Regulating valve knowledge

- Nov 05, 2019-

Performance

(1) Pressure regulation range: It refers to the adjustable range of the pressure reducing valve output pressure P2, within which the specified accuracy is required. The pressure regulation range is mainly related to the stiffness of the pressure regulating spring.

(2) Pressure characteristics: It refers to the characteristic that the output pressure fluctuates due to input pressure fluctuation when the flow rate g is constant. The smaller the output pressure fluctuation, the better the characteristics of the pressure reducing valve. The output pressure must be lower than the input pressure—the set value does not substantially change with the input pressure.

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

It reduces the higher liquid pressure in the pre-valve line to the level required for the post-valve line. The transmission medium here is mainly water. Pressure reducing valves are widely used in high-rise buildings, urban water supply networks, water pressure areas, mines and other occasions to ensure that the water supply system in the water supply system to obtain appropriate service water pressure and flow. Since the water leakage rate and the degree of waste are almost proportional to the water pressure of the water supply system, the pressure reducing valve has an improved system operating condition and potential water saving effect, and the water saving effect is about 30% according to statistics.

stainless steel Check valve

1. Close the gate valve before the pressure reducing valve, open the gate valve after the pressure reducing valve, and manufacture the downstream low pressure environment;

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

3. Slowly open the gate valve before the pressure reducing valve to fully open;

4. Turn the adjusting screw slowly clockwise to adjust the outlet pressure to the required pressure (based on the valve back pressure); after adjustment, it will lock

The nut is locked, and the gate valve is opened after the pressure reducing valve is opened;

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

Principle

Function principle: 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 pressure difference between the inlet and outlet of the membrane or the piston connected to the valve flap. The principle of constant pressure reduction is to use the water pressure ratio control of the floating piston in the valve body, and the pressure reduction ratio at the inlet and outlet ends is inversely proportional to the ratio of the piston area on the inlet and outlet sides. The pressure reducing valve works smoothly and without vibration; there is no spring in the valve body, so there is no spring corrosion and metal fatigue failure; the sealing performance is good and does not leak, so the pressure is reduced (when the water flows) and the static pressure is reduced (the flow rate is 0 o'clock); especially during decompression without affecting water flow.

Working principle: The pressure reducing valve adopts the opening degree of the opening and closing member in the control valve body to adjust the flow rate of the medium, reduce the pressure of the medium, and adjust the opening degree of the opening and closing member by the action of the pressure behind the valve to maintain the pressure behind the valve. Within a certain range, cooling water is sprayed into the valve body or behind the valve to lower the temperature of the medium. This type of valve is called a decompression and desuperheating valve. Pressure relief valve quick and easy automatic selection is included. The valve is characterized by keeping the outlet pressure and temperature within a certain range in the case of constant changes in inlet pressure.

Butterfly valve

Advantage

Although the water flow through the pressure reducing valve has a large head loss, it is still energy-saving in general because it reduces the waste of water and makes the system flow distribution reasonable and improves the system layout and working conditions. Where the medium is steam, a pilot piston type pressure reducing valve or a pilot bellows type pressure reducing valve should be used. For ease of operation, adjustment and maintenance, the pressure relief valve should normally be installed on a horizontal pipe.

Precautions

1. For ease of operation and maintenance, the valve is generally mounted upright on a horizontal pipe.

2. The installation of the pressure reducing valve must be consistent with the direction of fluid flow in strict accordance with the direction of the arrow on the valve body. If the water quality is not clean and contains some impurities, the filter must be installed at the upstream inlet of the pressure reducing valve.

3. In order to prevent post-valve pressure overpressure, a pressure reducing valve should be installed at not less than 4M from the valve outlet.

4. The pressure reducing valve plays a certain role in the pipeline. In order to prevent the damage of the water hammer, a small expansion tank can also be installed to prevent damage to the pipeline and the valve. The filter must be installed in front of the inlet pipe of the pressure reducing valve. The expansion tank must be installed after the pressure relief valve outlet!

5. If the pressure relief valve needs to be installed in a hot water system, you must install a check valve between the pressure relief valve and the expansion tank. In this way, the expansion tank can absorb the volume of water increased due to thermal expansion, and can prevent the influence of hot water return or pressure fluctuation on the pressure reducing valve, and ensure that the pressure reducing valve works normally for a long time.