Founded in 1952, Pres-Vac Engineering is the world’s leading supplier of high-velocity pressure/vacuum valves. With customers from all over the world, it has been supplying pressure vacuum valves and venting equipment to shipyards, naval architects and other partners on all continents.


The new PV-ECO & PV VOC valves are designed to minimize noise during operation.
Optimized nozzle reduces noise level by 10-15dB, compared to othervalves.

01. PV-ECO

Designed for use on Chemical Carriers and Product Carriers addressing the special requirements for P/V valves. The PV-ECO is configurable to match the requirements of the yards and the owners. It has been approved to work for long pipes, increasing the flexibility in the piping design for the yard.
The PV-ECO pressure valve has an advanced patented flow control design: the valve has a soft opening and closing phase, assuring efficient operation at low flow rates. A patented integrated dampener secures that the valve can operate non-hammering and non-oscillating on long pipes.
Compared to the previous generation, Pres-Vac simplifies the maintenance by reducing disassembly time by 60%.

02. PV-VOC

The PV-VOC pressure valve is designed to meet the requirements that larger Crude Oil Carriers have for the P-V valves. The two-step opening which secures that the opening and closing pressure is kept at the same pressure level during breathing phase (approximately about 50% of total flow capacity). This feature contributes to lowering VOC emission in all stages in the operation of an oil tanker.

03. PV-ECO/VOC Vacuum

The vacuum valve is designed to avoid excessive under pressure in the cargo tank during discharge operations.
When the tank vacuum exceeds the preset opening setting, the valve will open and let air into to the tank. The valve size is carefully selected from the pump capacity (discharge rate) and VECS operations.
The vacuum valve is also used as breather valve during voyage.


Gas Freeing Cover

Gas freeing onboard tankers is required for entry into cargo tanks, hot works, and inspection or washing for clean ballast tanks.
Before a cargo tank can be gas freed, it is required to purge the cargo tank with inert gas until the hydrocarbon gas content is below 2% by volume, to ensure the tank atmosphere is not in the flammable range.
Venting of toxic and flammable gas during gas freeing should be through the vessel’s approved gas freeing outlets, and therefore the exit velocity should be minimum 20m/s to carry the vapors clear of the deck.
Pres-Vac provides both vacuum integrated gas freeing covers type as well as separate gas freeing covers, approved for both IIA and IIB cargo groups.

Spare Parts

Pres-Vac supplies spares parts and a series of maintenance kits, to ensure that the valves operate and comply with the latest international Rules and Regulations.


Pres-Vac VOCON venting system is controlled by an electrical actuator that maintains the tank pressure between the set-pressure and the re-seating pressure.
The VOCON system is installed on the mast riser’s bypass line and controls the vapor pressure in all the cargo tanks during voyage for direct emission control, to reduce VOC loss from the tanks during voyage. By controlling the pressure in the venting system, it is possible to fully control the VOC emissions.
The VOCON system can be programmed to enable adjustment of the opening setting on the valve, according to what is optimal for the specific cargo.
Vocon is equipped with MARVOC, an advanced reporting system.

Aircaps and Air Release/Vacuum Breaker Valves

Aircaps and Air Release/Vacuum Breaker Valves serve two purposes: tank venting and prevent water from entering the tank. Aircaps are installed on service tank air pipes. A wire mesh prevents flames from entering the tank.


Liquid overfill protection devices

Liquid overfill protection devices are designed to prevent overpressurization of tanks due to overfilling, which may occur if the high-level alarm float is punctured.
Not using an overfill protection device could result in a ruptured tank and massive pollution.

Onboard test rigs

Onboard test rigs are used to verify the set-pressure after maintenance and to check for and measure leakage.