© 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

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© 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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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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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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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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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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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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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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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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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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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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Valve FailuresMalfunction Causes & Effects

Broken Valve Ring

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Piston Ring FailuresMalfunction Causes & Effects

Two-Piece Piston Ring

Worn RingWorn Ring

New RingNew Ring

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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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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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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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Time DomainData Evaluation Plot Formats

Trend Waveform

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Frequency DomainData Evaluation Plot Formats

Spectrum Waterfall (stacked spectrums)

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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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Crank Angle (θ) DomainData Evaluation Plot Formats

Pressure vs. Crank Angle (Waterfall)

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Displaced Volume DomainData Evaluation Plot Formats

Pressure vs. Volume (P-V)

Crank End

Crank End

Head End

Head End

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Rod PositionData Evaluation Plot Formats

Rod Position (vertical & horizontal) vs. Crank Angle

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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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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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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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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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Practice ExercisesPresentation Contents

• Introduction• Malfunction Causes & Effects• Data Evaluation Plot Formats• Diagnostic Strategy