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Steam condensate

Long time listener first time caller. I have a question about steam condensate. I have a hospital here in town (Helena MT) that is running 95 psi steam. There was a 4 story addition added about 12 years ago. They are bringing 95 psi steam up to the penthouse and knock the pressure down to lets say 15 psi up there to heat their loads. The condensates then drain into a condensate unit and pump up about 3 feet and over 20 feet before it drops 5 stories to the boiler room. Why would there be a pumped condensate receiver when it is 5 stories above the boiler room and they had room to gravity drain it? Any ideas would be greatly appreciated.
TonKa

Comments

  • pecmsg
    pecmsg Member Posts: 4,677
    Because the boilers operating at 95#’s
    the condensate is much lower pressure.  
    Mad Dog_2
  • bburd
    bburd Member Posts: 869
    edited January 2023
    Right. The static head from draining down five stories is about 22 psig, not enough to put the condensate back into the boiler. It has to be pumped to overcome the 95 psig steam pressure.

    Bburd
    Mad Dog_2
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,296
    In that case I would have gravity drained it to a boiler feed tank in the boiler room
  • sorensenplumbing
    sorensenplumbing Member Posts: 4
    I should have stated that at first. It does drain into a vented condensate receiver where the old boilers used to be. It does run horizontally across a pipe bridge before it gets there and the steam line has main line traps in it along the way. The whole boiler plant was redone about 6 years ago and things may have changed in the design when that was done. The condensate pump is a 20 psi discharge pump so it still couldn’t overcome the 95 psi in the boilers. I appreciate the feedback, thanks!
  • Mad Dog_2
    Mad Dog_2 Member Posts: 6,692
    Yeah because the concern there is your gonna have HP steam running amok in your returns if even more trap fails...just curios what are you supplying w the HP steam?
    Autoclaves, Sterilization? Process equipment?  Mad Dog. 
  • retiredguy
    retiredguy Member Posts: 878
    edited January 2023
    There may be a lot more to the explanation of this steam system that you wrote such as does it utilize a deaerator, which it should, since it has been updated a few years ago. The selection of the condensate pump system was selected by the the company that did the building engineering for the new addition. They could have opted for gravity return or pumped return of the condensate depending on many factors. Either type of condensate return would be acceptable depending on the piping and how it is configured as it returns the condensate to the boiler room. I have seen both types utilized. The pumped return system in a large building is usually more cost effective since a smaller diameter pipe can be routed anywhere it has to go. It is cheaper and easier to install.
  • The system does have a deaerator. They are more than likely supplying high pressure steam to reduce the size of the steam piping and to run autoclaves, sterilization and process equipment. I am trying to figure out why so much of it is running medium pressure steam when it gets to the point of use though. Generally, they are running 15-20 PSI after the pressure regulating valves. As a result, they keep burning up condensate pumps from flash steam and improper installation of the condensate units. I am fighting to explain why they are having issues and explain to them why things need to be changed to prevent the issues in the future. I am suggesting to remove the insulation off of the condensate lines to help cool the condensate off before it reaches the condensate units. Another option if we can't cool the condensate off would be to install a flash tank before the units to vent the flash steam and help cool the condensate. Another option where it would be feasible would be to drop the steam pressure as much as possible. I am not sure why they are running such high pressures (15-20 PSI) when the steam is just being used for hot water and heating a shell and tube heat exchanger in this area.
  • jumper
    jumper Member Posts: 2,206
    StationaryEngineer operating 95 psi steam hopefully knows what he's doing. Many authorities classify now by size of boiler rather than operating pressure. Not so unusual that >>As a result, they keep burning up condensate pumps from flash steam and improper installation of the condensate units.<<
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,296
    @sorensenplumbing

    Unless you or someone has the original drawings or specs to go off you are forced to try to reengineer the job backwards to find which steam pressure they need. It's a bit of work to do that.

    The first thing you need to know is the load it is heating and work backwards from that.

    The only other way is trial and error. Start cutting the steam pressure until someone starts crying
    Mad Dog_2
  • retiredguy
    retiredguy Member Posts: 878
    edited February 2023
    High steam pressure condensate lines should be piped directly to the deaerator, there should be a tapping for those lines, and only low pressure condensate lines return to a condensate tank. The condensate tank then pumps into the deaerator to make sure that the condensate is free of oxygen and contaminates. No condensate should ever be pumped into a high pressure steam boiler except through the deaerator. If condensate enters the boiler through any other means, except if is equipped with a Penberthy Automatic Injector which is used only in an emergency, then the piping is wrong.

    For any questions on the steam pressure settings being utilized anywhere in the building you need to get hold of the original engineering drawings and see what pressures the job engineers specified. Also check with the mfg of any connected device to see what their recommended steam pressure settings are. Heating steam pressures are rarely above 5-6 psig unless there is a reason for a higher pressure or a PRV is in need of repair or is set wrong. Remember this, the engineers for each job get paid to be right all the time even though they are not as infallible as they think they are but "Keep that to yourself".
  • I appreciate all of the input. This system is old and has had remodel on top of remodel and I am finding that nothing has been properly engineered. I am just trying to give them the best product with the least amount of maintenance and repairs down the road. I also don't think that anyone here has grasped high pressure steam and flash condensate ever or at least in a long time. We are starting to get them whipped into shape but there is still a lot to do.
  • JUGHNE
    JUGHNE Member Posts: 11,021
    If you do find original drawings they may not be necessarily correct.

    Small hospital here built in the mid 70's with low pressure steam drawings show 15 PSI relief valves and
    notation from PE states: "operate boilers at 15 PSI"........!!

    I did talk them down from 8 to 5 PSI.