Contractor-led commissioning with client witness

How does Contractor-led commissioning with client witness work, step by step?

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   Step 1: Fix the commissioning scope and the witness list early

   Before anything is installed, the design team and the contractor agree what will be commissioned, to what criteria, and which of those tests the client or his representative will attend. The criteria themselves belong to the designer and the specification - the commissioning team proves performance against them, it does not invent them. The witness list names the systems, the stage at which each test happens, how much notice the client gets, and who signs. On most projects the notice period is a week or so for major tests and a couple of days for minor ones. Getting this written down at tender stage is what stops the end of the project turning into a negotiation.

2. 2

   Step 2: Build the commissioning programme into the construction programme

   Commissioning is programmed backwards from the completion date with the dependencies made explicit: permanent power, clean and flushed pipework, ductwork tested for leakage, controls software loaded and networked, and safe access to every item of plant and every terminal. Those are the readiness conditions. A commissioning period that shows on the programme as a single bar with no predecessors is a commissioning period that will be eaten. The contractor holds the programme and reports against it, and the design team checks that the activities on paper match the state of the building.

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   Step 3: Static completion and pre-commissioning checks

   Before any system is run, the installing subcontractors work through static checks: installation complete against the drawings, supports and fixings in, insulation done where it has to be done before enclosure, systems cleaned, flushed and filled, electrical installation tested and certified, and rotation and safety interlocks proven. The commissioning engineer will not start on a system that has not been signed off as statically complete, because a fault found at this stage costs an hour and the same fault found mid-balance costs a day. Records from these checks form the base of the handover file.

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   Step 4: Set to work and dynamic commissioning

   Plant is started and run, systems are proven to operate safely and stably, and the air and water distribution is regulated so that each part of the building receives what the design allocated to it. Balancing is iterative - adjusting one branch moves its neighbours, so the engineer works round the system repeatedly until the readings settle within the tolerances the designer has specified. Control systems are then set up and their sequences demonstrated: occupancy modes, setback, interlocks, alarms and the operation of the building under fault conditions. The commissioning engineer records readings as he goes, on the sheets agreed at the outset.

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   Step 5: Witnessed tests and demonstrations

   The agreed tests are re-run in front of the client or his representative. On most projects that means a sample of the balanced readings taken again at random, a demonstration of the control strategy, and the integrated tests where several systems have to act together. Witnessing works best when the witness has the design intent in front of him and asks what the reading is supposed to be before the engineer takes it. A test that fails in front of a witness is rectified and re-witnessed, and the rectification is recorded rather than quietly overwritten. Life safety systems are witnessed against the criteria the designer and the specification set, and the regime for them belongs to the specialist and the approving authority, not to the site team.

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   Step 6: Assemble the records and the operating information

   Every reading, certificate, test sheet and rectification is compiled into the handover documentation along with as-installed drawings, manufacturers' literature, maintenance requirements, the controls description and the asset schedule. This is the part of the work with the longest life. An operator who has a complete, indexed and legible record can fault-find, retune and plan replacement for thirty years. An operator with a box of unsorted paper and no controls description pays for that gap every year the building stands. On most projects a draft file is required well before completion so the client can review it, not dumped on him on the last day.

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   Step 7: Demonstration, training and handover

   The contractor demonstrates the installed systems to the people who will run them, and trains them on the controls, the routine maintenance and the alarm responses. The value of this depends entirely on who turns up - training the wrong people, or training them three months before the building is occupied, is money spent for nothing. Attendance is recorded and, where the client wants it, sessions are filmed for the staff who join later. Handover then transfers the systems to the operator with a defined list of any outstanding items and dates for closing them out.

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   Step 8: Close out the outstanding items

   Almost no project hands over completely clean. Items that could not be finished - a control loop that cannot be proven until the building is loaded, a test that needs a season the project did not have - are listed, dated and owned by a named person. The list is worked down during the defects period with the client informed of progress. Items that quietly stay open are the ones that become disputes, and they are far cheaper to close in the first three months than in the last month of the liability period.