Desuperheater system design
Desuperheater system design
(OP)
thread124-198506
I am responsible for designing a spray water system for a desuperheater that utilises steam condensate. We are currently using boiler feed water but it is causing caustic embrittlement on the steam piping, hence the change.
I am sizing a pump and control valve for the new system and my questions are:
1) What minimum pressure is required of the spray water at the point of injection into the steam (relative to steam pressure)?
2) Is there a minimum pressure drop that is required over the spray water control valve to ensure proper desuperheating operation?
Thanks in advance.
I am responsible for designing a spray water system for a desuperheater that utilises steam condensate. We are currently using boiler feed water but it is causing caustic embrittlement on the steam piping, hence the change.
I am sizing a pump and control valve for the new system and my questions are:
1) What minimum pressure is required of the spray water at the point of injection into the steam (relative to steam pressure)?
2) Is there a minimum pressure drop that is required over the spray water control valve to ensure proper desuperheating operation?
Thanks in advance.





RE: Desuperheater system design
Valve pressure drop: a different Rule of Thumb is that one-third of syste pressure loss should occur across an open control valve. So if you have a 1000 psi source feeding a 900 psi steam header, That represents 100 psi system loss. So the valve needs to drop 33 psi in its wide-open configuration. Again, that depends upon the nature of the source pressure, pump curve, etc. but it's a place to start.
RE: Desuperheater system design
I have had bad experiences with desuperheaters, and in future will buy the best desuperheater, with the highest turndown, place the TI as far away as possible and keep to the recommended steam velocities.
RE: Desuperheater system design
You don't have a separate control valve as the desuperheater stem moves up or down as needed to achieve the required steam temperature. You just size your pump for the required head based on the range of steam pressures (Yarway prefers to have the water minimum 50 psi above the steam pressure).
Depending on the flucations in steam flow you may need to provide minimum flow protection for your pump.
RE: Desuperheater system design
Still, the concept should work well if you have adequate water pressure over (maximum) steam pressure at minimum pump discharge pressure (out on the curve). I am with JimCasey as part of the 50 psig school of thought.
Is your current system steam or mechanical atomized? What type of turndown do you expect? How much superheat are you trying to get rid of. Is 10F over sat good enough for your application? Is the rest of your system by the book; adequate downstream distance to next elbow, proper velocity in steam pipeline, etc?
rmw
RE: Desuperheater system design
deduperheater mfr.
Some require a certain piping "straight length" both upstream and downstream.
I have always liked the Copes Vulcan products. This company has been around forever...... has been in powerplant applications for many years.
http://
Talk with them about process requirements and turndown.
Please complete this thread and let us know more details about your specific application and your final choice..
-MJC
RE: Desuperheater system design
RE: Desuperheater system design
http://www.ccivalve.com/index.html
Do any of you have experience with CCI desuperheaters or with this cool mist nozzle?
RE: Desuperheater system design
RE: Desuperheater system design
Regards,
athomas236
RE: Desuperheater system design
http://www.komax.com/products/desuperheater.html
One thing to watch for is the presence of water droplets down stream of the desuperheater. These droplets can cause differential thermal cracking if they hit the wall.