Technical specifications of check valves

DN - nominal diameter - a conditional designation of the size of pipeline fittings. The nominal diameter value has no dimension and is approximately equal to the inner diameter of the opening in the connecting flanges of the check valve, measured in millimeters. Nominal diameters are adopted for the standardization of sizes of pipeline fittings and elements of pipeline systems.

PN - nominal pressure - the maximum allowable water pressure at 20°C, at which prolonged operation of the check valve is permissible.

Ppr - test pressure - the water pressure at a temperature of 5 to 70°C, at which the hydraulic test of the check valve for strength and tightness should be carried out.

Reverse valve opening pressure - the pressure difference between the inlet and outlet flanges of the valve at which the gate begins to open the passage. The pressure of full opening corresponds to the necessary pressure difference for the full opening of the gate.

Pp - working pressure - the maximum excess pressure for each temperature of the working medium at which prolonged operation of the check valve is permissible.

For most types of pipeline fittings, operation at nominal pressure with the maximum allowable temperature is not allowed. Therefore, with an increase in pressure to nominal, the maximum working temperature decreases.

Kvs - flow coefficient - its value corresponds to the water flow rate in m³/h at a temperature of 20°C, at which the pressure drop on a fully open check valve is 1 bar. The flow coefficient of the check valve is used in their selection and in hydraulic calculations of pipeline systems.

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