Welding Nuts to Vertical Hanger J-Bolts

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We're rehabilitating an overhead crane. The installer chose to shim the crane rails down from the overhead concrete support beams, with the result the nuts don't have full thread-up on the threaded hanger j-bolts. So the crane is locked out until we come up with a solution. It's over a deep pit, so there's no way to remove the beams to get at the shim plates, and it's too dicey to try holding it with a Pettibone as it drops away. We proposed just welding the nuts to the bolts. Seems simple. The local authority said nyet, claiming 1) the nut metallurgy doesn't match the threaded j-bolt metallurgy, therefore they 'can't be welded'; and 2) they claim that 'plug welds (circular fillet welds) can't be loaded in tension according to Code'.I'm just a welder, and since they didn't provide a Code reference, I have to call BS on their claim #1, and don't see any reason the circular fillet weld can't be loaded in tension, but made the mistake of calling it a 'plug weld', and now I've got to argue the case. Anyone ever hear of anything like it?
Reply:May need a PE stamp to over rule any objections by the AHJ
Reply:You can seriously weaken heat treated nuts and bolts by welding. Grade 8 or better nuts/bolts are usually heat treated.Also codes are usually very strict when dealing with cranes and other overhead lifting devises since failure is usually catastrophic and many times without warning. It's why the safety factor is so high when comparing things like crane beams to standard beams.It's not surprising to me at all that they nixed any modifications. Just the certs to weld on crane equipment is much more stringent than that required to do say structural welds..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:......Can you remove the shims and then get full thread engagement?...If not, then there is no easy/cheap way out of this.Well, other than perhaps negotiating with the inspector a 'reduced' load limit cert that the end user can live with.....As a boiler inspector, I routinely reduced max allowed working pressure to allow for thinning of pressure vessels.If the end user/owner of overhead crane truly doesn't need it's rated capacity, then perhaps he can get it rerated by inspector within a limit he can use...otherwise, it's a no go.Either way, his insurer will need to sign offThat said, the fastest way to make the whole thing illegal and forever condemned is to apply a welded 'fix' if the fix isn't properly engineered and signed off by both the inspector and insurer.Last edited by pigeonpoop; 01-19-2014 at 01:25 AM.
Reply:Sounds like the simplest solution would be to have new J-bolts made?
Reply:Originally Posted by toofast_28Sounds like the simplest solution would be to have new J-bolts made?
Reply:Originally Posted by pigeonpoop.Well, other than perhaps negotiating with the inspector a 'reduced' load limit cert that the end user can live with.....As a boiler inspector, I routinely reduced max allowed working pressure to allow for thinning of pressure vessels.
Reply:Originally Posted by Rock knockerBut who other than an engineer could generate those numbers?  The OP and the inspector would be pulling numbers out of air to do as you suggest.
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Reply:If you have a washer & nut you may be able to toss them and substitute a flange nut to get enough thread engagement. If not I can't think of any real cheap fix.There's just too much wrong with the idea of welding the nut to the J bolt on the end.Good luckMatt
Reply:Thanks, all.I found an expert at Portland Bolt, Greg Lindsay, who explained that under AISC Design Guide 1, sub-part 2.11.3, welding nuts to hangar bolts is not allowed. Dang!He suggests, as some of you also have, counting the threads that are engaged, dividing by total threads that should have been, and derating the crane accordingly.
Reply:is the pit narrow enough that it could be bridged with a shoring system? If you can shore the beam up and remove the shims you can gain some bolt length. Maybe grind the concrete beam rather than shim the crane beam to get level.
Reply:I have an idea. What about countersinking the plates and using a lug style nut. You would need a special countersinking tool, and probably special nuts. Crack myself up, special nuts... Attached ImagesIan TannerKawasaki KX450 and many other fine tools
Reply:Originally Posted by fortyonethirtyI have an idea. What about countersinking the plates and using a lug style nut. You would need a special countersinking tool, and probably special nuts. Crack myself up, special nuts...
Reply:What is above the concrete structure? Can you drill through the concrete and install bolts/rods from the top surface through to the necessary length to hang the crane beam? Or countersink the top and use a plate to distribute the load?---Meltedmetal
Reply:could the beam be drilled out  to a larger size hole and use a type of "Binding Post Barrel"  even if they had to be shop made, Attached Images
Reply:Can you affix a flange/thread system to where it becomes part of the beam?Arcon Workhorse 300MSPowcon 400SMTPowcon SM400 x 2Powcon SM3001968 SA200 Redface1978 SA250 DieselMiller Super 32P FeederPre 1927 American 14" High Duty LatheK&T Milwaukee 2H Horizontal MillBryan