valerus compression
DESCRIPTION
compresores ISO 13631 - API 618TRANSCRIPT
© 2012 Valerus. Confidential and proprietary. All rights reserved. © 2012 Valerus. Confidential and proprietary. All rights reserved.
Compression Split – Technical Seminar
September 26, 2013
Tom Birney, Director of Business Development
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COMPRESSION: COMPARISON OF HIGH / MEDIUM SPEED VS.
SLOW SPEED
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• Understand how a compressor functions NEWEST PRESENTATION
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• Overview of major components in the system
• Video – Compressor Package in Operation
PREAMBLE – RECIPROCATING COMPRESSOR BASICS
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COMPLETED PACKAGE
4
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SKID
5
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COMPRESSOR FRAME
6
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DRIVER & COUPLING
7
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COOLER & SHEAVES
8
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FUEL & UTILITY SYSTEM
9
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PULSATION BOTTLES
10
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SCRUBBERS
11
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PROCESS PIPING
12
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CONTROL PANEL
13
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EXHAUST SYSTEM & COOLER PLATFORM
14
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FINISHED!
15
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• Video – Compressor Package in Operation
• Arrow.wmv
PREAMBLE – RECIPROCATING COMPRESSOR BASICS
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API-11P (ISO-13631) VS API-618
API-11P (ISO-13631): High/Medium Speed Compressors
vs
API-618: Low Speed Compressors
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API-618 GENERAL OBJECTIVE
1st & 2nd Edition (1964)
• Reciprocating compressors in refinery business
• Drivers
– Integral & separable engines
– Electric motors
– Steam turbines
– Direct acting steam turbines
Current 5th Edition
• Reciprocating compressor in petrochemical, chemical and process gas industry services for handling process air or gas
• Applies to moderate to low speed in ‘critical service’ (Note: ‘critical service’ is not defined.)
• Drivers not covered
– Gas engine
– Steam engines (direct)
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API-618 GENERAL OBJECTIVE
• Design for a minimum 20 year service life
• Three (3) years of uninterrupted service (System design criteria)
• API-618 provides basic
• Compressor design standards
• Application limits
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HISTORY - API 11P / ISO-13631 VS API 618
• API-618 1st ed. published in 1964. to define standards for
reciprocating compressors for use in refinery service.
• In the early 1970s, packaged separable compressors became
prevalent in oil and gas production and API realized that API-618
was not applicable to this market. Hence, a standard that covers the
complete package was necessary.
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HISTORY - API 11P / ISO-13631 VS API 618
• API-11P - 1975 specifically covers packaged high-speed
separable reciprocating compressors for oil and gas
production applications.
• The 3rd edition of API-618, paragraph 1.1 was rewritten
to exclude “packaged high-speed separable engine-
driven reciprocating gas compressors.”
• The specification further defined “compressors covered
by this standard are moderate to low speed and in
critical services.” This addressed the growing use of
higher speed separable compressors for non-critical
services in refineries.
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HISTORY - API 11P / ISO-13631 VS API 618
• The 4th edition of API-618, states; “requirements for
packaged high-speed reciprocating compressors for oil
and gas production services are covered in API
Specification 11P.”
• The second edition of API-11P - November 1989
includes the following statement of applicability:
“This standard covers the minimum requirements for a
packager supplied, designed and fabricated, skid-
mounted reciprocating, separable or integral
compressor with lubricated cylinders and its prime
movers used in oil and gas production services…”
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HISTORY - API 11P / ISO-13631 VS API 618
• 618 Scope specifically states that 618 “does not cover gas engine
drivers”.
• In summary, applying API-618 to a packaged separable compressor
is contrary to the purpose and intent of API standards and could
result in lack of definition for critical requirements.
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Comments to API-618 5th ed. are available from most
manufacturers of separable compressors.
• Packagers can also provide complete packaging comments to API-
618.
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• In general it should be remembered that API 618 is
written for longer stroke, slower speed units that are
normally block mounted and driven by electric motors.
The logic for some of the requirements does not apply to
packaged shorter stroke compressors driven by either
gas engines or electric motors. It is also important to
note that it may take some time before standards
recognize technological improvements.
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Examples:
• paragraph 2.1.1 requires a design suitable for “expected
uninterrupted operation of at least 3 years.”
• A gas engine must be maintained on a monthly basis
and therefore it does not make sense to invest in backup
auxiliary systems such as dual oil filters. Maintenance
on oil filters can be performed concurrently with engine
monthly
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Examples:
• Paragraph 2.6.2.3 states that “unless otherwise specified, each cylinder shall have a replaceable, dry-type liner, not contacted by coolant.”
• The main reason for liners on the longer stroke units is to provide an economical means for repair.
On average, for smaller bore cylinders a replacement barrel is less costly than a liner. Additionally, a metal spray processes can be used to rebuild cylinders to original dimensions. Metal spray processes are an even more economical repair technique.
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Examples:
• Paragraph 2.6.2.3 continued
• Adding a liner to a 15” stroke adds very little clearance but it is a
significant increase on the shorter stroke separable units.
• This can reduces volumetric efficiency and the flexibility of the
Variable Volume Clearance Pocket.
Additional base Clearance
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Cylinder Water Jackets:
• Water jackets required to address thermal bore distortion in
long-stroke cylinders
• Originally API-618 asked that water jackets not be included
• Water jackets added in 2nd edition due a unit that ran without gas flow
• Never meant as a method to ‘cool’ gas
• Desire for water jackets ‘institutionalized’ by API-618 requirement for specific approval of ‘air cooled’ cylinders
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Examples:
• Paragraph 2.6.3.2 states “air-cooled cylinders shall not be furnished without the expressed written approval of the purchaser.”
• Air-cooled cylinders have been in use for over 30 years with thousands of cylinders in operation and millions of successful running hours. The impact of forced liquid cooling on higher speed units is not nearly as significant as it is on the slower speed units.
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Examples:
• Paragraph 2.7.2 requires the purchaser to specify if
valve unloading is required.
• The norm for process machines is to use automatic
valve unloaders for both start up unloading and capacity
control.
• The norm for separable compressors is to unload for
starting with a bypass and to use speed and recycle for
capacity control.
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Paragraph 2.10.1.1 states “type A distance pieces are
used only for non-flammable or non-hazardous gases.”
• Packaged units are typically designed for ease of
shipment and width is an important design criterion. There
are thousand of units compressing sweet natural gas and
operating safely with API 11P / ISO-13631 type 1 distance
pieces
• With the smaller diameter piston rods used in separable
compressors, shorter rods are preferred to provide proper
stiffness.
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DISTANCE PIECE
Slinger
High efficiency
oil wiper
Intermediate packing
with optional purge
Pressure packing with
water cooling and purge
Window size allows removal
of complete packing case
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DIFFERENCES - API 11P / ISO-13631 VS API 618
• Paragraph 2.14.2 table 1
imposes arbitrary
pressure limits for cast
cylinders.
• These limits have not
changed in over 25 years.
Despite QC, finite
element analysis and
manufacturing
improvements.
Ion-Nitrider
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CYLINDER DESIGN HISTORY
Year 1964 2000
CastingDesign
HistoricalAlgorithms
ComputerModeled
CastingQuality
Good Better
DimensionalStability
MovementCaused Problems
No MovementProblems
Piston RingMaterial
Metallic orHard Non-Metallic
SoftNon-Metallic
HardenedCylinder Bore?
No Yes
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CYLINDERS
Moderate-Speed Low-Speed
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API 11P / ISO-13631 VS API 618
In conclusion:
Specifying API 618 for high speed packaged compressors can add
considerable cost, for limited benefits and may leave important
packaging issues unspecified. It is better to follow the intent of API and
use API 11P / ISO-13631 . If there are specific issues from API 618
that are important to the purchaser they should be addressed
individually.
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CAN MODERATE SPEED COMPRESSORS BE APPLIED IN
TRADITIONAL API 618 APPLICATIONS?
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SPEED
Low-Speed Moderate-Speed
RPM 200 - 700 700 – 1200
Stroke mm (Inch)
229 – 508 (9 – 20)
76 - 203 (3 – 8)
•Low and Moderate Speed Definitions
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ALLOWABLE SPEEDS
• Piston Speed
• Piston rings
• Wear bands
• Packings
• Rotating Speed
• Valve cyclic (fatigue) life
• Forces and moments
created
Wear is effected by:
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PISTON SPEED LIMITS
• Current limits for 3 year operation
• Lubricated: 4.3 m/s (850 ft/min )
• Non-lubricated: 3.8 m/s (750 ft/min )
• Acceptable speeds vary with user
• Lower piston speed provide longer operation
• Other factors affect wear part life
– Lubrication
– Surface finish of counter-face
– Pressure loading on wear part
– Non-metallic material selection
– Gas composition and any particulate
– Operating temperature
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EFFECTS OF OPERATING TEMPERATURE
135° C
(275° F)
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PISTON SPEED VS. DRIVER SPEED
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SPEED COMPARISON
High Speed Moderate Speed Traditional Slow Speed
Drive Speed (RPM)
1000 - 1800 700 - 1200 300 - 700
Piston Speed Lubricated m/s (ft/min)
4.6 – 6.1 (900 – 1200)
2.8 – 4.4 (560 – 870)
2.8 – 4.8 (560 – 910)
Piston Speed Non-Lube
m/s (ft/min) Not Available
2.3 – 3.8 (450 – 750)
2.3 – 3.8 (450 – 750)
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ROTATING SPEED
• Effects of rotating speed
• Valve cyclic (fatigue) life
• Compressor forces and moments
• Driver RPM capability has increased
• Materials
• Technology
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ROTATING SPEED
• Valve cyclic (fatigue) life
• Improved technology and materials
• Non-metallic materials
• Prediction and control of impact velocity
• Impact velocity stress rather than bending stress determines life
• Current non-metallic valve experience
• 3 year time between maintenance
• 1200 rpm
• 7 m/s impact velocity
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EFFECTS OF VALVE LIFT / IMPACT VELOCITY
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EFFECTS OF VALVE LIFT / IMPACT VELOCITY
VALVE COMPARISON:
Hi Speed Low Speed
Valve Type Non-Metallic Plate, Ring or
Poppet
Non-Metallic Plate, Ring or
Poppet
Valve Lift Mm (Inch)
1.5 – 2.6 (0.06 – 0.1)
1.5 – 2.5 (0.06 – 0.1)
Expected Valve Life
24 Months 36 Months
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ROTATING SPEED VALVE LIFE
• Other factors effecting valve life
• Valve Type
• Unknown operating points
• Oil sticktion
• Liquids
• Dirt
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ROTATING SPEED HORIZONTALLY OPPOSED
Inertial forces act in opposite directions
Equal masses result in equal but opposite forces
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ROTATING SPEED COMPRESSOR BALANCE (1 MW)
• Low-speed horizontally opposed
• 25 to 50 lbs. (11 to 23 kg)
• Moderate-speed horizontally opposed
• 2.5 lbs. (1.15 kg)
• Components weighed and balance components selected during
assembly
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MODERATE-SPEED COMPRESSOR BALANCE
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PISTON
Moderate Speed Low Speed
Piston Material Ductile Iron Ductile Iron or Aluminum
Piston Ring and Wear Band
Configuration
Piston Ring + Separate Wear
Band
Piston Ring + Separate Wear Band
Piston Ring and Wear Band
Material
Non-Metallic As Required
Non-Metallic As Required
Wear Band Loading
N/mm2 (psi)
0.035 (5)
0.069 (10) or 0.035 (5)
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COMPRESSOR COMPARISON
Natural Gas Process
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CYLINDER
Moderate Speed Slow Speed
Material Ductile Iron
Forged Steel
Ductile Iron Cast Steel
Forged Steel
NACE Option Yes Yes
Water Jacket Not Required As Required or As an Option
Cylinder Liner No As Required or As an Option
Surface Hardness 61 Rc
(Nominal) 25 Rc
Typical
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CAN MODERATE SPEED COMPRESSORS BE APPLIED IN TRADITIONAL
API 618 APPLICATIONS?
With correct application engineering
YES