Technical specifications of relief valves

DN of the relief valve — nominal diameter of the opening in the connecting pipes. The DN value is used to standardize the sizes of pipeline valves. The actual diameter of the opening may slightly differ from the nominal diameter in either direction. An alternative designation for the nominal diameter DN, commonly used in the post-Soviet countries, was the conditional diameter Du of the relief valve. A range of DN sizes for pipeline valves is regulated by GOST 28338-89 'Conditional Passages (Nominal Sizes)'.

PN of the relief valve — nominal pressure - the maximum excess pressure of the working medium at a temperature of 20°C, at which long-term and safe operation is ensured. An alternative designation for the nominal pressure PN, commonly used in the post-Soviet countries, was the conditional pressure Ru of the relief valves. A range of PN nominal pressures for pipeline valves is regulated by GOST 26349-84 'Nominal (Conditional) Pressures'.

Kvs of the relief valve — coefficient of flow capacity corresponds to the water flow rate, in m³/h at a temperature of 20°C, at which the pressure drop on the relief valve will be 1 bar. The value of the flow capacity coefficient is used in hydraulic calculations to determine pressure losses.

Adjustment range — the range of pressures maintained by the relief valve, depends on the spring elasticity (force of the set point adjuster). As a rule, the wider the adjustment range of the relief valve, the less accurate the pressure maintenance.

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