What is mechanical completion in an EPC project?
Mechanical completion (MC) is the point in an EPC contract where construction is finished enough that a system or unit can be handed from the construction team to commissioning. The piping is installed, bolted, and pressure tested. The instruments are wired and loop-checked. The equipment is set, aligned, and ready to run water or air through it, not feedstock yet. MC is a contractual milestone, usually certified system by system or unit by unit, not one date for the whole plant.
Most EPC contracts spell out MC in detail because money and liability turn on it. A contractor typically can't invoice a major milestone payment, and a lender typically can't release a draw tied to that milestone, until MC is certified for the relevant systems. The contract will usually list what counts: permanent piping installed and tested, electrical terminations complete, instrumentation loop-checked, rotating equipment aligned, insulation and painting done except for items on an agreed punch list.
That punch list matters more than it sounds like it should. Almost no unit reaches MC with zero outstanding items. Contracts usually split punch items into "A" items, which must be closed before MC is certified, and "B" items, which can roll into the commissioning phase without blocking the certificate. A lender's independent engineer will often go through that punch list line by line before signing off, because a long B list quietly carried past MC can mask real schedule slip.
Mechanical completion vs commissioning
On site, people use "MC" and "commissioning" almost interchangeably in conversation, which makes a mess of progress reporting. They happen in sequence, and the two get mixed up constantly.
Mechanical completion means the hardware is built and static-tested. Nothing is running yet. Commissioning starts after MC and is the process of bringing systems to life: flushing lines, running motors, calibrating control loops, bringing in utilities like nitrogen, steam, or instrument air, and eventually introducing hydrocarbons for the first time. Commissioning itself usually breaks into pre-commissioning, which is dry checks with no process fluids, and wet commissioning, which brings in utilities and then feed.
So the typical sequence in a contract reads: construction, mechanical completion, pre-commissioning, commissioning, ready for startup, then startup and performance testing. Each one is its own milestone with its own certificate and, often, its own payment or draw trigger.
Ready for startup and the rest of the contract milestones
Ready for startup, or RFSU, is the milestone after commissioning, when a unit has been through its checks with utilities and is cleared to take feed. It's the handoff point from the commissioning team to operations. In a tolling or offtake agreement, RFSU is frequently the date that starts the clock on delivery obligations, so it gets just as much contractual attention as MC.
Between MC and RFSU sits most of the schedule risk that traders and lenders care about most. A contractor can report "on track for MC" for months while commissioning readiness, spare parts, operator training, and utility tie-ins slip behind schedule without anyone flagging it. The gap between a contractor's self-reported percent-complete and what's physically happening on site tends to widen in exactly that window, because commissioning progress is harder to verify from a desk than structural steel going up.
That's the practical reason outside parties don't want to rely only on the EPC's own progress reports between those milestones. A monthly, independent read on module placement and structure growth against the plan gives a lender or a trading desk something to check the contractor's narrative against, well before any MC certificate reaches the table. Refinery Progress builds that read from satellite imagery, tracking what's actually gone up on site each month against the startup date in the financing or offtake agreement.
If that gap between reported progress and built progress matters to your book or your covenant, that's what this site tracks.