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June 15 2016By The NumbersCompressor Performance1PROPRIETARY

Compressor Performance ReportWithout an accurate TDC, the report information has no value!2PROPRIETARY

Compressor Performance ReportIHP accuracy is notdependent on thecylinder health;however, the geometry,TDC accuracy, andsensor linearity mustbe accurate.3PROPRIETARYCapacity is the averageof the calculated flow rateat both suction anddischarge conditions.This number is a goodindicator of the actualcapacity only when thecylinder is healthy and allcollected data isaccurate.IHP/MMSCFD isIHP/calculated average capacity

Compressor Indicated Horsepower The horsepower measured at the compressor pistonface with an indicating device (e.g.: 100 IHP) Includes all thermodynamic losses Thermodynamic losses are equal to the indicatedhorsepower minus the theoretical horsepower Thermodynamic or compression efficiency equalsthe theoretical or gas horsepower divided by thecompressor indicated horsepower4PROPRIETARY

Indicated Horsepower The horsepower measured at the power pistonface with an indicating device Includes all thermodynamic losses 5PROPRIETARYPLAN/33,000P IMEPL STROKE in FEETA AREAN RPM33,000 ft-lb/minute 1 Horsepower

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Compressor & Power Master RodsRotation not neededPiston orCrossheadMaster Rod Setup Requires:1. Con Rod Length (in inches)Stroke (in)8PROPRIETARY2. Stroke (in inches)

FormulasForce Pressure * AreaWork Force * Distance (stroke)Power Work/TimeCompressor Cylinder Horsepower RelationshipsBrake Horsepower Indicated Horsepower Friction HorsepowerBrake Horsepower Indicated Horsepower / Compressor Mechanical EfficiencyFriction HorsepowerRing / Liner FrictionWrist Pin / Bushing FrictionConnecting Rod Bearing / Crankshaft Friction9PROPRIETARY

Compressor Performance ReportThese are the averagecalculated capacities foreach stage. They shouldhave a reasonableagreement for the sameproduct stream. Thecalculated capacitieshave a tendency toincrease when there areinternal cylinderleakages, while the actualcapacities arediminishing.These values areextremely dependent onthe TDC accuracy.10PROPRIETARY

Capacity scfd (dv * VE * rpm * 1440 * pressure correction *temperature correction) / Z scfd flow in std cu ft of gas/day dv area*stroke/1728 VE volumetric efficiency rpm compressor shaft revolutions per minute pressure correction absolute pr / standard pr temperature correction 520/absolute temperature Z compressibility (compensates for the compressioncharacteristics of the gas) Calculated at suction and/or discharge conditions mmscfd million standard cubic feet a day.11PROPRIETARY

Calculated CapacityIs only valid for a healthy cylinderSuction calculated capacity goes up with asuction valve, packing or ring leak.Suction calculated capacity goes down with adischarge valve leak.Discharge calculated capacity goes up with adischarge valve leak.Discharge calculated capacity goes down with asuction valve leak or ring leak.The average of the calculated suction anddischarge capacity goes up significantly withring leakage and, generally, up slightly for valveand packing leakage.12PROPRIETARY

Compressor Performance ReportThese items are used in the flow calculation at suction conditions. All 3 can beaffected by the mechanical condition of the cylinder. Even in a healthy cylinder,the values could be wrong. The temperature at the cylinder valve port is difficult toobtain. The pressure and volumetric efficiency accuracy can be affected bychannel resonance. The pressure can be affected by the sensor zero andlinearity.13PROPRIETARY

Compressor Performance ReportAbsolutecompression ratioThese items are used in the flow calculation at discharge conditions. All 3 can beaffected by the mechanical condition of the cylinder. Even in a healthy cylinder,the values could be wrong. The temperature at the cylinder valve port is difficult toobtain. The pressure and volumetric efficiency accuracy can be affected bychannel resonance. The pressure can be affected by the sensor zero andlinearity.14PROPRIETARY

15VOLUMETRIC EFFICIENCIES15PROPRIETARY

Compressor Volumetric EfficienciesSuction Volumetric Efficiency (VEs) is thepercent of the cylinder end's displacementmeasured by an imaginary line extended fromthe suction toe to the expansion line.Discharge Volumetric Efficiency (VEd) is thepercent of the cylinder end’s displacement thatis measured from an imaginary line extendedfrom the discharge toe to the compression line.16PROPRIETARY

Compressor(HE Volumetric Efficiencies)17PROPRIETARY

Compressor(CE Volumetric Efficiencies)18PROPRIETARY

Power Loss19PROPRIETARY

POWER LOSSPower loss is a percent of the indicatedhorsepower.20PROPRIETARY

21FLOW BALANCE21PROPRIETARY

Flow BalanceAccurate flow balance is dependent on the accuracy of theTDC reference, toe pressures, suction and dischargetemperatures at the valve ports, gas compressibility, andVE picks.Flow balance, by itself, is not a reliable way to determine thehealth of the compressor cylinder.Do not adjust the TDC offset in an effort to improve flowbalance alone.22PROPRIETARY

23TOE PRESSURE23PROPRIETARY

Pressure & Vibration Vs. Crank-Angle (toe points)All PT and PV compressor plots use gauge (psig) pressure24PROPRIETARY

COMPRESSION RATIO25PROPRIETARY

Compressor Pressure Compressor calculations use absolute pressure Absolute pressure gauge pressure atmosphericpressure (100 psig 14.7 114.7 psia) (200 psig 14.7 214.7 psia) The atmospheric pressure at the test location is notcorrected to sea level Compression ratio absolute discharge pressuredivided by absolute suction pressure (214.7 psia / 114.7 psia 1.872 CR) Standard pressure or standard atmosphere is thepressure of a standard cubic foot of gas26PROPRIETARY

SUCTION AND DISCHARGETEMPERATURES27PROPRIETARY

Compressor Temperature Theoretical compressor calculations use absolutetemperature (deg Rankin) Absolute temperature (R) degrees F 460 The Standard temperature for gas measurementis 60 degrees F (60 deg F 460) 520 deg R28PROPRIETARY

ROD LOAD29PROPRIETARY

Rod LoadThe piston rod is alternatively under compressionand tension and, being of a relatively narrow crosssection, is subject to high mechanical loads andhigh cyclic fatigue stresses.The gas rod load is the force in pounds applied tothe reciprocating parts due to internal cylinderpressure and area differentials across the pistonends.Some manufactures may include the effect ofinertia forces of the crosshead and pistonassemblies in their load limits.30PROPRIETARY30

Static or Gas LoadStatic or gas load is the force on the cylinderreciprocating components resulting from the gaspressure applied to the surface area of the pistonfaces.Analyzers calculate and plot the results for eachdegree of crankshaft rotation.Gas forces alone may or may not cause a forcereversal at the crosshead pin and bushing.31PROPRIETARY31

Static Gas Loadtensioncompression32PROPRIETARY2009 EGCR32

Inertia LoadInertia load is the force on the cylinder reciprocatingcomponents resulting from the change in theirvelocity.Analyzers calculate and plot the results for eachdegree of crankshaft rotation.Inertia forces are always reversing on everyrevolution of the crankshaft.33PROPRIETARY33

Crank MechanismReciprocating inertia forces are caused by theacceleration and deceleration of the reciprocatingmasses.2634PROPRIETARY

Inertia LoadingTension loadCompression load35PROPRIETARY35

Net LoadIs simply the sum of the inertia and gas loadforcesIs calculated for each degree of crankshaftrotationReversal occurs after the net rod load passesthrough 0 pounds and has met theManufacturer’s requirements for a reversal.36PROPRIETARY36

Net Loadtensioncompression139 deg37PROPRIETARY2009 EGCR37

38ROD REVERSAL38PROPRIETARY

Rod ReversalRod reversal occurs when the combination ofpressure and inertia forces on the reciprocatingcomponents cause a reversal in the loading of thecrosshead pin and bushing.This is sometimes referred to as load reversal.39PROPRIETARY39

Mechanical Specifications andDimensions Required for InertiaLoad Measurement Connecting RodLength Stroke Mass ofReciprocatingComponents Crank Phase40PROPRIETARY40

Reciprocating Mass CombinationsFor force at the piston-to-rod connectionPiston WeightFor force at the rod in front of crossheadPiston and rod assembly weightFor force at the piston rod-to-crossheadconnectionPiston, piston rod and jam nut weight41PROPRIETARY41

Reciprocating Mass CombinationsFor force at the cross-head pin and bushing (rod reversalmeasurement)All reciprocating weight excluding any portion of theconnecting rodFor pin fixed to crosshead, include pin weightFor pin fixed to connecting rod, do not includepin weightFor full floating pin, consult the manufacturer orsplit the weight42PROPRIETARY42

Design Requirements API 618The rod loads shall be calculated based on the internalpressure during discharge stroke (including ventilationlosses) and shall not exceed the manufacturer’smaximum allowable load at any specified operating loadstep.The duration of the rod load reversal shall be 15 rotation angle minimum. The magnitude of peak shall be3% minimum of the opposite peak.Simple bushing designs (un-grooved) may require aminimum of 45 of rod reversal and a 20% magnitude.Individual Manufacturer’s Requirements May Vary.43PROPRIETARY43

Rod Reversal RequirementsAriel:minimum of 30 degrees and 25%opposite forceAjax:minimum of 30 degrees and 3%opposite forceDresser-Rand: minimum of 30 degrees andX% opposite force (suggest 3%)GE Oil & Gas: minimum of 60 degrees and15% opposite forceKnox Western: minimum of 30 degrees and15% opposite forceSuperior:minimum of X degrees and X%opposite force (suggest 30 degrees and 15%)44PROPRIETARY44

45Theoretical Temperature45PROPRIETARY

Theoretical TemperatureT2 ((T1 460) * R ((K-1)/K))-460T2 Theoretical discharge temperatureT1 Beginning temperature degrees F.R Absolute toe compression ratio(absolute disch pr / absolute suct pr)K Ratio of specific heatsThe calculated discharge temperature goes up with any increasein suction temperature, compression ratio or K-value.46PROPRIETARY

Compressor Performance ReportcalculatedThe Theoreticaldischarge temperatureis calculated from themeasured suctiontemperature, thecompression ratio of thetoes and the K-value ofthe gas.47PROPRIETARYdifferenceMeasured(from page 1)The delta temperature willelevate as the cylinder leakagerates increase.

48Clearances48PROPRIETARY

Compressor Performance ReportcalculatedThe Set value is used inthe creation of thetheoretical PV models,log/log plots, and thepolytropic values (n). Itmust represent theactual clearances in theindividual cylinders.49PROPRIETARYIn a healthy cylend, the SWRcalculation willnormally agreeclosely with theset clearance ifthe setclearance is anaccurate value.differenceThese are the calculated clearances usingthe GPSA method. The actual clearance isnot needed to make this calculation. Theaverage value should be used as the setclearance for good diagnostic plots oftheoreticals. In a healthy cylinder with anaccurate TDC, the Suction and Dischargecalculations will be close together.

50Z FACTOR50PROPRIETARY

Redlich-Kwong1949The Redlich-Kwong equation of state was a considerableimprovement over other equations of the time. It is still ofinterest primarily due to its relatively simple form. Whilesuperior to the van der Waals equation of state, it performspoorly with respect to the liquid phase and thus cannot beused for accurately calculating vapor–liquid equilibria.However, it can be used in conjunction with separate liquidphase correlations for this purpose.The Redlich-Kwong equation is adequate for calculation ofgas phase properties when the ratio of the pressure to thecritical pressure (reduced pressure) is less than about onehalf of the ratio of the temperature to the critical temperature(reduced temperature).51PROPRIETARY