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Kane Ramsey and David Young v3 pdf - Enscope Limited - The layout of compressor stations and optimum offsite modularisation vs onsite build to increase construction efficiency

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Kane Ramsey and David Young delivered the presentation at 2014 Gas Compressor Stations Conference. …

Kane Ramsey and David Young delivered the presentation at 2014 Gas Compressor Stations Conference.

The Gas Compressor Stations Conference is the only conference specifically dedicated to the design, build and maintenance of gas compressor stations.

For more information about the event, please visit: http://www.informa.com.au/gascompressors14

More in: Business , Design
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  • 1. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 1 Selected Lessons Learnt from the Delivery of Gas Compressor Stations 30th April 2014
  • 2. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Observations from our personal experience as both Turnkey EPC Contractors and Owner Representatives • Each of us have direct experience working in a variety of roles on around 40 compressor stations projects over the past 20 years • David will touch on some of the engineering and design aspects, particularly modularisation • Kane will focus more on the commercial side and the consequent affect on the schedule • What has gone well and what hasn’t gone well 2 Introduction
  • 3. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Like all resources projects the key objectives in the delivery of compressor stations are; - lowest cost - best quality - shortest timeframe (safety is a given) • These objectives are generally not aligned • We believe that the focus should be on a “lowest cost per TJ compressed” basis 3 Key Objectives
  • 4. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Decision on Contracting Strategy should be taken early – ideally in the concept development stage • Factors to be considered include; - Owner’s appetite for risk - Schedule objectives - Capacity of the owner’s team to self-perform - Bankability requirements - Company procurement policies - Existing relationships - Resource availability 4 Contracting Strategy
  • 5. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Options available for the owner to consider include; - tendered engagement of consulting engineers and contractors on a Lump Sum basis - tendered engagement on a Schedule of Rates or Incentivised basis (risk/reward) - engagement of a head contractor on a Design and Construct basis – either tendered or sole-sourced - engagement of a head contractor on a Turnkey EPC basis - engagement on an EPCM basis - use of a full project Alliance model 5 Contracting Options
  • 6. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • There are many pro’s and con’s to the contracting model adopted • Compressor stations are generally not technically complex • Success factors include; - don’t reinvent the wheel – standardisation in concept from one project to the next has merit - early engagement of the contractor - use contractors that have previously performed - for contractors the carrot usually works better than the stick - flexibility in contract model to allow pre-commissioning to start before the construction is finished 6 Contracting Options (cont.)
  • 7. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Neither the owner nor the contractor wants to take risk – without suitable compensation • Risk apportionment workshops prior to contract award are a key success factor • Establishing possible scenarios and role play can help inform these workshops • Risk should lay with the party best placed to manage (or mitigate) • Residual risks should lay with the owner • Drafting the contract should then follow 7 Balance / Risk Apportionment
  • 8. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • To the extent possible contracts should be balanced • AS4900 suite provide a good basis, for example AS4902 (Design and Construct) includes; - Principal Project Requirements - Requirement for a “functional” design - Flexibility allowing a variety of contract models - Indemnity provisions for both parties - “Good faith” superintendant - No payment for unfixed plant • Ultimately, it is the owner that sets the terms… 8 AS4900 Suite of Contracts
  • 9. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Outside cost, time is usually the key project driver • The contract model selected has a direct bearing on the total time for delivery • The 3 slides that follow are reasonable for typical midline boost compression with a single GT driven compressor • NB: civils and earthworks disciplines removed for clarity 9 Typical Delivery Timeframes
  • 10. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Total delivery period of ~24 months 10 Traditional Sequential / Tendered approach FID 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 MONTHS FEED Detailed Design PlaceOrder for Compressor(s) Compressor Manufactureand Delivery Other LongLead EquipmentProcurement CompileConstruction ITT Completion ofDetailed Design Tender Period Negotiateand Award to Successful Contractor Construction Contractor ProjectTeamEstablishment OffsitePipingFabrication Arrival ofCompressors on site Arrival ofRemainingLongLead Equipmenton Site Mechanical and PipingInstallation Electrical /InstrumentInstallation Construction Contractor Practical Completion Precommissioning Gas Commissioning PipeAvailable CompressorsAvailable PracticalCompletion ReadinessforOperation TRADITIONAL SEQUENTIAL DELIVERY WITH COMPETITIVE TENDER APPROACH
  • 11. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Total delivery period of ~21 months 11 FID 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 MONTHS FEED Detailed Design PlaceOrder for Compressor(s) Compressor Manufactureand Delivery Other Long Lead EquipmentProcurement CompileConstruction Scopeof Work / Engagementterms Completion of Detailed Design Contractor Pricing and Finalisation of TargetPrice Construction Contractor ProjectTeamEstablishment OffsitePiping Fabrication Arrival of Compressors on site Arrival of Remaining Long Lead Equipmenton Site Mechanical and Piping Installation Electrical / InstrumentInstallation Construction Contractor Practical Completion Precommissioning Gas Commissioning PipeAvailable CompressorsAvailable PracticalCompletion ReadinessforOperation SOLE SOURCE TARGET PRICE / INCENTIVE APPROACH Sole Source Target Price approach
  • 12. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Total delivery period of ~19 months 12 FID 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 MONTHS Design and ConstructContractor Selected Prior to FID FEED Detailed Design PlaceOrder for Compressor(s) Compressor Manufactureand Delivery Other LongLead EquipmentProcurement Completion of Detailed Design OffsitePipingFabrication Arrival of Compressors on site Arrival of RemainingLongLead Equipmenton Site Mechanical and PipingInstallation Electrical / InstrumentInstallation Construction Contractor Practical Completion Precommissioning Gas Commissioning PipeAvailable CompressorsAvailable MechanicalCompletion ReadinessforOperation DESIGN AND CONSTRUCT APPROACH, CONTRACTOR SELECTED PRIOR TO FID Design and Construct approach
  • 13. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS A few selected observations; • Project success comes down to the people not the logo • There is a propensity to under-resource project teams • Engineering leading into procurement tends to drive the schedule more than any other single factor • Compressor delivery is rarely the critical path • The receipt date of vendor data can be overlooked • Valve delivery is nearly always a problem … and lastly – projects tend to go well when the contractor makes a reasonable profit. 13 Other Observations
  • 14. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Modularisation of compressor stations can be done in many ways and to varying degrees generally with the goal of reducing the overall project cost and delivery time. • Typically the mechanism by which the savings are generated is by reducing the number of the high cost and lower efficiency site hours and transferring a large proportion of these hours to a low cost, highly efficient workshop (locally or overseas). • In our experience the success of this modularisation process to meet the reduction in cost and time goals varies depending on the characteristic of the individual project and the manner in which the modularisation is executed. • We will look at 3 different types of Modularisation and assess there benefits for use in the delivery of Compressor Station Projects. 14 Modularisation
  • 15. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Large Module for LNG Storage Facility Boil Off Gas (BOG) compressor. Made Overseas and barged in. Weighs ~ 1,500 tons • Structural fabrication and Piping fabrication, PWHT, NDT, hydro testing surface treatment, final assembly and Instrumentation hook-up is completed offsite.15 Large Modules BOG COMPRESSOR BUILDING BOG COMPRESSOR MODULE
  • 16. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 16 Large Modules
  • 17. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • “Skids” are generally designed and manufactured to fit on a road transportable truck (say 2.4m -4.5m wide) and weight between 5-50 tons (single lift). Some do go up to 150T. • Structural fabrication and Piping fabrication, PWHT, NDT, hydro testing surface treatment, final assembly and E&I hook-up (to on-skid JB) is completed offsite to maximise work shop hours and reduce site hours. 17 Skids TYPICAL METERING SKID
  • 18. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 18 TYPICAL FUEL GAS SKID Skids
  • 19. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS Piping and Support fabrication, PWHT, NDT, hydro testing and surface treatment is completed of site with support installation, final bolt-up and electrical hook up completed at site. Reduces or removes the requirement for site fit and weld, PWHT, NDT, Hyro- testing and painting. 19 Complete Offsite Fabrication
  • 20. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 20 Can be used very effectively for brownfields work, especially when used in conjunction with laser scanning for tie-ins. Complete Offsite Fabrication
  • 21. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 21 Complete Offsite Fabrication
  • 22. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS Modularisation Experiences • Our experience of modularisation for compressor stations has seen mixed results. Projects these days seem to have tighter schedules and limited budgets (as a result of higher costs). • Orders are often placed late, vendor data comes in late, designs then run late, equipment arrives late, so modules often get shipped late or in an incomplete state. • This results in an erosion of the potential savings from modularisation. • Often the additional cost in added design and increase in structural steel is greater that the savings in marginal labour cost between the workshop and site. • To many COW’s in the BOG!! 22
  • 23. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS Modularisation Summary • We do not believe that large scale modularisation provides a cost effective or timely solution for compressor station design and construction. • Small to medium sized “skids” can provide a cost effective solution for compressors station particularly if there is a standardised design with known vendor information to allow early commencement of fabrication. • The use of complete offsite fabrication with the majority of all the Welding, PWHT, NDT, Hydro and Surface treatment being completed in the workshop, can provide a very cost effective solution for compressor station construction especially for brown fields work when combined with laser scanning to provide accurate fabrication dimensions. 23
  • 24. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Consider a 500km free flow pipeline • Front end compression to 14 MPag • Delivery at 8 MPag Assume Free flow capacity of 250 TJ/d • Simple pipeline pressure profile 24 Parallel vs Series • Selecting Parallel or Series configuration for your midline compressor station is an important decision to be made early in a projects life to ensure the design best meets the facilities functional requirements. 500250
  • 25. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Expansion required from ~250 TJ/d to ~300 TJ/d • Install mid-line compressor station with a single compressor unit or 2 units operating in duty and standby. • Pipeline pressure profile shows a typical ‘sawtooth’. • Compressor station suction pressure being drawn down, discharge pressure increases above free flow pressure 25 500250 Parallel vs Series
  • 26. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Single unit operation • The compressor wheeling or staging is selected to optimise efficiency at normal Operating Condition • Suitable surge margin is achieved 26 Single Unit 78% 80% 76% 74% Surge control line Area of choke flow or stonewall Surge 500250 Parallel vs Series
  • 27. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Simplified midline centrifugal compressor station configuration (valves removed). • Pig Launcher and Receiver • Suction scrubber/ filter/coalescer • Compressor • Aftercooler • Anti surge and cooled recycle 27 Parallel vs Series
  • 28. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • If further expansion is required from ~300 TJ/d to ~350 TJ/d • Most cost effective option maybe to install a second compressor at the existing midline compressor station • Pipeline ‘sawtooth’ shows compressor station suction pressure being FURTHER drawn down, discharge pressure increases above SINGLE UNIT pressure 28 500250 Parallel vs Series
  • 29. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Should the second unit be installed in SERIES with the existing unit or in PARALLEL? • SINGLE unit typical configuration 29 Parallel vs Series
  • 30. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • TWO units in PARALLEL- typical configuration • Common Suction Header and a common Discharge Header. • Units see the same suction and discharge pressure 30 Parallel vs Series
  • 31. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • TWO units in SERIES- typical configuration • Discharge of the upstream compressor delivers into the suction of the down stream compressor • Let’s consider the compressor wheelmaps for parallel vs series operation 31 Parallel vs Series
  • 32. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Initial configuration (single unit operation) operating point is located at optimal efficiency point on wheelmap • Two units in PARALLEL means less flow per unit but higher head • If the original wheeling is used for the new PARALLEL configuration, each unit will likely end up operating near surge and may require continuous recycle • This would result in inefficient operation as power is consumed to recycle gas and we are no longer operating in the highest efficiency envelope on the wheelmap. 32 Original Single Unit Actual Point Recycle required Required Point Surge Parallel
  • 33. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Continuous recycle is a poor outcome so the existing unit would likely need to be rewheeled or restaged. • The new units wheeling or staging would be selected for optimum efficiency for 2 units operating in PARALLEL (lower flow, higher head) • The issue now is that if the lower flow rate of 300TJ is required, the new unit or the existing re- wheeled unit are operating at a lower efficiency close to choke flow. 33 Original Single Unit No re wheel recycle 2 unit parallel operating point New Wheel map Parallel
  • 34. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Two units in SERIES means less head across and more mass flow through each of the units. • In SERIES configuration, the existing wheelmap may provide a suitable compressor selection for the upgraded operating conditions. • Avoids the need to rewheel the existing unit as both units operate at close to there highest efficiency envelope • Both units can be operated efficiently as a single unit if a lower flow rate is required. • It is recommended that the original unit should be the installed as the down stream unit as this is likely to see less change in the operating point. • So where is the downside? Stopping a Unit! 34 Original Single Unit Upstream Unit Down Stream Unit Series
  • 35. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Let’s consider what happens when both compressors are operating in PARALELL with our new optimised wheel map • What happens to the operating unit when the other unit has a FAST STOP/trip or is taken off load? • Initially the operating unit still sees the same suction pressure and delivers the same head. The flow through the station will effectively be halved. • Over time, the discharge pressure will reduce as the second unit is no longer assisting and the single operating unit will deliver more flow but at a reduced head. • No upset conditions created due to a single unit tripping or being taken off load 35 2 Units in Parallel Original Single Unit Single operating unit after trip Parallel vs Series
  • 36. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Compressors operating in SERIES • What happens to the operating unit when the other unit has a FAST STOP or is taken off load? • Immediately, the operating unit sees a large increase in head across the compressor • A unit stopping has created a potential surge event on the operating unit • The station will go into recycle (and flow may completely stop) until the head washes out and the single compressor can generate enough head to create station flow. 36 Unit in Series Compressor instantly moves towards surge Single operating unit after trip Required point after trip Parallel vs Series • Operating units in Series should include design measures to actively protect the units from these trips and the resultant potential surge events. • Surge margin equalisation and load sharing is recommended for both series and parallel operation.
  • 37. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 37 • In most application including upstream or front of line Compressor Stations Parallel configuration is likely to be the best option. • For midline compressor stations which experience very little variance in pipeline flow and where the fully compressed pipeline design only has one operating unit (ie duty/standby) parallel configuration will likely be the best option. • However, for midline compressor station with variable pipeline demand and where the fully compressed pipeline design has multiple units operating at each compressor station configuring your compressors in series should be considered. Parallel vs Series Summary
  • 38. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS • Unit Aftercoolers- has a single set of coolers per compressor train. • Unit Anti Surge • Unit Cooled Recycle • Station Aftercoolers- a single set of coolers for the entire station • Unit Anti Surge • Station Cooled Recycle 38 Unit vs Station Aftercoolers
  • 39. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 39 Unit vs Station Aftercoolers
  • 40. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS UNIT AFTERCOOLERS What are the benefits? • Simple to operate and maintain • Each set of coolers are designed for the individual compressor making selection easier. • No start up or cool down issues What are the downsides? • Lower utilisation of installed capacity resulting in reduced station capacity for the given capital cost (where the equivalent amount of coolers are installed). • Lower availability- If a cooler fan from one train fails and the compressor from the other train fails the station may not be operable at full capacity. 40 Unit vs Station Aftercoolers
  • 41. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 41 STATION AFTERCOOLERS Unit vs Station Aftercoolers
  • 42. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS STATION AFTERCOOLERS What are the benefits? • Lower capital cost (if only one cooler per compressor is provided) or, • If cooler bays for both units are installed you get better utilisation of the asset and more station cooling with one unit operating. • Availability is greater (i.e. Compressors do not rely on an individual aftercooler) What are the downsides? • Issues with cool down and start up due to temperature build up in anti surge line (particularly with parallel configuration). • Maintenance is more complex as process isolation of the cooler units will take out the entire station (unless additional valving is provided). 42 Unit vs Station Aftercoolers
  • 43. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS ON-SKID CLOSE FIT ENCLOSURES What are the benefits? • Low cost option • Medium level of acoustic attenuation • Good for ventilation What are the downsides? • Poor access for maintenance • Noise maybe a problem 43 Compressor Enclosures
  • 44. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS OFF-SKID CLOSE FIT ENCLOSURES What are the benefits? • Good acoustic noise attenuation • Medium for ventilation • Moderate level of access for maintenance What are the downsides? • Middle range cost option 44 Compressor Enclosures
  • 45. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS COMPRESSOR HALL What are the benefits? • Good access for maintenance • Good acoustic attenuation What are the downsides? • Highest cost option • Potentially higher insurance costs due to multiple compressors operating in close proximity (escalation) • Maintenance issues if the other unit/s are running • Large amounts of ventilation maybe required 45 Compressor Enclosures
  • 46. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS COMPRESSOR SHEDS What are the benefits? • Good ventilation (natural ventilation – i.e. mechanical ventilation system not required) • Low cost option • Good access for maintenance What are the downsides? • Low acoustic noise attenuation 46 Compressor Enclosures
  • 47. DEVELOPMENT | ENGINEERING | MANAGEMENT | COMPLETIONS 47 Conclusion • Key decisions such as contracting strategy, degree of modularisation, compressor and aftercooler configuration and the types of enclosures to be used are critical to the overall success of a compressor station project. • We would recommend careful consideration and selection of these options be made very early in the project life cycle (ie before commencement of the FEED) so as to increase the chances of overall project success. • All of the various options discussed in this presentation have there respective advantages and disadvantages and we would not promote any particular option. • In our experience the biggest factor in a projects success is ensuring it is suitably resources with experienced personnel from the outset, the key decisions are made early and these plans are executed in a timely manner.