Calculation of Pressure Regulators for Gases   Calculating the nominal diameter To keep pressure drop and noise within acceptable limits, certain flow velocities in the pipelines should not be exceeded. If no values have been specified we recommend the following: up to 10 mbar 2 m/s up to 100 mbar 4 m/s up to 1 bar 10 m/s up to 10 bar 20 m/s above 10 bar 40 m/s These rough guidelines apply to pipe diameters from DN 80 up. For smaller diameters lower flow velocities should be used. To calculate the flow velocity we need the flow rate figure under operating conditions. This may be calculated as follows: Accordingly in our example the flow rates upstream and downstream of the valve are as follows: m³/h m³/h The pipeline diameter can be calculated as follows: If in our example maximum flow velocities of 20 m/s upstream and 15 m/s downstream of the valve have been specified, the following pipeline diameters will be required: = 45,5 mm = 59,6 mm Consequently we would recommend a DN 50 pipeline upstream and a DN 65 pipeline downstream of the valve. For a given nominal diameter the flow velocity can be calculated as follows In our example we would thus obtain the following flow velocities m/s m/s For certain operating conditions a control valve may be selected whose nominal diameter is one or two sizes smaller than the nominal pipeline diameter. Downstream of the valve the pipeline diameter may be increased by one or two sizes depending on the flow velocity; this applies especially to valves with sense line. 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)