Investigation into the failure of elastic rail clips

Synopsis

Our client requested that we conduct examination on a batch of Elastic Rail Clips (ERC) that they had received from a supplier. The clips were seen to break on installation or shortly thereafter.  Specialist laboratory testing was required to investigate the failure. A sample of clips were provided for Corus to undertake a series of laboratory investigations to establish the cause(s) of failure and whether they were fit for purpose in accordance with the client’s specifications.

The client then received a replacement batch from their supplier and requested that Corus carry out an investigation to establish their fitness for purpose before accepting them.

Key Client Issues

• Clips from the initial batch breaking during or shortly after installation
• Uncertainty of fitness for purpose of replacement clips
• Limited knowledge and facilities available for investigation of the ERC within the client organisation

Solutions

Specialist laboratory testing was required to investigate the following:

• The reason(s) for failure
• To carry out a detailed metallurgical examination of the microstructure to establish whether they were within the supplier’s specification and correctly heat treated
• Hardness for comparison against the specifications
• Fitness for purpose and conformance to the client’s specification

We determined the causes of failure were due to:

• Incorrect quench for the 16mm diameter section size, resulting in the longitudinal cracks believed to be quench cracks
• Incorrect tempering treatment resulting in hardness levels greatly in excess of the specified 380-435 HV (40-44 RC)

A comparison was made between the two batches provided to the client from their supplier to detect any differences. All results were compared against the supplier’s specification.

Client Benefits

The laboratory investigation has contributed to:

• Improved track safety
• Mitigating potentially dangerous and expensive future failures
• Client awareness of the products fitness for purpose
• Improved business efficiency, reducing time lost due to defective clip installation