Reducing Emissions from Compressor Rod Packing Lessons Learned from Natural Gas STAR Producers...

Reducing Emissions from Reducing Emissions from Compressor Rod PackingCompressor Rod Packing

Lessons Learned from Natural Gas STARLessons Learned from Natural Gas STAR

Producers Technology Transfer WorkshopProducers Technology Transfer Workshop

Devon Energy CorporationDevon Energy Corporationandand

EPA’s Natural Gas STAR ProgramEPA’s Natural Gas STAR Program

April 20, 2005April 20, 2005

Reducing Emissions, Increasing Efficiency, Maximizing Profits

AgendaAgenda

Methane LossesMethane Losses

Methane RecoveryMethane Recovery

Is Recovery Profitable?Is Recovery Profitable?

Industry ExperienceIndustry Experience

Discussion QuestionsDiscussion Questions


Methane Losses from ProductionMethane Losses from Production

Production responsible for 42% of methane emissionsProduction responsible for 42% of methane emissions

Transmission & Storage Transmission & Storage 98 Bcf 98 Bcf

ProductioProduction n

150 Bcf150 Bcf

Processing Processing

36 Bcf 36 Bcf

Distribution Distribution 73 Bcf73 Bcf

25 Bcf25 Bcf

10 Bcf10 Bcf

18 Bcf18 Bcf

1 Bcf1 BcfOil Downstream Oil Downstream

2 Bcf 2 Bcf

Inventory of U.S. Greenhouse Gas Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990 - 2002Emissions and Sinks 1990 - 2002

EmissionsEmissions

ReductionsReductions


Methane Losses from Methane Losses from Compressor Rod PackingCompressor Rod Packing

Reciprocating compressors account for 2% of production Reciprocating compressors account for 2% of production sector emissionssector emissions Gas lost from rod packing is estimated to be overGas lost from rod packing is estimated to be over

350 MMcf/yr costing over $1 million (gas price of $3/Mcf)350 MMcf/yr costing over $1 million (gas price of $3/Mcf)

Inventory of U.S. Inventory of U.S. Greenhouse Gas Greenhouse Gas Emissions and Emissions and Sinks 1990 - 2002Sinks 1990 - 2002

Pneumatic Pneumatic DevicesDevices60 Bcf60 Bcf

Meters andMeters andPipeline LeaksPipeline Leaks11 Bcf11 Bcf

Gas Engine Gas Engine ExhaustExhaust12 Bcf12 Bcf

Well Venting Well Venting and Flaringand Flaring12 Bcf12 Bcf

Storage Tank Storage Tank VentingVenting23 Bcf23 Bcf

Other Sources Other Sources 15 Bcf15 Bcf

Reciprocating Reciprocating CompressorsCompressors3 Bcf3 Bcf

Dehydrators Dehydrators and Pumpsand Pumps14 Bcf14 Bcf


Compressor Rod PackingCompressor Rod PackingWhat is the Problem?What is the Problem?

Rod packing accounts for 12% of reciprocating compressor Rod packing accounts for 12% of reciprocating compressor emissions in production sectoremissions in production sector Over 44,000 reciprocating compressors in natural gas industryOver 44,000 reciprocating compressors in natural gas industry Over 31,000 compressors in gas production sectorOver 31,000 compressors in gas production sector

CompressorStation

CompressorStation

Production

31,750 Compressors Processing

4,250 Compressors

Transmission & Storage

8,000 Compressors

Distribution

0 Compressors

CompressorStation


Methane Losses from Methane Losses from Rod PackingRod Packing

Reciprocating compressor rod packing leaks Reciprocating compressor rod packing leaks some gas by designsome gas by design Newly installed packing may leak 11 cubic feet Newly installed packing may leak 11 cubic feet

per hour (cf/h)per hour (cf/h) Worn packing has been reported to leak up to Worn packing has been reported to leak up to

900 cf/h900 cf/h

Distance PieceDistance Piece

Piston RodPiston Rod

(Side View, Cut in Half)(Side View, Cut in Half)

OILOIL

CylinderCylinder

SuctionSuction

DischargeDischarge

PistonPiston

Rod Packing CaseRod Packing Case


Reciprocating Compressor Reciprocating Compressor Rod PackingRod Packing

LubricationLubrication

FlangeFlange

GasGasLeakageLeakage

(Side View, Cut in Half)(Side View, Cut in Half)

Cylinder WallCylinder Wall

High Pressure High Pressure

Gas Inside Gas Inside

CylinderCylinder

Two RingsTwo Rings

(In Three Segments)(In Three Segments)

SpringsSprings

Packing CupPacking Cup

Piston RodPiston Rod

A series of flexible rings fit around the shaft to A series of flexible rings fit around the shaft to prevent leakageprevent leakage

Rings held in place by springs and packing cupsRings held in place by springs and packing cups


Methane Loss Sources from Methane Loss Sources from Rod PackingRod Packing

Leakage occurs Leakage occurs Around packing case through nose gasketAround packing case through nose gasket

Between packing cupsBetween packing cups

Around rings due to movement of the piston rodAround rings due to movement of the piston rod

Between rings and piston rodBetween rings and piston rod

Leaking gases escape either through vents on Leaking gases escape either through vents on the packing flange or into the distance piecethe packing flange or into the distance piece

Leakage gradually increases from normal wear Leakage gradually increases from normal wear of rings and rodof rings and rod


Leak rates from rod packing eventually Leak rates from rod packing eventually increase to a level that economically justifies increase to a level that economically justifies packing replacementpacking replacement Frequency of economic replacement depends Frequency of economic replacement depends

on lubrication, rod alignment, rod wear, rod on lubrication, rod alignment, rod wear, rod material and economic hurdle-ratematerial and economic hurdle-rate

Benefits of economic packing replacementBenefits of economic packing replacement Reduced methane emissionsReduced methane emissions Gas savings with lower leakage ratesGas savings with lower leakage rates Extended service life of compressor rodsExtended service life of compressor rods

Methane Recovery with EconomicMethane Recovery with EconomicRod Packing ReplacementRod Packing Replacement


Rod Packing Replacement Decision Rod Packing Replacement Decision ProcessProcess

Compare current leak rate to initial leak rateCompare current leak rate to initial leak rateto determine leak reduction expectedto determine leak reduction expected

Monitor and record baseline packing Monitor and record baseline packing leakage and piston rod wearleakage and piston rod wear

Assess costs of replacementsAssess costs of replacements

Determine economic replacement thresholdDetermine economic replacement threshold

Replace packing and rods where cost-effectiveReplace packing and rods where cost-effective


Establish Baseline LeaksEstablish Baseline Leaks

Step 1: Monitor and record baseline leakage Step 1: Monitor and record baseline leakage and rod wearand rod wear

Measure leaks immediately after installing new Measure leaks immediately after installing new seals (or new rods and seals)seals (or new rods and seals)

Monitor rods periodically for shaft dimensions Monitor rods periodically for shaft dimensions and surface roughness when replacing rings and surface roughness when replacing rings

““Out-of-round” rod seals poorly causing uneven wear Out-of-round” rod seals poorly causing uneven wear and allowing more leakage and allowing more leakage

It also causes uneven wear on the seals shortening It also causes uneven wear on the seals shortening the life of both seal and rodthe life of both seal and rod


Establish Leak Reduction ExpectedEstablish Leak Reduction Expected

Step 2: Compare current leak rate to initial Step 2: Compare current leak rate to initial leak rate to determine leak reduction expectedleak rate to determine leak reduction expected

Leak Reduction Expected (LRE) = Current Leak Leak Reduction Expected (LRE) = Current Leak Rate (CL) – Initial Leak Rate at the last ring/ rod Rate (CL) – Initial Leak Rate at the last ring/ rod replacement (IL)replacement (IL)

Example: The current leak rate is measured as Example: The current leak rate is measured as 50 cf/h, the same component leaked 10 cf/h 50 cf/h, the same component leaked 10 cf/h when first installedwhen first installed

LRE = 50 cf/h – 10 cf/hLRE = 50 cf/h – 10 cf/hLRE = 40 cf/hLRE = 40 cf/h


Step 3: Assess cost of replacementsStep 3: Assess cost of replacements Packing ring replacement costs depend on the Packing ring replacement costs depend on the

number of cylinders and the type of ringnumber of cylinders and the type of ring Cost of a set of rings:Cost of a set of rings: $ 500$ 500 to to $ 800$ 800

(with cups and case)(with cups and case) $1500$1500 to to $2500$2500

Rod replacement costs vary with rod dimension Rod replacement costs vary with rod dimension and rod typeand rod type Cost of Piston Rod:Cost of Piston Rod: $1800$1800 to to $3500$3500

Installation costs roughly equal equipment costsInstallation costs roughly equal equipment costs

Assess Costs for Economic Rod Assess Costs for Economic Rod Packing ReplacementPacking Replacement


Replacement Threshold for Economic Replacement Threshold for Economic Rod Packing ReplacementRod Packing Replacement

Step 4: Determine economic replacement thresholdStep 4: Determine economic replacement threshold Economic replacement threshold defines the specific Economic replacement threshold defines the specific

point at which it is cost effective to replace rings and point at which it is cost effective to replace rings and rodsrods

Discounted cash flow methodDiscounted cash flow method Economic replacement threshold (cfh)Economic replacement threshold (cfh)

= (CR*DF*1,000) / (H*GP)= (CR*DF*1,000) / (H*GP) where, CR = cost of replacement ($)where, CR = cost of replacement ($)

H = hours of compressor operation per H = hours of compressor operation per yearyear

GP = gas price ($/Mcf)GP = gas price ($/Mcf) DF = discount factor = i*(1+i)DF = discount factor = i*(1+i)n n / (1+i)/ (1+i)nn – 1 – 1 i = discount rate or company hurdle ratei = discount rate or company hurdle rate n = payback period selectedn = payback period selected


Is Recovery Profitable?Is Recovery Profitable? Step 5: Replace packing and rods when cost Step 5: Replace packing and rods when cost

effectiveeffective Example:Example:

Rod and RingsRod and RingsRings:Rings: $1,200$1,200Rod:Rod: $7,000$7,000Gas:Gas: $3/Mcf$3/McfOperating:Operating: 8,500 hrs/yr8,500 hrs/yr

Rings OnlyRings OnlyRings:Rings: $1,200$1,200Rod:Rod: $0$0Gas:Gas: $3/Mcf$3/McfOperating:Operating: 8,500 hrs/yr8,500 hrs/yr

Based on 10% interest rateMcf = thousand cubic feet, cfh = cubic feet per hour

Leak Reduction Expected Payback Period(cfh) (years)52 127 219 315 412 5

Leak Reduction Expected Payback Period(cfh) (years)354 1185 2129 3101 485 5


Industry Experience on New Rod Industry Experience on New Rod Packing Material and CoatingsPacking Material and Coatings

New packing materials can improve the life New packing materials can improve the life and performance of equipmentand performance of equipment Carbon impregnated TeflonCarbon impregnated Teflon®® rings cost almost rings cost almost

the same as bronze rings but last about one the same as bronze rings but last about one year longeryear longer Other factors like proper installation, cooling and Other factors like proper installation, cooling and

lubrication play an important rolelubrication play an important role

Piston rods coated with tungsten carbide or Piston rods coated with tungsten carbide or chromium increase service life of rodschromium increase service life of rods

Axially loaded packing installed in one of the Axially loaded packing installed in one of the last two cups reduces emissionslast two cups reduces emissions


Axially Loaded Three Ring Rod PackingAxially Loaded Three Ring Rod Packing


Discussion QuestionsDiscussion Questions

What is your practice on replaced rod What is your practice on replaced rod packing in reciprocating compressors?packing in reciprocating compressors?

How can the Lessons Learned study be How can the Lessons Learned study be improved upon or altered for use in your improved upon or altered for use in your operation(s)?operation(s)?

What are the barriers (technological, What are the barriers (technological, economic, lack of information, regulatory, economic, lack of information, regulatory, etc.) that are preventing you from etc.) that are preventing you from implementing this technology?implementing this technology?

Reducing Emissions from Compressor Rod Packing Lessons Learned from Natural Gas STAR Producers...

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