Advisory Desk Note 544 Washers for preloaded bolting assemblies

Publication Year

2025

Document Status

Current

Abstract

This SCI Advisory Note provides guidance on the correct use of washers in preloaded bolting assemblies to prevent loss of bolt preload due to washer indentation. It highlights the importance of using hardened washers, as mandated by BS EN 1090-2 and the NSSS, particularly under rotating components of the joint. Requirements vary by bolt property class and steel grade, with specific standards governing washer types and placement. The note also clarifies that standard hardened washers are unsuitable for direct use with oversized or slotted holes, where plate washers with hardened washers above are required to maintain joint integrity.

Document History

June 2025 edition.

Publisher Information