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Excessive stress on horn of saddle

Excessive stress on horn of saddle

Excessive stress on horn of saddle

A 60" piping (D/t=150) & sees thermal cycles have encountered cracking and inward denting at three circumferential butt welds.

The pipe has developed ovality due to improperly designed saddle support( saddle angle is just 70 deg).
Excessive stress exists on the horn of the saddle.Does it alone explain inward denting and cracking between 4 o'clock & 8 o'clock at circumferential welds ?(The circumferential butt welds that failed are about 4 to 5 feet from the saddle support).

Would weld cracks be fatigue  failures?.

As the line was repaired by engineered clamp a proper failure investigation could not be done.However it is not believed to be a stress corrosion cracking nor a failure due to thinning.


RE: Excessive stress on horn of saddle

Where is this piping located ?

What are the pressures and temperatures of operation and..

Why can't the original designers be located ?


RE: Excessive stress on horn of saddle

It is a Flare line. Designed for 50 Psig @ 815 F. Normal operating pressure is 5 to 10 Psig.The line is insulated and electrically heat traced, for freeze protection.

Original design calculations for saddle are not available.I believe that piping desiner has overlooked the fact that the supports should have been designed like a pressure vessel saddle ,since D/t >100 .  

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