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Installation and Maintenance Best Practices for Loose Flange Connections

Installation and Maintenance Best Practices for Loose Flange Connections

Apr 09,2024

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The performance and characteristics of pressure reducing valve and other basic knowledge

The pressure reducing valve reduces the higher liquid pressure in the line before the valve to the level required in the line after the valve. The transmission medium here is mainly water. Pressure reducing valves are widely used in high-rise buildings, areas where the water pressure of the urban water supply network is too high, mines and other occasions to ensure that each water point in the water supply system obtains proper service water pressure and flow. Since the leakage rate and waste of water are almost proportional to the water pressure of the water supply system, the pressure reducing valve can improve the operating conditions of the system and potentially save water. According to statistics, the water saving effect is about 30%.


1. The working principle of the pressure reducing valve

(1) The pressure reducing valve reduces the water pressure by the local resistance of the flow passage in the valve to the water flow. The range of the water pressure drop is automatically adjusted by the diaphragm connecting the valve disc or the inlet and outlet water pressure differences on both sides of the piston. The principle of constant ratio decompression is controlled by the water pressure ratio of the floating piston in the valve body, and the decompression ratio at the inlet and outlet is inversely proportional to the area ratio of the piston at the inlet and outlet. This pressure reducing valve works smoothly and without vibration; there is no spring in the valve body, so there is no concern of spring corrosion and metal fatigue failure; good sealing performance and no leakage, so it reduces both dynamic pressure (when water flows) and static pressure (flow rate is 0 hours). In particular, it does not affect the water flow while decompressing.

(2) The pressure reducing valve adjusts the flow of the medium by controlling the opening degree of the opening and closing parts in the valve body, reduces the pressure of the medium, and at the same time adjusts the opening degree of the opening and closing parts with the help of the pressure behind the valve, so as to keep the pressure behind the valve. Within a certain range, cooling water is sprayed into the valve body or behind the valve to reduce the temperature of the medium. This valve is called a decompression and temperature reduction valve. Quick and easy automatic selection of pressure reducing valve is included. The characteristic of this valve is to keep the outlet pressure and temperature within a certain range when the inlet pressure is constantly changing.

2. The performance of the pressure reducing valve

(1) Flow characteristics: it refers to the characteristics of the input pressure-timing, the output pressure changes with the output flow. When the flow changes, the smaller the change in output pressure, the better. Generally, the lower the output pressure, the less it fluctuates with the output flow.

(2) Pressure regulating range: it refers to the adjustable range of the output pressure of the pressure reducing valve, within which the specified accuracy is required. The pressure regulating range is mainly related to the stiffness of the pressure regulating spring.

(3) Pressure characteristics: It refers to the characteristics of output pressure fluctuations caused by input pressure fluctuations when the flow rate is a fixed value. The smaller the output pressure fluctuation, the better the performance of the pressure reducing valve. The output pressure must be lower than the input pressure - a fixed value that basically does not change with the input pressure.

3. Pressure adjustment steps of the pressure reducing valve

(1) Close the gate valve before the pressure reducing valve and open the gate valve after the pressure reducing valve to create a downstream low pressure environment.

(2) Turn the adjusting screw counterclockwise to the uppermost position (relative to the lowest outlet pressure), and then close the pressure reducing valve.

(3) Slowly open the gate valve in front of the pressure reducing valve until it is fully open.

(4) Slowly rotate the adjusting screw clockwise to adjust the outlet pressure to the required pressure (subject to the gauge pressure behind the valve); after adjustment, tighten the lock nut and open the pressure reducing valve.

(5) If the outlet pressure is higher than the set pressure during adjustment, it must be readjusted from the first step, that is, it can only be adjusted from low pressure to high pressure.

Although the water flow through the pressure reducing valve has a large head loss, it is still energy-saving on the whole because it reduces the waste of water, makes the system flow distribution reasonable, and improves the system layout and working conditions. When the medium is steam, pilot piston type pressure reducing valve or pilot bellows type pressure reducing valve should be used. For the convenience of operation, adjustment and maintenance, the pressure reducing valve should generally be installed on the horizontal pipeline. The above is about the basic knowledge of the performance and characteristics of the pressure reducing valve. If you have any questions, you can consult us!

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