Design

[Mech 3D]

Hello fellow engineers, I need your help to verify if I can drill new holes on around the same PCD for this flange since the old holes are corroded and cannot be rethreaded, the operating pressure is about 35bars and the actual flange is only 160mm thick , the holes are about 55mm deep. Any software that I use to verify this?

 

[Eufalconimorph]

Wrong subforum. This one is for discussions of the eng-tips.com forum itself.

 

[BEMPE16524]

yes you can, make sure good flush weldment.
what do you want to verify with the software? if you are making new holes (same number and size as the old ones) and removing the old ones, software verification is less needed unless you really want to and for other specific reason. to cover the old holes, you must make sure it is 100% clean.

the other way is using helicoil on existing holes. have you considered it?

the best way to verify is to test it after you are done.

 

[MintJulep]

Helicoil or similar insert is a much better option.

1. Easier
2. Faster
3. Less Expensive
4. Lower risk

With welding you would need to worry about the heat affected zone, distortion and all of the things that could go wrong.

 

[GregLocock]

You are also weakening the general area of the bolt ring, ultimately you'd end up with the old 'please tear here' perforations.

 

[LittleInch]

Why don't you just drill out the existing holes to say 110mm deep and thread that section of the hole?

It you analyse this it will probably need some sort of fancy FEA model.

surely a new flange is cheaper than the risk of failure?

 

[Orange_kun]

I've seen such a condition successfully repaired by drilling out the old holes, adding weld buildup to the enlarged holes, and retapping to the original thread size. Not sure what material you have, and how well it accepts the heat. This was on some nickel alloy that was relatively insensitive to HAZ. And, the welder needs to be competent.

Could you also not just re-tap at the next size up? To me, that would seem safer than making the "tear here" PCD previously mentioned. Although new hardware size might be a pain for other reasons.

 

[Dynamics_Eng]

Drill the holes to the next larger size. For example, if the current holes are 1.125", enlarge them slightly beyond 1.250". This adjustment will make the process easier.

 

[MintJulep]

surely a new flange is cheaper than the risk of failure?

Risks are free!

It's only the failure that incurs cost, and those can be avoided by wishful thinking.

 

[BEMPE16524]

Risks are free!

It's only the failure that incurs cost, and those can be avoided by wishful thinking.

agree.