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Commissioning is a process whereby all machinery and the associated facilities are incorporated into an integrated system that functions according to its design and operating intent. The commissioning phase usually begins at the end of the installation phase and lasts through the training of operators and the first weeks of operation.
Commissioning strives for improved communication among parties for final design reviews, verification of installation, cleaning and flushing. It seeks to provide confirmation of functional needs, documentation of final activities, and the creation of pending lists.
All hidden problems surface at this stage and each requires consideration to facilitate start-up. Unforeseen activities often crop up. If commissioning of turbomachinery was done in isolation, it should be repeated later when integrated into the facility.
Pre-commissioning includes cleaning, flushing, testing and verification. It should begin about 80% of the way through the installation phase. Watch out for incomplete tasks or missing valves. All pressure parts should be subjected to pressure leakage testing. All items should be cleaned and flushed. Every stage of pre-commissioning needs documentation.
Foreign particles in piping, machinery and equipment must be guarded against. Small, hard particles can cause rapid wear and damage valve trim clearances or internal parts. To prevent contamination problems, clean all associated pipework and equipment so it is free of loose weld splatter, slag and particles. Clean and flush using chemical cleaning and force-full blowout.
The commissioning manager should be a specialist assigned to the task. The entire commissioning team should be onsite at the start of pre-commissioning. Participants should include machinery engineers, operations personnel, maintenance personnel, vendor representatives and start-up staff. A start-up and commissioning plan should be compiled during installation, which also identifies necessary spares, tooling and first fills.
In general, commissioning activities are divided into cold commissioning and hot commissioning. In cold commissioning, individual machines and systems are initiated in isolation without any job fluid. Only when this stage has been successfully completed can hot commissioning commence. In hot commissioning, integrated systems are run with job fluids for real operation.
Commissioning of all turbomachinery and packages should be subject to a full functional and performance test following its installation to confirm proper installation of all elements. The manufacturer’s certified shop test data should be available for comparison during site testing. This is usually witnessed by representatives of the owner and manufacturer.
Any installation issues are identified and corrected. A formal, written site acceptance test procedure is prepared. The performance test should include verification of all instrumentation, control and alarm functions and start-up in all designated modes, interfaces with other supervisory systems, operational verification and mechanical operability or completeness. Painful decisions often have to be taken, particularly relating to deviations and sub-standard system operation.
A pre-start-up safety review (PSSR) is conducted prior to commissioning and start-up to ensure that installations meet the original operating intent. A PSSR should catch and re-assess any potential hazard due to changes during engineering, installation and commissioning. A PSSR covers machinery, equipment, procedures and training. Risk mitigation measures should be provided, such as firewater and temporary firefighting systems.
Measurement, records, reports, forms, pending lists, checklists, handover notes and other forms of documentation play a major role in machinery commissioning. A record of vibration amplitude is not that useful; a better option is complete vibration data of amplitudes and frequencies. The best approach is full recording of vibration graphs, including vibration over time and associated frequencies. It is better to record more data than what might seem necessary rather than losing data later that cannot be recovered.
All tests should be witnessed. Performance tests are critical as final machinery acceptance depends on it meeting specified performance. All test reports, commissioning information and related documentation should be kept neat and organized.
Any failure of machinery to achieve its specified duty should be reported promptly. Contributory and root causes should be recorded. Action to remedy the situation should not delay completion, pre-commissioning or commissioning unless the fault is serious.
Shafts and rotor assemblies should be checked for freedom of rotation. Care should be taken to ascertain that no tools or materials are left in the piping, ducts and machinery as these can cause damage during start-up.
Check direction of rotation of the electric motor, preferably before connecting to a coupling. This is particularly important where thrust bearings are employed. The correct direction is usually shown by an arrow on the casing. When two machines are coupled, ensure the two shafts are correctly aligned at ambient temperature as well as running temperature.
A successfully operating control system requires proper start-up and testing, not merely the adjustment of a few parameters, such as set points and throttling ranges. A thorough plan is needed for checking, testing and verification of all logic and control systems.
Begin by checking every control device, instrument and piece of control hardware to ensure they are installed and connected correctly. Each electrical, electronic, hydraulic and pneumatic connection should be verified, as well as interlocks to machinery, pumps, electric motors and equipment.
After start-up closely monitor turbomachinery and assess performance against design expectations. Prolonged machinery operation at low loads should be avoided as damage can result.
After the various tests and pilot runs have been completed and operating criteria have been satisfactorily achieved, new machinery can be formally handed over for operation. This includes as-commissioned drawings, operating and maintenance instructions, lubrication schedules, spares lists, commissioning records, test certificates, certificates of origin and compliance, guarantees and warranties. A close-out report shows major events and problems encountered.
Shortly after start-up, commissioning should be formally terminated and normal operation officially announced. Factors influencing the timing of termination of commissioning activities include: Competence of permanent operating staff; reliability achievement; low likelihood of further modifications; acceptable routine quality standards; and agreement on maintenance strategies and tasks.