Oil and gas schedules often show healthy float through construction. Packages are green. Mechanical completion looks near. Then commissioning begins and the float vanishes. The usual cause is not a surprise weld. It is an interface that was never a real predecessor: vendor presence, isolation windows, utilities, permits, punch-list quality, or a brownfield neighbour who still owns the asset.
Hidden float is soft logic. It looks like space in the Gantt until the system needs everything at once.
Where oil and gas interfaces hide float
- Vendor FATs and SATs sitting outside the network as calendar notes.
- Brownfield access assumed available without notice or isolation activities.
- Utilities and nitrogen, power or control media treated as “by others.”
- Punch lists allowed to trail mechanical completion without gating tests.
- Multiple EPCs each green while the integrated system path is red.
Why commissioning exposes the truth
Construction can progress in parallel packages. Commissioning needs a system. Incomplete interfaces that were tolerable during install become hard stops when you need a safe, controlled, documented ready state. The schedule then discovers that the float was between packages, not in front of the commissioning gate.
| Soft interface | Looks like in construction | Becomes at commissioning |
|---|---|---|
| Vendor date in email | Float on install | Critical path overnight |
| Open punch list | Mechanical % complete | Test hold |
| Assumed brownfield access | Parallel progress | Stand-down |
| Utility by others | Package green | System not live |
| One bar for commissioning | Simple plan | No prerequisite visibility |
Plan interfaces as logic, not optimism
Build the path backwards from the commissioning or startup gate. Name the procedure, the prerequisites, the vendor support, the isolations, the completions criteria and the EPC work that creates them. Hang remaining construction from that system logic. Package percent complete can follow; it cannot lead.
Controls habits that protect the finish
- One integrated schedule owner across EPC and commissioning.
- Interface milestones with named owners and durations for notice periods.
- Completions criteria that match what commissioning will accept.
- Float reported to the next energisation, startup or outage gate.
- Change that looks minor in construction assessed on the system path immediately.
What directors should see in the pack
Lead with the next commissioning or startup gate. Show open interface prerequisites, vendor status and residual float to that gate. If the pack only shows construction SPI, assume the hidden float is still hidden.
Recovery when commissioning has already started late
Do not add commissioning hours onto incomplete systems first. Freeze what can be tested, clear the driving interfaces, and re-sequence EPC to the next real gate. Acceleration without readiness spends money to confirm the same failure.
EVM Solutions plans oil and gas programmes with system-based interface logic through commissioning and startup. If your float looks comfortable until testing begins, send the commissioning milestone list and the integrated schedule. The missing predecessors are usually visible there before the next window is lost.
