The Working Principle Of The Pressure Relief Valve

The pressure relief valve is composed of needle valve I, pressure gauge 2, main valve 3, pilot valve 4 and connecting pipe.
It is a type of hydraulic control valve. The main valve is divided into two parts by the diaphragm, the lower cavity of the diaphragm is the water flow channel, and the upper cavity is the control room, which controls the opening and closing of the main valve disc. The pilot valve itself is a pressure relief valve, it also has a control room and water flow channels, and the opening and closing of the valve disc is controlled by the control room. The needle valve is the throttle valve, which controls the flow of water in the connecting pipe.
During the operation of the fire water supply system, the main pipeline water flow direction from left to right, all the way to control the water into the pilot valve control room, when the pressure of the water is less than the set pressure relief value, the thrust of the pilot valve spring is greater than the pressure of the water, and the pilot valve disc is in a closed state. The other way controls the water through the throttle needle valve into the upper cavity of the main valve to produce a static pressure, the pressure of the upper cavity is equal to the pressure in the raw flow channel. Since the upper plane of the main valve disc is larger than the lower plane, the pressure of the upper cavity on the valve is greater than the push of the water on the valve in the main channel, so that the main valve is in a closed state. If the water flow pressure of the main pipeline rises and exceeds the set pressure relief value, the water flow pressure entering the conduit control room through the control pipe increases, and the water pressure is greater than the spring thrust At this time, the pilot valve is opened, and the pressure relief begins on the upper part of the main valve. Due to the control of the throttle valve, the water replenishment is insufficient, resulting in a decrease in the pressure of the upper cavity of the main valve, and the main valve is ice under the same lobe.