There is much discussion in the market on weld repairs and what is allowable and what is not. One of the first things that you become aware of when visiting foundries in the low cost countries is weld repairs and the extent thereof. Surely as you see so much it must be the norm and acceptable?
I have been fortunate to visit foundries where you can count the number of welding stubs used for weld repair on one hand demonstrating that good castings are available. These have been designed correctly utilizing good sand, moulds and pouring techniques resulting in quality trouble free castings.
Why is there a difference in weld repairs between foundries?
It revolves around technical expertise and knowledge coupled with investment and operational costs. Many poor foundries know what is required but strategically have decided to produce at the lower end. The supply chain is driven by “low costs” whether that is from the end user, distributor or western valve manufacturer. The foundry sees a continuous demand for low quality castings. Of course the supply chain ensures “compliance” with international codes supplying appropriate NDT, documentation and certification. End users have seen in some instances casting failures as a result of this practice. End users react to this by either banning the foundry concerned or usually attempt, through permanent inspectors, to control and improve the casting quality. This is often a waste of time as it just turns into a paper generating exercise and the casting product itself does not improve. (Whoops I expect some readers will take exception to that statement?)
So how does the End user auditing foundry begin to address the above?
A suggested 30 point check list
- During the technical discussions prior to visiting the actual foundry try to establish the extent of minor and major repairs. The easy answer will be presented in a percentage of production.
- Ask how they arrived at such percentages? The usual answer is “by experience” rather than a quantifiable method of quality control.
- Ask what has been the level of weld repair over the past 3 years to establish whether they are trying to improve?
- Are the castings heat treated after all minor and major weld repairs? Some foundries heat treat the castings prior to weld repair. They argue that the repair is only minor.
- Seek evidence that the foundry welders and foreman clearly understand the difference between minor and major weld repairs and associated NDT.
- Are weld procedures available in the welding location? Ensure they are actually used and have been read. Check for example the welding weld consumable against the WPS. Even ask the welder about the WPS. Be aware of numerous English WPS’s being displayed and the welder unable to read them!
- Seek evident and documentation that major repairs are actually executed and recorded correctly with appropriate crack detection and radiography.
- Do look historically at the weld repair records as often the “show” is only put on for auditor visits.
- This is a silly statement but ensure the weld repair data is actually collected by QA or similar rather than just left at the repair area.
- Then whilst in the foundry establish the following:
- Control of storage, issue and return of welding consumables.
- Who has the authority to issue welding consumables?
- Follow by example(s) the stated controls looking for the paper trail but more importantly witness the control in action.
- Is the storage room humidity and temperature controlled?
- Is the principle of “first in” “first out” followed?
- Audit the heating / holding ovens. Check, as normal, calibrations
- Ensure good separation and control of different weld consumables are in place.
- Actually look in the ovens to discuss material segregation and control.
- What is the welding consumable condition? Do they look new? Or do they appear to have been re-heated many times or over baked? Challenge the foundry if in doubt. Again “first in” “first out” should be applied.
- Are the welders actually following the weld procedures, for example cleaning the defect area by wire brush or similar?
- Actually ask to see a wire brush….it should be near by and worn and not brand new unused.
- Check the welding quivers used to hold the welding consumables locally.
- Are the quivers plugged in and warm? Are there any cold quivers that are holding welding consumables?
- Are the welding quivers calibrated?
- Check when possible at the change of shifts whether the welder indeed returns unused welding materials to the ovens/ stores?
- When walking around the foundry check to see if there are any welding consumables just lying around that are obviously uncontrolled.
- Do look in closed cupboards …its amazing what you find!
- Are any weld repairs being recorded indicating the defect location and weld repair size?
- Review the repair sheet to ensure the relevant and correct information is recorded.
- Having been advised of the percentage of repair the auditor should assess for themselves if the figures are realistic or not?
- Is the weld repair uncontrolled and carried out anywhere in the foundry or are the castings brought to a specific weld repair location?
By following the above this will enable the auditor to establish an informed position. By no means is it a complete check list.
One foundry stated “Mr Kirkman I am an ISO auditor that approves foundries and offers training but I never knew about the welding control process you have described. Where did you learn this?” I am not normally lost for words but on this occasion I was…..
During one audit behind a closed door a whole mound of castings had been hidden from the audit trail as the foundry had claimed they did not weld repair. The scraped trail of the dirt on the floor leading to the door gave away the deception. Do look in weld areas to see if indeed the floors have been swept in preparation for the audit. Foundries also remove welding equipment out of sight.
Footnote to end users / purchasers; unless it stated in the purchase order that documented evidence / certification is required for major weld repairs the foundry will not provide such evidence.
A quick thank you to the various readers who have taken the time to comment on previous articles!
Please contact me if you have any questions or different views. They are most welcome.
Barrie Kirkman, BSc CEng MIMechE, writes a regular column for Valve World, bringing his own personal views from inside the valve business.
Barrie can be reached on: email@example.com.