High pressure steam to low pressure push pull vacuum steam condensate trouble

rossc1986

Ok so here we go. I am a new service journeyman and limited experience with steam systems and have landed myself in an account where I am working in a water treatment plant with high pressure steam generators supplying 80psi steam to the mains which head off to reducing stations (which were pretty much all bad, and I have replaced) and the condensate reciever tanks on the low pressure sides are vacuum receivers that pump back to the boiler feed tanks. Sounds simple right?!? Well the problem I'm having is that one of the buildings is having trouble with the reciever tank blowing steam and condensate out through the vent. I found bad traps and have replaced them all, and have been able to get the return from the low side down to around 165*fitter, but there are 3 traps (2-ft125h3, and 1- b2250a installed last year by another fitter who retired) the 2 f&t traps are in the high pressure main running down the hall and the bucket is the end of main trap at the inlet of the reducing station. I am having trouble running the reciever in vacuum, because I can't keep the in coming condensate at a low enough temp., the condensate from the 3 high pressure traps is over 200*f (normally between 212 and 216 if I'm lucky). The manufacturer says the pumps max temp it can handle is 199*fitter, and it honestly doesn't seem to like that. I guess my question is, are those traps the wrong size or type? Should they not be piped into the vacuum reciever, but into the main return line, passed the check valves after the pumps? I'm kind of at a loss. When I first got on site none of the reciever tanks were running vacuum, they were switched to float or continuous, and theyou were trying to maintain 5psi-9psi using the bypass valves, or just had no heat in many of the buildings. Most of the buildings are 1-2 stories with a basement, the building i'm having the above issues with is 4 stories with the reducing station and receiver in the basement. Hope someone understands any of what I wrote and can help! Thanks in advance for any help I can get.

bob_46

I think you should pipe those high pressure traps to a flash tank.
Do you have a copy of Sarco's Hook-Ups ? You should get one. It sounds like you are doing a good job and are on the right track.

jumper

Superheat from pressure reducing station?

EBEBRATT-Ed

@Bob is right on with this one. Sarco's book is available on line and you can download and print it (takes a little searching).

Sounds like your getting more flash steam than the vacuum pump can handle.

Look for Sarco "Design of Fluid systems" & "Steam system utilization"

Something doesn't sound right. Sounds like you have high pressure returns mixed with low pressure returns which will cause problems if the HP traps go bad or if their are to many of them. You may need to separate the high pressure returns from the low and run the HP into a flash tank as @Bob mentioned

If you need help find out from your supply house who your local Sarco rep is and make contact with him. They can help you with this

jumper

Not OP's call but in long run steam to steam is preferable to expanding steam. For one thing low pressure condensate doesn't have to be pumped back up to high pressure.Decades ago Roth Pump used to sell packages to handle boiling condensate and I think they stopped.

stopgogo

flashtank