Effect of subsea bolt tightening on bolt preload and slip factor

High-strength steel bolts and bolted connections according to general European steel construction standards are currently also used in an underwater environment. Due to recent bolt failures, the practicality of these standards regarding subsea application was investigated. Tightening methods, preload behavior and slip factor were examined under water using special testing equipment. It was found that lubrication of high-strength steel bolt assemblies according the standards applied does not seem suitable for underwater use. Design surface class of specially coated faying surfaces was verified, but seems to be different from regular conditions when determined under water.