Scope freeze
A scope freeze is the point in a turnaround or project schedule after which no new work may be added to the agreed scope without passing through formal change control. It locks the worklist so planning, materials, and resource loading can proceed against a stable baseline.
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A turnaround lives or dies on its worklist. In the months before the event the scope is built up from inspection findings, deferred work, modifications, and statutory tasks, then frozen on a published date so that planning can convert it into a schedule, a materials order, and a labour plan. After the freeze, anything new has to be justified through a change board rather than slipped quietly onto the list, because every late addition competes for the same critical path and the same shutdown window. The frozen scope includes the instrument and valve worklist, the isolation list, and the tie-in list, all of which are planned against the register that was current at the freeze. A register that is accurate on the freeze date protects the estimate. One that is stale carries error straight into the plan.
Why a scope freeze exists.
The freeze protects the critical path. Once the worklist is locked, planners can size labour, order long-lead materials, and sequence the work with confidence that the target is not moving. Without a freeze, late additions accumulate until the window can no longer absorb them and the turnaround overruns.
What gets frozen.
The frozen scope is the full worklist. It holds inspection and maintenance tasks, modifications, the instrument and valve list, the isolation and lock-out list, and the tie-in list for any new connections. Each item is planned against the engineering records that are current at the freeze, so those records need to be reconciled before the date, not after.
Change control after the freeze.
Work identified after the freeze is handled through a change board, which weighs each request against the critical path and the available resource. Emergent or discovery work found once equipment is opened is a recognised category with its own approval route, kept separate from scope that could have been planned earlier.
Scope freeze versus design freeze.
A design freeze locks the engineering. Drawings and specifications stop changing so procurement and fabrication can proceed. A scope freeze locks the execution worklist for a turnaround or project phase. A project can hold a design freeze long before the scope freeze for the shutdown that installs the work.
Frequently asked.
When does scope freeze happen in a turnaround.
It is set well before the event, often several weeks to a few months ahead, timed so that planning, procurement, and resource loading can finish against a stable worklist. The exact lead time depends on the size of the turnaround and the longest-lead material it has to order.
What is the difference between scope freeze and design freeze.
A design freeze stops engineering changes so drawings and specs can be built from. A scope freeze stops additions to the execution worklist. They serve different stages. A design freeze protects the engineering, and a scope freeze protects the shutdown plan.
Can work be added after the freeze.
Only through formal change control. A change board reviews each late request against the critical path and available resources. Emergent work discovered once equipment is opened is handled as its own category with a defined approval route.
What is emergent scope.
Emergent scope is work that could not be foreseen until equipment was opened or inspected during the turnaround, such as corrosion found inside a vessel. It is expected and planned for as contingency, distinct from late additions that should have been on the frozen list.