System-by-system commissioning with progressive handover

How does System-by-system commissioning with progressive handover work, step by step?

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   Step 1: Divide the plant into systems and fix the sequence

   The designer, the technology supplier, the contractor and the operator agree how the plant is divided into systems and the order in which they will be proved. The sequence follows dependency, not geography: utilities before what they serve, electrical before what it powers, nitrogen and safety systems before anything containing hydrogen. On most projects this system breakdown is agreed early enough to shape the construction programme, because building in a different order to the one commissioning needs is expensive.

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   Step 2: Build the commissioning organisation and the permit interface

   Commissioning is run by a team with its own leadership, drawn from the operator, the contractor and the technology supplier, with the split of responsibility written down before anything starts. Most importantly, the point at which construction control gives way to the operator's permit system is defined for each system. Everyone on site has to know which regime applies where, and the arrangement for telling them - marking, demarcation, briefing and access control - is set up before the first handover.

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   Step 3: Complete and check each system mechanically

   Before a system can be prepared it has to be finished and verified as finished: installation complete against the drawings, joints recorded, supports set, instruments installed and labelled, and the outstanding items list closed or accepted. This check is done system by system against a defined list rather than by walking round. On most projects a system that is declared complete when it is not is the single biggest cause of commissioning delay, because the team discovers it at the worst possible moment.

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   Step 4: Prove electrical, control and protective functions

   Electrical distribution, instrumentation, control and protective functions are energised and proved for each system, including the detection, alarm and shutdown arrangements. Signals are demonstrated end to end rather than assumed from a loop drawing, and protective functions are shown to do what the safety design says they do. This work happens before the system contains anything hazardous, which is why the sequence puts it where it does.

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   Step 5: Prepare the system and prove it tight

   Each system is cleaned, dried and prepared for service as the designer and the technology supplier require, and its integrity is established before anything hazardous is introduced. Purging, inerting and leak testing are the most hazardous activities on the whole project. They are planned and executed by specialists under the operator's permit system, to procedures written for that plant and approved for it. There is no generic version of this work and none of it is described here.

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   Step 6: Introduce hydrogen under the operator's control

   First fill of any system is carried out by specialists under the operator's permit system to procedures written for that plant. It is the point at which a system stops being a construction product and becomes a hazard that behaves nothing like the rest of the site. Access is controlled, the area is cleared to whatever extent the procedure requires, and the operation proceeds only when every prerequisite has been demonstrated and recorded.

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   Step 7: Hand the system over as a documented event

   Handover is a formal transfer with the completion records, the test results, the joint register, the device certificates, the settings and the outstanding items attached. From that moment the system is operating plant: access changes, the permit system applies, and any remaining work is done under the operator's control. Marking and briefing tell everyone on site what has changed. On most projects several handovers happen while construction continues elsewhere, so the boundaries have to be unmistakable.

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   Step 8: Repeat through the sequence to full plant operation

   Each handover shrinks the construction site and grows the operating plant until the last system is transferred. Because the two coexist for months, coordination between the commissioning team and the remaining construction works is a daily activity rather than a periodic meeting. The final stage is a demonstration that the plant as a whole performs as intended, followed by the transfer of the documentation, spares, training and maintenance regime the operator will run on.