API 650 – Welded Tanks for Oil Storage Practice Test 2026 - Free Oil Storage Tank Practice Questions and Study Guide

The maximum allowable misalignment for horizontal joints in plates that are less than 5/16" thick is indeed 1/16". This specification is established to ensure structural integrity and proper weld performance. When dealing with thinner materials, tighter tolerances are necessary because any misalignment can significantly impact the quality of the weld and the overall strength of the joint. A misalignment that exceeds this limit could lead to issues such as reduced weld penetration, increased stress concentration, and potential failure of the joint under load conditions. Therefore, adhering to the 1/16" limit ensures that the welded connections maintain their designed performance and structural reliability.

Other values like 1/8", 1/32", and 1/4" would either be too permissive or impractical for the thickness category in question, which could compromise the quality of the weld and the safety of the structure.