“The Good, the Bad and the Ugly”
A brief review of valve casting weld repairs as seen during my numerous audits. All foundries say they comply with ISO, API etc……
Some ASTM casting standards define major repairs and require stress relieving after the repairs are completed. There is no stress relieving requirements for weld repairs not meeting the major repair criteria. ASTM’s A217, A995, and A494 define major repairs. ASTM A216 has the same requirement but does not use the term “major repair”. ASTM’s A703 and A985 specifies major repairs shall be subject to prior approval of the purchaser but does not define major repair nor does it specify stress relieving after completion of repairs.
A Survey of Valve Manufacturers
A survey was taken and most valve manufacturers do not know if weld repairs and, more specifically, if major weld repairs have been made unless a requirement are included in the purchase order to notify purchaser. No one had any requirements for minor weld repairs.
Developing Valve Repair records
Ideally weld repairs of all pressure components should be undertaken against approved weld repair procedures, appropriate NDT and heat treatment when required.
What actually happens?
• In general the foundries establish “Minor” & “Major” repair criteria.
• Approval by the Purchaser before major repair is VERY RARE.
• Major repairs by the foundry “are reported” when required in Purchase order. However this is RARELY REQUESTED.
• In most cases weld repairs are left to the FOUNDRIES NORMAL PRACTICE.
o Weld repair practices vary widely and often do not comply with procedures
o Records vary widely from foundry to foundry o Purchase requirements often get lost in the supply chain.
o Weld repair maps and analysis are the exception than the rule.
o All castings are repaired irrespective of casting defect size.
It is a real pleasure to audit foundries where weld repairs are typically less than 1.5 % and weld repair data are presented to substantiate such claims. In general investment castings weld repairs are less than sand casting weld repairs. Also geographically there are also some countries that are better than others. I have observed over that past 3 years, with the arrival of new foundries and use of modern technology in China, that the casting integrity gap between the East and the West is reducing. Also the supply of materials beyond carbon steel and low end stainless steels is gathering momentum.
Market information on minor and major repairs
General definition of “major weld repair” for WCB materials and similar
> 20% of wall thickness
> 25.4 mm in depth
> Weld repair is more than 65 cm2
General definition of “minor weld repair” for WCB materials and similar
< 20% of wall thickness
< 25.4 mm in depth
< Weld repair is less than 65 cm2
Note; There are variations to the above… 25%, 30%....10mm
Weld repairs can be up to 15% / 30% for minor weld repairs and up to 30% / 50% for major weld repairs for investment casting / sand casting respectively.
Some valve manufacturers take weld repair very seriously and they can show auditors how they achieve low repair levels. Regretfully though a very large market segment of the valve castings lack adequate control of weld repairs.
The photographs illustrate ‘The Good, The Bad and The Ugly’ for casting weld repairs and welding controls. I think most of the slides are self explanatory.
“The Good”; some examples showing excellent casting surface finish, good welding consumables in a controlled environment, recording of weld repairs and control of welding stubs.
“The Bad”; some examples showing uncontrolled weld repairs, flange surface repairs, quivers not heated and poor welding control.
“The Ugly”; some examples showing more uncontrolled weld repairs, ball repairs and unbelievable welding consumable controls.
Often I am challenged with my observations “When I visit foundries why is it that I do not see much weld repair”.
My response; There are possibly two answers to this question.
Answer 1; There are those foundries that indeed have minimal weld repairs and audits do show this. When you ask for repair data information is available to show the percentage of such repairs. This typically would be 1.5%. Also as you undertake your audit you can tell that this information is correct by looking at the castings within the total production line. How much weld repair is seen?
Answer 2; Unfortunately the foundry prepares for the audit. They tidy up the weld area, remove all weld stubs, brush the floors and remove the welders. When you ask for weld repair data there is great difficulty to present meaningful data. In some instances such data is just not available. Any given percentage of weld repairs given by the foundry is by observation. As already mentioned you can also see the quality the production valves.
On one particular audit the foundry stated that no weld repairs were undertaken on a particular valve brand. As I walk around one particular door of a building was closed. I noticed that the dust on the floor in front of the door indicated that something had been dragged along the ground. The door was locked. However the door three metres away was unlocked. I naturally went in to have a look. I found at least 25 cast valves stacked with weld repair markings of the brand concerned. I was informed that these valves were scrapped yet they were not in the appropriate “reject areas”.
On another audit I have seen “A4 folders” positioned at the weld repair area. The folders were brand new with just one page in. As I examined the information it was showing repair data for 2 days, May 2nd and 3rd. I was visiting on the 6th June. When I asked why the data was not up to date the reply was that no repairs had been undertaken since the May 3rd. My suspicion was that an important End User had audited the foundry on 4th May and the folder was presented for their benefit.
• Foundries are aware of API requirements for weld repair
• Interpretation of API requirements varies from foundry to foundry
• Foundry practices for weld repairs, NDT and heat treatment vary
• Weld repairs are often not on the End User / Purchasers “Radar Screen”
• Is the above “Acceptable” and “Safe”?
• Should API or similar review their current requirements?
• Should End Users review their requirements?
Tel: +44 (0) 7791 497111
Published in Valve User Magazine Issue 18
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