pipe hanging from OWSJ

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Our building is approximately 40 or so years old, as is the heating/heat recovery system. Recently it was decided, wayyyy above my pay grade to update the heat recovery and ventilation system throughout the complete plant, this leads to my question.The roofing is supported by OWSJ I'm guessing 24-30" deep 2-2 x 2 or 3 x 3 angles back to back which make up the bottom and top chord on each size of the vertical diagonal zig-zag  rod, typical joists. The contractor is hanging off, on one angle only 3 runs of pipe, 2-6" and one 4". The pipe is hung using a saddle type hanger, hung from 1/2" threaded rod which is clamped to one bottom chord angle. This to me seems to be a lot of weight hung from one angle, even from the ground you can see the angle twisting, and that's without and liquid in the pipe. I did the math and its 38lbs per ft of 6" and 17lbs per ft of 4" when it's full. If I were hanging the pipe, I'd go across both angles, straddle them, and go down between with the threaded rod, at least the load wouldn't be trying to twist the angle. Not only that but it's suspended off every other joist. Looking at the original plumbing, which is smaller they have used some fancy looking support that comes off both angles so the load is symmetrical, not only that but the original is only 4" and they've used every joist .Here's a couple of pics, not very good because of the lighting but I think you get the drift .Anyone got any comments or am I being paranoid.....Mike
Reply:I would think you are correct, especially if the empty pipe is already bending the angle."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:Most of the time it is against bar joist manufacture to hang off bottom chord. That should be hung from top chord with a beam clamp. With 6'' I would have staggered the hangers so you transfer the weight on multiple joists. You would have hangers on almost every joist for better weight distribution.  6'' schedule 40 pipe is 31.48 pounds per foot with water. It is 1.50 gallons per foot.  4''      ''        ''    ''    ''  16.30   ''        ''      ''     ''      ''     It is   .66 gallons per foot.
Reply:1/2 allthread seems kinda light for 6 inch I would think 5/8 or 3/4.  Is there concrete poured on top. Of ceiling? If so red heads would b an option.  Or coming up in between both pieces of angle with allthread and securing with but and washer on either sure.  This way u spread weight evenly to both pieces of angle rather than just one.  That would prolly b cheapest
Reply:I would definately have the contractor talk to a structural engineer about their hanging methods. Usually the hangers are specified for the project by the mechanical engineer but they rarely talk to structural with concerns about hanging pipe, they will talk about hanging units though, it just seems that everyone forgets about the pipes.
Reply:This is what we get with anything hanging from a bar joist. Hopefully my attachment will work. Attached ImagesJOIST.pdf (137.8 KB, 114 views)
Reply:not sure how to have it show a pic instead of a link.
Reply:Originally Posted by ct18111/2 allthread seems kinda light for 6 inch I would think 5/8 or 3/4.  Is there concrete poured on top. Of ceiling? If so red heads would b an option.  Or coming up in between both pieces of angle with allthread and securing with but and washer on either sure.  This way u spread weight evenly to both pieces of angle rather than just one.  That would prolly b cheapest
Reply:Or coming up in between both pieces of angle with allthread and securing with but and washer on either sure