Vacuum pressure relief valves: How pressure vacuum valve operation protects tanker safety
Vacuum pressure relief valves are critical components installed on cargo and storage tanks, especially aboard chemical and product tankers. These valves are designed to maintain tank integrity by automatically relieving over-pressure or vacuum conditions caused by temperature changes, cargo loading or unloading, and other operational variables.
What is a vacuum pressure relief valve?
A vacuum pressure relief valve, also known as a PV valve, is a safety device that protects tanks against excessive internal pressure and dangerous vacuum. Installed on the tank’s vent line, the valve operates by opening and closing at predefined set points to maintain tank conditions within safe limits.
Pressure vacuum valve operation: The principle explained
The core function of a PV valve hinges on its ability to respond automatically to pressure changes inside the tank. Under normal operating conditions, the valve remains closed, preserving the tank’s atmosphere and preventing product loss. During cargo loading, tank pressure rises. If it exceeds a specified safe threshold, the pressure side of the valve opens to release excess vapours safely. Conversely, during unloading or temperature drops, a vacuum may form inside the tank. The vacuum side of the valve opens to admit air, preventing implosion or structural damage. Once equilibrium is restored, the valve reseals, maintaining system integrity.
Safety and compliance: Why correct operation matters
Proper operation of the pressure vacuum valve is essential to prevent tank collapse, product loss, and environmental hazards. The International Maritime Organization (IMO) mandates the use of certified PV valves to satisfy MARPOL regulations, particularly to avoid emissions and ensure the safety of crew and vessel. Failure of these valves can lead to catastrophic tank failures, hazardous vapour release, or even explosions. For this reason, selection, maintenance, and operation of vacuum pressure relief valves must follow stringent guidelines and comply with international standards, including IMO 1621 and ISO 15364.
Pres-Vac PV valves: Industry-leading design for enhanced tank safety
As a part of G&O Maritime Group, Pres-Vac stands out with its advanced non-hammering design, which ensures smooth and gradual valve action, reducing stress on tank structures. The unique engineering delivers constant pressure regulation and low blowdown, meaning the pressure returns to safe levels quickly after valve actuation. Pres-Vac PV valves hold leading certifications (IMO 1621, ISO 15364, and ATEX), supporting complete compliance and peace of mind for shipowners and crews alike.
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