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Drop Header

Billy_3
Billy_3 Member Posts: 42
How come people install drop headers on steam boilers. Is it better for any reason? I never install them unless I need one to get the 24" above the water line. What happens if you use a regular header?

Comments

  • Steamhead
    Steamhead Member Posts: 14,704
    First, they're much easier to put together

    since you have two swing joints on each riser. You just install your horizontal nipples and union, swing them into place and make up the union. No more fighting to put the header together!

    Second, the double swing joint is much easier on the boiler as it expands and contracts.

    Third, you really can't get too much height between the waterline and the header. 24 inches is a minimum, more is better. A drop header lets you make those risers higher.

    We now use drop headers on all our steamers.

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  • nickdu
    nickdu Member Posts: 23
    edited October 2012
    Building a drop header

    As I think the main problem with my steam system is the near boiler piping, I've been trying to research headers and drop headers.  Not sure if this is something I'll attempt to tackle myself or not, but I did want to understand steamhead's post here.



    What are the two swing joints in the drop header?  My guess was that the bottom connector on either end of the horizontal pipe can be rotated and thus is one swing joint, and the entire vertical member could be rotated through the top elbow and that would be another swing joint.  Is that correct?  I guess a normal header only has one swing joint?



    Is there a prescribed way to build a drop header?  I've seen some, based on pictures I've seen in posts on this site, that have no union in the header but a union in each riser.  I guess this method let's you build the entire header first and then connect it to the risers.  Other pictures I've seen have no union in the risers but a union in the header.  Is one way better or easier than the other?



    Thanks,

    Nick
  • Rod
    Rod Posts: 2,067
    edited October 2012
    Dropheader

    The sections of the boiler are like slices of bread bolted together. With the standard boiler piping the tees in the header hold the risers rigid so that when heat expands the header pipe, tension is put on the boiler sections, trying to force them apart. With the drop header the header pipe can expand and the elbow to tee joint can, if necessary, slightly move which results in less tension on the boiler sections. 

       The unions in the boiler risers make the piping easier to put together and allows you to disconnect the boiler from the piping if ever necessary for maintenance or replacement.

    I've only helped pipe a couple of headers but the ease at which the dropheader goes together I'm sure makes up in saved labor over the cost of a few extra fittings especially if you misjudge one of the measurements a bit.

    As Steamhead mentioned it is the height of the risers that counts and the dropheader allows you to get plenty of height in the risers. (See attached drawing)

    - Rod
  • nickdu
    nickdu Member Posts: 23
    Drop header and swing joints

    The point you made about unions on the riser for easily disconnecting the boiler makes sense.



    I'm still having a hard time understanding the forces and the swing joints.  Based on steamhead's post it sounds like a normal header has one swing joint so I guess that provides some relief for the expansion forces.  And a drop header adds another swing joint thus providing more relief.  If anyone has a picture of the forces at play for both a normal header and a drop header and also pointing out the swing joints and the axis of rotation to alleviate those forces that would help out.



    Also, I've read in several of these posts that a drop header is much easier to build, possibly saving an hour in time.  I'm trying to visualize this.  In the picture that Rod posted I can't imagine the big time savings in going the drop header route.  I believe it, but just can't figure out where it comes from.  I'm sure it would become apparent when I went to go build both.



    Thanks,

    Nick
  • Gordan
    Gordan Member Posts: 891
    I think the two benefits have a shared cause

    In that picture, see how with the drop header the drop part of the riser connects to the tee along the vertical axis? That's the same axis as where the riser connects to the boiler. That means that those two threaded joints allow for either the horizontal header section or the boiler sections to expand, and also allow for some slop when connecting the header to the boiler. The horizontal part of the riser doesn't have to be at a right angle to the header, which gives flexibility with assembly and flexibility to absorb expansion forces.



    With the regular header, both risers are parallel to each other at all times. Any expansion or assembly slop would have to be absorbed through deformation in the pipes or the boiler.



    Sorry if I mangled the terminology; I'm not a steam guy. Just trying to explain the mechanics of it.
  • Rod
    Rod Posts: 2,067
    Dropheader

         Gordan did a good job of explaining the mechanics involved.  It think it also helps you understand it better if you mentally do an assembly of both types of header.  Nick asked about unions and why some are placed in the boiler risers and some are placed in the header. You have to use one or the other to get the header piping connected together.  To understand this, mentally install the piping, one piece at a time, staring at the boiler and working toward having a completed header. How do you connect the pipe between the two tees located on the header that lead to the risers coming out of the boiler?  You would need a union!   The only other way to do it is with unions on the risers coming out of the boiler and using unions on the boiler risers has the added benefits which I mentioned in my post above.

        Now that we are thinking in our heads about doing the actual assembly of the two types of headers, let’s throw in another factor. We have to cut and thread pipe. On the boiler risers and cross pieces, the length of each can vary slightly as long as one riser is the same length as the other and the cross pieces are both the same length.  The critical piece is the pipe that connects the two riser tees on the header.  In the standard  header this connection must be prefect (the proper length) or else it will put tension on the boiler sections.  To do this we need to get the exact measurement between the two tees and add the correct amount to the length to account for the  “bury” of the pipe threads on both ends of the pipe.  Even if we do our measuring  perfectly we then run into the problem of  “All threads are NOT created  equal!”  Some will require more turns to get the fitting tight (resulting in a deeper than standard “bury”) Doing this regularly, the pros know the difference in brands of fittings and threaders and can adjust for this. With the amateur it’s a matter of trial and error. You may end up cutting and threading the connecting pipe several times.

           I’ve only done one “standard” header and on it, the risers had to be spread slightly (connecting header pipe too short) to get them hooked  up.  We didn’t feel that this was a problem as the tension compressed the boiler sections together and expansion would  neutralize the tension. If the connecting pipe ended up too long and we would  have had to pull the risers together to get them to fit, we would  have had to redo the piping as the tension cold and the expansion tension would have been too much.

        With the dropheader, none of this is a problem as the joints to the header allow some flexibility. You just swing the risers into place and hook them up - no tension at all!  Plus if there is any excessive tension from expansion, the fittings can adjust for that. This flexibility also allows you to use precut nipples which may be close but not be exactly the right length you need.  The other advantages to using a dropheader is that you can have higher boiler riser pipes and with the lower header you have better options in the riser configuration from the header to the steam  mains. With the top entry into the dropheader  there isn’t as much disturbance of the condensate flow on the bottom of the header as there is with having side entry.

    Savings? - Just having the benefits of the dropheader over the standard header sells it to me. The potential for problems using the standard header (especially for the amateur) far out weigh the cost of a few extra fittings.

    - Rod
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,357
    Take a look at mine.

    http://www.heatinghelp.com/forum-thread/142719/Peerless-G-561-W-S-Repipe



    Notice that the swing-arms are far from parallel. You couldn't do something like this wth tees, yet it is critical to achieve the right spacing for optimal separation in a short header. I had to play around with the spacing a little to get the boiler to sit right, but this was my first header.



    As you can see from the pictures, there is plenty of headroom. Those risers are more than three feet long, putting almost 48" of vertical between the maximum water level and the first elbow. What you might not get a sense of from the pictures is just how cramped this little boiler room is. If I had needed to extend the header to accommodate the right swing-arm, the equalizer would have been directly above my DHW heater instead of being directly above the return leg. That would have meant bringing the equalizer back at an angle, which is not ideal, and would have cost me as much in 45° elbows as I would have saved in 90s. Add that to the cost of the longer 3" nipples to make the header longer, and a standard header starts looking pretty unattractive. And I'd probably still be fiddling with it trying to make it fit together.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • nickdu
    nickdu Member Posts: 23
    I'm starting to get it

    Thanks for the picture and reasoning behind it.  Things are starting to sink in now.  I still have to go an read Rod's post and understand the steps you need to go through to build one, though your post does explain some of the reasons behind building it a certain way.



    Nick
  • nickdu
    nickdu Member Posts: 23
    Think I got it, but a couple clarifications needed

    Rod,



    Thanks for the explanation.  I think one trouble I have (/had?) is the reference to tee.  I assumed tee meant a tee fitting.  So when you said "how do you connect the pipe between the two tees on the header", I thought to myself, I only see one tee on the header, not including the one out near the end going to the main.  It seems by tee you mean the riser and it's horizontal piece.



    Thanks,

    Nick
  • Rod
    Rod Posts: 2,067
    Dropheader

    Hi Nick- "TEE" equals tee fitting.  Sorry for the confusion. I was thinking about the header we did and we used a plugged tee instead of an 90 degree elbow to attached the end boiler riser to the header. The problem is still the same. Just think about how you would physically screw the fittings together and connect them to the boiler and you will soon see it can't be done unless you use either unions in the boiler risers or a union in the the connecting pipe between the 90 deg elbow and the tee which each boiler riser attach.

    - Rod
  • crash2009
    crash2009 Member Posts: 1,484
    edited October 2012
    Nick

     I contracted Pat Girioux, out of Detroit to do mine.  This is what was complete when I got home for lunch.  Looks like Pat started with the riser to the left, then went up, over, and down.  At this point, I would assume that the slope of the header is set.  Then, he worked his way to the right, and went up over and down to the union.
  • nickdu
    nickdu Member Posts: 23
    Seeing it partially finished does help

    Crash, seeing the work partially done does help, thanks.  And based on where he placed the union it does seem he worked on the left and then the right.



    Thanks,

    Nick
  • nickdu
    nickdu Member Posts: 23
    Thanks, and one more thing

    Yeah, the two tee thing really had me going.  I don't think it was just your previous post.  I think I've seen others that mentioned the two tees and I kept saying to myself, where are these two tees?  I see one elbow and one tee.  After reading your description however it became apparant that the critical section you were talking about was between the elbow and the tee.



    One more thing which is a bit confusing to me.  I didn't ask about it in my previous post because I was thinking it might make sense, but I still need to make sure I understand it.  The part about that critical section being too short and thus having to spread the risers.  Or if the length was too long you'd need to pull the risers together.  The opposite would seem true.  If the pipe is too short I would think you'd need to squeeze the risers together (compress).  And if the pipe was too long you'd need to pull apart (expand) the risers.  The only way your description would seem to make sense is if the horizontal members of the riser rotated about a point in the middle of the horizontal member.



    Thanks,

    Nick
  • crash2009
    crash2009 Member Posts: 1,484
    edited October 2012
    A couple more "options"

     that you might want to add to yours.  Full size supply T's will further help to dry the steam.  King valves for maintenance and testing.
This discussion has been closed.