Safety/EH&S: Extremely important. If there are injuries on site, your insurance goes up as does bad PR – could mean the end of a project (plus, no one wants an injury, and it’s extremely easy to get injured – Also while an activity may not get someone injured, it could be something to get you fined or shut down based upon your local and governing regulations.)
Electrical: Wiring, electrical design, electrical testing. I’ve never seen someone argue against having an electrical discipline present. Sometimes electrical personnel also end up do Instrumentation checks. When you have them doing both, it’s a lot of work. If that’s not scheduled right, your project could be out of time or out of money.
Mechanical: Strongly needed in all three phases as well. Sometimes people tend to over look the mechanical presences needed in the commissioning field as once the power is on, they tend to start thinking process but tolerances and other variables still need to be checked for integrity and reliability purposes.
Process Engineer (sometimes chemical, sometimes other): I’ve seen them in design and in commissioning. Once intial checks are done usually with a safe fluid (normally water) and we are ready to move on into system checks or process checks, this is a roll that tends to spear head the group and manage others.
Automation / DCS: Logic checks are another thing that can easily become a bear. It’s easy to physically see how much work goes into electrical, mechanical, and process, and how important safety is – but sometimes people don’t realize how long it takes to document, fix, and update programming. Sometimes they will help with electrical and instrumentation aspects as well, especially if there’s communication difficulties.
I’m torn in terms of the 6th person, as you should have an instrument person (I&C). But you also do need someone to help with scheduling and finances. On top of that, if you get out of the initial commissioning section, you’ll need an operations group to assist with full system and whole plant performance testing.
I think the way I would do it, is add in a financial/scheduling person. Then initially, it would be a Mechanical lead of this six person management group. The mechanical lead would coordinate with electrical, DCS, process, safety, etc to get the cold checks and initial testing done with schedule and finances controlled by the sixth person. I&C would hopefully be people working under electrical and dcs (like I said, it’s great to have this separate). Then once cold checks and initial equipment checks are complete, we would switch to the Process engineer running lead on the management group. They would be over an operations group and lead everyone in safely brining up systems, checking out full scale processes, and once all the bugs get worked out, help with training.
Murphy’s law is extremely true in startups and commissioning’s, so you could easily need other than those listed. An example would be suddenly having structural steel and foundation issues – then you’ll need a civil person and some things would suddenly be back in the design phase in that section while you’ll still commissioning everything else.