Hot commissioning

How does Hot commissioning work, step by step?

1. 1

   Step 1: Hold a formal readiness review before first firing

   First firing does not happen because the plant looks ready. It happens after a formal review at which the commissioning team, the operator, the plant supplier and the contractor confirm that the necessary systems are turned over and proved, that protections and emergency systems are tested and available, that the outstanding item list contains nothing that prevents firing, that the procedures are approved and the personnel are trained and briefed, and that the area is clear. The review is minuted and the decision is recorded.

2. 2

   Step 2: Admit fuel and fire the plant under a controlled procedure

   Fuel is admitted to the plant and the unit is fired for the first time by the commissioning team and the plant supplier under the operator's permit-to-work system, following an approved procedure with defined roles and defined abort criteria. The area is cleared of all personnel who are not part of the operation and other work in the vicinity is stopped. This is a specialist operation carried out by people qualified for it, and its detail belongs to the operator's procedures rather than to the construction method.

3. 3

   Step 3: Bring the plant up in planned stages

   After first firing the plant is raised in defined stages set by the plant supplier, with hold points between them. Rates of change are limited to protect thick components from differential expansion, and those limits are applied exactly as issued. At each hold the team takes readings, checks behaviour against expectation and decides whether to proceed. The ability to stop and come back down is maintained throughout, and stopping is treated as a normal outcome rather than a failure.

4. 4

   Step 4: Watch expansion, movement and supports as things get hot

   Pipework, casings and structures move as they heat, and this is the first time they ever have. Expansion is monitored at the points the designer identified, spring hangers are checked as they take up their hot positions, guides and anchors are watched, and clearances are confirmed. Anything restrained that should be free, or free that should be restrained, shows itself here. Hot walkdowns are carried out by trained personnel with the plant in a defined state, and findings are acted on before going further.

5. 5

   Step 5: Find and deal with hot leaks safely

   Joints that were tight cold commonly weep once hot, and finding them is part of the process. Leaks are located from a safe position using the operator's procedures, never by approaching a suspect joint on a hot system. Anything requiring work is dealt with by taking the affected system to a safe state, isolating it under permit and then repairing it. The temptation to make a quick adjustment on a hot line is where people get seriously hurt, and it is designed out by the permit regime.

6. 6

   Step 6: Tune controls and prove protections under real conditions

   Control loops that could only be roughly set cold are now tuned against real process behaviour, and the plant's response to load changes and disturbances is observed. Protections and trips are demonstrated under the conditions they are actually meant to act in, following planned tests with agreed criteria. Any setting is applied by the operator under their own change control. The operating team runs the plant during these tests wherever possible, which builds the familiarity they will need.

7. 7

   Step 7: Run the plant through its operating envelope

   Once stable the plant is taken through its intended operating range, including starts, stops, load changes and the transitions between operating modes. Behaviour is recorded and compared with what the plant supplier predicted. This is where the practical characteristics of the machine become known - how quickly it responds, how it behaves during a start, where it runs comfortably and where it does not. That knowledge is captured for the operating team rather than left in the commissioning team's heads.

8. 8

   Step 8: Manage remaining construction work under permit

   There is always work left, and it now has to be done in a live plant. Each item is assessed, planned and executed under the operator's permit system with the plant in a defined state, sometimes waiting for an outage. Construction personnel working in commissioned areas are inducted into the permit regime and escorted or supervised as the operator requires. Most projects find this work takes several times longer than the same work would have taken before turnover, and they plan for that rather than discovering it.