Calculation of Pressure Regulators for Gases   Calculating the Kv-value The selection of a valve requires first of all that the Kv-value is determined from the operating data under which the valve is to operate.For subcritical pressure drops, i.e. if use formula or for supercritical pressure drops, i.e. if use formula Kv Flow Coefficient m³/h QN Volume Flow m³/h Q1 Volume Flow Upstream of the Valve m³/h Q2 Volume Flow Downstream of the Valve m³/h pN Density kg/m³ Δp Differential Pressure ( p1-p2 ) bar p1 Inlet Pressure ( abs.) bar p2 Outlet Pressure (abs.) bar t1 Temperature at Inlet °C t2 Temperature at Outlet °C w1 Velocity before the Valve m/s w2 Velocity behind the Valve m/s d1 Nominal Diameter before the Valve mm d2 Nominal Diameter behind the Valve mm Example: We are looking for a stainless steel pressure reducing valve for QN max. 1200 m³/h CO2, operating temperature 20 °C, density 2 kg/m³, inlet pressure 10-12 bar above atmospheric, controlled outlet pressure 7 bar above atmospheric. The pressure drop is subcritical, as , namely 3 < . Hence = 11,54 m³/h To the Kv-value calculated from the operating data we add an allowance of 30 % and thus obtain the minimum Kvs-value which the valve to be selected should have. Kvs-value = 1,3 x Kv-value = 1,3 x 11,54 = 15 m³/h Continue Liquids Gases Steam   Kv-value   Kv-value   Kv-value   Nominal diameter   Nominal diameter   Nominal diameter   Valve selection   Valve selection   Valve selection download the PDF-file: Calculation of pressure regulators / PDF (156 kb)