Bolted-Joint Inspection: Cracking, Corrosion and Clamp Load

Keep the questions separate

Visual examination can document corrosion, damaged threads, missing components and evidence of movement. Suitable surface or ultrasonic examinations may address particular crack concerns. None of those observations alone proves that the joint has its required preload.

An ultrasonic bolt-load measurement is a different application from ultrasonic flaw detection. Its suitability depends on the bolt, reference condition, measurement arrangement and qualified procedure. Do not infer load from a generic NDT scan.

Review the joint as an assembly

Collect the bolt specification, joint drawing, service conditions and available installation records. Identify changes such as substituted fasteners, coatings, lubrication or repeated reuse for the responsible engineering team to evaluate. Access to one end of a bolt may not permit the examination needed for a suspected flaw.

Decide whether the joint can be examined in place and who controls any disassembly. Inspection should not lead to unauthorised loosening, tightening or loading of an operating assembly.

Report evidence without overstating it

Identify each fastener or location, the accessible surfaces and the examination limits. Distinguish an observed indication from an engineering conclusion about load capacity. Where a trend is required, retain the same location and measurement basis. Refer disposition, tightening requirements and continued-service decisions to the authority responsible for the joint.

References and next steps

ASNT’s ultrasonic testing overview provides further background. Use the governing specification and approved procedure for the actual job.

Discuss the examination scope. Include the component, material, service history and decision the inspection needs to support.