Case Study - Mistake ProofingMajor Pipe Manufacturer - NSW, Australia

A major manufacturer of gas pipelines was experiencing excessive rework and reject rates associated with their seam welding process.

Any pipe that made it into the field with a defective seam weld would have the potential to cost the business up to $500,000 in recovery costs as well as reputation and market share.

The challenge was to completely eliminate welding defects from the process and implement a series of tests that guaranteed pipe delivered to the customer would be free of defective seam welds.

An EnterpriseIS team member undertook a Lean Six Sigma project to reduce the levels of welding defects.  It was found as an outcome of the analysis work, that the quality of manufacture of the conductor/electrode assembly was below the required standard.

There were three basic styles of assembly.  An assessment of the variation in quality revealed that none of the assemblies were within the tolerances specified.

Using Lean Six Sigma techniques to analyse and assess the measurement systems used to manufacture the assemblies, it showed that it was unrealistic to expect, that a diligent tradesperson could manufacture an assembly to the tolerances required, using the tools and techniques available.

As this was a critical step in the manufacturing process, a conscious effort was made to use mistake-proofing techniques to eliminate the possibility that an assembly could be manufactured incorrectly.

Drawing and tolerances were standardised using statistical methods with all components manufactured in a mistake-proofed process.