Valve criticality ranking: consequence, isolation role and evidence quality

Criticality is about consequence, not valve size

A large valve is not automatically critical. A smaller valve may protect the only safe isolation boundary for people, equipment or supply.

Start with the event created when closure or sealing fails. Then examine whether another verified isolation point can control that event.

This approach connects asset importance with real operating duty. It also stops familiar, accessible valves receiving attention while hidden risks remain.

Build the ranking from four evidence groups

A useful ranking records the reason behind each judgement. Keep assumptions visible, especially where records or tests are missing.

1. Consequence. Describe effects on people, the environment, production and connected equipment. Use site risk rules rather than unsupported universal bands.
2. Isolation role. Record whether the valve is a primary block, emergency boundary, bypass control or redundant isolation point. Confirm the actual line arrangement against current drawings and field labels.
3. Condition evidence. Use travel checks, seat tests, maintenance records and direct inspection. Noise, position indication and downstream pressure are screening evidence only.
4. Evidence quality. Grade each input by source, date and test relevance. A recent witnessed seat test carries more weight than an old note saying “serviceable”.

Our guide to field seat-leak testing explains what common methods prove. The isolation readiness guide covers evidence needed for emergency duties.

Separate importance from present condition

Criticality and condition answer different questions. Criticality describes what matters if the valve fails. Condition describes the evidence that failure may occur.

Keep both values visible. A critical valve with good recent evidence may need planned monitoring. A critical valve with poor evidence may need prompt survey work.

Likewise, a low-consequence valve can be badly degraded without becoming the first network priority. It still needs a safe response, but the ranking explains sequencing.

Treat weak evidence as work, not reassurance

Missing records should not be scored as good condition. Mark the uncertainty, then plan the safest action needed to reduce it.

Field screening can identify where confirmation is needed. Pressure rise, noise and flow indication may suggest passing, but a suitable seat test confirms it.

Travel indication can show commanded movement, not tight shut-off. See why full travel does not prove sealing before relying on actuator feedback.

Turn the ranking into a funded programme

Use criticality tiers to set survey depth, evidence needs and review order. Do not let the score prescribe one maintenance method.

1. Confirm the line duty, isolation arrangement and credible consequences.
2. List available evidence and record its date, source and limits.
3. Identify gaps that could change the ranking or operating decision.
4. Assign survey, testing or planning actions with named owners.
5. Review the rank after tests, process changes or line modifications.

The network budgeting guide shows how tiers can focus limited funds. A structured valve survey then supplies comparable evidence across the network.

Where condition supports in-service treatment, several gates apply first. Injection fittings must be in good condition, the design and service must suit injection, OEM guidance applies, and operations must permit the work. Our field services can assess those gates and document the result. Place the ranking inside a wider valve integrity management programme.