High-velocity relief valve （pressure vacuum valve）  is the controlled venting system which is necessary for oil tanker and chemical tanker.

The series of CF-type P/V valve is a new generation production without vibration and anti-collision. It is the safest production for oil tanker and chemical tanker.

The pressure/vacuum valve is installed on the vent pipe of oil tanker and chemicals tanker. It is the only entry and exit for liquid cargo tank. 1.When loading the liquid cargo or ballasting, the pressure valve in the high velocity relief will open, then jet out combustible liquid cargo vapour/air-mixture in liquid cargo tank with the rate of more than 30m/s, and dilute in the air so that it will never drop on the deck.  2. When unloading the liquid cargo, the vacuum valve in the high velocity relief valve will open, then supply air to cabin safely so as to avoid the cabin is over-vacuumed. 3.When the tank navigate on sea, the high velocity valve can automatically adjust the pressure oscillation in the cabin which caused by temperature changes

.The experiment of pressure/vacuum valve for cargo ships is done in the lab that is approved by the state organs. It is ratified by China Classification Society and some other classification societies through the following tests according to the above standards:

1. Fire Resistant Test 2. Re-burning Test  3. Frozen Test  4. Corrosion Resistant Test  5.Flowing Test