7.4.1]


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Committee Statement

CommitteeStatement:

The correlating committee recommends that the 664 committee reconsider its action on this FRbased on the negative ballot comments. This material is in a section on storage and the use of theterm "storage" may be more consistent.

First Revision No. 57-NFPA 664-2014 [Section No. 8.10.4.4]


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MOLTEN SULFUR FIRE SEALING STEAM REQUIREMENTS

Proposed Modifications to NFPA 655

Alan D. Mosher Principal Process Engineer Black & Veatch Corporation

Overland Park, KS, USA [email protected]

Sean M. McGuffie Senior Engineer

Porter McGuffie, Inc. Lawrence, KS, USA

[email protected]

Dennis H. Martens Consultant and Technical Advisor

Porter McGuffie, Inc. Lawrence, KS, USA

[email protected]

To Be Presented at the Brimstone Sulfur Symposium

Vail, Colorado

September 14-18, 2015

Abstract National Fire Protection Association (NFPA) 655 Standard for Prevention of Sulfur Fires and Explosions (current edition: 2012), Chapter 5, Handling of Liquid Sulfur at Normal Handling Temperatures, Section 5.5, Fire Fighting, states that protection of covered liquid sulfur storage tanks, pits and trenches shall be by one of the following means: (1) inert gas system, (2) steam extinguishing system capable of delivering a minimum of 2.5 lb/min (1.13 kg/min) of steam per 100 ft3 (2.83 m3) of volume, or (3) rapid sealing of enclosure to exclude air. The NFPA snuffing steam rate stated in the standard results in a large steam rate being fed to sulfur tanks and sulfur pits that typically have a low design pressure. The sulfur tanks and sulfur pits are typically designed with air sweep systems to prevent the accumulation of hydrogen sulfide (H2S) in the vapor space, thereby eliminating the flammable mixture. The air intake and exhaust systems are typically designed with very low pressure drops for normal operation. If snuffing steam is fed to sulfur tanks and sulfur pits at the rate specified in NFPA 655, the built-up back pressure typically far exceeds the design pressure of the enclosure. For these reasons, the refining and gas plant industry has tended to choose not to follow the NFPA 655-specified snuffing steam rate. Actual operating data from sulfur fires in sulfur tanks and sulfur pits indicate that a lower sealing steam rate is adequate to extinguish the fire by sealing the sulfur tank or sulfur pit from air ingress and purging some of the air as the fire is extinguished by lack of oxygen. Some computational fluid dynamics (CFD) modeling has been completed that supports the field data showing that a lower steam rate is adequate to extinguish the fires. This paper focuses on the potential problems caused by the current NFPA 655 snuffing steam rate, analysis of actual field data for fires in sulfur tanks and pits, and a recommendation for the NFPA 655 committee to consider regarding a steam rate to seal the enclosure and extinguish the fire in a sulfur tank and sulfur pit. The paper also includes comments on good engineering practice resulting from the calculations and CFD analyses that were completed. NFPA 655 is currently being updated and will be reissued in 2017. This paper was initially prepared to document issues with the current NFPA 655 snuffing steam rate for molten sulfur and to recommend a reduced rate to NFPA during the first public comment period that ended on January 5, 2015.

MOLTEN SULFUR FIRE SEALING STEAM REQUIREMENTS|PROPOSED MODIFICATIONS TO NFPA 655

i

Table of Contents

Executive Summary .............................................................................................................................................. 1

1.0 Introduction .............................................................................................................................................. 2

2.0 Brief History of NFPA 655 Snuffing Steam Requirements ........................................................ 3

2.1 1968 Edition ................................................................................................................................................ 3

2.2 1982 Edition ................................................................................................................................................ 3

2.3 1993 Edition ................................................................................................................................................ 4

2.4 2001 Edition ................................................................................................................................................ 4

2.5 2007 Edition ................................................................................................................................................ 5

2.6 2012 Edition ................................................................................................................................................ 6

2.7 2017 Edition ................................................................................................................................................ 6

2.8 Equivalency of various required snuffing steam rates .............................................................. 7

3.0 Issues with Current NFPA 655 Snuffing Steam Requirement ...................................................... 8

4.0 Attempted Oxygen Concentration Dilution Calculation .......................................................... 13

5.0 Actual Operating Data for Molten Sulfur Fire Extinguishing Steam ................................... 14

5.1 Detection of Sulfur Pit and tank Fires ............................................................................................ 15

5.2 Sulfur Pit Fires ......................................................................................................................................... 17

5.3 Sulfur Tank Fires .................................................................................................................................... 22

6.0 Computational Fluid Dynamics Modeling of a Sulfur Pit ........................................................ 24

6.1 Selection and Construction of Computational Domains ........................................................ 24

6.2 Development of Computational Grid ............................................................................................. 24

6.3 Selection of Domain Physics .............................................................................................................. 26

6.4 Selection of Boundary Conditions ................................................................................................... 26

6.5 Solution ...................................................................................................................................................... 28

6.6 Results ........................................................................................................................................................ 28

6.6.1 Current Configuration Results ....................................................................................... 28

6.6.2 Relocated Configuration Results .................................................................................. 30

6.6.3 Velocity Streamline Comparisons ................................................................................ 31

6.7 General Discussion ................................................................................................................................ 33

7.0 Potential Rapid Sealing Steam Rate ................................................................................................ 34

8.0 Good Engineering Practice for Use of Sealing Steam ................................................................ 38

9.0 Conclusions .............................................................................................................................................. 40

10.0 Recommendations ................................................................................................................................ 41

11.0 Acknowledgements .............................................................................................................................. 42

12.0 References ............................................................................................................................................... 42


ii

LIST OF TABLES Table 1 Snuffing Steam Rates for Molten Sulfur Listed in NFPA 655 .................................................. 7

Table 2 Existing Sulfur Tanks with Steam at 2.5 lb/min per 100 ft3 ................................................. 10

Table 3 Existing Sulfur Pits with Steam at 2.5 lb/min per 100 ft3 ..................................................... 12

Table 4 Existing Sulfur Tanks with Steam at 1.0 lb/min per 100 ft3 Compared to 2.5 lb/min per 100 ft3 .................................................................................................................................. 35

Table 5 Existing Sulfur Pits with Steam at 1.0 lb/min per 100 ft3 Compared to 2.5 lb/min per 100 ft3 .................................................................................................................................. 37

LIST OF FIGURES Figure 1 Incinerator Stack SO2 and Sulfur Pit Vapor Space Temperature during a

Sulfur Fire .................................................................................................................................................. 16

Figure 2 Sulfur Pit Fire DCS Temperature Data .......................................................................................... 20

Figure 3 Domains Used for CFD Analyses ...................................................................................................... 25

Figure 4 Computational Grid Developed for CFD Analyses .................................................................... 25

Figure 5 Boundary Conditions Applied for Current Configuration Analysis ................................... 26

Figure 6 Boundary Conditions Applied to Steam Inlet Moved Model ................................................ 27

Figure 7 Common Boundary Conditions Applied to Models .................................................................. 28

Figure 8 Oxygen Concentrations in Sulfur Pit Vapor Space .................................................................... 29

Figure 9 Oxygen Concentrations in Sulfur Pit Vapor Space, Air Inlet, and Ejector Suction ............. 30

Figure 10 Oxygen Concentration in Sulfur Pit Vapor Space with Steam Relocated Near Air Inlet ...................................................................................................................................................... 31

Figure 11 Velocity Streamlines for Current Configuration Analysis ..................................................... 32

Figure 12 Velocity Streamlines for Moved Steam Inlet Case .................................................................... 32


1

Executive Summary On the basis of the data collected and analysis performed for this paper, the authors

recommend the following changes to National Fire Protection Association (NFPA) 655, Standard for

Prevention of Sulfur Fires and Explosions (current edition: 2012), Chapter 5, Handling of Liquid

Sulfur at Normal Handling Temperatures:

5.5 Fire Fighting.

5.5.1 Protection for covered liquid sulfur storage tanks, pits, and trenches shall be by one of the

following means:

(1) Inert gas system in accordance with NFPA 69, Standard on Explosion Prevention Systems

(2)*Steam extinguishing system capable of delivering a minimum of 2.5 lb/min (1.13 kg/min) of

steam per 100 ft3 (2.83 m3) of volume.

(3) Rapid sealing of the enclosure to exclude air

(3)*Rapid sealing of the enclosure to exclude air. For sulfur tanks and sulfur pits, the use of

a steam rate of 1.0 lb/min (0.45 kg/min) of steam per 100 ft3 (2.83 m3) of total tank or pit

volume is expected to develop a positive pressure in the enclosure, thereby sealing the

sulfur tank or sulfur pit, preventing air ingress, and extinguishing the fire.

5.5.2 Snuffing Steam and Sealing Steam Precautions.

5.5.2.1 The vent systems on enclosed sulfur tanks and sulfur pits must be designed to allow the

required snuffing steam rate or sealing steam rate to vent without overpressuring the enclosure.

The vent systems must also be designed for proper operation during normal operation.


5.5.2.13.1 Liquid sulfur stored in open containers shall be permitted to be extinguished with a fine

water spray.

5.5.2.23.2 Use of high-pressure hose streams shall be avoided.

5.5.2.33.3 The quantity of water used shall be kept to a minimum.

5.5.34 Dry Chemical Extinguishers. Where sulfur is being heated by a combustible heat transfer

fluid, dry chemical extinguishers complying with NFPA 17, Standard for Dry Chemical Extinguishing

Systems, shall be provided.

A.5.5.1(3) For enclosed sulfur tanks or sulfur pits with air sweep systems, the sealing steam

should be fed into the enclosure very near the air inlets. As the sealing steam vents backward

through the air inlets, the sealing steam will quickly stop air ingress to the fire. Sealing steam

should be fed into the sulfur tank or sulfur pit for a minimum of 15 minutes or until the

temperature has returned to near normal. For further information and good engineering

practice regarding sealing steam see Molten Sulfur Fire Sealing Steam Requirements.


Mosher, A. D., McGuffie, S. M., and Martens, D.H., Molten Sulfur Fire Sealing Steam

Requirements, Brimstone Sulfur Symposium, Vail, CO, September 2015.


2

1.0 Introduction National Fire Protection Association (NFPA) 655, Standard for Prevention of Sulfur Fires and

Explosions,(1) contains information about snuffing steam requirements for extinguishing fires in

sulfur tanks and sulfur pits. The rate that is listed in Chapter 5, Handling of Liquid Sulfur at Normal

Handling Temperatures, is excessive and causes problems with the venting systems of these

enclosures and can cause built-up back pressure within these enclosures that exceeds the original

design pressure.

Sulfur produced in oil and gas facilities contains quantities of hydrogen sulfide (H2S). This

H2S is slowly released from the molten sulfur during storage. To eliminate the flammable mixture,

sulfur tanks and sulfur pits in these facilities are typically designed with air sweep systems to

prevent the accumulation of H2S in the vapor space. Continuous sweeping with air also prevents

accumulation of pyrophoric iron sulfide (FeS) by oxidizing the material. The FeS is generated by

corrosion of carbon steel components in contact with H2S. The air intake and exhaust systems for

sulfur tanks and sulfur pits must be carefully designed with consideration for very low pressure

drops during normal operation, must account for the buoyancy effect of the heated air intakes, and

must account for the effect of wind blowing across the vents. Developing a vent design that

accounts for all the normal operating parameters can be quite difficult and can become impractical

when the vents must also be capable of venting the snuffing steam fed at the NFPA 655 rate of

2.5 pounds per minute (lb/min) per 100 cubic feet (ft3) of volume.

This paper focuses on the potential problems caused by the current NFPA 655 snuffing

steam rate. The paper presents analysis of available actual field data for extinguishing fires in

sulfur tanks and sulfur pits provided by owners of oil and gas facilities. This paper provides the

basis for a recommendation to the NFPA 655 committee to consider defining a steam rate to

suitably seal the sulfur tanks and sulfur pits to exclude oxygen and, thereby, safely extinguish sulfur

fires. This paper recommends a sealing steam rate based on documented industry practice for

extinguishing fires in sulfur tanks and sulfur pits and computational fluid dynamics (CFD) studies.

The paper also includes comments on good engineering practice resulting from the analysis of the

information gathered and from CFD modeling that was completed. NFPA 655 is currently being

updated and will be reissued in 2017. This paper was initially prepared to document issues with

the current NFPA 655 snuffing steam rate for molten sulfur fires and recommend incorporating a

sealing steam rate to NFPA during the first public comment period that ended on January 5, 2015.

Note: No part of this document addresses fire fighting for solid dust sulfur fires. This

document only addresses steam requirements for molten sulfur fires.


3

2.0 Brief History of NFPA 655 Snuffing Steam Requirements The fire fighting techniques listed by NFPA for molten sulfur have evolved since the initial

adoption of NFPA 655 in 1940. The following information was taken from documents such as

revision history, Technical Committee Reports, etc., available on NFPA’s website.1

2.1 1968 EDITION The Technical Committee Report for Amendments to be included in the 1968 edition of

NFPA 655 included the following text:

45. Fire Fighting.

4501. Covered liquid sulfur storage tanks should be provided with some inert gas system

for extinguishing fires that may occur in the tank. The inert gas may consist of carbon

dioxide, nitrogen, flue gas or steam. Since the inert must be supplied rapidly enough to

displace the ventilation air from the vents, steam is usually the most effective and

economical choice.

4502. Where liquid sulfur containers are of sufficiently small size to permit such action, it is

recommended that they be so arranged so that they can be sealed rapidly to exclude air in

case of fire; formation of sulfur dioxide will exhaust the oxygen in the enclosure and

smother the fire. The system should be allowed to cool below 154C (310F) before

reopening it to the atmosphere.

4503. Liquid sulfur stored in open containers can best be extinguished with a fine water

spray. Avoid the use of pressure hose streams which may scatter the burning liquid sulfur.

The quantity of water used should be kept to a minimum.

2.2 1982 EDITION The Technical Committee Report for Amendments to be included in the 1982 edition of

NFPA 655 included the following text:

4-4 Fire Fighting.

4-4.1 Covered liquid sulfur tanks shall be provided with a gaseous fire extinguishing system.

(See Appendix E of NFPA 86A, Standard Ovens and Furnaces, Appendix E, and NFPA 69,

Standard on Explosion Prevention Systems.)

4-4.1.1* Where a fixed inerting system is used, thin Teflon ® rupture discs shall be placed

over the inerting nozzles so that sulfur cannot condense within the nozzle.

1 NFPA’s website is www.nfpa.org

http://www.nfpa.org/


4

4-4.2* Where liquid sulfur containers are small enough, they may be arranged so that they

can be rapidly sealed to exclude air in case of fire. The sulfur dioxide produced by the fire

will smother the fire. In such cases, the system shall be allowed to cool below 154C before

reopening.

4-4.3 Liquid sulfur stored in open containers may be extinguished with a fine water spray.

Use of high pressure hose streams shall be avoided. Quantity of water used shall be kept to

a minimum.

2.3 1993 EDITION The Report of the Committee included the following recommendation, which was accepted

and became part of the 1993 edition:

1. Revise 4-4.1" and add an Exception to read:

4-4.1* Covered liquid sulfur tanks shall be provided with a steam extinguishing system or

an inert gas system in accordance with NFPA 86, Standard for Ovens and Furnaces and

NFPA 69, Standard on Explosion Protection Systems.

Exception: Where liquid sulfur containers can be rapidly sealed to exclude air, the SO2

produced will smother the fire. In such cases, steam extinguishing systems or inert gas

systems shall not be required. The system shall be allowed to cool below 154 C (309 F)

before reopening.

2. Delete existing text of 4-4.2.

2.4 2001 EDITION The Report of the Committee included the following recommendation, which was accepted

and became part of the 2001 edition:

RECOMMENDATION : Revise 4-4.1 as follows:

4-4.1 Protection for covered liquid sulfur storage tanks, pits and trenches shall be by one of

the following means:

(a) Inert gas system in accordance with NFPA 69, Standard for Explosion Prevention

Systems.

(b)* Steam extinguishing system capable of delivering 8 lbs/min of steam per

100 cu ft of volume. – Bold added by current authors

(c) Rapidly seal the enclosure to exclude air.

A-4-4.1(b) The steam should preferably be introduced near the surface of the molten sulfur.

See NFPA 86, Standard for Ovens and Furnaces, Appendix E-3.


5

SUBSTANTIATION: This recommendation brings the steam flooding requirement in line

with NFPA 86. The recommendation is based on 1934 FMRC fire test of a gasoline fire

where the steam was applied above the gasoline fire and combustion air was introduced

below the steam injection point. It in essence requires supplying 200 cu ft/min steam for

every 100 cu ft of enclosure volume. For hot enclosures (above 220 F) where the steam is

injected at the surface of the liquid sulfur, a supply capable of 4 cu ft/min per 100 cu ft of

enclosure volume would be satisfactory. This requirement ensures that the available steam

supply is adequate to furnish enough steam at a rate sufficient to extinguish the fire.

2.5 2007 EDITION The Report of the Committee shows a recommendation and acceptance of a complete

revision of the 2001 edition of NFPA 655 to become the 2007 edition. The 2007 edition showed the

following text:

5.5 Fire Fighting.

5.5.1 Protection for covered liquid sulfur storage tanks, pits, and trenches shall be by one of


(1) Inert gas system in accordance with NFPA 69, Standard on Explosion Prevention

Systems

(2)* Steam extinguishing system capable of delivering a minimum of 2.5 lb/min

(1.13 kg/min) of steam per 100 ft3 (2.83 m3) of volume – Bold added by current authors


5.5.2* Where a fixed inerting system is used, thin corrosion-resistant rupture discs shall be

placed over the inerting nozzles so that sulfur cannot condense within the nozzle.


5.5.3.1 Liquid sulfur stored in open containers shall be permitted to be extinguished with a

fine water spray.

5.5.3.2 Use of high-pressure hose streams shall be avoided.

5.5.3.3 The quantity of water used shall be kept to a minimum.

5.5.4 Dry Chemical Extinguishers. Where sulfur is being heated by a combustible heat

transfer fluid, dry chemical extinguishers complying with NFPA 17, Standard for Dry

Chemical Extinguishing Systems shall be provided.


6

2.6 2012 EDITION The Report of the Committee shows a recommendation and acceptance of a revised

wording of the 2007 edition of NFPA 655 to become the 2012 edition as follows:

5.5 Fire Fighting.

5.5.1 Protection for covered liquid sulfur storage tanks, pits, and trenches shall be by one of


(1) Inert gas system in accordance with NFPA 69, Standard on Explosion Prevention

Systems

(2)* Steam extinguishing system capable of delivering a minimum of 2.5 lb/min (1.13 kg/min)

of steam per 100 ft3 (2.83 m3) of volume


5.5.2* Where a fixed inerting system is used, thin corrosion-resistant rupture discs shall be

placed over the inerting nozzles so that sulfur cannot condense within the nozzle.


5.5.2.1 Liquid sulfur stored in open containers shall be permitted to be extinguished with a

fine water spray.

5.5.2.2 Use of high-pressure hose streams shall be avoided.

5.5.2.3 The quantity of water used shall be kept to a minimum.

5.5.3 Dry Chemical Extinguishers. Where sulfur is being heated by a combustible heat

transfer fluid, dry chemical extinguishers complying with NFPA17, Standard for Dry

Chemical Extinguishing Systems, shall be provided.

2.7 2017 EDITION The next edition of NFPA 655 is due to be published in 2017. The public input closing date

was January 5, 2015.


7

2.8 EQUIVALENCY OF VARIOUS REQUIRED SNUFFING STEAM RATES Table 1 provides a comparison of different snuffing steam rates for molten sulfur that have

been listed in different editions of NFPA 655.

Table 1 Snuffing Steam Rates for Molten Sulfur Listed in NFPA 655

LB/MIN per

100 FT3

FT3/MIN per

100 FT3 COMMENT

2001 Edition 8 214 Based on 1934 Factory Mutual

Research Corporation (FMRC)

fire test of a gasoline fire.

2001 discussion

prior to issue of

official edition

0.14 3.8 Comment made as part of

substantiation of item above.

When steam is injected at the

surface of the liquid sulfur, this

rate would be satisfactory.

2007 Edition 2.5 67


8

3.0 Issues with Current NFPA 655 Snuffing Steam Requirement Most existing and new sulfur recovery units (SRUs) within oil refineries and gas processing

facilities have enclosed below grade sulfur pits and/or above grade sulfur tanks for storage of

produced molten sulfur. Many of these sulfur pits and sulfur tanks have been designed with air

sweep systems in the vapor space to maintain the concentration of H2S below 25 percent of the

lower flammable limit (LFL) in accordance with NFPA 69, Standard on Explosion Prevention

Systems(2), Chapter 8, Deflagration Prevention by Combustible Concentration Reduction. Because of

safety concerns regarding possible venting of H2S to the environment through leaks in the sulfur

pit, many of the sulfur pits and sulfur tanks are operated with a slight vacuum. The vacuum is often

created by mechanical blowers or ejectors that pull the required amount of sweep air through the

vapor space of the enclosure and then discharge that air/vapor to an appropriate disposal

location/device at a slightly elevated pressure. Because of the buoyancy effect, the vacuum can also

be created by the height difference between a heated vent stack and the heated air intake. The

typical design internal and external pressures of sulfur tanks are low (approximately -3 to +10 inch

water column [”WC] or less), and therefore, the vent systems must be carefully designed to prevent

excessive vacuum from causing damage to the sulfur tank. Unlike tanks or vessels, sulfur pits may

or may not be designed with the intention of having a specific internal design pressure. However,

sulfur pits are typically designed with a concrete roof thickness of 12 to 15 inches. Based solely on

the weight of the roof slab, the sulfur pit should be able to contain a pressure of 1-1.3 pounds per

square inch (psi) (28-36 ”WC). However, sulfur pit roofs frequently contain access hatches. Precast

concrete hatches typically range from 4 to 6 inches thick and can therefore withstand an internal

pressure of only approximately 0.35-0.51 psi (10-14 ”WC) before lifting. Roof hatches or deflagration

hatches can also be made from thin aluminum sheet material that is much lighter than the concrete

and therefore able to withstand an internal pressure of only approximately 0.25-0.50 ”WC before

lifting. The air inlets to the sulfur pit or sulfur tank are typically heated with steam (steam jacketed)

to prevent sulfur solidification and the resulting plugging within the air inlet. The heating of the air

intakes causes a buoyancy effect to occur, and the sulfur pit or sulfur tank must be operated under a

slight vacuum to overcome this buoyancy effect and ensure that air is flowing into the sulfur pit or

sulfur tank. Wind blowing across the roof of a sulfur tank also causes uplift on the leeward side that

can cause a reversal of air flow from the air intakes and vent the vapor space out through the air

intakes rather than out through the exhaust. The typical operating pressure of the vapor space of a

sulfur pit or sulfur tank is in the range of 0.01-1 ”WC vacuum. The number and size of the air inlets

must be carefully selected so that the air inlets will provide enough air flow to achieve the required

air sweep but also induce enough pressure drop so that the vapor space remains at or below the

required vacuum needed to offset the buoyancy effect and uplift caused by wind. If there is too much

air inlet area, the air intakes can draft backward and allow the air intakes to exhaust H2S to the

atmosphere. Therefore, the air inlet area is set on the basis of the required air rate for a proper sweep

of the vapor space but, at the same time, making sure that the vapor space stays at a vacuum level

greater than the buoyancy effect caused by the heated air intakes.


9

After the air intake area is set for normal operation (and in the absence of a relief valve,

which most sulfur pits and sulfur tanks do not have), then that is the only area available to vent

snuffing steam when steam is used to extinguish an internal fire. The current snuffing steam

extinguishing system requirements in NFPA 655 of 2.5 lb/min per 100 ft3 of volume become a very

high steam flow rate for most sulfur tanks and some sulfur pits so that this rate can easily

overpressure the sulfur tank and sulfur pit, causing the sulfur tank or sulfur pit to rupture. It is not

practical to design a sulfur tank air sweep system to provide the necessary vacuum to prevent flow

reversals in the air inlets during normal operation and provide the necessary air intake area to vent

the required snuffing steam rate during a fire scenario.

To illustrate the issues with overpressure of sulfur tanks, the authors evaluated six existing

sulfur tanks that were designed for air sweep of the vapor space to reduce the H2S concentration

and the resulting back pressure if steam is fed to snuff a fire according to NFPA 655’s rate of

2.5 lb/min per 100 ft3 (refer to Table 2).

As shown in Table 2, the NFPA 655 snuffing steam rate ranges from approximately 30 to

200 times the original sweep air rate. This snuffing steam rate results in a built-up back

pressure within the sulfur tank of 0.23-59.3 ”WC. This built-up back pressure would exceed the

design pressure of 4 out of 6 of the sulfur tanks, as shown by the red text in Table 2. Tanks C and

D have lower built-up back pressure, and they have a total volume less than 6,000 ft3. All the tanks

with a volume of approximately 50,000 ft3 and larger would have built-up back pressure far higher

than their design pressure. A general statement can likely be made that the vents on smaller tanks

may be able to vent the current NFPA 655 snuffing steam rate, but it is likely that the vents on

larger tanks cannot vent the current NFPA 655 snuffing steam rate without the built-up back

pressure exceeding the tank design pressure.


10

Table 2 Existing Sulfur Tanks with Steam at 2.5 lb/min per 100 ft3

TANK A TANK B TANK C TANK D TANK E TANK F

Dimensions 66-6" Dia x 35'-0" H 59-6" Dia x 48'-0" H 19'-8" Dia x 17'-9" H 14'-5" Dia x 16'-4" H 42'-8" Dia x 32'-10" H 47'-6" Dia x 24'-10" H

Volume, ft3 138,500 148,635 5,800 2,833 48,885 49,435

Design Pressure, "WC -3 / +10 -1.5 / +2.5 -3 / +10 -3 / +10 -1.1 / +3.2 -0.9 / +3.5

Air Inlets Six - 10" Two - 16" Three - 6" Three - 6" Six - 6" Six - 6"

Air Outlet One - 10" One - 16" One - 8" One - 8" One - 18" One - 8"

Air Movement Method Blower sucks air

through tank and

pushes through

caustic scrubber

Natural draft

2 inlets, 1 outlet

Natural draft

3 inlets, 1 outlet

Natural draft

3 inlets, 1 outlet

Natural draft

6 inlets, 1 outlet

Natural draft

6 inlets, 1 outlet

Normal Op Pressure, "WC -0.05 -0.0031 -0.00005 -0.00008 -0.029 Unknown

Air Sweep Objective <16% H2S LFL,

with 150 ppmwt

H2S in Sulfur feed

<21% H2S LFL,

with 150 ppmwt

H2S in sulfur feed

<50% H2S LFL,

with 150 ppmwt

H2S in sulfur feed

<50% H2S LFL,

with 150 ppmwt

H2S in sulfur feed

<25% H2S LFL,

with 300 ppmwt

H2S in sulfur feed

Unknown

Pressure "WC with steam at

2.5 lb/min/100 ft3

59.3 50.8 1.05 0.23 8.1 29

Steam volumetric rate

(@ 2.5 lb/min/100 ft3)

compared to sweep air rate

29 x 190 x 198 x 79 x 53 x Unknown


11

To illustrate the issues with overpressure of sulfur pits, the authors evaluated five

existing sulfur pits that were designed for air sweep of the vapor space to reduce the H2S

concentration and the resulting back pressure if steam is fed to snuff a fire according to NFPA 655’s

rate of 2.5 lb/min per 100 ft3 (refer to Table 3).

As shown in Table 3, the NFPA 655 snuffing steam rate ranges from approximately 10 to

31 times the original sweep air rate. This snuffing steam rate results in a built-up back pressure

within the sulfur pits of 17.6 ”WC – 1,585 ”WC (50 psig). This built-up back pressure would exceed

the pressure rating of the hatch covers on all five sulfur pits, as shown by the red text in Table 3. For

all five sulfur pits analyzed, the hatch covers would lift if steam was fed at the current NFPA 655 rate

of 2.5 lb/min per 100 ft3. No calculations were performed to determine the resulting built-up back

pressure that would remain in the sulfur pit after the hatch covers lifted, because that would require

extensive and difficult calculations. The one sulfur pit that would theoretically achieve 50 psig

pressure in the pit (if the hatch covers did not lift) is large, with a total capacity of 60,665 ft3. This

sulfur pit is associated with an SRU with a capacity of approximately 675 long tons per day (LTPD),

which is a big plant, but certainly there are other existing plants that are much larger. This

particular sulfur pit has a large reduction in inlet line size--8 inches down to 4 inches to feed into a

flow meter. The flow reaches sonic velocity in this 4 inch diameter section, resulting in very high

built-up back pressures. A general statement can likely be made that the vents on most sulfur pits

associated with an SRU cannot vent the current NFPA 655 snuffing steam rate without the built-up

back pressure exceeding the pressure that can be contained by the hatch covers. When these hatch

covers lift, steam containing H2S and sulfur dioxide (SO2) will vent to the atmosphere at ground

level and cause a serious safety concern.


12

Table 3 Existing Sulfur Pits with Steam at 2.5 lb/min per 100 ft3

PIT A PIT B PIT C PIT D PIT E

Dimensions 24'-0"W x 35'-0"L x 10'-6"D 47'-7"W x 72'-2"L x 17'-8"D 14'-0"W x 34'-0"L x 11'-0"D 13'-2"W x 49'-10"L x 9'-2"D 21'-0"W x 30'-0"L x 8'-0"D

Volume, ft3 8,820 60,665 5,236 6,015 5,040

Design Pressure, "WC -unknown / +9.5 set

by precast concrete

access hatch covers

-unknown / +0.54 set

by aluminum hatch

covers

-unknown / +9.6 set

by precast concrete

access hatch covers


by precast concrete

access hatch covers


by aluminum hatch

covers

Air Inlets One - 6" Two - 8" One - 4" One - 4" One - 6"

Air Outlet One - 6" Two - 8" One - 4" Two - 3" One - 6"

Air Movement Method Ejector sucks air through

air inlet and pushes to

thermal reactor

Ejector sucks air through

air inlets and pushes to

thermal reactor



thermal reactor



incinerator



incinerator

Normal Op Pressure, "WC -0.22 -6.9 -1.2 -0.30 -0.22


with 300 ppmwt

H2S in sulfur feed

<25% H2S LFL,

with 300 ppmwt

H2S in sulfur feed

<25% H2S LFL,

with 300 ppmwt

H2S in sulfur feed

Unknown Unknown


2.5 lb/min/100 ft3

57.8 50 psig if hatch covers

do not lift, sonic

velocity back through

air inlets

266 230 21.4/17.6(Note 1)


(@ 2.5 lb/min/100 ft3)


16 X 31 x 17 x 30 x 9.7 x

Notes:

1. The second value listed is the built-up back pressure for this sulfur pit based on the ejector staying in operation. All other

sulfur pits analyzed have a safety instrumented system (SIS) that will trip ejectors when fire is detected.


13

4.0 Attempted Oxygen Concentration Dilution Calculation When considering a new approach to determining an adequate steam rate to extinguish a

sulfur fire, the authors first considered a dilution calculation for oxidant concentration reduction or

combustible concentration reduction as described in NFPA 69, Standard on Explosion Protection

Systems. To be able to complete the dilution calculation, the limiting oxygen concentration (LOC) or

LFL of the vapor mixture must be known. Surprisingly, the LOC and LFL for molten sulfur could not

be found. Several searches were conducted: an internet search, a search of common reference

books, and a search of sulfur specific books. Several research organizations and numerous

engineering/operating/simulation companies that specialize in SRUs were contacted. The LOC and

LFL of molten sulfur are not readily available at any of these sources. Some material safety data

sheet (MSDS) were located that showed an LFL of molten sulfur, but further investigation showed

that the LFL listed was actually for H2S. Some MSDS actually added a footnote indicating the value

listed is for H2S, and others did not include the detail. At the normal temperature that molten sulfur

is typically stored, it could be argued that the sulfur vapor pressure is so low that the real danger

for fire is based on the concentration of H2S that has evolved from the sulfur and not the sulfur

itself. The LOC and LFL for H2S are available.

It has been shown experimentally that the LFL of a substance typically decreases with

increasing temperature. Zabetakis(3) developed some correlations for predicting the temperature

effect on the LFL for paraffin hydrocarbons. The LFL of a paraffin hydrocarbon approaches zero at

temperatures above approximately 2,192 F (1,200 C). The LOC of a substance also typically

decreases with increasing temperature. The LFL and LOC of a substance also vary with the specific

inert that is present. Without experimental data for H2S and molten sulfur with steam as the inert,

it can only be speculated on what happens to the LFL and LOC in gas mixtures near an existing fire.

However, it could reasonably be speculated that the LFL and LOC of H2S and molten sulfur will fall

to near zero, if the fire raises localized temperatures to where they approach 2,192 F (1,200 C).

Even at lower localized temperatures, the LFL and LOC concentration will be very low. Therefore,

once a fire has started, considering LFL and LOC as parameters to target for snuffing steam dilution

calculations is not productive.


14

5.0 Actual Operating Data for Molten Sulfur Fire Extinguishing Steam

The authors were unable to find any published data on testing completed on molten sulfur

fires or data collected from actual fires in industrial molten sulfur applications. Through various

molten sulfur production forums (technical conferences, sulfur production specialist user groups,

etc.) and personal contacts in the industry, the authors contacted a broad spectrum of sulfur

production specialists at the major refining and gas plant companies in North America that operate

SRUs to request data on any sulfur fires that have occurred in sulfur pits and sulfur tanks at the

owner’s facilities. The sulfur production specialists contacted should have had access to data from

approximately 75 locations in North American that operate SRUs. Some locations operate more

than one SRU and some locations have as many as 10 sulfur pits or sulfur tanks. On the

conservatively low side, the request should have been able to gather data from 100 to 200 sulfur

pits and sulfur tanks. The request was made with the promise that the sources of all data would

remain anonymous.

The request elicited some useful information about actual molten sulfur fires that have

occurred in sulfur pits and sulfur tanks. Many owner responses indicated they had been fortunate

enough to never have experienced a fire. Several owner responses indicated that they have had

fires, but they occurred more than 10 years ago and therefore cannot remember much about them.

Some owner responses indicated that they had experienced fires, but their corporate practice is

such that they could not get corporate legal approval to allow data released outside of the

organization. Some owner responses indicated that they had experienced sulfur fires, but they

were unable to find sufficient documentation to indicate how the fires had been extinguished, or

they knew that steam had been used, but they had no way to determine how much steam was used

and the duration of the steam flow. One owner indicated that fires had occurred in three separate

sulfur pits at one location and the fires were extinguished with a combination of steam and

nitrogen, but no rate information was available.

The authors analyzed the sulfur fire data that were made available by four owners. The rest

of this section describes the data that were collected and the analysis of that data.


15

5.1 DETECTION OF SULFUR PIT AND TANK FIRES As a side note, one outcome of the data collection was to discover how some owners

detected and responded to sulfur pit fires.

For newer unit designs, it is relatively common to have a Safety Instrumented System (SIS)

that receives inputs from instrumentation around the sulfur pit. If unsafe conditions are detected,

the SIS will isolate certain systems around the sulfur pit in an attempt to prevent damage to

equipment, environmental releases, and exposure of operators to toxic or dangerous environments.

It is not uncommon for the SIS to monitor the vapor space temperature of a sulfur pit, and if the

temperature increases above a high set point, the SIS will trip the ejector system and stop drawing

air through the sulfur pit. This trip system is in place to prevent air from being drawn through the

sulfur pit and intensifying the fire.

One owner responded that it specifically did not want its ejector system to shut down on high

sulfur pit vapor space temperature. That owner wanted the ejector system to stay online during a fire

so that the majority of the SO2 generated could be routed by the ejector to the SRU incinerator,

allowing the emissions to be tracked and recorded. If the ejector system was shut down, the owner

would need to estimate the emissions to be able to report them to the regulator agency. This

particular owner experienced a number of sulfur pit fires in two sulfur pits over a 5 year period

before the systems could be analyzed and modified to eliminate the sources of the fires. During this

5 year period, the owner’s operations staff determined that whenever they experienced a rapid

increase in the incinerator stack SO2 emissions (the concentration would increase from a normal

value of 75-90 parts per million by volume [ppmv], through the alarm point at 125 ppmv, to

1,000-1,200 ppmv), it was typically a sulfur pit fire. This causal relationship was so strong that

procedures were modified to train the operators to immediately start steam to the sulfur pit

whenever they saw the incinerator stack SO2 emissions climb rapidly. The operators would start

steam to the sulfur pit and allow the steam to flow for 15 minutes before shutting it off. After the

steam was shut off, the operators would monitor the incinerator stack SO2 emissions, and in most

cases, the emissions levels returned to normal. If the emissions limits did not return to normal, the

operators would then look at other causes, such as an upset in the tail gas treating unit (TGTU).

This owner stated that when a fire occurred in the sulfur pits, the results could be seen in the

incinerator stack first, then, about 30 seconds later, the sulfur pit vapor space temperature would

begin to rise. The sulfur pit vapor space temperature would only increase approximately 50-60 F

(28-33 C) during a fire. The operators considered the sulfur pit vapor space temperature increase

as confirmation of a fire but used the incinerator stack emissions increase as their indication to

immediately start steam to the sulfur pit.


16

Figure 1 is a plot of the distributed control system (DCS) data showing the incinerator stack

SO2 emissions and the sulfur pit vapor space temperature during a typical sulfur pit fire for this

owner. The data on Figure 1, show a 30 to 40 second difference in the time between when the

incinerator stack SO2 emissions start to increase and when the sulfur pit vapor space temperature

starts to increase. Figure 1 is a re-plot of the raw data and not the actual plot the operators would

see. When operators look at a plot trend generated by the DCS, it will have different scales

associated with each parameter. In fact, the incinerator stack SO2 emissions are reported by both a

low range analyzer 0-500 ppmv and a high range analyzer > 500 ppmv. Therefore, it makes sense

that the operators would notice the initial rapid increase in the incinerator stack SO2 emissions

more easily than the slower increase in the sulfur pit vapor temperature. Because of the quick

action by the operators, the incinerator stack SO2 emissions decreased below the alarm setting of

125 ppmv within 25 minutes of the initial alarm.

Figure 1 Incinerator Stack SO2 and Sulfur Pit Vapor Space Temperature during a Sulfur Fire


17

It should be considered that, for the example described above, the thermocouple that was in

the sulfur pit vapor space never indicated a significant temperature increase during fire events.

This is likely due to the location of the thermocouple compared to the location of the fire within the

vapor space. It could be concluded that, during the fires experienced in the sulfur pit examples

described above, the fires were somewhat localized and did not consume the entire vapor space.

For configurations that intend to leave the ejectors operating through a fire event, locating the

temperature indicator in the ejector suction line is likely better than locating it in the sulfur pit

vapor space. At least with the temperature indicator in the ejector suction line, the thermocouple

will see an “average” temperature of the gas passing through the sulfur pit vapor space rather than

seeing a point temperature at a single location within the vapor space.

Sulfur tanks typically do not include an SIS with high temperature input, and therefore, the

typical method for sulfur fire detection is a visual indication of a yellow plume being vented from

the tank. Some tanks do have a temperature indicator that operators can use to indicate that a fire

is occurring.

5.2 SULFUR PIT FIRES Owner No. 1 experienced a number of sulfur pit fires in two sulfur pits over a 5 year

period before the systems could be analyzed and modified to eliminate the sources of the fires.

This owner provided data on how sulfur pit fires are extinguished. The sulfur pits in question are

21'-0" W x 30'-0" L x 8'-0" D, and each has a single 2 inch steam line from the header that reduces to

1 ½ inches near the connection on the roof of each sulfur pit. The sulfur pits are typical concrete

pits that are completely enclosed, with one air inlet line and one air exit line that feeds an ejector

for each sulfur pit. The ejector sweeps air through the vapor space of the sulfur pit and discharges

to an incinerator. When a sulfur fire is suspected, the operators immediately open the 2 inch gate

valve in the steam line to start steam flow to the sulfur pit. The owner reported that the operators

will open the gate valve to a point where they see steam flowing out of the single 6 inch air intake

line on the sulfur pit, which indicates they have put in enough steam to overcome the capacity of the

sulfur pit ejector and sealed the enclosure/sulfur pit. The owner reported that the 2 inch gate valve

is approximately one-third open when the operators see steam exiting from the air intake line. The

steam is left flowing for a period of 15 minutes, then the flow is stopped, and the operators look at

the incinerator stack SO2 emissions to see if they have returned to normal. In almost all cases that

this owner experienced, after 15 minutes of steam flow, the fire had been extinguished. The owner

could only recall one incident when the fire returned after the steam was stopped. The owner

speculated that for this one case, a re-ignition event may have occurred, rather than lack of

suppression of the first fire.


18

Owner No. 1 provided the piping isometric for the steam line. Hydraulic calculations were

completed for the steam based on the steam header pressure, the one-third open gate valve, and

information from the piping isometric. The analysis showed that the steam flow achieves sonic velocity

in the 1 ½ inch section of pipe near the steam line exit into the sulfur pit. The flow of the steam was

calculated to be 2,644 lb/hr. The total volume of the sulfur pit is 5,040 ft3. Calculating the steam rate to

sulfur pit volume ratio shows that the steam rate this owner has been using is 0.87 lb/min per 100 ft3 of

total sulfur pit volume. The owner reported that multiple sulfur fires have been successfully

extinguished in the sulfur pits with this rate when the steam has flowed for 15 minutes. This rate is 2.87

times less than (or about 35 percent of) the current NFPA 655 specified value of 2.5 lb/min per 100 ft3

for snuffing steam methodology. The owner reported that no damage has been experienced in these

sulfur pits by the numerous fires because of the fact that the fire can be extinguished in 15 minutes.

It is difficult to accurately determine the resistance coefficient (K) for a partially opened

gate valve without having true flow test data from the manufacturer of the actual gate valve. The

authors determined that, with a completely open full port gate valve (K values are available), the

flow of steam would only increase to 2,900 lb/hr because the steam flow hits sonic velocity in the

1 ½ inch section near the sulfur pit roof. Therefore, the maximum flow of steam possible with the

existing piping configuration is 2,900 lb/hr. Calculating the steam rate to sulfur pit volume ratio

shows the maximum steam rate this owner could possibly feed, assuming a completely open gate

valve, would be 0.96 lb/min per 100 ft3 of total sulfur pit volume. This number is not substantially

different from the estimated rate with the gate valve only one-third open.

It should be considered that for the sulfur pit evaluated above, the operators specifically

adjust the steam flow until they see steam coming out of the air intake piping. The flow of steam

effectively seals the air intake and prevents air from entering the sulfur pit. The steam is also

diluting the air that is in the vapor space and pushing some of it out of the air intake piping. In

Section 6.0 computational fluid dynamics (CFD) is used to determine the oxygen concentration

during the 15 minute period when steam is fed.

As the fire consumes sulfur and oxygen from the air, SO2 is produced. This SO2 is heavy and

could possibly sit on the surface of the molten sulfur, helping to limit the fire access to oxygen in the

vapor space. Alberta Sulphur Research Ltd (ASRL) has completed some preliminary evaluations of

fires in rail cars. According to Clark [Clark, P.D. personal communication October 8, 2014], ASRL

completed experiments that simulated what happens if a rail car of solid sulfur ignited. What they

observed was that the sulfur started to burn only after it became liquid. In addition, they saw that

the flame temperature never reached the maximum value in air (ca. 1,200 F [650 C]) but stalled

around 840 F (450 C), after all of the solid had liquefied. They preliminarily concluded that the SO2

produced at the sulfur surface prevented mass transfer of air to the sulfur, limiting the rate of

combustion. These experiments were done in an open box without a lid. Clark also speculated that

since the surface of the liquid sulfur was adjacent to the hot vapor at 840 F (450 C), evaporation of

liquid sulfur to the gas phase may be impeded by a viscous sulfur layer at or near the surface. Thus,

the equilibrium vapor pressure at the bulk liquid sulfur temperature (ca. 356 F [180 C]) might not

be obtained during a fire in a pit due to the kinetic effects of evaporation.


19

Even if the SO2 is well dispersed within the vapor space, by effectively sealing all air

entrances to the sulfur pit with steam, the fire becomes self-limiting and is quickly extinguished.

Owner No. 2 experienced a sulfur pit fire in one sulfur pit recently. This owner provided the

authors with data on how the sulfur pit fire was extinguished. The sulfur pit in question is

19'-6" W x 57'-0" L x 10'-0" D and has a single 2 inch steam line from the header that branches into

three separate 2 inch lines, which each feed a 3 inch connection with a rupture disk on 3 inch

connections on the roof of each sulfur pit. The three connections on the sulfur pit roof are roughly

20 feet apart and feed the common vapor space above different sections within the sulfur pit. The

sulfur pit is a typical concrete pit that is completely enclosed with one air inlet line and one air exit

line that feeds two ejectors (one ejector can be used to feed the sulfur pit sweep air to the

incinerator, and the other can be used to feed the sulfur pit sweep air back to the front end of the

SRU at the thermal reactor). The owner reported that when an increase in temperature of the

sulfur pit vapor space was noticed (120 F [66.7 C] in just a few minutes), the steam 2 inch ball valve

was opened about one-quarter. The steam was left flowing for a period of approximately 2 minutes,

the sulfur pit vapor space temperature began to decrease, and the steam flow was stopped. The

operators then monitored the sulfur pit vapor space temperature and noticed that, approximately

30 minutes after stopping the steam flow, the temperature started to increase again. At that point,

the operator cracked open the 2 inch ball valve in the steam line and let the steam flow for an

additional minute until they saw the sulfur pit vapor space temperature start to decrease. The

steam valve was then closed, and the fire did not return.

Figure 2 is DCS data showing the temperature of the sulfur pit vapor space and the liquid

sulfur temperature during the fire in Owner No. 2’s sulfur pit. As can been seen, the sulfur pit vapor

temperature increased 120 F (66.7 C) approximately 8 minutes after a sulfur pump tripped due to

high viscosity (molten sulfur viscosity increases as temperature increases). Steam was started for

2 minutes and, when the operators saw the temperature begin to decrease, the steam was stopped.

The sulfur pit vapor space and liquid sulfur temperature continued to decrease to normal values

over an approximate 30 minute period. Then a second temperature spike occurred in the sulfur pit

vapor and liquid sulfur. A small amount of steam was added for about 1 minute, and the

temperatures again started to decrease toward normal values.


20

Figure 2 Sulfur Pit Fire DCS Temperature Data

When the steam flow was initially started, only one of the three rupture disks actually burst.

The rupture disk that was closest to the steam supply valve was the disk that burst. The other two

rupture disks remained intact through both steam events. Although not perhaps apparent during

the original design, but obvious in hindsight, having multiple rupture disks on a single steam supply

line will likely result in only one disk bursting. The rupture disks are located directly on the sulfur

pit nozzles to prevent sulfur pit vapors from backing into the steam line, condensing, and then

solidifying and plugging the line during normal operation. The rupture disks are located at

practically the lowest pressure in the piping system. Therefore, with slight differences in the actual

bursting pressure of the rupture disks and slightly different pressures in each section of piping

feeding the rupture disks, it is logical that only one of the rupture disks would burst, and all the flow

would enter the sulfur pit at that location.


21

Owner No. 2 provided the piping isometric for the steam line. Hydraulic calculations were

completed for the steam based on the steam header pressure, the one-quarter open ball valve, and

information from the piping isometric. The flow of the steam was calculated to be 891 lb/hr. The

analysis shows that the steam flow only achieves about 10 percent of sonic velocity in the upsized

3 inch section of pipe near the steam line exit into the sulfur pit. The total volume of the sulfur pit is

11,115 ft3. Calculating the steam rate to sulfur pit volume ratio shows the steam rate this owner

used was 0.13 lb/min per 100 ft3 of total sulfur pit volume. This rate likely was successful in

extinguishing the initial sulfur fire in the sulfur pit when this rate was used for only about 2 minutes.

The owner did experience a second fire 30 minutes later, but it was likely a re-ignition event. The

authors did not calculate a steam rate for the second event because the operators said they only

cracked the valve open slightly for 1 minute. Therefore, the steam rate fed the second time was

less than the first rate shown above. The steam rate above is 19 times less than (or about

5 percent of) the current NFPA 655 specified value of 2.5 lb/min per 100 ft3.

The rate discussed above of 0.13 lb/min per 100 ft3 is practically the same value as listed in

Table 1 of Section 2.8 regarding a statement made in substantiation of changes to the 2001 edition of

NFPA 655, namely, that, if steam is injected at the surface of the sulfur, 4 ft3/min per 100 ft3 of

enclosure volume would be satisfactory (4 ft3/min per 100 ft3 is equal to 0.14 lb/min per 100 ft3).

It is difficult to accurately determine the resistance coefficient (K) for a partially opened ball

valve without having true flow test data from the manufacturer of the actual ball valve. The authors

determined that with a completely open full port ball valve (K values are available), the flow of

steam would only increase to 2,779 lb/hr. The velocity at this rate was still only 29 percent of sonic

velocity in the 3 inch section near the sulfur pit roof. The maximum flow of steam possible with the

existing piping configuration is 2,779 lb/hr. Calculating the steam rate to sulfur pit volume ratio

shows the maximum steam rate this owner could possibly feed, assuming a completely open ball

valve, would be 0.41 lb/min per 100 ft3 of total sulfur pit volume. This number is more than 3 times

the estimated rate with the ball valve only one-quarter open. However, this steam rate is still 6 times

less than (or about 16 percent of) the current NFPA 655 specified value of 2.5 lb/min per 100 ft3.


22

Owner No. 3 experienced a sulfur pit fire in one sulfur pit in December 2013. That fire was

the first known sulfur pit fire in the 21 years of operation of that unit. This owner provided data on

how the sulfur pit fire was extinguished. The sulfur pit in question is 12'-0" W x 36'-6" L x 8'-0" D

and has a single 2 inch steam line from the header that branches into three separate 2 inch lines,

each of which feeds a 3 inch connection on the roof of the sulfur pit. The three connections on the

sulfur pit roof feed the vapor space in the sulfur pit. The sulfur pit is a typical concrete pit that is

completely enclosed, with one air inlet line and one air exit line that feeds an ejector. The steam

driven ejector sweeps air through the vapor space of the sulfur pit and discharges to an incinerator.

The owner stated that their written procedure for a sulfur pit fire is to open the 2 inch valve in the

steam line 100 percent and keep the steam on for at least 15 minutes. The owner reported that,

when troubleshooting high incinerator stack SO2 emissions, they reduced the motive steam flow to

the ejector, and almost immediately (less than 5 minutes) the incinerator stack SO2 emissions

returned to normal. By temporarily reducing the motive steam flow to the ejector, the ejector

pulled less air through the sulfur pit, and the fire extinguished itself. No steam flow was required

for this particular sulfur fire.

5.3 SULFUR TANK FIRES Owner No. 4 experienced a few sulfur tank fires. This owner provided data on how the sulfur

pit fires were extinguished. The sulfur tank in question is 20'-0" Dia x 32'-0" H and has a 4 inch steam

line from the header that feeds four 2 inch connections on the roof of the sulfur tank. The sulfur tanks

are typical carbon steel tanks with a fixed roof and with multiple air inlet lines around the periphery

of the roof and one center air exit line that vents to the atmosphere. The owner reported that, when

they noticed a fire in the sulfur tank, they opened the steam 4 inch ball valve about one-quarter. The

steam was left flowing for a period of 30 minutes and then the flow was stopped. The owner stated

that they noticed the temperature in the tank decreased after 5 to 10 minutes, but they kept the steam

on for 30 minutes to be sure the fire was completely extinguished.

The authors completed hydraulic calculations for the steam based on the steam header

pressure, the one-quarter open valve, and information regarding the piping routing. The flow of the

steam was calculated to be 10,840 lb/hr. The analysis showed that the steam flow achieves only

about 60 percent of sonic velocity in the downsized 2 inch sections of pipe at the nozzles on the

sulfur tank. The total volume of the sulfur tank is 123,150 ft3. Calculating the steam rate to sulfur

pit volume ratio showed the steam rate this owner has been using is 0.15 lb/min per 100 ft3 of total

sulfur pit volume. The owner reported successfully extinguishing the sulfur fire in the sulfur tank

with this rate when the steam flowed for 30 minutes (fire was likely out in 5 to 10 minutes). This

rate is 17 times less than (or about 6 percent of) the current NFPA 655 specified value of

2.5 lb/min per 100 ft3. The owner reported that no damage was experienced in the sulfur tank by

this fire, because it was likely extinguished in 5 to 10 minutes.


23

It is difficult to accurately determine the resistance coefficient (K) for a partially opened

valve without having true flow test data from the manufacturer of the actual valve. The authors

determined that with a completely open full port valve (K values are available), the flow of steam

would only increase to 14,836 lb/hr. The velocity at this rate was still only 80 percent of sonic

velocity in the 2 inch section of pipe at the nozzles on the sulfur tank roof. The maximum flow of

steam possible with the existing piping configuration is 14,836 lb/hr. Calculating the steam rate to

sulfur pit volume ratio shows the maximum steam rate this owner could possibly feed, assuming a

completely open valve, would be 0.20 lb/min per 100 ft3 of total sulfur pit volume. This number is

not substantially different from the estimated rate with the valve only one-quarter open.

Owner No. 4 reported that fires had occurred in sulfur tanks at another location, but it had

been 10 years or more since the last one. For this site, when a fire occurred steam valve(s) would

be opened for a period of 20 to 30 minutes.


24

6.0 Computational Fluid Dynamics Modeling of a Sulfur Pit A CFD model of the first sulfur pit described in Section 5.2 was created. The CFD model was

set up to determine concentrations of oxygen and steam as well as the velocities throughout the

model. The model did not include the effects of actual combustion of oxygen with sulfur.

Therefore, all changes in oxygen concentration are a direct result of dilution of the oxygen with

steam and exhausting the oxygen-containing air from the sulfur pit through the ejector suction line

and backward through the air intake line. All reported oxygen concentrations are, therefore,

conservative, and the actual values would be lower because of the consumption of oxygen by

combustion of sulfur. Two flow conditions were considered with the model: a current

configuration model and a model that considered a relocation of the steam inlet. It should be noted

that the disturbance of the sulfur’s surface by possible high-speed jets, which would result in more

sulfur available for a pit fire, was not considered in these analyses.

As has been shown in a previous publication by one of this paper’s authors(4), the following

steps are involved in all CFD analyses:

Selection and construction of computational domains.

Development of computational grid.

Selection of domain physics.

Application of boundary conditions.

Solution.

The following subsections detail how each of these steps was implemented for the CFD

analyses, the results and general discussion from the analyses.

6.1 SELECTION AND CONSTRUCTION OF COMPUTATIONAL DOMAINS The model was based on the overall internal dimensions of the sulfur pit, along with the

dimensions of the air inlet and ejector suction lines. The overall domain for both models included

the pit vapor space at a 45 percent fill level. Figure 3 shows the three geometric domains created

for the analyses, the main pit space (steel blue light, 40 percent transparent) and the two

abandoned sparger boxes (turquoise green).

6.2 DEVELOPMENT OF COMPUTATIONAL GRID The computational grid was constructed using Star-CCM+’s automatic polyhedral mesher

with wall prism layers enabled. The final computational grid contained 1,001,116 cells and is

shown on Figure 4.


25

Figure 3 Domains Used for CFD Analyses

Figure 4 Computational Grid Developed for CFD Analyses


26

6.3 SELECTION OF DOMAIN PHYSICS The following physics models were enabled for the analyses:

Space – 3-dimensional.

Time – Implicit unsteady.

Material – Multispecies, gas (H2S, H2O, O2 and N2).

Equation of state – Ideal gas.

Turbulence - RANS, Realizable k-, All y+ Wall Law.

Segregated fluid temperature.

Gravity (-9.81 m/s in y-direction).

6.4 SELECTION OF BOUNDARY CONDITIONS Figure 5 shows the boundary conditions applied for the current configuration analysis. The

steam inlet is denoted by the dot in the red circle and the air inlet is denoted by the top of the pipe

in the blue circle. The ejector outlet is shown in yellow. The steam inlet was defined as a mass flow

inlet, with an inlet flow rate of 2,456 lb/hr. The steam inlet was sized to have an inlet velocity of

0.7 Mach, as sonic flow would require considerably more computational resources to solve. The air

inlet was defined as a stagnation inlet at atmospheric pressure. The ejector was defined as a

velocity outlet with a flow rate based on the design data sheet value of 350 actual cubic feet per

minute (acfm).

Figure 5 Boundary Conditions Applied for Current Configuration Analysis


27

Figure 6 shows the boundary conditions applied to the steam inlet moved model. The air

inlet is circled in blue, the steam inlet is circled in red and the ejector outlet is circled in yellow.

Since this model was originally run with a pressure boundary at the ejector outlet, there is a

contraction to prevent backflow. The same values listed above were applied to this model.

Figure 6 Boundary Conditions Applied to Steam Inlet Moved Model

Figure 7 shows the common boundary conditions applied to the models. The unheated

sparger walls are shown in magenta. The heated sulfur level is shown in yellow, and the sulfur

rundowns are shown in white. Both the sulfur level and rundowns were set to a defined

temperature of 315.5 F (157.5 C).


28

Figure 7 Common Boundary Conditions Applied to Models

6.5 SOLUTION The transient solutions were conducted on a high-performance computing cluster (HPCC)

using 120 processors. An adaptive time-step was used so that the maximum convective Courant

number was below 1 for each time-step.

6.6 RESULTS The following subsections detail the results for the two configurations that were analyzed.

6.6.1 Current Configuration Results

The maximum and the average oxygen concentration in the sulfur pit vapor space versus

time, for the current configuration case, are plotted on Figure 8. As can be seen on the figure, at the

end of the 15 minute steam period, the maximum oxygen concentration in the sulfur pit vapor

space is about 0.24 mole%. However, the average oxygen concentration is only about 0.015 mole%.

The average oxygen concentration is 16 times lower than the maximum value, indicating that there

are very few locations within the vapor space of the sulfur pit with oxygen concentrations near the

maximum. The very low average oxygen concentration supports the field data that the sulfur pit

fire is extinguished before the steam is stopped after 15 minutes. The actual oxygen concentration

in the sulfur pit vapor space will be even lower than indicated on the figure because the CFD model

does not account for the oxygen consumed by the sulfur fire.


29

Figure 8 Oxygen Concentrations in Sulfur Pit Vapor Space

Data were also extracted from the CFD model to show the maximum oxygen concentration in

the sulfur pit air inlet line and in the suction line to the ejector. These data, along with the maximum

oxygen and the average oxygen concentration in the sulfur pit vapor space, are plotted on Figure 9.

The figure shows that the maximum oxygen concentration in the ejector suction line immediately

starts to decrease after the steam is started. This is as expected since the steam is fed into the sulfur

pit near the nozzle on the sulfur pit that feeds the ejector suction. The figure shows that the

maximum oxygen concentration in the air inlet line remains at the ambient value of 21 mole% for

about 15 seconds as the steam passes through the vapor space of the sulfur pit to reach the air inlet

on the far side of the sulfur pit. After about 15 seconds, the maximum oxygen concentration in the

air inlet line begins to decrease (as steam begins flowing backward through the air inlet line) and

basically matches the maximum oxygen concentration in the ejector suction line after 90 seconds.

The maximum oxygen concentration in the ejector suction and the maximum oxygen concentration

in the air inlet line practically lie on top of the line for the average oxygen concentration in the

sulfur pit vapor space, making it difficult to distinguish the three lines in the figure. Although not

shown on the figure, the average oxygen concentration and the maximum oxygen concentration in

the ejector suction line do not differ by more than 1 percent after about 25 seconds of elapsed

purge time. The fact that the maximum oxygen concentration in the ejector suction line, air inlet

line, and the vapor space are basically the same value indicates that the sulfur pit vapor space is

fairly well mixed and venting the same concentration from both ends of the sulfur pit.


30

Figure 9 Oxygen Concentrations in Sulfur Pit Vapor Space, Air Inlet, and Ejector Suction

6.6.2 Relocated Configuration Results

The maximum and the average oxygen concentration in the sulfur pit vapor space versus

time for the current steam location, with the steam relocated near the air inlet line, are plotted on

Figure 10. As can be seen on the figure, relocating the steam inlet near the air inlet line significantly

lowers the average and maximum oxygen concentration in the sulfur pit vapor space compared to

those same parameters with the steam at its existing location. The model was stopped after about

12 minutes (720 seconds) because the oxygen concentrations were so low. At the end of 12 minutes,

the maximum oxygen concentration in the sulfur pit vapor space was less than 0.0005 mole%, and

the average oxygen concentration in the sulfur pit vapor space was less than 0.00003 mole%.

Again, the actual oxygen concentration in the sulfur pit vapor space will be even lower than

indicated on the figure because the CFD model does not account for the oxygen consumed by the

sulfur fire. It is obvious from the data that introducing the steam near the air inlet line will seal the

air inlet line quicker and thereby drive the oxygen concentration in the vapor space to low levels

much faster than locating the steam on the far side of the sulfur pit near the ejector suction line.

The data indicate that by relocating the steam feed to near the air inlet line, after about 5 minutes

the maximum and average oxygen concentrations in the sulfur pit vapor space can be decreased to

values similar to the values achieved in 15 minutes with the existing steam location.


31

Figure 10 Oxygen Concentration in Sulfur Pit Vapor Space with Steam Relocated Near Air Inlet

6.6.3 Velocity Streamline Comparisons

Figure 11 shows the velocity streamlines for the current configuration analysis. As can be

seen, the high-speed jet impinges on the liquid sulfur surface and then travels around the

perimeter. In this flow condition, little purging is occurring in the center of the pit, which results in

the longer purge times shown on Figure 8 through Figure 10.

Figure 12 shows the velocity streamlines for the steam inlet relocated configuration. As can

be seen in this case, a large portion of the steam enters the pit and is immediately exhausted

through the air inlet. This will result in rapidly stopping all O2 flow into the pit.


32

Figure 11 Velocity Streamlines for Current Configuration Analysis

Figure 12 Velocity Streamlines for Moved Steam Inlet Case


33

6.7 GENERAL DISCUSSION Additional CFD studies are needed to verify the impacts of locating the steam connection

near the air inlet lines for other sulfur pit configurations. However, it is logical to conclude that by

locating the steam near the air inlets, the steam will quickly seal the air inlets and thereby stop

ingress of oxygen that would maintain the sulfur fire. It is also logical to assume that locating the

steam near the air inlets rather than near the ejector suction allows more time for the ejector to

remove the existing sulfur pit vapor space gas mixture (air, sulfur vapor, H2S, SO2) before the

mixture begins to be diluted with steam. Therefore, the oxygen is removed from the sulfur pit

vapor space more quickly.

Additional CFD studies are also needed to confirm how the oxygen concentration is reduced

for designs where the sulfur pit ejector is tripped off on the basis of the sulfur pit vapor space

temperature.

Porter McGuffie Inc. estimates that it would take approximately 3 man-days to set up a new

sulfur pit model and execute one set of conditions. Each additional set of conditions would require

about 1.5 man-days to execute.


34

7.0 Potential Rapid Sealing Steam Rate On the basis of the data collected and the analysis completed in Sections 5.0 and 6.0, it

appears that a steam rate of 1.0 lb/min per 100 ft3 would be sufficient to extinguish sulfur fires in

enclosed sulfur tank and sulfur pits. This value is still higher (more conservative) than the rates

collected from any of the owners that provided data. It is possible that an even lower steam rate

could be used successfully, but not enough data could be collected to justify a lower rate.

It is apparent that industry has successfully extinguished fires in sulfur tanks and sulfur pits

without using the NFPA 655 snuffing steam rate recommendation but by using a lower steam rate

that effectively seals the enclosures, prevents air ingress, and extinguishes fires safely.

The authors completed evaluations of the sulfur tank vent systems for six existing sulfur tanks

when steam was fed at a rate of 1.0 lb/min per 100 ft3 of volume. The sulfur tanks evaluated were the

same sulfur tanks that were evaluated in Section 3.0. Table 4 shows the same data presented in Table

2 in Section 3.0, except that two additional rows (shown in yellow) have been added to the bottom to

show the built-up back pressure with steam flowing at a rate of 1.0 lb/min per 100 ft3 and how the

volume of steam compares to the original air sweep rate.

As can be seen in Table 4, the steam rate of 1.0 lb/min per 100 ft3 ranges from about

12-80 times the original sweep air rate. This steam rate results in a built-up back pressure within

the sulfur tank of 0.04-9.1 ”WC. This built-up back pressure would exceed the actual design

pressure of two out of six of the sulfur tanks, as shown by the red text in Table 4. However, if the

sulfur tanks had been specified with a consistent design pressure of -3 / +10 ”WC, then the steam

rate of 1.0 lb/min per 100 ft3 could be vented from the sulfur tanks without exceeding the design

pressure and without needing to modify the venting systems on the sulfur tanks.


35

Table 4 Existing Sulfur Tanks with Steam at 1.0 lb/min per 100 ft3 Compared to 2.5 lb/min per 100 ft3

TANK A TANK B TANK C TANK D TANK E TANK F

Dimensions 66-6" Dia x 35'-0" H 59-6" Dia x 48'-0" H 19'-8" Dia x 17'-9" H 14'-5" Dia x 16'-4" H 42'-8" Dia x 32'-10" H 47'-6" Dia x 24'-10" H

Volume, ft3 138,500 148,635 5,800 2,833 48,885 49,435

Design Pressure, "WC -3 / +10 -1.5 / +2.5 -3 / +10 -3 / +10 -1.1 / +3.2 -0.9 / +3.5

Air Inlets Six - 10" Two - 16" Three - 6" Three - 6" Six - 6" Six - 6"

Air Outlet One - 10" One - 16" One - 8" One - 8" One - 18" One - 8"

Air Movement Method Blower sucks air

through tank and

pushes through

caustic scrubber

Natural draft

2 inlets, 1 outlet

Natural draft

3 inlets, 1 outlet

Natural draft

3 inlets, 1 outlet

Natural draft

6 inlets, 1 outlet

Natural draft

6 inlets, 1 outlet

Normal Op Pressure, "WC -0.05 -0.0031 -0.00005 -0.00008 -0.029 Unknown


with 150 ppmwt

H2S in sulfur feed

<21% H2S LFL,

with 150 ppmwt

H2S in sulfur feed

<50% H2S LFL,

with 150 ppmwt

H2S in sulfur feed

<50% H2S LFL,

with 150 ppmwt

H2S in sulfur feed

<25% H2S LFL,

with 300 ppmwt

H2S in sulfur feed

Unknown


2.5 lb/min/100 ft3

59.3 50.8 1.05 0.23 8.1 29


(@ 2.5 lb/min/100 ft3)


29 x 190 x 198 x 79 x 53 x Unknown


1.0 lb/min/100 ft3

9.1 7.9 0.17 0.04 1.3 5.0


(@ 1.0 lb/min/100 ft3)


11.7 x 76 x 79 x 32 x 21 x Unknown


36

The authors evaluated the sulfur pit vent systems for five existing sulfur pits when steam

was fed at a rate of 1.0 lb/min per 100 ft3 of volume. The sulfur pits evaluated were the same sulfur

pits that were evaluated in Section 3.0. Table 5 shows the same data presented in Table 3 in Section

3.0, except that two additional rows (shown in yellow) have been added to the bottom to show the

built-up back pressure with steam flowing at a rate of 1.0 lb/min per 100 ft3 and how the volume of

steam compares to the original air sweep rate.

As can be seen in Table 5, the steam rate of 1.0 lb/min per 100 ft3 ranges from approximately

4-12 times the original sweep air rate. This steam rate results in a built-up back pressure within

the sulfur pit of 2.1-49 ”WC. The largest sulfur pit (total capacity of 60,665 ft3) could reach a

pressure of 366 ”WC (13.2 psig), if the covers did not lift. This particular sulfur pit has a large

reduction in inlet line size, 8 inches down to 4 inches to feed into a flow meter. The flow reaches

sonic velocity in this 4 inch diameter section, resulting in very high built-up back pressures. The

built-up back pressure would exceed the pressure rating of the hatch covers on four out of five

sulfur pits, as shown by the red text in Table 5. However, if the sulfur pits had been specified with

precast concrete hatch covers instead of aluminum and a slight adjustment made in the air inlet line

size, the steam rate of 1.0 lb/min per 100 ft3 could likely be vented from the sulfur pits without

exceeding the design pressure. It appears that to be able to vent a steam rate of 1.0 lb/min per 100 ft3,

the typical sulfur pit design pressure and sulfur pit vent system would require more modifications than

those that would be required for typical sulfur tanks. However, it does appear possible to design a

sulfur pit system to accommodate the lower steam rate of 1.0 lb/min per 100 ft3. Additional

engineering studies, including the use of CFD, may be appropriate to establish an even lower sealing

steam rate for an existing sulfur pit.


37

Table 5 Existing Sulfur Pits with Steam at 1.0 lb/min per 100 ft3 Compared to 2.5 lb/min per 100 ft3

PIT A PIT B PIT C PIT D PIT E

Dimensions 24'-0"W x 35'-0"L x 10'-6"D 47'-7"W x 72'-2"L x 17'-8"D 14'-0"W x 34'-0"L x 11'-0"D 13'-2"W x 49'-10"L x 9'-2"D 21'-0"W x 30'-0"L x 8'-0"D

Volume, ft3 8,820 60,665 5,236 6,015 5,040

Design Pressure, "WC -unknown / +9.5 set by

precast concrete access

hatch covers

-unknown / +0.54 set by

aluminum hatch covers



hatch covers



hatch covers


aluminum hatch covers

Air Inlets One - 6" Two - 8" One - 4" One - 4" One - 6"

Air Outlet One - 6" Two - 8" One - 4" Two - 3" One - 6"

Air Movement Method Ejector sucks air through


thermal reactor


air inlets and pushes to

thermal reactor



thermal reactor



incinerator



incinerator

Normal Op Pressure, "WC -0.22 -6.9 -1.2 -0.30 -0.22


with 300 ppmwt

H2S in sulfur feed

<25% H2S LFL,

with 300 ppmwt

H2S in sulfur feed

<25% H2S LFL,

with 300 ppmwt

H2S in sulfur feed

Unknown Unknown


2.5 lb/min/100 ft3

57.8 50 psig, if hatch covers

do not lift, sonic velocity

back through air inlets

266 230 21.4/17.6(Note 1)


(@ 2.5 lb/min/100 ft3)


16 X 31 x 17 x 30 x 9.7 x


1.0 lb/min/100 ft3

8.9 13.2 psig if hatch covers

do not lift, sonic velocity

back through air inlets

49 39 3.5/2.1(Note 1)


(@ 1.0 lb/min/100 ft3)


6.4 x 12 x 6.9 x 12 x 3.9 x

Notes:

1. The second value listed is the built-up back pressure for this sulfur pit based on the ejector staying in operation. All other

sulfur pits analyzed have an SIS that will trip ejectors when fire is detected.


38

8.0 Good Engineering Practice for Use of Sealing Steam On the basis of the data collected for this paper and the analysis completed, the following

points (not listed in any particular order) could be considered good engineering practice for sulfur

tanks and sulfur pits to address extinguishing fires:

Sulfur tanks should be designed with design pressure of at least -3 / +10 ”WC.

Sulfur pits need to be carefully evaluated and designed to allow the chosen sealing

steam rate to vent from the air inlets without lifting the hatch covers.

The valve that is used to supply sealing steam to the sulfur tank or sulfur pit should

be located at a safe location (typically at least 50 feet away) away from the sulfur

tank or sulfur pit. The valve should be located near grade elevations, easily

accessible, and clearly marked.

Sealing steam lines should contain a drip leg and steam trap ahead of the valve used

by operators so that the line will remain warm and not collect condensate ahead of

the valve. Feeding built-up condensate through the sealing steam line to the sulfur

tank or sulfur pit when the steam valve is opened will result in a very large increase

in pressure in the enclosure and possibly result in overpressuring the enclosure.

Sealing steam should be fed near the air inlet lines to sulfur tanks or sulfur pits so

that steam will quickly backflow out of the air intakes and prevent further oxygen

ingress during a fire.

Preliminary CFD results show that slowing the steam down (oversized inlet nozzle)

prior to the entrance to the sulfur tank and sulfur pit may help limit agitation of the

liquid sulfur surface and, thereby, reduce the amount of fuel that is available to burn

in the vapor space. Additional CFD work is still needed to clarify the effect of the

steam entrance velocity.

Sealing steam systems that use rupture disks to prevent sulfur vapor from backing

into the line, condensing, and solidifying should have a separate steam supply valve

for each rupture disk instead of multiple rupture disks fed from one steam supply

valve. An alternative to having separate steam supply piping/valve for each rupture

disk would be to oversize the supply pipe so that the vast majority of the pressure

drop is across the section that contains the rupture disks. A careful hydraulic study

would need to be performed to ensure that even if one rupture disk burst, there

would still be enough pressure in the steam supply line to burst all remaining

rupture disks.

If rupture disks are not used to help prevent plugging in the steam supply system

near the connections to the sulfur tank or sulfur pit, the open sealing steam line

should be tested on a routine basis (at least monthly) by passing steam through the

system to ensure the steam supply lines and nozzle are free of solidified sulfur.


39

The location of the thermocouple that is used to detect a fire in a sulfur pit needs to

be evaluated carefully. For configurations that intend to leave the ejectors operating

through a fire event, locating the temperature indicator in the ejector suction line is

likely better than locating it in the sulfur pit vapor space. At least with the

temperature indicator in the ejector suction line, the thermocouple will sense an

“average” temperature of the gas passing through the sulfur pit vapor space rather

than a point temperature at a single location within the vapor space. For systems

that will trip the ejectors during a fire event, it is suggested that more than one

thermocouple be used as input to the SIS. One thermocouple should be close to the

ejector suction line to sense the temperature of the vapor mixture as it exits the

sulfur pit, and other thermocouples should be located in suspected low velocity

areas where temperature increases may be noticeable. A CFD model could be used

to help place the thermocouples in optimum locations.

A CFD model can be used to evaluate flow patterns in the sulfur tank or sulfur pit

vapor space both during normal operation and during sealing steam injection. The

results of the CFD model can help the designer to determine proper placement of air

inlet nozzles, vent nozzles, thermocouples, and sealing steam injection locations.


40

9.0 Conclusions The following conclusions can be drawn from the results of this paper and the authors’

experiences while preparing this paper:

1. The vent systems on typical sulfur pits and sulfur tanks (for storage of molten sulfur) must

be carefully designed to ensure that the proper environment is maintained within the vapor

space to prevent flammable mixtures from forming.

2. For sulfur pits and sulfur tanks that use an air sweep system to prevent flammable mixtures

from forming, the enclosures are typically operated under a slight vacuum to prevent stray

emissions of H2S and sulfur vapor. This vacuum level is set according to the required air

sweep rate and air inlet line sizes. The vacuum level needs to be set so that the buoyancy

effects of the heated air intake lines are accounted for, and for sulfur tanks, the vacuum level

should consider the effects of wind blowing across the outer surface of the tank.

3. It is extremely difficult and impractical to design the air sweep systems for sulfur tanks and

sulfur pits without exceeding the design pressure of the enclosure if they also must be able

to vent the current NFPA 655 snuffing steam requirement of 2.5 lb/min per 100 ft3 of total

volume.

4. It appears that a sealing steam rate of less than 1.0 lb/min per 100 ft3 of total volume has

been successful in extinguishing numerous fires in sulfur tanks and sulfur pits.

5. New sulfur tanks and sulfur pits can be designed to vent a sealing steam rate of 1.0 lb/min

per 100 ft3 of total volume without major changes to the typical design parameters already

being following by a number of companies. Typical sulfur pits may need more changes than

typical sulfur tanks; however, the changes required are not onerous.

6. Sealing steam should be fed into the sulfur tank or sulfur pit for a minimum of 15 minutes

or until the temperature has returned to near normal. If the sulfur does not cool down

before the sealing steam is stopped and the air sweep system reestablished, re-ignition can

occur.

7. The sealing steam will almost immediately seal the air intake(s) to prevent further oxygen

ingress and will begin to purge oxygen out of the enclosure. The actual operating vapor

space volume in the sulfur tank or sulfur pit will only affect the time it will take for the fire

to be fully extinguished.


41

10.0 Recommendations The following recommendations can be drawn from the results of this paper and from the

authors’ experiences while preparing this paper:

1. The authors recommend that NFPA modify the sealing method in NFPA 655, Standard for

Prevention of Sulfur Fires and Explosions (current edition: 2012), Chapter 5, Handling of

Liquid Sulfur at Normal Handling Temperatures, Section 5.5, Fire Fighting, to recommend a

sealing steam rate of 1.0 lb/min of steam per 100 ft3 of volume.

2. The authors also recommend that the good engineering practice points defined in Section

8.0 be considered and implemented on sulfur tanks and sulfur pits as applicable.


42

11.0 Acknowledgements The authors wish to thank the efforts of all the sulfur production specialists that were

contacted for data for this paper. The authors also thank Lon Stern (Stern Treating & Sulfur

Recovery Consulting, Inc. - [email protected]) for posting their request for data on the Amine

Best Practices Group Data Exchange Network.

12.0 References (1) NFPA 655, Standard for Prevention of Sulfur Fires and Explosions, National Fire Protection

Association, 2012 Edition.

(2) NFPA 69, Standard on Explosion Prevention Systems, National Fire Protection Association,

2014 Edition.

(3) Zabetakis, M.G., Flammability Characteristics of Combustible Gases and Vapors, Bureau of

Mines Bulletin 627, U.S. Department of the Interior, TN23.U4 no. 627, 622.06173, 1965.

(4) McGuffie, S.M., Porter, M.A., Hirst, T.H., Use of CFD in Design, Presented at the 2012 American

Society of Mechanical Engineers Pressure Vessels & Piping Conference, Toronto, Canada.

technical committee on handling and conveying of … · cv technology, inc. 15852 mercantile court...

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