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Flash tank venting

JoeC
JoeC Member Posts: 43
in THE MAIN WALL
Our rather large 30# steam system has a flash tank located in a basement(dungeon),and its 2"vent runs straight up and out. Somebody has suggested that the vent be rerouted horizontally in several loops to 'radiantly heat' an outdoor train staging area. I'm not to sure this is a smart thing to do, I'm worried that the additional piping will create further back-pressure in the condensate return system, the condensate that forms in the added piping may cause hammering, said condensate will have the potential of freezing, and because the condensate that does form will be to costly to put back into the system by design, it's planned to be dumped into a drainage system. Personally, I feel a form of GFHX (gravity flow heat exchanger) in-line with the current vent would be a better way to go. Your comments will be appreciated! Joe

Comments

  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,600
    How about

    a shell-and-tube exchanger, installed upside down so that the flash goes into the steam opening and vents to the roof from what would be the exchanger's condensate drain. Pipe this directly above the flash tank. Use the tube side of the exchanger for you heating. Set that up with a circulator, compression tank, three-way valve and whatnot.
    Retired and loving it.
  • JoeC
    JoeC Member Posts: 43
    Thanks Dan!

    I'm glad somebody responded, it's not because I just received your E.D.R. mailing today, right?! Seriously, the engineers in my neighborhood have me wondering sometimes. The flash tank re-(in)vent idea they told me today, "Will help eliminate the plume of steam from that flash tank vent all together!", "And obviously one of the traps that you rebuilt is still having a problem." (Not only were all 175 traps rebuilt, but re-inspected ultra-sonically) I left a copy of page 144 & 145 from "The Lost Art of Steam Heating" next to the office coffee pot, with a handwritten note to "Please read and initial", it was awfully quiet in the office at quitting time!
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 16,600
    Great story.

    Thanks, Joe!
    Retired and loving it.
  • Tony Conner
    Tony Conner Member Posts: 549
    You Need To Be Really Careful...

    ...that the vent doesn't get restricted. I've seen guys install valves in condensate tank vents so the flash steam could be re-directed for heat recovery. You need to make very sure that the tank can't be over-pressured by a failed trap. You can suddenly get a lot of pressure in a tank that isn't rated for it. (It's usually some rusty, 40 year old bone of a tank, too.)

    Be careful what gets done on 30# steam systems. There are code issues to be considered. And this is in addition to screwing-up the heating system.
  • Art Pittaway
    Art Pittaway Member Posts: 230
    If you go the shell and tube route,

    order the shell's condensate opening at an appropriate size for venting, otherwise you will get whatever the Mfg. uses on that size shell. If your 30psi flash (???lbs/hr) is known, you can size it. Spirax-Sarco has some nice tables and data on industrial steam applications. Art
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