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DA tank vent discharge

DA tank vent discharge

DA tank vent discharge

I have a new steam boiler plant installation with a 26,000 #/hr spray type dearator. We run the DA tank at the recommended 5 psi. The DA tank vent where the steam and bad gases continuously vent off was installed with a couple of elbows in it. We are getting intermittent spouting of liquid condensate out the vent pipe. I am pretty sure that the offsets are causing the liquid spouting out the vent on the roof, but am looking for some re-assurance an 2nd opinions here. If the contractor re-pipes the vent straight out the roof (no offset elbows) should I expect steam with a few droplets coming out? Or no drops of condensate (purely steam vapor) coming out the vent? I have seen other DA vents and just seen straight steam vapor though I didn't really study them.


RE: DA tank vent discharge

I'd wager that you're correct in that some condensate is collecting in the run between the two elbows - most likely, there's a bit of a low spot there (I doubt they sloped the pipe back toward the DA). I wouldn't expect to see any sputtering of water out of that vent during steady-state operation. If taking the vent straight out isn't an option, consider replacing the 90s with 45s and slope it back toward the DA - that should alleviate any condensate collecting in a low spot also.

Edit: This issue reminds me of a somewhat similar issue I encountered in the past. Another engineer had installed an atmospheric vent on a raw water line (to get rid of an air release valve). Every so often, the vent would "burp" and spray raw water all over the room it was routed too - turns out, the line was routed with multiple, local low spots. During system transients, these low spots would accumulate water, until the transients eventually pushed the water out at the top.

RE: DA tank vent discharge

IMO, it may be help to enlarge the vent pipe size to let the gas passing through.
Or, replace one elbow with a tee and add a small drain pipe to grade. So, the water can be knocked down at tee and drained.

RE: DA tank vent discharge

We proceeded with re-piping the DA tank vent with 45 degree elbows instead of the 90 degree elbows thinking that the less friction / easier flow path would prevent the condensate from forming (if that is what the water is). After putting back in service the problem first appeared to be gone, but only briefly. In the days since the problem still persists with essentially no change in the amount of water that spouts out the DA vent. I now wonder if eliminating the elbows altogether will solve the problem or not, or if there is a problem with the internals of the DA.

RE: DA tank vent discharge

Are you maintaining water level where it is supposed to be?

RE: DA tank vent discharge

Can you give us a quick sketch of your piping, along with the pipe size you are using?

Edit: Upon receipt of the DA, was the spray system (and specifically, spray nozzles) inspected to ensure they were free from damage? That may be another possible source of water entrainment in the vent...

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