Welding Close Jack Bolts on flanges 1

[Nichyin]

Good morning,

Some engineers from my client's company have asked my company to change the location of jack screw holes on some flanges they have purchased due to the conflict
in instrumentation on the pipeline. They want us to plug the jack holes with a bolt, weld them shut, machine the welding joint flat, and drill 1 more jack screw hole on each flange in a separate location.

I would like to know if this is generally practiced? They said that the jack screws are not critical for service and the operation is in low temperature (about 70-80 degrees) and in a non corrosive environment.

Thank you very much.

 

[Gator]

Is this a test of some kind?

Piping Design Central

 

[Nichyin]

Good morning Gator,

They will be using this item in service at a plant.

Regards.

 

[MJCronin]

This particular one has to be among the top ten most bizzare posts ever...

Some questions:

1) Are these standard ASME/DIN flanges ? What is the pressure class and range of diameters ? How many flanges are involved ?

2) In my piping experience, the holes used for flange jacking are outside of the pressure envelope, are these different ?

3) If the point of flange jacking must change, why cant the flanges be simply be cut from the piping system, rotated and the reinstalled ? Won't this accomplish the same purpose.

4) If you have a demanding, inexperienced client making detailed design changes, but with little piping experience, disaster will most often result. ASME piping codes do not allow random rework/ redesign of piping flanges without expensive engineering requalification. Has this been addressed ?

Jack screws are not always needed to separate piping flanges. They are a convenience feature for large flanges only

Tell us more....

MJCronin
Sr. Process Engineer

 

[LittleInch]

Intriguing alright.

a bit of a search shows that two jacking bolts are common in orifice flanges (B 16.36). I've looked at a couple of sizes and they appear to be identical to standard 16.5 flanges in mechanical terms. Two jack screws are provided / allowwed for.

The jack screw is outside the bolt circle diameter and generally appears to be about half the diameter of a normal bolt hole.

As such, if your jacking bolt is outside the bolt circle diameter and as small as possible (< 1/2 the bolt hole size", then the suggestion looks fair, but unless this is going to be a common procedure, there are other ways of springing flanges.

Also this was discussed some time ago -

http://www.eng-tips.com/viewthread.cfm?qid=345364

how many jack screws / sizes / location are we talking about here? - a good sketch would help....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[racookpe1978]

Well, they certainly want "you" to go to a LOT of effort to make a cosmetic "fix" (put in a bolt in an threaded existing hole outside the bolt circle, cut it off, weld it up, grind it off, paint it out, drill a new hole, tap a new thread, put in a new jack bolt ...) for nothing. The "original" hole and threaded tapped hole is still going to be there and is NOT any stronger nor more resilient for the welding and grinding.

Each new hole only adds more stress risers and two ? additional threaded holes.

If the existing jack holes are outside the gasket seating area - leave them alone.