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Understanding the Quality Failure in Valve Body Cracking: A Case Study in Global Supply Chain

In April 2008, severe cracking was discovered in valve bodies used in submarines, prompting an extensive testing program to assess the chemical composition of 1460 valves. The root cause was identified as manganese levels below specification, exacerbated by excessive grain size. Immediate containment actions were implemented to identify faulty materials, leading to the establishment of a three-tier material assessment process. This case highlights the need for improved visibility and control over supply chains, rigorous quality standards, and modern verification processes to ensure product integrity and safety in the industry.

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Understanding the Quality Failure in Valve Body Cracking: A Case Study in Global Supply Chain

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  1. Our "SHIFT" #2

  2. Globalisation ‘The missing link’ Major Quality Failure

  3. The Failure • April 2008 cracking found in a Valve Body. • Testing programme undertaken to assess chemical composition of all Work In Progress (1460 valves fitted on each submarine).

  4. Grain Size Problem

  5. CONTAINMENT • Cause of cracking was the Manganese was below specification and in conjunction with excessive grain size was responsible for the failure. • Containment action initiated immediately to identify out of specification material and scale the size of the problem. • Three tier material assessment process established to check and confirm the acceptance of material. • Sort, using X-Ray fluorescence analysis (XRF) • Confirm material composition by analysing a scraping from below specification valve body determined by the XRF tool. • Detailed material analysis using sample sections from valve bodies.

  6. Source Mill India Make Bar Italy Manufacture UK T1 Supplier UK Make Bar France Forge Bodies Italy Submarine UK Stockist Germany Supply Chain Investigation

  7. Source Mill Investigation • The method of mixing the alloy in its molten state was not effective in ensuring the homogeneity throughout the ingot. • The extrusion procedure was inadequate and did not meet the NES requirements e.g. soak time and the reduction ratio were inadequate. • No control over calibration standards. • Wet Sample records and spectrometer results did not match. • Identification throughout the plant varied from permanent stamping to chalk which was considered inadequate and could result in loss of traceability. • C of C stated that material was annealed yet the company did not anneal that particular size

  8. Investigation Recommendations • Improve visibility of the entire supply chain. • Insist on original documentation accompanying transposed certificates. • Ensure appropriate balance of product verification and documentary evidence. (BS EN 10204:2004 Para 3.2 certification introduced) • Drive the development and modernisation of industry Quality Standards including MOD’s SSCP25 and ISO 9001 alternatives • Increase the use of commercial specifications e.g. define grain size • Continue with Positive Metal Indication (PMI) testing of in-coming material. Ensuring a safe quality product ………

  9. Any Questions?

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