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Proper expansion bracing

Rocky_3 Member Posts: 232
120' run of 4" copper. Will have a Metro-flex "U-shaped" flex joint in middle of supply and return. Question is, I need to secure run at each end to "force" expansion to take place at flex joint, as opposed to each end's connection to system/boiler piping? Also, loop hangers or roller hangers? Sorry for simple questions, but have never really run such long runs of big copper before and am unfamiliar with best methods.



  • Brad White_184
    Brad White_184 Member Posts: 135
    Anchor(s) Away!

    Metra-Flex loops are a worthy product.

    Here is my take on their use versus conventional expansion loops:

    With conventional expansion loops, the forces are greater at the anchor points. The loops (2:1 hairpin ratio) have "spring-back" forces equal to their expansion forces. The forces are imposed on both sides of the loops, actually from anchor to opposite anchor, broken or mitigated by the loop in the middle. (Still with me here? Hard to explain, at least for me anyway.)

    Such installations have anchors (immovable points) at the ends or defined points. The expansion forces grow away from these anchor points, through guides and on toward the loop, through the loop and on to the next anchor point. (Expansion also grows away from the higher to the lower temperature by the way.)

    With Metra-Flex and other such products, the expansion force is absorbed entirely or almost entirely by the loop; little if any expansion force is passed to the opposite side of the loop. The loop essentially cuts the expansion force length in half. Think of "shooting pool with a rope" :)

    Now, you asked about forces imposed. The key is "maximum allowable stress" as imposed on the pipe and fitting joints. This is determined by the piping type, material, temperature etc. I would rather not do this for you over the internet you see... Perhaps Metra-Flex can assist you or a local engineer?

    You may well be able to not use anchors and allow the pipe to "float", absorbing stresses by natural bends, as one thought.

    Some key points to consider: Use anchors to define the lengths over which expansion is to be created and absorbed. Use guides, at least two (2) on each side of each expansion loop. The guides are as critical if not more so than the anchors because they prevent twisting and rubbing and allow the loop to do what they are supposed to.

    This was a direct-buried system was it not? If so and you are using a pre-insulated piping system, that manufacturer can also engineer the system to absorb the stresses and size any anchors.

    Sorry to ramble but I have no neat way to do this in specifics from here.
  • bob_46
    bob_46 Member Posts: 813

    are you going to hang the pipe or direct bury it? You are looking at 2" of expansion for 120' of copper witha 150 degree rise.
  • Rocky_3
    Rocky_3 Member Posts: 232
    Hanging the pipe

    This is not a direct burial. This will be hung from ceiling or wall.

    Thanks for the replies,
  • Brad White_184
    Brad White_184 Member Posts: 135
    All the better, Rocky

    Still, the Metra-Flex folks can guide you so to speak.

    Anchoring steel piping is easy in that the spine and attachments can be welded. Copper is a friction situation. All are braced to structure.

    Over and out.

  • Pipe hanging/support/installling experiences 30 foot up...

    Hi Rocky, Happy New Yewar from Denver Colorado!

    My first experience handling and hanging big bore pipe probably doesn't stand a chance against some of the REAL pipe fitters around here, but being the Father of Invention, we came up with some pretty danged innovative ways of getting through our 2000' debacle for the Target snowmelt.

    Hangers: We used a laser level to set all of the hanger rods from the top joist on the open truss steel bar joist used to support the roof. Once set in place, you can leave it (laser) there and just turn it on and off as needed. We had 800' from the start of our major run to the other in a building that was 1000' long, and the laser made installing this stuff extremely accurate. We were out in the middle of the building, so it wasn't easy getting a frame of reference from the outside walls. As for cutting the all thread, use one of the Dewalt Multi-Cutters. You can cut 4 pieces at once, and it is the cleanest cut you will ever see. No burrs and no futzing around with the ends 30' off the floor. We preinstalled our beam clamps and the rod. We didn't install the auto grips until we were actually setting the pipes to keep them from getting in our way. Our pipes had to be perfectly level over a span of 800 feet, and the building roof was not... It took me one week with an apprentice on the ground doing the cutting and stocking to get the hangers into place.

    Getting them up:

    We devised a method of lifting the pipes off the gound using ropes hung from the bar joists. We would raise the pipes high enough to be able to pull our man lifts underneath them. When we picked up the pipes, we had an arragement of bungie cords connected to the lifting ropes that would pull the ropes off of the end of the pipes to clear them so we could take off with the pipes connected to the man lift. This required keeping an apprentice on the ground to do the rope/bungie work. Myself and another fitter were operating our own (2) seperate man lifts. Each lift was eqipped with the pipe supports and tools/equipment necessary to put the 21 foot extremely heay pipes in place. Only one lift was used for lifting/transporting the pipe. The other car was used to hang and secure the ends of the pipes. We were using roll grooved Victaulic fittings and schedule 40 steel pipe. THe pipe was pre-grooved. Car one would position the pipe under the pre-set hangers. Car 2 would secure the hangers, and approximate the final resting position. Car one would drop out from under the pipe, thereby loading the support system, and cars one and two would level the pipe. Car 2 would stay in position while car one went back to the staging area for another stick. When the pipe was in place, end connections were made, pipe leveled from teh "mother" pipe, and so on and so forth. We ran 800 foot of straight pipe in 4 days. It then took another week of cutting and roll groving the side branches going to the distribtuion (5) manifolds. Did I mention that the other trades people put their stuff into place before us and we were the highest trade in the vertical profile? It was a challenge parallel parking 21 foot sticks of 300 pound pipes with duct work, fire protection and temporary lighting hanging in place. But we Got'erdone.

    As for anchoring the pipe to the structure for controlled growth, we simply clamped the 4" pipe using conventional unistrut pipe clapms into long pieces of unistrut, and then tied that yunistrut clamping device into the roofs steel structure, basically thrust blocking it in both directions.

    As part of our testing/commisioning process, we thermally shocked the system a dozen times to make sure things were working the way WE wanted it to, and it was. Just to be sure, we also hydraulically shocked the system a couple of time by allowing the fluids to get up to full flow, then quickly threw a ball valve closed, causing the system as a whole to LURCH violently. You could hear the structural steel engineers sphincter doing the Momba from 800 feet away... But I DIDN'T want this piping system coming loose or getting leaky over the top of customers and merchandise. It held up well.

    In your case, steel will be significantly less than copper, and compatible with the fluids you are dealing with, and can be used with the same expansion compensator.

    Alternatively, you could go ProPress or Gruv-Loc for copper. PP is obviously faster, but at a significantly higher expense per joint ($100 vs $30 for material alone)

    We were working side by side with some plumbers who were having to silver solder all of their copper potable water distribution lines. They initially laughed at our pipe launching methodology, but after seeing how quick it worked, they too found a bunch of bungie cords.. Funny how that works. We were the first to show up with the Multi-Cutter as well. The following Monday EVERYONE had MultiCutters on the job. No more burning your way through pipe with carbide grit blades...

    Good luck with your project, and take lots of pictures.

  • Rocky_3
    Rocky_3 Member Posts: 232
    Mark, speaking of pictures....

    Do you have any to share with us regarding the hanging of the pipe at the Target job? I would be really interested to see what that looks like! 800 feet of pipe, all hung nice and neat is quite an undertaking.

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