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

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.

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.

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