tell-tale hole problem

[abangbikerz]

just received a shell flange for our heat exchanger project from korea. the problem is we find out that the tell tale hole is not fabricated according to our design.On drawing, the hole starts at the back side of the flange where it is threaded and turn 90 degrees towards the shell. But on the actual parts, they machine the hole straight and penetrate to the other side of the flange. is that a problem??

feel free to view my attachment for the design drawing.

 

[nickelkid]

As manufactured you will be able to monitor leackage on both potential leak passages of the pressure containing weld. It would not be hard to argue that it is an improvement of the design.

 

[jbeckhou]

Without seeing the whole drawing, my first thought is the hole thru the ID can not be machined.

Petrotrim Services

http://www.petrotrim.com

 

[bernoullies123]

The first question would be, was there proper controls in place for this change against the design.

With the first aside, I reckon either design would pick up the two potential leak paths. I don't think one or the other only picks up one or two.

For manufacturing, of course the straight through is much simpler and quicker, but the port is further from the higher potential leak path (shortest distance of weld). But given the chamfer on the backing plate it should pick up a leak just a well as the one in your design.

If my memory serves me correctly, I was on a job many years back and we specified the same design as yours, but our Korean fabricator was probably a bit more clued in than us, and they proposed the straight through. Excellent fabricators, and excellent product.

 

[jtseng123]

The 90 degree turn is kind of weird design. Straight through is commonly seen.

 

[saplanti]

The tell-tail hole can be used for two purposes:

1. During the welding the trapped gases can excape easily without causing a problem to the welds.
2. Testing the weld for leak as indicated above.

I see that there is chamfer on the flange side next to the inner full penetration and fillet weld. So the surfaces of the flanges are not going to be 100% tight after the welding and inner diameter area of the flange and welded face area and they will always be connected. Therefore extending the hole to that face is not going to change the purpose.

Regards,

Ibrahim Demir