Isolation readiness: evidence a sectionalising valve will close and seal

Treat readiness as three separate functions

A sectionalising valve may move without reaching its true closed stop. It may also reach that position while product still passes across a damaged seat.

Readiness therefore needs evidence for movement, closure and sealing. The valve integrity management programme should store each result against the individual valve.

1. Movement: the valve travels when commanded, without abnormal resistance or interruption.
2. Closure: the obturator reaches the intended mechanical closed position.
3. Seat integrity: an approved test shows leakage stays within the accepted field criterion.

Do not confuse indication with proof

A local pointer, actuator signal or control-room status can show a commanded position. It does not by itself prove mechanical closure or seat tightness.

Downstream pressure rise, flow indication and noise can suggest passing. They remain screening evidence because heat, equalisation, trapped volume and instrument error can produce similar signs.

Confirm suspected passing with an approved field seat test. The methods and boundaries belong in the work instruction. The planned field seat-leak testing guide compares pressure decay, bleed checks and acoustic screening.

Plan an evidence-producing exercise

Applicable regulation, service risk, valve history and OEM guidance should set the interval. ASME B31.8 does not prescribe one universal exercise or closure-test interval for every installed valve.

Industry practice includes cycling valves at least twice yearly to reduce seizing risk. This is reported practice, not a rule. Operations permission and valve condition still govern every movement.

1. Review the valve record, line state, operating limits and previous defects.
2. Confirm that movement will not upset the process or remove required protection.
3. Observe travel, actuator behaviour, stop position and any abnormal resistance.
4. Apply the approved closure test under a known and recorded configuration.
5. Record results, uncertainty, restrictions and the next required action.

Read the ASME B31.8 overview for the standards boundary.

Use test evidence that can be repeated

A useful record states the test arrangement, instrument, starting condition, duration and acceptance basis. A simple pass mark without these details cannot support later comparison.

Trend the same measures where the method allows. Rising operating effort or weaker seat performance can trigger a shorter review interval, even before failure.

API 598 and ISO 5208 address leakage testing and acceptance at defined test conditions. They do not declare an installed valve ready forever. Field acceptance must match the operator's purpose and approved procedure.

Respond to a failed readiness check

First protect the operating boundary and identify another available isolation point. A failed test needs a proper assessment before anyone assumes the cause.

Common causes include incomplete travel, stop settings, actuator faults, debris, seat damage and instrumentation error. Inspection should separate these possibilities.

Injection is not universally possible. Before cleaner or sealant is considered, fittings must be in good condition, valve design and service must suit injection, OEM guidance must allow it, and operations must permit the work.

Where those gates pass, use controlled amounts within fitting and equipment ratings. Watch pressure response and stop on abnormal behaviour. Our field services can support the assessment and controlled work.