Control systems Desuperheaters
4
Strainer Spirax Sarco recommends that a strainer is incorporated in the cooling water supply line to protect both the cooling water control valve and the small bores within the desuperheater from becoming blocked. Isolation valves To allow maintenance to be safely carried out, isolation valves are recommended upstream of: - The superheated steam pressure control valve. - The cooling water control valve.
Safety valve In applications involving simultaneous pressure reduction, a safety relief valve may be needed to protect both the desuperheater and downstream equipment from the effects of:
- Excess pressure in the event of pressure control system failure. - Excess temperature in the event of temperature control system failure.
It is essential that the desuperheater and downstream equipment are suitable for the maximum temperature of the superheated steam. This is to protect these items in the event of a failure of both the pressure and temperature control systems. Recycle loop For SAD steam atomizing desuperheaters with a very high turndown a 'catchpot and recycle loop' are often installed as shown on the diagram below. The recycled condensate is hot which leads to faster absorption. The desuperheater generates a small suction effect to draw the recycle water back to the desuperheater ensuring that the water doesn’t 'by-pass' the desuperheater.
4.8 17
Combined pressure reducing/desuperheating station for steam atomizing type desuperheaters
Pressure controller
Pressure regulating control valve
B
Steam supply
Desuperheater
A
10 ft (3 m)
On/off control
Check valve
Cooling water
Temperature controller
Temperature regulating control valve
TI-P475-06 CTLS Issue 4
Page 7 of 12
Desuperheater Online Program Sizing Guidance
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