Double Pipe weld failure

[Bill3752]

I have a double pipe exchanger. Per API 521 (5.19.6), if both are schedule pipe, then it is acceptable to base the relief scenario on something other than a tube failure. However, it does make sense to look at possible weld failures. My question is "what is a reasonable failure size to use for such a case?" Presumably, the rupture disk will fail with even the slightest weld failure - well before it enlarges. Is there a good rule of thumb to use?

 

[Chance17]

One commonly used concept is the "corrosion hole" typically size 1/4" diameter.
This would be "worse case" prior to an actual tube rupture.
Maybe thia works for you.