PV-VOC
Pres-Vac PV-VOC — Crude oil tankers - high velocity pressure/vacuum valves.
Inspector Detail
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Common issues
- Valve sticking from wax deposits or corrosion on the pallet/disc
- Seat damage causing loss of tank overpressure or vacuum protection
- Gasket and seal deterioration from cargo vapour exposure
- Icing in cold climates affecting free movement of the pallet
- Corrosion of external components from prolonged deck exposure
Inspection checklist
- Function test opening and closing at rated pressure/vacuum setpoints
- Visual inspection for corrosion, deposits or damage on the housing and pallet
- Check seat and disc/pallet condition for wear or fouling
- Confirm drain holes and pressure-sensing passages are clear
- Check flame screen condition where fitted
- Verify associated venting pipework is unobstructed
Service intervals
| Function/setpoint test | at each drydock or per the vessel's PMS, whichever is more frequent |
| Visual inspection | regular deck rounds per PMS |
Critical spares
- Seat and disc/pallet set
- Gasket kit
- Flame screen (where fitted)
Safety
- Handles flammable hydrocarbon vapour - any tampering with the pressure/vacuum setpoint compromises tank overpressure and explosion protection
- Working at height/on deck near cargo tank vents
- Flammable atmosphere around vent outlets during cargo operations
Class survey
Tank venting arrangements including P/V valves are part of the tanker's venting system survey - opening/closing setpoints are typically verified against the valve's test certificate.
Components & Design
Component data being added…
Technical Data
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Common failures & inspection points
Visual inspection for corroded areas, dents, distortions, and surface defects on all exposed valve components and connections
Pressure test for tightness with soap/water solution on all joints under pressure; verify blowdown and leakage per ISO 15364:2021 Annex J; document bubble sizes (isolated small bubbles acceptable, numerous larger bubbles indicate exceedance)
Verify valve holds prescribed pressure for minimum 10 minutes; confirm relief pressure setpoint remains within specified range (12 kPa minimum for HS-ISO); inspect internal wear parts without tools per Pres-Vac design
Visual inspection of flame screens (0.65 MESG rating); verify removable elements can be accessed; check for salt deposit, oil accumulation or marine corrosion on flame path; test pressure drop remains within specifications
Verify smooth opening/closing operation without sticking; confirm pressure drop performance matches baseline; inspect sealed internal components for water ingress or debris; test responsiveness to pressure changes
Type-general inspection and maintenance points for this equipment category — not model-specific.
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