Flash tank needed?

jacobsond

We are having a new system installed on campus. The current setup is on an 85 psi steam supply.The supply goes to a heat exchange for a hot water heating system. The contractor has piped the out of the exchanger through a trap right to the condensate tank.. When the exchanger is in operation with a 50psi input live steam comes out of the vent on the condensate tank. This is not right. Should there be a flash or buffer tank before it gets to the condensate tank? Contractor is currently checking out what needs to be done. I am trying to get information so when they come up with a solution I can be satisfied with the fix. My steam experience is mostly self taught 10yrs read everything I can.I think there should be a flash tank installed because of the super-heated condensate leaving the exchanger.

Intplm.

When you say steam system? Do you mean a new boiler? Commonly, a system would be the piping. This is helpful for discussion purposes.

You mention some very high steam pressures. 85 and 50 psi. Why so high? Often, steam would be 0-15 psi and theoretically considered low pressure. Medium pressure is at times and theoretically, 16-80psi and high pressure is above 80 psi. What is this "system" doing? Is there a pressure-reducing station?

From your description, a "flash tank" would be necessary, but I'm unsure of its design/location.

Pumpguy

I don't know anything about this system, but in a large campus setting, the steam would come from a central steam plant at a high pressure; in this case 85 PSI. Typically, this would go through a pressure reducing station at each building, and then into the building rads.

In this case, the steam is supplying HX for a hot water heating system. It may be that this HX is sized for steam at that pressure; around 325*F.

If not, then the steam pressure should be reduced to provide the steam temperature the HX was sized for.

The need for the flash tank would depend on the temperature of the outgoing condensate.

Another question is what is to be done with the steam that resulted when that high temperature condensate flashed back to steam in the flash tank?

jacobsond

This is a steam system at a college. The pressure on the main line is 85. A contractor installed in a new building a so called high pressure heat exchanger. They said no PRV will be needed. I kind of questioned that decision at the time,but what do I know. Now when the heat exchanger is under full load its running at 50psi. Just one little steam trap. If I had to guess the condensate coming out of the trap is superheated well over 212. Probably closer to 230 or more. When it hits the 0 psi condensate return the stuff turns to steam. I believe it needs a buffer or flash tank to get that temp down. We have tanks like that all over campus before the PRVs on the drip traps. Im waiting on their engineer for the fix. The condenstate needs to be less than 210 coming into the condensate tank/pump. This will be the only building on campus without a PRV.

pecmsg

At MSG our HW generatorwas 15# steam. 85 sounds high.
find and review the original design specs.