Dears,

Can we use socket weld CS conn for <=2"NB high pr vibrating H2 piping ?

As per B31.3:2004 clause 311.2.4(c) for >2"NB, socket weld shall not be used under severe cyclic conditions.

If we find socket weld connections breaking repeatedly due to vibration, can it be inferred that an equivalent effect of severe cyclic condition of B31.3:2004 is existing ?

What are the solutions available - higher thickness piping, reduce clearance at nearby main piping guide/stop, relocate to nearby rigid piping support of main pipe, reduce main piping support span locally or provide stiffening bracings holding the overhung heavy vibrating valves or anything else ?

Can changing socket weld connections with butt welded connection give better fatigue resistance?

regards,
sam

Decent support of concentrated masses and bracing of pipe can reduce the risk of fatigue failure, as can increasing the wall thickness. Avoiding socket welds would be obvious, given that B31.3 App. D (Note 14) assigns an SIF of up to 2.1 to a socket weld, whereas a butt weld is 1.0.