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Steam boiler piping question

Dairon421 Member Posts: 80
Hey guys so I install penco steam boilers and I always pipe it according to figure 5. My question is why  do one need  two supply's coming off the boiler and the other only have one? Also why do one have swing joints (figure 5) and the other don't? 


  • Jamie Hall
    Jamie Hall Member Posts: 23,559
    Side outlet boilers like that are much happier -- and have more even interior water levels -- when they have two outlets, one on each side. Also, each one only gets half the steam flow, so the velocities are correspondingly half as much and much less water gets carrier over into the steam flow.

    As to the swing joints, they serve to take most of the stress off the boiler as the header piping expands and contracts differently from the boiler (there is an alternate, even fancier arrangement for drop headers in which there are effectively two swing joints on each riser, which takes all of the stress off. It only works, of course, with threaded pipe, since the joints can give a little in rotation (not much -- just enough!). It doesn't work at all with soldered copper, not does it work with welded rather than threaded pipe, since those joints -- though the geometry is the same -- can't rotate even a little. One (of several) reasons to avoid copper for near boiler piping.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,157
    Also the Figure 4 piping does not connect the left section riser with the right section riser. (or front and back depending on the viewpoint) So, the need for the swing joint to keep stress off the boiler sections does not apply.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • mattmia2
    mattmia2 Member Posts: 9,843
    Very small side outlet boilers work ok with one riser if the spec is followed because they aren't producing much steam and it doesn't have to travel across too many sections. If the piping size is smaller than the spec or it is a larger boiler, a single riser will work poorly and produce wet steam which will cause water hammer and spitting vents and will corrode the mains which have much more liquid water in them than just condensate.