Valve manufacturer's approved sub-supplier list

Valve manufacturer’s approved sub-supplier list - Part 7

Barrie Kirkman - 11 June 2015

Review of the valve manufacturer’s approved sub-supplier list is a critical part of the end user’s evaluation process.

About the author

Mr Barrie Kirkman
Barrie Kirkman, BSc CEng MIMechE, writes a regular column for Valve World, bringing his own personal views from inside the valve business.
Sub-Supplier Management

Review of the valve manufacturer’s approved sub-supplier list is a critical part of the end user’s evaluation process. Too often issues arrive in plant operation as a direct result of poor or inadequate sub-supplier control of materials and manufacturing operations. A major end user at Valve World Americas highlighted the importance of inspection of all valve internals prior to assembly as many issues had occurred of which some were from sub-suppliers. Another example was machining issues with poor surface and stuffing box finishes noted by an end user. They discovered that the valve manufacturer sub-contracted 90% of their machining to various machine shops which were not adequately audited nor QA/QC controlled. It was claimed that “other reputable valve manufacturers use this machine shop so we thought they were alright to use”. Oh dear!

The basic requirement

The Basic Requirement

The valve manufacturer should have a well-defined process with the appropriate persons and review period for:

  • Approving new sub-suppliers.
  • Maintaining existing sub-suppliers.
  • Removing poor performing sub-suppliers.

Too often complacency creeps into the process;

  • New suppliers are used by-passing the process for costs or urgent delivering reasons.
  • New employees are not correctly trained to follow procedures.
  • The valve manufacturer procurement team makes decisions without involving other key disciplines.
  • Over familiarity with the supplier, as business has been done with them for many years, results in by-passing the process.
  • Not all suppliers are on the sub-supplier approved list.
  • Contractor services are not on the list.

So who should be involved in the sub-supplier approvals?

Approved Sub-supplier list

Normally the activity is led by procurement with the direct involvement of quality and engineering. These three disciplines work together to establish “An approved sub-supplier list”. When it is required, specific input from other disciplines may be added, for example production with their knowledge.

Sub-supplier’s contract

The sub-supplier’s contract should have quality performance criteria and other key performance indicators applied such as commercial and delivery. (Please go and check your contracts? It’s amazing how often these are missing).

Ranking of sub-suppliers

Sub-suppliers should be ranked in importance and criticality to the valve. Typically level 1, 2 and 3 or A, B and C are used. Linked with this criticality ranking are requirements for internal assessment and external assessment such as QA and engineering audits and ongoing performance monitoring. End users expect such assessments to be undertaken on an annual basis and recorded with a full audit trial.

This is where a wide interpretation occurs with respect to involvement of procurement, quality and engineering. I have witnessed on many occasions procurement undertaking quality and engineering assessments which is of concern especially for new level 1 suppliers. There is a reluctance to audit the sub-supplier. Obviously requirements can be adjusted to reflect criticality of the sub-contract and ongoing performance whether good or not so good. The balance between “desk top assessments” and “actual audit assessments” needs to be right. Internal team meetings are a must for effective management of this list with evidence that such meetings have taken place.

ISO versus non ISO sub-suppliers

An interesting discussion often held is the use of ISO 9000 sub-suppliers versus experienced non ISO 9000 sub-suppliers? Where sufficient evidence is provided I have accepted either though I have had to reject some who clearly were not operating in a quality manner. Rejection of balls for ball valves sometimes falls into this category, also machine shops. Some end users are stricter and only allow ISO9000 sub-suppliers.

Performance of sub-suppliers

Performance sub-supplier list

The performance of the sub-suppliers also needs to be quantified. How is this done? Does the valve manufacturer visit the sub-suppliers to undertake QA/QC checks? Are nonconformance reports (NCR) issued at either the sub-supplier plant or from goods inward inspection? Is the NCR data analyzed and fed back into the annual Quality assessment?

The end user can easily see if such checks are effective during their audit as they inspect sub-supplier components quality and check compliance. Too often such poor quality is not identified until well into the manufacturing process at which time the decision to correct or reject has to be made. This is not cost effective and runs the risk of slowing production. During my audits I see QC requirements for goods-in with photographs of what’s acceptable and what is not. I think some inspectors are “blind” or “have poor eyesight”? Components and parts pass the inspection which should have been rejected and moved to the quarantine area. Common areas are casting surfaces and machine finishes. Various excuses are given such that the part is required to meet the production schedule or it’s ok as it will pass the hydrotest…

Management of the approved sub-supplier list

The approved sub-supplier list should be a controlled document in accordance with QA document procedures. A strict discipline is required by the valve manufacturer to ensure procedure compliance and only certain authorized persons are able to amend the list. The authorized persons should be from upper management. The annual Quality Performance meeting should review the performance of the approved sub-suppliers taking any action necessary to maintain or improve.


The end user will assess the valve manufacturer’s capability on controlling their sub-suppliers. Where processes are clearly being followed with continuous improvements or high standards of performance approval is relatively easy and quick and the auditor will quickly move onto the next subject. In the event they are not adequate a non-conformance report is issued to highlight the importance of the approved sub-supplier list.

Thank you for your continued support. Please contact me if you have any questions or different views.

Barrie Kirkman, BSc CEng MIMechE, writes a regular column for Valve World, bringing his own personal views from inside the valve business.

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