What are the usual pressure and vacuum levels required to activate the P/V valves?
MARPOL Annex VI and IMO MSC Circ 585 "Standards for Vapour Emission Control Systems" require that P/V valves in such a system on an oil tanker should relieve the pressure or vacuum once they reach specified levels in a cargo tank:
Pressure: 1 psi (0.069 bar)
Vacuum: 0.5 psi (0.034 bar)
