44
Control systems Pressure reducing/surplussing valves
Steam capacities chart
4.6 160
Upstream pressure bar
DN15LC
DN15
DN20
DN25
DN32
DN40
DN50
DN80
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 reducing from 6 bar to 4 bar. Find the point at which the curved 6 bar upstream pressure line crosses the horizontal 4 bar downstream pressure line. A perpendicular dropped from this point gives the capacities of all DP sizes under these conditions. A DN32 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 of superheat the factor is 0.95 and for 100 °C of superheat the factor is 0.9. Using the example given for saturated steam, the DN32 valve would pass 740 x 0.95 = 703 kg/h if the steam had 55 °C of superheat. It is still big enough to pass the required load of 600 kg/h.
TI-P470-08 CTLS Issue 5
Page 8 of 12
DP27T and DP27TE Pilot Operated Pressure/Temperature Control Valves with SG Iron Bodies
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