Flexible Coupling

What is a valve "champer"?

How much thermal expansion/contraction is expected in this pipe?

How much flexibility does the pipe already have, such as nearby elbows?

A sketch might help.

I can't see the point in installing two flexible joints. Just one will give you flexibility while the valve is held securely by the non-flexible joint. Fit two and the valve is effectively floating.

...which is sort-of-what-happened to the temporary bypass pipe at Flixborough!

man you are using a high pressure flexible coupling. I would strongly recommend you look at not using one, loop the pipe a bit.

I personally like to get rid of all the expansion forces before the valve. So that by the time the valve is supported, at that size it will have to be, you not sitting with a moving support.

Is it really necessary to use an expansion coupling, or is it there to service the valve. In that case I would recommend a taper flange instead. You are working at a quite high pressure; the side forces are enormous at that diameter (if I am right they will be about 160 ton). How are you going to retain them and still have an expansion joint.

If the pipe is 700mm and cement lined, it sounds like it's going to be ductile iron pipe. You can't use expansion loops, but the joints are designed to cope with expansion/contraction if properly installed. Tapered joints can be manufactured to suit the valve.

Sounds to me the valve (welded) is located near a cement wall. The wall acting as an anchor. An expansion loop, or leg, is mid pipe span. I have not normally installed a flex coupling for a valve. If the valve is hanging in space, you'll need a sepparate support. Once i had equipment that was to have minimum stress alowed to the matting flange which required an engineered support and flex couplings and a concrete box to contain, plus other stuff.

Are we looking for a breakout connection ? My experience is with process pipes, a civil type might have better luck understanding question if line is burried.

So we do agree on this on, bit of a shifty situation. Had a bad night about this. I normally stop using flexible couplings and joins at 16 bar ( had one at 24 bar but that was only a NB250 pipe and still needed rather heavy anchor blocs, defeating the advantage of having a flex joint in the system.

By the way where do you get a joint like that? Can you please send me the specs ? would love to add that to my interest. At the same time can the manufacturer not give us all a hind of how to use them at that pressure rating?