Dimensional Tolerances

The ASME code has surprisingly few dimensional tolerances. In fact, in section U-5, the Code states that tolerances are not fully addressed, and allowable tolerances should be based on engineering judgment and standard practices. The tolerances that are included in the code have to do with the integrity of the pressure vessel and preventing failures or unsafe conditions. There are code tolerances for roundness of shells (UG-80) and the shape of heads (UG-81). There are also mismatch tolerances for welded joints in UW-33. Tolerances for locations of vessel components such as nozzles and supports are not included in the code since they do not affect vessel integrity. Component location tolerances are usually based on industry standards such as TEMA, end-user requirements, or manufacturer’s standards. Contact us if you have any questions about the code or tolerances.

Above are Ward’s standard tolerances for columns and towers while below Figure F-1 are the tolerances per TEMA for heat exchangers.