Re: DA Tank overfill

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Posted by AKP on July 30, 2001 at 08:12:21:

In Reply to: Re: DA Tank overfill posted by Manny Silva on July 29, 2001 at 12:49:08:

: What hookie setup .It should be as follows all make-up should be from the water softener and go in the D.A over the trays or sprays when the D.A.calls for water.The condensate should drop in to the top of the storage section of the D.A.On you condensate tank you need a level control,when you have condensate in the tank it is pumped to the D.A. Now you need a diversion valve installed on the condensate line after the condensate pumps and before the D.A you need a controller on the D.A that when the level in D.A is to high the Divert valve will dump excess condensate to the sewer.You only need make-up if there is not enough condesate.Put sulfite in your condensate tank.

It appears that you are referring to a much larger system than we operate. Many larger plants, power generating plants, etc., will have a different arrangement than these small heating plants typically have. Some larger plants will have a DA/Storage tank combination, in a T configuraton with the DA tank in a vertical position physically connected to the horizontal feed storage tank. The last power generating plant I worked at had two 10,000 gallon Graver tray type deaerators that fed a separate 100,000 gallon feed storage tank. It is fine to admit maek-up water into the DA tank if it is designed to work that way, ours is not. In many of these smaller heating plants, this one for example, the configuration is usually something like this. There is a single spray nozzle, horizontal, (and trayless) DA tank, that runs between 5 and 10 psig. The tank has little reserve storage, enough to run at full load for 10 min without condensate/make-up feed to the DA tank. The condensate tank is separate and receives condensate, both pumped and drip, and make-up. The condensate feeds the DA tank when it calls for water. This arrangment is very typical for these types of plants. All chemical O2 scavengers are fed into the DA tank. In this situation, to feed the make-up water into the DA tank, only to overflow it to fill the condensate tank, is a circus, the overflow valve is not designed for it, the entire system was not designed for it. The make-up is heated and deaerated twice, and does nothing to combat our (former) problem with O2 contamination, in fact, the change to admitting make-up feed into the DA tank to combat O2 contamination was done after the problem was gone. The O2 pitting problem occured with the contractor who built it, and later possibly with bad mechanical seals on the feed pumps (which was a continual problem until the pumps were replaced). The entire setup may be "hookie", as you state, but it is very typical for these types of plants, that might be because of some government criteria that dictates this system, my 25 years of operation of power plants, boiler plants,etc., have all been government, so in my experience it is a typical setup for a high pressure steam heating plant.


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