Amin Almasi v2 - FYFE Earth Partners - Commissioning of Compressor Stations


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Amin Almasi 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:

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Amin Almasi v2 - FYFE Earth Partners - Commissioning of Compressor Stations

  2. 2. COMMISSIONING OF COMPRESSOR STATIONS Commissioning is the use of a disciplined, systematic and professional methodology, to convert the constructed compressor station into a working compressor station within a gas transmission system. Three stages of commissioning: • Pre-commissioning. • Core commissioning. • Start-up. Use: disciplined, systematic method. Avoid: Trial and error during commissioning.
  3. 3. COMMISSIONING OF COMPRESSOR STATIONS PRE-COMMISSIONING: The whole process during the end of construction and installation phase that prepares a compressor station to move to the core (main) commissioning phase. CORE (MAIN) COMMISSIONING: Systems of a compressor station are first put into operation. The power and utilities are provided and the compressor station is made operational for the first time. Start-up: the compressor station is brought into actual operation. COMMISSIONING PREPARATION: Development of a commissioning plan, preparation of commissioning documentations, development of operating procedures, and handover procedures.
  4. 4. COMMISSIONING OF COMPRESSOR STATIONS Commissioning is a series of checks, tests and final activities that confirm a compressor station is fit for operation and finally prepare a compressor station for the start-up and continued operation at rated conditions. Design flaws, manufacturing hidden problems and installation errors will show themselves at commissioning. Modifications and corrections should be implemented in a very busy schedule simultaneously with commissioning activities. The key is a standardized and systemized approach to “commissioning”.
  5. 5. COMMISSIONING OF COMPRESSOR STATIONS • A correct and realistic plan for the commissioning. • A correct mixture of various engineers including machinery, mechanical, piping, electrical, instrument, operation and others are required for the commissioning team. • Properly empowering each commissioning team member to implement their responsibilities. Commissioning include: o cleaning activities. o commissioning punch-listing. o acceptance tests. o handover to operation.
  6. 6. COMMISSIONING OF COMPRESSOR STATIONS Expected failures at commissioning: • Design, material and fabrication defects. • Assembly and installation errors. • Errors in operation (or Off-design operation). Definitely the third reason, “error in operation” is responsible for a large portion of all failures. Unintended conditions (temperature, pressure, velocity, load, and others) have caused many troubles and even catastrophic failures in compressor stations.
  7. 7. COMMISSIONING STAFF Commissioning staff should make themselves familiar with all site specific regulatory, codes, specifications, procedures and work instructions. Each commissioning engineer is actually the manager of a team of other engineers and technicians for an assigned commissioning task; the team is responsible for some packages and systems. Each commissioning team normally can handle 4 - 10 systems or packages. Operation and maintenance staff presence at a commissioning team is usually recommended.
  8. 8. COMMISSIONING BUDGET Commissioning cost: about 3.5-4.5% of the total capital cost. Commissioning budget: typically includes 65-75% manpower expenses; the balance could be consumable and rental equipment expenditures. Contingency: 15-35% of total commissioning budget. Modifications: significant factor.
  9. 9. SAFETY Safety: one of the most important aspects of commissioning activities. Commissioning representatives should attend various safety studies such as HAZOP (Hazard and Operability Studies) and the pre-start-up safety review (PSSR). The pre-start-up safety review (PSSR) is known as the last stage to catch and solve any safety issue before the start-up. 1. All handling and physical activities. 2. No equipment (no machinery) can be brought into service until its registration, documentations and safety checks have been completed.
  10. 10. MANAGEMENT OF CHANGE (MOC) The Management of Change (MOC) is one of challenges of commissioning stage, which require a very systematic and sound procedure. Changes could present many safety and reliability issues.
  11. 11. PRIORITY AND SCHEDULE At the end of the installation phase (85-90% of installation and completion), the site group should switch from their installation philosophy (which could be an “area” philosophy) to the philosophy needed for the commissioning. Pre-commissioning should be started at right time; it should not be too early, since a commissioning team involvement in the construction job could often be problematic. All engineering and installation changes should be implemented before pre-commissioning (to avoid re-works).
  12. 12. PRIORITY AND SCHEDULE For commissioning, a “backward” method is usually selected. In this way, the compressor station completion order could be: 1. Power, light, utility, water, air, and similar (including power generation packages – if any, utility packages and similar). 2. Control systems. 3. The gas discharge system (pipeline) or recycle loop for start-up and initial operation on the recycle mode. 4. The main units including compressor packages. 5. The gas suction system (pipeline). Commissioning team should necessarily be involved in final completion activities, tests, the cleaning or flushing jobs and last-stage inspections.
  13. 13. PRIORITY AND SCHEDULE Priority should be given to units and items that when completed and commissioned add value and can be utilized for the commissioning of other systems or can be handed-over to operation. A simple example: Sometimes lighting system has been one of the last systems delivered by installation team probably because of low progress associated to it or a miscalculation by the installation team that this might not be so important. Lighting systems: operational ASAP. Great benefits and safety. It reduces hazards and risks.
  14. 14. PRIORITY AND SCHEDULE Any activity that can cause a load on a machinery nozzle can change the alignment, which requires re-alignment. The proper time duration should be considered for the re-alignment of machinery. The time required for oil flushing of machinery is nearly always under-estimated. Correct time frames should be set for cleaning checks and internal inspections.
  15. 15. COMMISSIONING OF COMPRESSOR STATIONS At each commissioning stage, P&IDs, instrument and setting lists, commissioning “Logbook” and commissioning checklists should be at hand by commissioning team for the check and record. If everything is left to the handover, it could be common to experience many problems such as: • Control systems and control valves do not operate when requested. • Some piping may leak. • Some loops do not operate. • Alarms do not work.
  16. 16. COMMISSIONING PACKAGES Each commissioning package should be an operable entity or system that operation team can take over and run. A commissioning package is a system that can be finally tested and it should be big enough for the operation to take over. Well-known examples of modifications at commissioning are: • Undersized or oversized control valves, actuators, and equipment. • Incorrectly-configured instrumentation. • Control system problems. • Piping modifications.
  17. 17. COMMISSIONING PUNCH-LISTING The commissioning punch-listing is one of the most critical and important steps in any project. A well-prepared, properly-detailed punch-list is a good indication of a high- quality commissioning. For example, the lubrication in a machine, gasket presence, bolt tightening, piping supports, instruments, valve installation, labelling, and others, should be checked. Missing a gasket in a piping is a common punch-list item. The leak test is one of the first commissioning activities after the completion of punch-listing
  18. 18. COMPRESSOR COMMISSIONING Two important issues for packaged compressor trains are: • To identify and solve all issues and defects at the vendor shop. • To complete as much pre-commissioning activities at vendor shop as possible. A realistic performance test of compressor packages at the vendor’s shop (such as the ASME-PTC type-1 performance test for turbo-compressors) can facilitate the start-up; even for some compressors it could save 1-2 months during the commissioning and start- up. The cost of site hours for modifications and repairs for compressor packages is more than 3-times the cost in the manufacturer shop.
  19. 19. COMPRESSOR COMMISSIONING • DRY COMMISSIONING: Checks, tests and activities that are conducted where there is no job gas (natural gas) introduced to compressor packages. Examples of these tasks are interlock tests, control system sequence checks, short run of electric motors, initial operation of auxiliary systems such as lubrication oil system, cooling system, etc. • WET COMMISSIONING: The job gas (natural gas) is introduced to compressor packages and putting the compressors through their operating scenarios.
  20. 20. COMPRESSOR COMMISSIONING Four particular items that can cause confusion and problems: • Cleaning procedures and details. Many machinery and equipment have been damaged due to debris and dirt being left inside piping, equipment and machineries post installation activities. Sometimes it is very useful to take pictures and collect additional proof of cleanness of machinery casings or equipment internals which will be closed and sealed (particular final closure of machinery casings, vessels, etc). • Proper leak test. There have been concerns on leak testing since in case of any issues, the final result could be the “leak of gas”. • The client or operator witnessing performance tests of compressor packages. • Handover to operation.
  21. 21. COMPRESSOR COMMISSIONING The initial power-up of electrical and control hardware is important. Compressor Control include: fine tuning of control loops, re-checking and redefining control parameters; and alarm and trip settings. Special attention should be given to complicated control systems such as gas turbine control systems and variable-speed drive (VSD) control systems.
  22. 22. COMPRESSOR COMMISSIONING Machinery vibration could be unpredictable and can get out of control in a very short time. The rotating machine malfunctions can usually generate vibrations at sub- synchronous frequencies (such as ½×) or frequencies not related to the rotating speed. If vibration amplitude of any of these vibrations approaches around 20% of the 1× vibration amplitude, there could be an issue. Auxiliaries are responsible for more unscheduled shutdowns than the main machinery.
  23. 23. COMPRESSOR COMMISSIONING A significant issue is the lubrication oils (or generally “oils”); usually who purchase the “oils” and who will actually install the “oils” is ill-defined for many compressor stations. Lubrication oil skids could be fabricated by a sub-vendor (selected based on the lowest cost). Risk of static electricity build-up in oil system. Expansion joints and flexible hoses are poor options because of fatigue failure risks and other reliability and safety issues (such as a fast failure in a fire case).
  24. 24. START-UP Start-up protocols are procedures to provide guidance and instructions for bringing packages and installations online, starting from non-operational systems and packages (usually completed and pre-commissioned facilities). Start-up procedures and different shutdown procedures (normal shutdown, emergency shutdown, etc.) should also be prepared, checked and verified. After all these tasks and final checks of HAZOP and pre-start-up safety review (PSSR), compressor packages should be commissioned with job gas (wet commissioning).
  25. 25. HANDOVER TO OPERATION Handover of all commissioning documents (known as “as-commissioned”) to the operations team should be done in a very organized way, usually in a series of one-to- one and team meetings. Final checks and confirmations are the last stages of commissioning (commissioning close-out). Sets of critical documents prepared by a commissioning: 1. Training materials. 2. Operating procedures. 3. Handover procedures.
  26. 26. CASE STUDY ELECTRIC- MOTOR DRIVEN COMPRESSOR The use of an insulation resistance meter that helps to verify the condition of electrical insulation. The testing of correct rotational direction of all drivers. The lubrication oil should be at a right temperature, before the start of a compressor. The lubrication oil in oil reservoir should first be heated (usually above 20°C or sometimes 25°C or 28°C) by means of the oil heater. Case Study: commissioning of electric-motor driven turbo-compressors for a gas compressor station.
  27. 27. CASE STUDY ELECTRIC- MOTOR DRIVEN COMPRESSOR Dry gas seals installed inboard bearings and they require a separation seal section (barrier seal). The main function of the separation seal section (barrier seal) is to protect the dry gas seal against the lubrication oil (bearing); it also prevents the compressed gas leaking to the lubrication oil system. Even a small amount of lubrication oil can destroy a dry gas seal. Before a lubrication oil pump is started, the separation gas (usually “nitrogen”) system should be in operation and the separation gas should be supplied to barrier seals.
  28. 28. CASE STUDY ELECTRIC- MOTOR DRIVEN COMPRESSOR The initial test run of a turbo-compressor should be performed in the recycle mode. The turbo-compressor loop is isolated only at final discharge from the gas piping; for example, suction valves open and final discharge valve closed. The coolers, inter-stage coolers and discharge coolers should also be included in the turbo-compressor loop. Often, 3-4 hours running on a full recycle is recommended for the first operation of a turbo-compressor. All performance data should be recorded every 5-15 minute. It is advised to implement the emergency shutdown procedure for the first stop of a turbo-compressor.
  29. 29. CASE STUDY ELECTRIC- MOTOR DRIVEN COMPRESSOR Two important temperatures at the first operation: • The turbo-compressor suction temperature or the gas temperature should be within designated ranges. Since the turbo-compressor is working in the recycle mode, in case of a cooler problem the gas temperature can increase very fast (even 1°C per second have been reported for some turbo-compressors). • The lubrication oil temperature, as a rough indication, it should usually be kept below 65°C. During shutdown, the following verifications needed: o Measure and record the compressor run-down time. o Check the fast opening of anti-surge valve(s). o Check the opening of valves to flare and the closing of shut-off valves.
  31. 31. BONUS OIL FOR TRANSIENT CASES Coast down time (to stop) could be a risky period which can present serious challenges with respect to lubrication oil requirements and seal issues. For some turbo-machines, it could take 2-5 minutes to come to the stop. Transient issues such as a temporary electric power dip (for example, a 3-seconds electric power dip because of a network issue) can also present some challenges. The supply of an oil accumulator can be a good solution to face with some transient issues (or an oil-pump change-over problem). For vessel capacity, some codes recommended 4-seconds and some references advised 10- seconds or more. Probably 5-7 seconds could be sufficient for many rotating machines.
  32. 32. BONUS LUBRICATION Insufficient lubrication could cause bearing damages. These damages can progress very fast to a failure. If there is an insufficient lubrication flow, it will be an inadequate heat removal from a bearing, which could result in the discoloration, black colour on bearing components and the mechanical strength reduction. Low lubrication cases could show themself in many different forms, such as shiny areas, frosty areas, glassy surfaces, and others. It is necessary to ensure any machinery receiving a proper lubrication.
  33. 33. BONUS HIGH TEMPERATURE & HIGH VIBRATION Too high bearing temperature is a well-known signal in the commissioning of turbo- compressors. This could be because of a damaged bearing (such as wrong alignment) or the incorrect oil supply to bearing. Another important malfunction is too high vibration of a turbo-compressor. Possible causes: • Damaged turbo-compressor rotor assembly. • Misalignment. • Loose or broken foundation bolts. • A bearing damage or a bearing problem. • working at or near the surge area. • Malfunction of a vibration sensor, control and monitoring system.
  34. 34. BONUS DRY GAS SEAL The gas leakage through the primary seal vent line at expected flow-rates could be a good health indicator for dry gas seal systems. Too high leakage could be because of a primary seal problem; for example, a sticking stationary seal ring, a damaged seal ring or even a primary seal failure. Low gas flow through the primary vent line could also be an indication for a problem, such as a secondary seal issue or even its failure.