Calculating minimum pipe wall thickness is performed in accordance with piping design codes, such as ASME B31.3, to ensure pipe safety against failure due to hoop stresses resulting from internal pressure. By performing stress analyses, a piping engineer can ensure piping safety against failure due to excessive plastic deformation, incremental collapse and low cycle fatigue. Design codes achieve this by providing rules on how piping loads and stresses caused by internal pressure, self-weight, thermal expansion and occasional loads due to earthquake, snow and wind are evaluated for stresses. These combined stresses are then compared against the allowable limits to confirm compliance.
Equipment connected to piping is susceptible to failure due to excessive loading. The loads that are exerted by the piping during all operating or standby conditions should be correctly evaluated. Rotating machines, such as turbines, compressors and pumps, are particularly sensitive to loads transferred by piping, which can cause misalignment, vibration and reduced design life.
A detailed stress analysis of the connected piping will reveal the loads under various conditions, such as the heatup and cooldown of the tower, ground settlement of the tank foundation and the hot, cold and standby conditions of the turbine, compressor and pump. A piping stress engineer will then take further measures to limit these loads within the acceptable range, which ensures the full design life of costly equipment and can prevent accidents.
