Castings: An Introduction and Requirements in Review of ...

Further, API committee decided to producer numerous codes on casting quality, these are created by Com. 20 &#;Supply Chain Management&#; at API. 

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ASME B16.34 addresses the Casting requirements per clause 5.1.3 and 8.3, etc.

• MSS-SP-55 is a code on &#;Quality Standard for Steel Castings for Valves, Flanges, Fittings and Other Piping Components &#; Visual Method for Evaluation of Surface Irregularities&#; 
• MSS-SP-93 is a code on &#;Quality Standard for Steel Castings and Forgings for Valves, Flanges, Fittings and Other Piping Components &#; Liquid Penetrant Examination Method&#; 
• MSS-SP-94 is a code on &#;Quality Standard for Ferritic and Martensitic Steel Castings for Valves, Flanges, Fittings, and other Piping Components &#; Ultrasonic Examination Method&#; 
• MSS-SP-147 is a code on &#;Quality Standard for Steel Castings Used in Standard Class Steel Valves-Sampling Method for Evaluating Casting Quality&#; 

A few discussion questions with a Foundry with response as below: 

a) How to identify porosity and voids? 

Answer: Surface porosity can be found either visually or with MT. MSS-SP55 standard &#; it has a large number of pictures as well as whether the defects found would be acceptable or reject- able. Internal porosity / voids are found using UT or RT &#; the standards for this are MSS SP 94 for UT and MSS SP 54 for RT. We can also look at ASME section XIII for NDT testing. 

b) What porosity and voids are considered detrimental? 

Answer: This would depend entirely on what the castings are used for &#; load bearing components are normally tested to API 8C (or similar) with a level 1 for critical areas and level 2 for non- critical. Castings for heaters are level 3 or 4 again depending on if it is a critical area or not. You will never find a casting that would be 100% level 1 in the entire part (unless they are small castings and possibly investment castings) 

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c) How are they fixed and reinspected? 

Answer: This depends on what standard you are testing to. Each ASTM standard has this spelled out in one of the sections (blend out the defect or weld it up) &#; you would have to check the standard that the castings were made to, to determine any repair procedures. 

d) What documentation is required for cosmetic and other than cosmetic repairs? 

Answer: Some customers require a weld map (pictures of where the defect was in relation to the casting) but generally if the cavity of the weld is greater than 20% of the wall thickness, you will have to RT that area and the report from the testing company would be sufficient. 

e) What processes and techniques are allowed for repairs at foundry and at machine shop? 

Answer: Castings in a foundry are usually welded using stick welding and then tempered to relieve the stresses, on a machined surface sometimes they will use MIG to keep the heat to a minimum depending on the size of repair necessary ( all depends on what was found and marked up as a repair). 

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