Bolt Torquing of Piping Flanges

If bolt torquing is delayed until after the hydro test, then the test will fail due to leaks, and will need to be repeated. Better to flog 'em up first!

Drat Crabtree you bit me to ze pist! I was hopping to get 'ere fist!

It seems an odd question unless I'm being thick?

I would guess that re-torquing after any test may be appropriate in case there has been any settling/shift due to pressure.

Suggest leave all bolts loose then do Hydo Test... the answer will then be self evident. (If this attempt at humour misses some valid point about testing then I appologise in advance!)

Are we torquing serious pressures and BIG P.C.Diameters or is this just a little squirt?

The first trick is to line the pipe up, then do up the bolts evenly.

To do this we tighten bolts on opposite sides of the flange. That is diagonally. Not working our way around the flange clockwise or anticlockwise. Going clockwise or anticlockwise may lead to overtime but it is not the way to victory.

All bolt should be in tight and even before torquing is commensed.

As an old hand at torquing structural steel and working as a pipe fitter too. It depends on the bolt size. There are pre-established torque measurements for the bolt size and the expected pressure of the plate face. You can start with the torque before pressurizing the pipe and check after for leaks. Most time the pipes are already to go.

If you are attempting to proof test a built up system, for any reason, ie insurance, safety, integrity; then the system should be finished and presented for operational standards. Therefore you need to finish torque the bolts to the correct torque for operation.

The whole system should be presented for test as for operational conditions.

hello, regarding bolt torquing of pipe flanges before hydro test, in my opinion sequence torquing must be done first,leaving some small percentage of torque. and if the application is for hot service like steam/ chemicals, and the joint is passed through the hdro test, hot torquing should be done after system operation from 40 to 48 hours.

Before. A hydrotest is to verify the integrity of the design and installation as it will be utilised, not before it will be utilised. If you touch anything (ANYTHING) on one of my projects after hydro, I make you do it again. In my world, a hydro can be some pipes on a shop floor for a lube oil system, or a 48 inch 2000 km long pipeline.