Commissioning/startup is the most critical and busiest phase of a project. Design flaws, hidden manufacturing problems, and construction and installation errors will become apparent during commissioning/startup and usually will mandate immediate modifications and corrections. Addressing such issues adds to the high stress already posed by the tight schedule and the economic penalties of any delay.
Three factors are key to a successful and less-stressful commissioning/startup:
1. developing a correct and realistic plan;
2. assembling an appropriate team, i.e., one that includes a suitable mix of mechanical, machinery, piping, electrical, instrument and other engineers for the particular process and equipment; and
3. properly empowering all team members to implement their responsibilities.
I generally don’t recommend delegating commissioning/startup to the engineering/construction contractor responsible for building the unit. Commissioning and startup involve very special types of work that require very specific skills. This expertise normally resides within operating companies, specialized commissioning/startup agencies and, often, equipment vendors. Keep the construction/installation team and the commissioning/startup team separate to the maximum extent possible.
Many commissioning/startup efforts suffer from avoidable errors such as:
• mis-sized control valves, actuators and equipment;
• incorrectly configured instrumentation and control systems;
• undersized hydraulic return lines;
• improperly laid out piping;
• misaligned equipment;
• insufficient amount of heat tracing;
• inadequate coverage by the fire water system; and
• lack of essential spare parts.
Correcting these mistakes during commissioning/startup takes time; getting a necessary part can cause considerable delay. Moreover, the needed modifications can have consequences such as changes in machinery alignment, requiring a realignment. Commissioning planning often neglects the time demanded for such realignment work.
Recommissioning activity is another item frequently forgotten in commissioning planning. If machinery (or a package) has been commissioned, it should be recommissioned when hooked up with all other systems in the integrated unit. Only then can the equipment be tested in a situation that resembles the actual working full-load condition. So, it’s essential to provide adequate time and resource allowances for the recommissioning activities for different packages.
The time needed for the oil flushing of equipment nearly always is under-estimated. The actual oil flushing usually should continue for two or three times longer than the time given by commonly used estimates. For special/complex lubrication-oil systems, a complete/high-quality oil flushing could take 3–12 days (depending upon the specifics of the machinery and the oil system).
In addition, too little time usually is allocated for cleaning checks, internal inspections and borescoping. The machinery package handed over by construction to commissioning should be properly inspected for cleanliness; usually equipment isn’t as clean as required.
Take full advantage of equipment installed for construction and maintenance activities (Figure 1). Commissioning often can benefit from temporary facilities, too. For example, for a plant that will be generating its own power, at the start of the commissioning process there’s usually not enough electrical load to adequately test the power generation unit. Temporary generators can supply power until equipment with sufficient electrical load to meet the minimum load requirements of the permanent generator is operating.
Because the main power generator or the main power transmission systems usually are on the critical path of a project, such temporary power-generation facilities could offer good flexibility in the commissioning.
At many plants, air, nitrogen, oxygen and water systems/packages or other utilities may be commissioned late because of a problem, delay or issue. Temporary sources for the affected utilities can facilitate the commissioning of the core areas. These temporary units are expensive rental equipment; special care is required to ensure correct timing.
Identifying the commissioning (or takeover) packages is an important step in preparing for commissioning. Each package should consist of a unit or system suitable for integrated final testing and big enough for the operations team to take over and actually run. Prepare a dedicated drawing for each commissioning package. There should be no confusion about the commissioning package scope.