High Velocity PV Valve

The High Velocity PV Valve for cargo ships is also called as high velocity relief valve or pressure/vacuum valve. It is a controlled venting system necessary for oil tanker and chemical tanker.
The series of DF-ISO high velocity relief valve which are produced by our company is a new generation production that is without vibration and anti-collision. It is the safest production for oil tanker and chemical tanker once operated by the Manual.

Standards & Regulations:
The DF-ISO type High Velocity PV Valve (high velocity relief valve) is designed, manufactured and tested by the following standards and stipulations:
1 .IMO.MSC/Circ.677 Revised Standards of Designing, Testing and Installing the Device that can Stop the Flame into the Liquid Cargo Tank;
2 .IS015364 Ships and Marine Technology-Pressure/Vacuum Valve for Cargo Tank;
3. IMO.MSC/Circ1324;
4. EN12874-2001 Requirements, Testing Methods and Usage Scope about the Flame Arrester.

Usage:
As the sole breathable port of oil tanker and chemical tanker, the pressure vacuum valve is installed on the top of each compartment. When the hydraulic compartment is loading cargo. the pressure valve effluent mixed gas at a speed of more than 30 m/s vertically upwards. When discharge cargo, the vacuum valve add air to the cabin automatically to prevent the hydraulic tank from over pressure and pressure loss. Pressure vacuum valve made in accordance with the above standards can prevent the flame into the hydraulic tank even under the working condition.

Tests:
The cargo-oil-tank-pressure/vacuum-valve test of our company is examined in the laboratory which is approved by the national competent authority, and we passed all the tests of following items in accordance with the above standard, obtained the approval of china classification society(CCS) and some foreign classification societies.
I.Fire Resistant Test.
2. Re-burning Test.
3. Frozen Test.
4. Corrosion Resistant Test.
5. Flowing Test.

1. The Pressure Vacuum Relief Valve with different specifications have the same diameter and performance parameter;

2. The opening pressure of the vacuum valves are -3.5kPa, the opening pressure of the pressure valves for the oil tank is 14kPa, but for the chemical tank is 20kPa. The opening pressure of the pressure may be different, but the differences of opening pressure and flow range is inapparent if the pressure valves have the same diameter.

The standardized flange of the high-velocity relief valve is connected with the pipe flange of the cargo oil tank, and the mixed compressed gas will be formed when the cargo oil tank is loading cargoes. The valve on the pressure valve with the block will spring out in a flash, at the same time the valve will open while the pressure of the compressed gas reaches to the set pressure (the oil tank is 14KPa, chemical tank is 20KPa), then releasing the mixed compressed gas to the air with the speed of more than 30m/s (it will be more then 30m/s under the regular operation).

The vacuum will be formed while the cargo oil is tank unloading. the valve will open automatically while the vacuum reaches to the set pressure (it is -3.5KPa), and then the air will go into the tank through the flame screen.

If the pressure is too high while the ship is sailing, the high-velocity relief valve will automatically release the pressure and balance it.

The Pressure-Graph of Pressure Valve 

The Pressure-Graph of Vacuum Valve

The simulant loading and unloading tests shall be done on each graph of the pressure valve according to the operation pressure which provide by Ship Desing & Research Institute, then provide the following graph and flow datum under different pressure to the ship-owner.

Pressure operation testing shall be done on each DF-ISO high-velocity relief valve, make sure it can be operated smoothly during the process of increasing or decreasing the pressure.

As the above-mentioned, assemble the pressure/vacuum valve with different specifications on the ship according to its loading rate, ensure the pressure of the tank is under the specific working pressure, then the pressure valve and vacuum valve will work smoothly no matter the pressure increases or decreases.

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