Technical requirements for valves
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I am planning to purchase a batch of 600LB ANSI valves for use in the methanol desulfurization process. According to ASME B16.34 standards, 100% flaw detection is required for both forgings and castings. However, from conversations with those who work in this field, it seems that such practice is rarely carried out, as it results in high costs. I would like to ask whether 100% flaw detection is indeed necessary for castings and valve components, how people actually proceed in practice, and how quality can be ensured for valve castings if flaw detection isn’t performed
Cast valves should ideally be 100% inspected for defects, as sand holes may be present
Our requirements are as follows for the poster’s reference: 1. For all valves ≥CL900, the pressure-bearing welds and pressure-bearing castings must undergo 100% radiographic testing (RT) + magnetic particle testing (MT) or liquid penetrant testing (PT)； Pressure-bearing forgings must undergo 100% ultrasonic testing (UT) + magnetic particle testing (MT) or liquid penetrant testing (PT) ； The RT testing complies with ASME B16.34 requirements; the acceptance criteria for defects of types A, B, CA, CB, CC, and CD are not lower than the grade 2 requirements specified in ASTM E446 or ASTM E186, while defects of types D, E, and F are not permitted ； The inspection and acceptance of MT, PT, and UT shall comply with the provisions of ASME B16.34 Appendices II to IV. 2. For valves with CL600≥, the inspection ratio shall be determined through consultation between the owner and the designer, or shall be set by the owner themselves. 3. Except in cases where other design requirements apply.
≥What is a suitable proportion for flaw detection on 600Lb materials? Is it necessary to conduct flaw detection on all WC6 materials?
For stainless steel, PT is recommended; for chromium-molybdenum steel, MT is recommended. For 600LB materials, partial RT is suggested. The cost of RT is indeed much higher. Nowadays, many organizations set high requirements, specify low bid prices, and award contracts to the lowest bidder, which makes it difficult to ensure quality.
First, examine the inspection requirements for materials used in valves as specified in ASTM105/182/216/216/351; then determine whether to add additional inspection items or increase the inspection frequency based on the importance of the valve. This is something that can be negotiated (the procurement cost will certainly increase), and once a technical agreement is reached, the manufacturer can proceed with the implementation.
For 600LB valves, 100% radiographic inspection is absolutely necessary; otherwise, serious problems are likely to occur.
More participation is welcome. This is the current situation; companies need to change their approach, and in light of the current conditions, they should also strengthen re-inspections