Urgent..Flange Holes Don't Match

[niravpshah]

Friends,

We have run into a REAL huge problem. Our testing is just 1 week away and we found out that flange holes on two casing don't match.

We are connecting two casings and flange on each casing has 14+2=16 holes. 14 holes are of 5/8 and 2 holes are 3/4 in diameter. The spacing for the bigger two holes (3/4) is slightly different than the other equally spaced 14 holes.

During the design phase, I did Appendix Y calculation for metal to metal contact flanges and our design was adequate.

Now we have found out that the vendor made mistake on one of the flange and two big holes and three small holes, in total five out of sixteen holes are not lining up. On one side of the flange (Left) we have through holes and the other side of the flange(Right) we have tapped holes.

In the interest of time, we are considering the following scenario, Please help by commenting which one will have less adverse effects.

1) Plug the holes (five) by welding on left flange and redrill at exact location.

Concern: Heat from weld may mess up the surface finish..What about strength penalty?

2) Get the new flange and cut the existing flange and and weld it on the casing. For this we will have to stress relieve this on the right side of the flange.

Concern: this may result in change in dimension for the left side of the flange.
And it will result in some thickness loss (1/64) in the shell of the casing.


I am thinking that this type of problems are quite common and there must be some technincal papers out there to assess the life after repair. Could you guys comment on this and direct me where I can find some technical literature?

Thanks in advance for your precious time.

Shah

 

[niravpshah]

Folks,

Has anyone run into problem like this?

 

[deanc]

You will have great fun trying to drill and tap weld metal.

Suggest you mill the existing holes off center/tap and use a threaded insert for the proper location.

 

[unclesyd]

Offhand it would be best to get rid of the odd flange.

Come back with what type/figure flanges, material, sizes. and service or any other pertinent information.

 

[waskillywabbit]

If it is truly a vendor mistake then the vendor should fix it properly w/ a replacement and take the time/overtime to get it to you on schedule. Mistakes are made, that is a part of the gaem, but they should also own up to their mistake and make it right by you.

As suggested above, don't try and drill and tap welded metal...real pain in the old hiney.

I'd make sure to document the occurance and be sure to notify your customer of the problem up front and don't let them find out about it posthumously.

Good luck.