Victaulic Couplings - transmit or decouple pipe loads?

[sprintcar]

OK Guys - what's your opinion on Victaulic Couplings - do they transmit 100% of piping loads/forces to the pump nozzle or is the rubber piece enough to decouple the pipes? It seems the clamp is metal-to-metal with the pipe sections, although it could be somewhat flexible.
Thanks Keep the wheels on the ground
Bob
showshine@aol.com

 

[TBP]

In Grinnell's literature (they have "Gruvlok", a competitor to Vic) they show the gaps between the pipe ends at the joints as the expansion allowance. If a piping run for a hot water heating installation doesn't have enough joints, then an expanion joint is required. Contractors don't like more joints, as they are expensive. They also don't like buying expansion joints for the same reason. So they install as few joints as possible to connect the system, and no expansion joints. This is the primary cause of chronic leaks in these systems. The pipe heats up and expands. The little gaps between the pipe ends close-up. If the line keeps heating up and expanding, it'll squirm in the hangers, and cock the joints.

I would think that unless some force, like thermal expansion, closes the gap under the gasket ring, then you should be OK.

 

[stanier]

It depends upon the coupling you selct. The standard coupling gives flexibility whereas the "zero Flex" has angled faces that enable the coupling to securely grip the pipe.

Victaulic recommend multiple couplings to decouple for vibration. A single coupling should prevent transfer of pressure loads onto the pipe as the thrust is taken up in the ring/groove.

I have used many couplings in pump istallations and not found a problem. Press their agent for for the black design manual rather than the composite one they issue to first time enquirers. Thats more techincal detail in there.

 

[sprintcar]

Thanks guys!
The black book of coupling design,,, I hope its easier to get than my copy of Cameron Hyd Design was !

I've seen the Vic style used everywhere with good results and the Maint guys like them. We build a test rig using them for faster changeout, with Zero leaks compared to the old flange style.

Thanks again for the info!

Keep the wheels on the ground
Bob
showshine@aol.com

 

[saxon]

Beware of applying any lateral loads to this type of pipe connection. They're not very strong in resistng this type of load. As matter of fact, in 1996, one of these failed in a potable water service meter pit and killed four workers.

Just a heads up.

 

[KernOily]

Saxon, do you have a cite or an article where I can read about that accident?

Sprintcar - I think the question would be phrased more accurately as to which TYPES of loads a Vic connection will transmit. Obviously they do transmit 100% of the axial tensile and compressive forces because they do carry the full axial thrust of the line under pressure.

Knowing what I do about a Vic, I would say that its capability to transmit or resist moments about any axis is very low. It might transmit a moment about the pipe CL due to the clamping force and friction of the clamp. As someone also said above, its capability to transmit a lateral load would be pretty low. If you were modeling a line containing Vic coupligs in a stress analysis porgram you would have to place a node at each coupling and then figure out how to handle the stiffnesses of the connections to get any kind of accurate solution. I'd suspect that the Vic people have been up against this in the past and would have some guidance in this regard so I would check with them. Thanks!
Pete

 

[saxon]

74Elsinor, I picked up on this article at "

http://www.pipingdesign.com".

It appears to be an article from the Detroit News.

Saxon