Precommissioning

Precommissioning is a phase in the project lifecycle of industrial facilities during which installed systems are prepared and verified for commissioning and eventual start-up. It follows construction and mechanical completion and precedes performance testing and operation. The aim is to ensure that equipment, systems, and components are installed in accordance with design, properly integrated, and ready for safe, reliable function.

Typical activities include verifying documentation and drawings, finalizing tagging and isolation schemes, cleaning and flushing pipelines, chemical cleaning where required, drying and inerting of vessels and lines, hydrostatic or pneumatic pressure testing, leak testing, and removal of construction debris. It also covers electrical and instrument checks, wiring verification, calibration, functional checks of control loops, and ensuring safety systems are in place. Mechanical completion, insulation, and insulation verification are commonly part of precommissioning, as are gas freeing or nitrogen purge of enclosed spaces and moisture or contamination control.

Documentation and deliverables include a precommissioning dossier, punch lists, as-built drawings, equipment manuals, and certificates confirming readiness for commissioning. The phase involves coordination among owners, engineers, contractors, vendors, and commissioning teams, with permits, lockout-tagout, and safety procedures prominent.

Precommissioning differs from commissioning, which focuses on testing performance against design criteria, and from start-up, which refers to initial process operation. Proper execution reduces risk during commissioning and start-up and helps ensure safe, reliable operation of the facility.