How a safety valve works

Safety valve is designed to protect pipeline systems from exceeding the pressure above the maximum allowable value. When the maximum allowable pressure is reached, the safety valve opens and releases the excess volume of water. The valve's shutter remains in the open position, and water is discharged until the pressure at the installation site of the safety valve drops to an acceptable value.

The principle of operation is demonstrated using an example of a proportional safety valve with a spring set, installed in a system filled with water.

The principle of operation of the safety valve is based on the counteracting forces on the shutter: the force of the water attempting to open the valve, and the force of the spring, which aims to keep the shutter in the closed position.

The safety valve remains closed until the pressure of the water on the shutter exceeds the force of the spring holding it closed. It should be noted that the pressure at which the valve starts to open exceeds the safety valve setting pressure by approximately 3%.

After the shutter is lifted, further pressure increase will cause a proportional rise in the shutter and an increase in the volume of water being released. The full opening of the safety valve occurs when the pressure exceeds the safety valve's setting pressure by approximately 13%.

After releasing the excess volume of water, the pressure at the installation site of the safety valve begins to drop, and as soon as the force of the spring exceeds the static and dynamic pressure of the water flow, the shutter will block the passage. The full closure of the safety valve occurs when the pressure at its installation site drops to 20% less than the setting pressure, which is due to the additional counteraction of the dynamic pressure of the water flow.

For more details on the setting pressures, opening start pressure, full opening, and closing of the safety valve, refer to the section Technical Specifications.

Normally closed safety valve is named as such because its shutter remains in the closed position when there is no pressure at the installation site or when the pressure is lower than the opening pressure.

Proportional safety valve is named as such because the speed and degree of shutter displacement are proportional to the speed and degree of pressure exceeding the set value.