flange maximum allowable force to alignment 1

[gordonmech]

Dear friends,
can anybody address a standard that specify the maximum allowable forces which we can apply to a flange to align it.
Thank you

 

[SugarRat]

I would thnk that you would have to do a stress analysis on the piping including the force you would need and see what the piping is going to do under that stress. What kind of misalignment are you trying to deal with?

Generally its much easier to have a site contractor cut and refeb the pipe on-site to eliminate all the stress. I have been a site piping supervisor quite often and I never sign off on a pipeline that is installed under stress.

Regards

Kobus

 

[unclesyd]

I agree with the post above bur don't see the requirement for an analysis. A good piping engineer should be able to call out any problems. Like a lot of things it should fit right to start with. We see very little problem with CS, but SS give a lot people fits. On long runs of pipe we usually don't get upset if someone uses a little more force.

On pipe 4' and above, except for ring joint flanges we allow a fitter to use a 500lb chain fall at the discretion of our inspector.

We usually design as much flexibility as possible in the piping system which helps mitigate any external forces.

One little trick we use to assemble heavy wall jacketed piping is to loosely bolt the spools together before a final tightening.

 

[BigInch]

if that does't work, see Appendix "D9".

 

[JJPellin]

The answer may also depend on what the piping is connected to. For our pipe strain standards, the piping must be aligned well enough and flexible enough that it can be moved into position with just your bare hands well enough to slip all of the studs into the holes. But, our standard is a rotating machinery standard for piping bolted up to pumps. We require this level of alignment/flexibility in order to avoid pipe-strain related pump failures. If it was connected to a heat-exchanger, the fixed equipment engineers might not be quite so particular.

Johnny Pellin

 

[C2it]

You should also consider that whilst only a moderate force may be needed to 'align' a pair of flanges, if they are not rotationally aligned too, a huge external moment may be required to pull them in, and could be a serious leakage risk.

 

[racookpe1978]

If the flange and pipe are not aligned "hand tight" as recommended above, one or the other (or both) WILL distort as they are pulled into place and torqued down.

Regardless of analysis or desired stress levels your millwrights or pipefitters have now "hand-cranked" your pipe and vessel/pump assembly past the metal's original yield point and into plastic deformation.

The question becomes, "Will that deformation be enough to cause short or long-term damage during operation, or can the assembly live with the deformation?"