Common issues
- Vent bore in the ball becomes blocked with cargo residue or paint, giving a false 'no pressure' reading on the gauge
- Seat leakage develops after repeated cycling, especially if the valve was left throttled rather than fully open or closed
- Spindle and handle seize from corrosion if the valve sits unused for long periods in an exposed manifold location
- Packing gland weeps around the stem after thermal cycling or vibration loosens the gland nut
- Threaded connection galls or the threads are damaged by over-torquing during gauge changes
- Cargo residue crystallizes inside the bore on repeat cargoes, restricting flow to the gauge
Inspection checklist
- Confirm the manifold system is depressurized and isolated before removing the valve or gauge
- Cycle the valve through its full travel and check for smooth, even operation without excessive force
- Check the vent bore is clear by observing venting when the valve is opened to atmosphere
- Inspect the packing gland for weeping under test pressure
- Check the threaded connection for gall marks, thread damage or cross-threading
- Look for external corrosion or coating damage on the body, especially at the base of the handle
- Verify the pressure rating marking on the body is still legible
- Function-test with a calibrated test gauge to confirm the reading matches a known reference
Service intervals
| Functional cycling and visual check | at each cargo operation or per the vessel's planned maintenance system, whichever is more frequent |
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| Packing gland adjustment/renewal | as required when weeping is found - no fixed interval published for this valve size, follow the vessel's PMS |
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| Seat/seal renewal | condition-based, on evidence of leakage - confirm any fixed interval against the manufacturer's manual |
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| Pressure rating/marking check | at each annual cargo system survey |
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Critical spares
- Valve seat and seal kit, size and pressure class as fitted
- Packing/gland set for the stem
- Handle/lever assembly
- Gasket or thread sealant appropriate for the screwed connection
- Spare pressure gauge for the line this valve isolates
Safety
- Sudden release of pressurized cargo vapour or liquid if the seat or gland fails under pressure - never work on the valve without confirming the line is depressurized and isolated
- The vent bore can spray liquid product under pressure when the valve is opened - keep hands and face clear
- Confirm the valve material is compatible with the specific cargo before use, especially for chemical or aggressive cargoes
- Do not over-torque the handle to force a stuck valve - this can crack the body under pressure
Class survey
Part of the cargo piping/pressure-gauge arrangement checked during tanker cargo system surveys; the surveyor typically wants evidence of functional gauge cocks/valves at manifold pressure points and, where fitted, records of any pressure testing of the cargo piping system rather than a certificate for the valve itself.