| OTM-7.4 |
Oil Tanker Manual OTM Setting of Venting System |
Doc No.: OTM 7.4
Revision: 01 Date: 15 Oct 2024 Issued by: DPA Approved by: MD |
1 SETTING OF VENTING SYSTEM
- Setting of venting system
- Setting for pressure sensor and alarm systems
The vessel should always use closed loading. All ullage-ports are to be closed and checked prior to commencement of Loading.
Purge – pipes (if installed) to be closed and checked.
All cargo tank vents should be set to the loading position. PV valves to be set to ensure the high exit velocity of vented gas.
Ensure that inert-gas plant is shut down, the deck isolation valve is shut and lashed, and that the main inert-gas venting valves are open.
Precautions should be taken and the venting system set accordingly to ensure compatibility of vapour when loading different grades of cargoes.
Setting for independent pressure sensors and alarm provided in cargo tanks as means of secondary protection:
| Tank atmosphere | High pressure settings | Low pressure settings |
|---|---|---|
| Inerted vessel | 10% above the normal actuation settings of pressure valve | Above zero (Tank should never be allowed to fall below zero) |
| Non-inerted vessel | 10% above the normal actuation settings of vacuum valve |
Setting for pressure sensor and alarm on vapour line when in use:
| Tank atmosphere | High pressure settings | Low pressure settings |
|---|---|---|
| VRL (Inerted vessel) | Not more than 90 percent of the lowest pressure relief valve setting (PV Valve / Mast riser breather valve, etc.) of the cargo tank venting system. | Not less than 100 mmWG or (0.144 PSI) |
| VRL (Non-Inerted vessel) | Not less than lowest Vacuum Valve setting |