Desuperheater Advantages

Turndown ratio		Compact designs		Outlet superheat		Materials
Pressure drop		Design codes		Water conditions		Orientation

Water conditions

Graham desuperheaters require the water pressure at the desuperheater nozzle to be at or above the main steam pressure. However, recommended water pressure for all of Graham's desuperheater designs is 5 psi over the main steam pressure. This allows for pressure losses between the nearest pressure control valve and the point of use.

Water temperature should be as close as possible to saturation, so that water droplets do not have to absorb sensible heat to warm up to the saturation point before vaporizing. Using subcooled water increases the likelihood that water will drop out of suspension without vaporizing, resulting in less desuperheating, thus, high temperature sensor readings. From a mechanical viewpoint, unevaporated water can cause erosion on the bottom of the pipe line, or cause thermal stress that may result in cracking of the downstream pipe.

Graham Venturi desuperheaters are fabricated with a "thermal sleeve" around the water inlet to warm up the water before it enters the spray nozzle. Our R&D testing confirms that this extra measure is sufficient for our designs. Our steam-atomizing desuperheaters do not require the thermal sleeve, due to operation of the nozzle, which mixes the water with high pressure steam before injecting the mixture into the main steam pipe.

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