Abstract :
Piping system in industries like petroleum rigs and power plants is used to carry chemically reactive
substances with high pressure and temperature from one place to another, which could cause a negative effect on
health and environment. This is the reason why we need correctness and precision in design code. A piping system
with high pressure causes stresses in pipes, especially in elbows. The reason being elbows are more flexible than
straight pipes. Whenever a pipe has bent the cross-section of the pipe is no longer circular, it slightly changes from
circular to ovular. Bend can cause thickening of the inner surface and thinning of the outer surface. This causes
uneven distribution of stresses in elbow which makes it the weakest link in the piping system. Due to this change in
cross-section, stresses developed in the elbow leads to the phenomenon called “ratchetingâ€. Ratcheting or fatigue
ratcheting is nothing but cycle by cycle accumulation of strain on the application of cyclic load characterised by
constant stress amplitude along with non-zero mean stress. Severe ratcheting may result in premature failure due to
either accumulation of deformation or fatigue cracks. This work presents the effect of ovality on ratcheting
Keyword :
Petroleum rigs, chemically reactive substances, High pressure, Ratcheting, Ovality.