## Piping Vibration Fatigue Risk Assessment

Vibration is not really what we want to thoroughly assess piping vibration risk –we should instead use mechanical stress range and load cycles to estimate the risk for vibration fatigue. There is an established methodology where mechanical stress range is assessed with respect to fatigue risk with the help of so called SN-data, where S signifies Stress range (Pk-Pk) and N is the Number of load cycles. A combination of stress ranges and load cycles can be added together using Miner’s rule to assess fatigue risk and estimate a pipe’s lifetime. Link Given this, why do we measure...

read more## Small Bore – a Low Cost Element that can become very costly

Piping vibration can be troublesome in itself. Small Bore Fittings (a.k.a. Appurtenences) can be worse and usually are the things that first fatigue and break on a piping system and thereby add system risk. There exists vibration fatigue risk criteria for piping vibration failure. These usually are expressed as vibration velocity for the simple reason that it is vibration velocity that is proportional to mechanical stress at resonance, i.e. at the a frequency where we expect vibration/stress to be the highest. Here is a small derivation as to why vibration velocity is proportional to...

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