Rigid Victaulic pipe couplers - How much moment can they carry?

[Naturallycurious]

I have been asked to certify the support system for a 200 dia pipe system carrying water for a fire system. Most of these systems that I have designed in the past have been in motorway tunnels and we have used flexible couplers rather than rigid couplers for a variety of reasons. In this case my client has used Victaulic pipes and their rigid Victaulic 005 roll groove couplings. The Victaulic design handbook suggests that the system will act like a welded system in that it will behave rigidly but cautions about bending the pipes. Given that there are thousands of these hanging form buildings using rigid couplers they can clearly carry some bending. Every time loads move over the slab for example it causes some amount of bending in the pipe. In long span prestressed structures with large diameter pipes suspended below the stress in the pipe adjacent to couplers from traffic in a carpark will be large (say 200MPa) but in many office situations the bending moments on the rigid couplers will be minimal (say <50MPa).

Unfortunately here in Australia the reps for Victaulic seem to have no idea what bending moments these couplers can be designed for. If anyone out there can lend some light to the subject I'd be very appreciative?

 

[Ron]

None that you can count on!

 

[moltenmetal]

They can handle at least as much bending as a concrete structure...

 

[cvg]

They do provide a small amount of flexibility, but they are not designed to handle bending, only to provide axial restraint. suggest you post this in the piping forum to determine what type of bending they can be expected to resist. I would expect much less than welded pipe.

http://www.eng-tips.com/threadminder.cfm?pid=378

 

[Naturallycurious]

Thanks for the assistance guys. Victaulic just weighed in themselves with some recommendation (see attachment)from their head office. This should get me out of trouble.

 

[Ron]

How does that solve your issue? The tables assume a continuous pipe. The Victaulic coupling is almost a hinge. At the least, bending compromises the Victaulic proprietary connection slot.

 

[JStephen]

The text says that is the moment capacity of the coupling, about 1/3 or so the capacity of the pipe, and I would think entirely reasonable.

 

[Naturallycurious]

How does that solve your issue? The tables assume a continuous pipe. The Victaulic coupling is almost a hinge. At the least, bending compromises the Victaulic proprietary connection slot

Some of the couplers Victualic supply use are fixed (eg 005) and some are flexible (eg 07). The manual suggests that in terms of performance you can consider that the pipe will behave rigidly (like a welded pipe) if fixed couplers are used. This most recent advice from Victaulic appears to be suggesting that the fixed couplers are designed to carry quite a decent load. For example my 200 dia pipe can carry 11.31kNm. Stress in the pipe under this moment is only 51MPa so I assume the coupler is the weak link. I still need to enquire as to what factors of safety have been used and whether this represents a working stress or ultimate load limit etc but I appear to be heading in the right direction.