Mechanical completion: definition, certificate, checklist and dossier
Deskely Completions team Singapore
Mechanical completion (MC) is the point at which a system or subsystem is built, installed and inspected to the design, and is ready to be handed from construction to commissioning. It is static: nothing has been energised or run yet. It is also, on most projects, a contractual milestone that both sides watch closely.
This guide covers what mechanical completion means, the criteria by discipline, what goes in the MC certificate and dossier, how the walkdown and punch list decide it, and what most often holds it back.
- MC means built and inspected to design, not working. Working is proven in commissioning.
- It is certified per subsystem, when every A ITR is signed and every A punch item is closed.
- The MC certificate is backed by a dossier of ITRs, test packs, punch lists and redlines.
- Missing test pack records and open A punch are the commonest reasons MC slips.
What is mechanical completion?
Mechanical completion is the milestone at which construction declares a system or subsystem complete: every item installed to the drawings and specifications, every construction inspection and test done and signed, and the punch list reduced to items that do not stop commissioning. After MC the subsystem passes to the commissioning team, who energise it and prove that it works.
On industrial and offshore projects MC is certified per subsystem, not for the whole plant at once, so that commissioning can start on the first subsystems while construction finishes the rest. See systems and subsystems in commissioning 101 and mechanical completion vs commissioning.
Many EPC contracts make mechanical completion, or a related milestone, a contractual event, so its definition and the evidence behind it are agreed in the contract and the project completions procedure.
Mechanical completion criteria by discipline
| Discipline | Typical MC criteria |
|---|---|
| Piping | Installed to isometrics, welds inspected and NDT accepted, pressure tested, flushed, reinstated, supports complete |
| Mechanical | Equipment set, aligned and grouted, internals installed, vendor installation checks done |
| Electrical | Cables pulled, glanded and terminated, insulation resistance tested, earthing complete, equipment installed |
| Instrumentation | Instruments installed to hook-up drawings, impulse lines and tubing leak tested, cables terminated |
| Structural and architectural | Steelwork, gratings, handrails, access and escape routes complete |
| Insulation and coatings | Insulation, painting and passive fire protection complete or punch-listed |
| Safety | Safety equipment installed, Ex inspections done in hazardous areas |
The exact criteria come from the project completions procedure and the ITP. Each criterion is proven by a signed inspection and test record against the tag.
The mechanical completion certificate
The MC certificate (sometimes MCC) is a one-page record that the subsystem meets the MC criteria. It typically shows:
- The project, system and subsystem, with the subsystem boundary drawing reference.
- Confirmation that all A ITRs are complete and signed, often with the count.
- The pressure test packs for the subsystem and their status.
- The open punch items, by category, with A items at zero.
- Exceptions agreed by both parties, if any.
- Signatures from construction, quality, commissioning and often the owner.
Once it is signed, care of the subsystem moves to commissioning, and changes to it go through commissioning's control.
The MC dossier
Behind the certificate sits the MC dossier (or MC package): the evidence that the criteria are met. It usually contains the subsystem scope and tag list, every A ITR, the pressure test packs, flushing and cleaning records, insulation resistance records, the punch list, vendor installation records and the as-built red-line markups.
Assembling these dossiers by hand for hundreds of subsystems is one of the heaviest administrative loads at the end of construction. It is far easier when every record is already held against its tag and subsystem.
Walkdown and punch list
Before MC, construction, commissioning and usually the owner walk the subsystem together. Anything incomplete or wrong becomes a punch item, categorised by how much it blocks:
| Category | Meaning | Effect on MC |
|---|---|---|
| A | Must be closed before mechanical completion | MC cannot be signed while any are open |
| B | Must be closed before start-up or handover | Carried into commissioning |
| C | Can be closed later, often during operation | Carried to handover or operations |
Projects use their own letters and rules, but the principle is the same. See the punch list template.
MC, RFC, RFSU and handover
| Milestone | Means | Who certifies |
|---|---|---|
| Mechanical completion (MC) | Built and inspected to design, static | Construction, accepted by commissioning |
| Ready for commissioning (RFC) | Pre-commissioning done, B ITRs signed | Commissioning |
| Ready for start-up (RFSU) | Commissioned, safe to introduce hydrocarbons or process fluids | Commissioning and operations |
| Handover | Care, custody and control pass to the owner or operator | Contractor and owner |
Names vary: some projects use RFC for the milestone after MC, others go straight from MC to commissioning. The commissioning checklist follows one subsystem through all of them.
What holds mechanical completion back
- Test packs: pressure tests done but the packs not closed, or reinstatement not signed off.
- Unsigned ITRs: work done in the field but the records not completed, signed or entered.
- Open A punch: items found on the walkdown, or carried from fabrication, still open.
- Drawing changes: a late revision invalidating signed records, so checks must be redone.
- Visibility: nobody can say, per subsystem, exactly what is still open until someone counts by hand.
In Deskely every ITR, test pack and punch item is held against its tag and subsystem, so the open items blocking each subsystem's MC are visible live, and the MC dossier is assembled from records that already exist.
The Deskely products for this
Frequently asked questions
What is mechanical completion?
The milestone at which a system or subsystem is built, installed and inspected to the design, with all construction checks signed and all A punch items closed, so it can pass to commissioning.
What is a mechanical completion certificate?
A signed record that a subsystem meets the mechanical completion criteria, listing the ITRs, test packs and open punch items, signed by construction, quality and commissioning.
Does mechanical completion mean the system works?
No. MC means it is built correctly and is static. Commissioning proves that it works, after MC.
Is mechanical completion done for the whole plant at once?
Usually not. On industrial and offshore projects it is certified per subsystem, so commissioning can start on finished subsystems while construction continues on others.
What is an MC dossier?
The package of evidence behind the MC certificate: the ITRs, test packs, flushing and insulation records, punch list, vendor installation records and redlines for the subsystem.
What comes after mechanical completion?
Pre-commissioning and ready for commissioning (RFC), then commissioning, ready for start-up (RFSU) and handover. Projects name these stages slightly differently.
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