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Compressor
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© 2007 General Electric Company. All rights reserved.
Condition Monitoring
Reciprocating CompressorsCondition Monitoring & Diagnostics
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© 2007 General Electric Company. All rights reserved.
Presentation Contents
• Introduction• Malfunction Causes & Effects• Data Evaluation Plot Formats• Diagnostic Strategy
3
© 2007 General Electric Company. All rights reserved.
Introduction
Reciprocating compressors endure large cyclic forces:
• Cylinder gas pressure• Inertial forces• Moment forces• Piping pressure pulsations
RecipAnimation0001.aviClick to open file.
(2-throw machine end view)
OffsetThrowForces.gif(2-throw machine top view)
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© 2007 General Electric Company. All rights reserved.
Condition MonitoringIntroduction
Mac
hine
Con
ditio
n
Time
Point where failure starts to occur
P
Point where we can first detect a problem
FPoint where machine fails
P-F Interv
al
P-F Interv
al
P = potential failureF = functional failure
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© 2007 General Electric Company. All rights reserved.
Monitoring MethodsIntroduction
Periodic Monitoring• Temporary installation• May miss short P-F intervals• No protective trips
Continuous Monitoring• Permanent installation• Appropriate for short P-F
intervals• Provides protective trips
Permanent Monitoring InstrumentsPortable Diagnostic Instruments
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© 2007 General Electric Company. All rights reserved.
Overall Equipment EffectivenessIntroduction
– Availability: % of time that production equipment is available.
– Performance: % of maximum possible production.– Quality: % of production that meets specifications.
– Example Calculation:
QualityxPerformancexAvailabilityOEE=
%6.64%95%85%80 == xxOEE
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© 2007 General Electric Company. All rights reserved.
Malfunction Causes & Effects
Causes
• Normal Component Wear• Process Gas Contamination• Abnormal Component Motion• Support System Problems
Effects
• Valve Failures• Pressure Packing Leaks• Piston Ring Failures• Rider Band Wear• Crosshead & Pin Wear
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© 2007 General Electric Company. All rights reserved.
Typical Maintenance CostsMalfunction Causes & Effects
• Valves are usually the most troublesome component in a reciprocating compressor.
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© 2007 General Electric Company. All rights reserved.
Normal Component WearMalfunction Causes & Effects
Fatigue• cyclic stresses caused by
normal compressor operation
Erosion• frictional contact between
moving components
Fatigue and erosion can be minimized, but never eliminated completely, since they occur as part of normal operation.
Rock-n-Roll.gif (movement exaggerated)
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© 2007 General Electric Company. All rights reserved.
Process Gas ContaminationMalfunction Causes & Effects
• Abrasive Particles– “Dirt” (silica), corrosion products (rust), debris from broken
valves…
• Coke Deposits– Solid carbon particles from decomposed lubricating oil…
• Corrosive Substances– Acidic attack from “sour gas” (hydrogen sulfide) and others…
• Liquid Slugs – Condensation of process gas, problems with liquid separators…
• Process Gas Polymerization– Sticky long-chain molecules formed from some process
gases…Compressors do not operate in isolation. They are susceptible to contamination anywhere in the process (see next slide)
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© 2007 General Electric Company. All rights reserved.
Process Gas ContaminationMalfunction Causes & Effects
CatalyticReactor
Preheater
Regen. Heat Exchanger
Cooler
High Pressure Separator
Low Pressure Separator
Fractionator
Purge Gas
Naphtha
Jet Fuel & Diesel Fuel
Recycle Stream
Heavy Feed Oil
HydrogenHot Feed & Hydrogen
Qu
en
ch G
as
Hydrogen Recycle Compressor
Hyd
rog
en
11
22
33
44
55
66
77
88
99H2
Simplified Hydrocracker Unit Diagram
Hydrogen Makeup Compressor
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© 2007 General Electric Company. All rights reserved.
Abnormal Component MotionMalfunction Causes & Effects
• Valves– fluttering, slamming, sticking...
• Piston Rings– misalignment, sticking, excessive shifting in piston groove…
• Pressure Packing– seizing, not floating…
• Crosshead– knocking impacts due to excessive clearance…
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© 2007 General Electric Company. All rights reserved.
Support System ProblemsMalfunction Causes & Effects
• Support systems strongly influence compressor operation:
– Control System– Cooling System– Gas Composition Monitor– Instrument Air System– Lubrication System– Unloaders
TemperaturesEquipment Status
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© 2007 General Electric Company. All rights reserved.
Valve FailuresMalfunction Causes & Effects
Broken Valve Ring
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© 2007 General Electric Company. All rights reserved.
Piston Ring FailuresMalfunction Causes & Effects
Two-Piece Piston Ring
Worn RingWorn Ring
New RingNew Ring
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© 2007 General Electric Company. All rights reserved.
Rider Band WearMalfunction Causes & Effects
Worn Piston & Rider Bands
Rider
Band
Rider
Band
Rider
Band
Rider
Band
Scuffing
Scuffing
Piston Ring
Groves
Piston Ring
Groves
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© 2007 General Electric Company. All rights reserved.
Pressure Packing LeaksMalfunction Causes & Effects
Vent to Disposal System (flare)
Buffer Gas Leakage
Buffer Gas Purge
Process Gas Leakage
Piston Rod
Piston Rod
Cylinder Head
Cylinder Head
Packing Case Flange
Packing Case Flange
Packing Cups & Rings
Packing Cups & Rings
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© 2007 General Electric Company. All rights reserved.
Data Evaluation Plot Formats
Horizontal (x-axis) units:• Crank Angle (θ)• Cylinder Volume• Displacement (Rod Position)• Frequency• Time
Vertical (y-axis) units:• Acceleration or Velocity• Displacement (Rod Position)• Force• Pressure• Temperature
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© 2007 General Electric Company. All rights reserved.
Time DomainData Evaluation Plot Formats
Trend Waveform
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© 2007 General Electric Company. All rights reserved.
Frequency DomainData Evaluation Plot Formats
Spectrum Waterfall (stacked spectrums)
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© 2007 General Electric Company. All rights reserved.
Crank Angle (θ) DomainData Evaluation Plot Formats
Pressure vs. Crank Angle Crank Angle Overlay
Head End
Head End
Crank End
Crank End
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© 2007 General Electric Company. All rights reserved.
Crank Angle (θ) DomainData Evaluation Plot Formats
Pressure vs. Crank Angle (Waterfall)
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© 2007 General Electric Company. All rights reserved.
Displaced Volume DomainData Evaluation Plot Formats
Pressure vs. Volume (P-V)
Crank End
Crank End
Head End
Head End
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© 2007 General Electric Company. All rights reserved.
Rod PositionData Evaluation Plot Formats
Rod Position (vertical & horizontal) vs. Crank Angle
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© 2007 General Electric Company. All rights reserved.
Diagnostic Strategy
What is the problem?
What do I already know?
What does it tell me?
Do I need additional data to prove my analysis?
How do I get the data? What formats?What operating modes?
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© 2007 General Electric Company. All rights reserved.
Compressor SensorsDiagnostic Strategy
Frame Vibratio
n
Piston Rod
Position
Valve Temperat
ure
Main Bearing
Temperature
Crosshead Accelerati
on
Discharge Gas
Temperature
Continuous Rod Load
Suction Gas
Temperature
Cylinder Pressure
Packing Temperat
ure
Crosshead Guide Temp
Crank Angle &
RPM
**
** Dynamic cylinder pressure sampling enables processing of performance parameters: Degrees Rod Reversal, Discharge & Suction Power Loss, Gas Rod Load, Indicated Horsepower, Peak Rod Loads, etc.
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© 2007 General Electric Company. All rights reserved.
Example SymptomsDiagnostic Strategy
• Abnormal temperatures or pressures can indicate:– overheated bearings, leaky valves, piston rings or packing…
• Unusual forces or impacts can indicate:– Worn crosshead shoes, loose pins, excessive clearances,
unbalanced rod loads…
• Excessive vibration can indicate:– Broken foundation bolts, piping hangars, structural
resonances, improper unloader operation…
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© 2007 General Electric Company. All rights reserved.
Determine Compressor in Stress
•Compressor Component Approaching Critical Temperature
•Rod Load Reversal Inadequate
•Combined Rod Load (MARL) Exceeded
•Compressor Capacity Inadequate• Affect on Process Unit Capacity
•Overall Frame Vibration Exceeding Critical Level
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© 2007 General Electric Company. All rights reserved.
Practice ExercisesPresentation Contents
• Introduction• Malfunction Causes & Effects• Data Evaluation Plot Formats• Diagnostic Strategy