High-velocity PV valves feature isolated dual-head mechanisms dedicated to managing positive over-pressure on one side and negative vacuum pressure on the other. The pressure head utilizes calibrated weights or adjustable spring tension to hold a precision seal closed until internal tank pressure overcomes the setting, forcing the seal open to blast gas upward at high speed.
Conversely, the vacuum side operates in reverse to prevent catastrophic tank collapse during rapid liquid discharge. When internal pressure drops below atmospheric levels, external air pressure forces the vacuum seal upward, allowing ambient air to enter and instantly restore equilibrium across the cargo tank.
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