Control systems Pressure reducing/surplussing valves
4
Steam capacities chart
Note The capacities quoted above are based on valves fitted with an external pressure sensing pipe. Reliance on the internal balance pipe will mean that capacities may be reduced. In the case of low downstream pressure this reduction could be up to 30% of the valve capacity. How to use the chart Saturated steam A valve is required to pass 600 kg/h (1323 lb/h) reducing from 6 bar to 4 bar (87.0 psi to 58.0 psi). Find the point at which the curved 6 bar (87.0 psi) upstream pressure line crosses the horizontal 4 bar (58.0 psi) downstream pressure line. A perpendicular dropped from this point gives the capacities of all DP sizes under these conditions. A DN32 (1¼") valve, is the smallest size which will carry the required load. Superheated steam Because of the higher specific volume of superheated steam a correction factor must be applied to the figure obtained from the chart above. For 55 °C (131 °F) of superheat the factor is 0.95 and for 100 °C (212 °F) of superheat the factor is 0.9. Using the example given for saturated steam, the DN32 (1¼") valve would pass 740 x 0.95 = 703 kg/h (1550 lb/h) if the steam had 55 °C (131 °F) of superheat. It is still big enough to pass the required load of 600 kg/h (1323 lb/h).
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TI-P107-01 CTLS Issue 13
Page 9 of 14
DP163, DP163G and DP163Y Pilot Operated Pressure Reducing Valve with Stainless Steel Bodies
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