Tankerman · Cargo Properties — True Vapor Pressure
True Vapor Pressure (TVP) is more relevant than RVP for assessing tank venting losses because TVP:
- AIs always lower than RVP
- BReflects the actual vapor pressure at the cargo's stowage temperature, which can be well above the 100°F RVP reference✓ Correct
- CIgnores temperature entirely
- DApplies only to water
Explanation
RVP is a single-temperature (100°F) index, whereas TVP is the actual equilibrium vapor pressure at the storage temperature. For evaluating breathing/working losses and venting in service, the TVP at the real cargo temperature governs how much vapor is produced.
Authority: API MPMS; ISGOTT
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