isp dust overview 2010

8/10/2019 ISP Dust Overview 2010

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Dust Hazards Overview2010


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Imperial SugarPort Wentworth, Georgia

2/27/2008


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CTA AcousticsCorbin, Kentucky

2/20/2003


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West PharmaceuticalsKinston, NC

1/29/2003


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What is Required?

Ignition Source Fuel (Combustible Dusts)

Confinement

Oxygen

Dispersion

(Suspension)


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Combustible DustA combustible particulate solid that presents a fire or

deflagration hazard when suspended in air or some other oxidizing medium over a

range of concentrations, regardless of particles size or shape.

DeflagrationPropagation of a combustion zone at a velocity that is less than the

speed of sound in the unreacted medium.

DetonationFlame spread above the speed of sound

ExplosionRapid release of high pressure into an environment

Hybrid MixtureA mixture of flammable gas (or evaporated liquid) with a

combustible dust

Common Terms & Definitions


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MECMinimum Explosible ConcentrationThe Minimum concentration of acombustible dust suspended in air, measured in mass per unit volume, that willsupport deflagration.

MIEMinimum Ignition EnergyThe minimum amount of energy released as apoint in a combustible mixture that causes flame propagation away from the point,under specified test conditions (ASTME 2019)

PmaxThe maximum pressure developed in a contained deflagration of anoptimum mixture.

KstThe deflagration index of a dust cloud. Kst= (dp/dt)max(V 0.333) bar-m/sec(per ASTME 1226 testing). Higher Kstvalues indicate a higher rate of combustion.

LOCLimiting Oxidant ConcentrationThe concentration of oxidant below whichdeflagration cannot occur. Typically the oxidant is oxygen.

Common Terms & Definitions


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Friction

Spark

Chemical Action

Hot Work

Burner Flame

Electricity

Static Electricity

Overheating

Hot Surfaces Hot Embers

Potential Ignition Sources


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Minimum Ignition Energy (MIE)


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Product MIEMilli-Joules

Sugar 400-700 mJ

Acrylidone LM 1.7 mJ

Polylclar 10 4 mJ

PVP K-90 14 mJ

PVP K-30 25 mJ

Gantrez AN-169 1.2 mJ



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Use only Equipment Rated properly for Division II Areas

Ensure Proper Grounding & Bonding by an Annual PM of the Entire System.

Verify Proper Grounding & Bonding following any Opening of Process Equipment for

Maintenance and/or Cleaning

Use only Conductive Materials Hoses with Proper Straps/Grounding Wires, Baghouse

Bags & Cages, and Flex Boots with Conductive Wiring (or Jumpers) Use only Appropriate Cleaning Equipment (Vacuums)



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Deflagration


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Particle Size & Dispersion

When an Explosible Material is reduced in size it becomes more dangerous. The smaller the

particle size, the more Surface Area Available for ignition.

The smaller the particles the greater the chance for an explosion to occur.


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Measured most often in Grams per Cubic Centimeter (cc)

Also related to the LEL or Lower Explosive Limit and the LFL or LowerFlammable Limit.

This is the value of weight of material per Unit Area that will, in a Cloudform/propogate a Deflagration/Explosion.

This value is Highly Important and key to Determining the Actual RISK in an

Explosive Environment. It is often the value used to Determine if Additional Protection is Required.

Minimum Explosible Concentration

(MEC)


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Product MEC (Grams per Cubic Meter)

Sugar 55-65 g/m3

Acrylidone LM 60 g/m3

Polyclar 10 40 g/m3

PVP K-90 65 g/m3

PVP K-30 65 g/m3

Gantrez AN-169 60 g/m3

Minimum Explosible Concentration

(MEC)


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Kst

Kst is the Deflagration Index for Dusts

Kst Test results provide an indication of the Severity of a Dust Explosion

Kst is essentially the Maximum Rate of Pressure Rise generated when dust is tested in a

confined enclosure

Kst provides the best Single Number estimate of the anticipated behavior of a Dust

Deflagration.

Kst values are the basis for Relief Panel Design


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Kst

Dust

Explosion

Class

Kst

(Bar.m/sec)

Characteristic

ST 0 0 No Explosion

ST 1 >0 to 200 Weak

Explosion

ST 2 >200 to

300

Strong

Explosion

ST 3 >300 Very Strong

Explosion

Powder Class Kst Value

Sugar ST-1 172

Acrylidone LM ST-2 278

Polyclar 10 ST-2 210

PVP K90 ST-1 138

PVP K30 ST-1 179

Gantrez AN-169 ST-2 249


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Primary vs. Secondary


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Primary Explosions

Primary ExplosionA primary explosion can develop pressures that will approach 10 times the initial

pressure of the system. For a primary explosion to occur a dust/powder cloud with the combustible

materials concentration above the MEC must exist, the oxygen concentration must be above the LOC, an

ignition source of sufficient energy must be present and there needs to be an element of confinement.

Prevention is normally attained through preventing the formation of the dust clouds with a dust

concentration above the MEC, by keeping the oxygen concentration below the LOC, by controlling all

ignition sources (electrical, electrostatic, thermal, mechanical) and by defining envelopes for safe

operating conditions as it pertains to self heating. Mitigations normally evaluated include containment,suppression, and explosion venting.


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Primary Explosion Safegaurds

Operate the Equipment below the Minimum Explosible Concentration (MEC)Powder

Conveyance, Dust Collectors, Drying Chambers, Blenders, etc.

Control Ignition SourcesUse only Rated Equipment suitable for Combustible Dust

Atmospheres.

Control Oxygen Level below the LOC (Limiting Oxyen Concentration)Processes operated

under Inert Atmospheres.

Explosion Venting to Safe Location

Suppression Systems & Containment


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Primary Explosion Safegaurds


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Product LOCOxygen Concentration

Acrylidone LM 12%

Polylclar 10 13%

PVP K-30 12%

Gantrez AN-169 9%

Limiting Oxidant Concentration (LOC)


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Propogating Explosions

Propagating ExplosionA propagating explosion normally starts as a primary explosion in a piece of

equipment or pipeline that propagates to all of the interconnected equipment. Higher pressures can be

developed because the initial pressure is above atmospheric pressure. Prevention is normally attained

through preventing primary explosions and by installing isolation systems in the interconnecting ducts,

piping, conveyors, etc. Mitigation is normally addressed by both explosion isolation & explosion venting,

or suppression of the interconnected equipment.


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Propogating Explosion Safegaurds

Prevent the Primary Explosion

Equipment Venting , Suppression & Segregation to prevent Interconnected Equipment from

Fueling the Event.


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Secondary Explosions

Secondary ExplosionSecondary explosions are the most severe and destructive of the dust/powder

explosion types. They occur when the powder/dust laying on the floor, beams, building supports, and

equipment are all jarred loose and thrown into one large dust cloud and ignited from the fireball from the

Primary and/or Propagating Explosion. Normally it is the primary explosion occurring in a facility where

housekeeping is below standards that causes the secondary dust cloud to form and has the energy

required to ignite it. Prevention is normally attained by preventing the primary explosion and by

preventing the buildup or accumulation of combustible material. There is very little that could be done to

mitigate the Secondary Dust Explosion. It is imperative that a strict housekeeping policy be followed toensure that accumulations and buildups are kept to a minimum.


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Appendix A of NFPA 654 points out that a dust layer 1/32 inch (0.8 mm) thick on the floor

would, when uniformly suspended create a dust hazard concentration of .35 oz/ft3 (350

g/m3) in a room 10ft high.

As a reference this is about the thickness of the lead on a mechanical pencil, or half the

thickness of a dime.

Annex D of NFPA 654 indicates that immediate cleaning is warranted whenever a dust layer

or 1/32 (.8 mm) thickness accumulates over a surface area of at least 5% of the floor of the

facility in any given room. The 5% factor should not be used if the floor area exceeds 20,000

ft2, in which case a 100 ft2 layer of dust is the upper limit.

Accumulations on overhead beams, joists, ducts, tops of equipment, and other surfaces

should be included when determining the dust coverage area. Even vertical surfaces should

be included when determining the dust coverage area.

Housekeeping


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Product Equivalent Thickness

Polyclar (.30 g/cc) 3.2 mm

PVP K-90 (.48 g/cc) 2 mm

PVP-I (.63 g/cc) 1.5 mm

PVP K-30 (.60 g/cc) 1.6 mm

Gantrez AN-169 (.45 g/cc) 2.1 mm

HousekeepingAn alternative method for considering the Acceptable thickness of dust accumulations from NFPA

654 (6.2.3.2) for powders with bulk densities less than 75 lb/ft3 is as follows:

Equivalent Thickness = (0.8mm)(1.2 g/cc)/Bulk Density of Powder


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Each Department (Area) within the plant shall develop a documented Housekeeping Procedure whichmust include the following elements (Example Housekeeping Checklists included in Appendix A):

Guidelines as to when Equipment should be shut down for repairs concerning powder/dustincluding: Powder - Dust/Leaks from Gaskets, Flexible Boots, Removable Covers, etc.

Packaging System malfunctions leading to excess dust in drumming rooms.

Excess build-up from Nuisance leaks that have exceeded the 1/32 requirement when considering beams,joists, and other supports.

A weekly cleaning schedule (at minimum) unless determined & justified as to an adjustedfrequency. Weekly Cleaning schedule must include assignments as to which job function (positions) are responsible for

which areas within the process.

Weekly cleaning schedule must include Operator Sign-off.

Weekly cleaning documentation shall be maintained by the Area for a period of 6 months.

Acceptable methods of Cleaning must be identified in the cleaning procedure as well as any additionalprecautions that must be taken.

Vacuuming (Fixed Pipe House-Vacuum Systems & properly rated portable cleaners are acceptable)

Dry Sweeping & Bagging of Material

Washing the affected Area.

The use of Steam or Compressed Air to blow down Equipment is prohibited.

Housekeeping


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Housekeeping

A Quarterly Cleaning Documentation (unless determined & justified to an adjusted

frequency) to include verification of the weekly cleaning and the following additional

considerations:

Inspection of Any Dust Control Devices (House-Vac Systems, Dust Collection Systems,

Ventilation Systems, etc.)

Inspection of All Drop Ceiling located in the Packaging & Processing Areas to ensure no

build-up of powder under the ceiling tiles.

Quarterly inspections Documentation should be maintained for a period of at least 1

year.

Annual Cleaning Documentation

An Annual cleaning checklists should be developed to ensure that hard to clean areas

are cleaned during Annual Shutdowns, in an attempt to prevent downtime during the

remainder of the year.

Annual cleanings should include Preventative Maintenance on Dust Collection Systems.

It is acceptable to limit the extent of dust migration & size of the room that must be cleaned.

NFPA 654 permits the use of physical barriers to limit dust migration in order to minimize the

extent of the housekeeping zone.


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Additional Information

ISP Corporate SHP-511 -- Major Hazard Analysis Guidelines for Systems Processing

Combustible Dusts & Powders

http://iportal/departments/Environmental%20Health%20and%20Safet/pages/polici

es.aspx
http://iportal/sites/ehs/Product%20Explosibility%20Data%20Sheets1/Forms/AllItems.aspxhttp://iportal/sites/ehs/Product%20Explosibility%20Data%20Sheets1/Forms/AllItems.aspxhttp://iportal/sites/ehs/Product%20Explosibility%20Data%20Sheets1/Forms/AllItems.aspxhttp://iportal/sites/ehs/Product%20Explosibility%20Data%20Sheets1/Forms/AllItems.aspx


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PEDSProduct Explosibility Data Sheets

Maitained by ISP Corporate for Specific Products

http://iportal/sites/ehs/Product%20Explosibility%20Data%20Sheets1/Forms/AllItems.as

px
http://iportal/departments/Environmental%20Health%20and%20Safet/pages/policies.aspxhttp://iportal/departments/Environmental%20Health%20and%20Safet/pages/policies.aspxhttp://iportal/departments/Environmental%20Health%20and%20Safet/pages/policies.aspxhttp://iportal/departments/Environmental%20Health%20and%20Safet/pages/policies.aspx


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CSB Video on Dust Hazards

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Videos\DUST.wmv
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