Why this matters

Subsystem-based completion lets utilities and ICSS reach RFSU first, so process systems can be energised, instrument-air can be supplied, and loop checks can run before bulk commissioning. Without this sequencing, commissioning teams stall waiting on cross-discipline readiness.

Common field problems

Teams declare full systems 'mechanically complete' too early, hiding rework; A-punches accumulate because B/C are deprioritised; vendor scopes (compressors, ICSS) aren't sequenced with operations acceptance windows.

Best practice

Lock turnover boundaries early; treat A-punches as walkdown blockers; track RFSU per subsystem, not per system; involve operations in walkdowns from MC-1 onward; keep preservation logs alive until startup.