steam heater regulation

[lorang]

hello

I'm working on the regulation of a steam heater. It's capacity is about 2000 kW. So there are a control valve at the inlet of the steam. It controls the temperature of water at the outlet by controlling the flow of steam. A steam trap is at the outlet.
The problem is that the power required varies a lot (0 to 100%). So, there is a risk of stall of the heater.
The condensate line can be at 2 bara. We don't want to put a pump trap for cost reasons and because there are not a lot of place under the heater.
So, to eliminate the problem of hammer in the heater when there is a demand of power, I thing to put a deltaP gauge on the trap. When the temperature controller send a signal to open the control valve, this signal will be limited by a control of deltaP on the trap during of a period T. So at the start, there will be only a few amount of steam, that will limit hammer.
We are agree that there will be a bad control of temperature when the power is low, but this is not a real problem.
What do you think about this solution?
Thank you for your advise.

 

[MJCronin]

lorang...

Sometimes the problems of steam heater "hammer" and stall will go away if there is adequate volume for collection of condensate.

Steam hammer and "stall" are transient phenomina where the levels of condensate swing violently within the heater due to problems outside of the heater.

Have you considered putting a "collection pot" beneath your heater ? (I am assumming, of course, that you have a horzontal shell-and-tube type unit)

Try these links:

http://www.spiraxsarco.com/learn/html/13_1_01.htm

http://www.spiraxsarco.com/learn/html/13_5_01.htm

and page 29 of this document...

http://www.nrel.gov/docs/fy04osti/35106.pdf

As a common courtesy of a professional, please come back to us with your fix and the reasons for it...

My opinion only


-MJC

 

[lorang]

we have a collecting pot beneath the heater. The problem is that the power of heater can be very low for several hours and after the power demand will increase rapidly. So, with traditional regulation, the steam control valve will open rapidly and the water in heater (stall) will be ejected with a big velocity that can create a hammer. It's to avoid this that I suggest the regulation describe above.