What is a turnaround?

For a large refinery, petrochemical plant, LNG facility, or power station, turnarounds are the most consequential operational events outside of a major incident. They consume hundreds of millions of dollars, take months or years to plan, and produce or destroy operating margin depending on how well they execute.

Typical frequency

Turnaround intervals depend on the equipment, the regulatory environment, and the facility's operating philosophy. Common cycles:

• Refinery major turnarounds: every 4 to 6 years per major process unit, with different units on staggered cycles
• Petrochemical plants: 3 to 5 years for most units, with specialty equipment on tighter cycles
• LNG facilities: 4 to 6 years for major turnarounds
• Power generation: varies widely by technology and duty cycle

The longer the interval, the larger and more complex each turnaround becomes. The economic tradeoff is between lost production during the shutdown and accumulated maintenance deferrals.

Turnaround planning phases

Major turnarounds are planned over long horizons. A typical sequence:

• T-24 months to T-36 months. Long-lead equipment identification and procurement. Strategic scope definition.
• T-18 months. Scope freeze for major work. P&ID review and MTO development begins.
• T-12 months. Detailed scope development, execution planning, contractor bidding.
• T-6 months. Work packages finalized. Site mobilization planning.
• T-3 months. Final material deliveries. Resource mobilization.
• T-0 (shutdown). Execution window. Typically 30 to 90 days for major work.
• T+30. Post-turnaround review, as-built documentation, lessons learned.

The role of P&IDs in turnaround planning

Turnaround scope is defined by reference to the facility's P&IDs. Every work item — valve replacement, piping modification, equipment inspection, instrumentation upgrade, tie-in for a future project — is identified, located, and specified against the governing drawings.

MTO for a major turnaround is one of the most demanding engineering extraction exercises in an operator's annual cycle. A typical refinery turnaround may involve 500 to 1,500 P&IDs in scope, each requiring structured extraction of the piping, valves, instruments, and equipment affected by the planned work.

Manual MTO for a turnaround of this scale consumes thousands of engineering hours — and the accuracy of the MTO directly determines whether materials are staged in time, whether work packages are complete, and whether the shutdown window holds.