Spirax Sarco - Catalogo Agosto 2017

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Upstream pressure bar

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DN15LC

DN15

DN20

DN25

DN32

DN40

DN50

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DN80

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.

SDP143 Pilot Operated Pressure Surplussing Valve with Cast Steel Body TI-P004-01 CH Issue 6

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