Sand hole problem in cast valves
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This post was last edited by Refiner on 2015-8-12 07:42. 1. What potential hazards exist during the use of cast valve components that have sand holes, after those holes have been repaired and welded properly? 2. For each batch of valves of a given model and specification, are there any requirements regarding the acceptance rate for sand holes? For example, if there are 10 valves of a particular model, how many sand holes are allowed? Is there a relevant standard code for this?
1. If a cast valve has sand holes and those holes are repaired by welding successfully, what potential risks exist during its use? It cracks easily due to insufficient strength. 2. Is there any requirement regarding the acceptance rate for sand holes in each batch of valves of a given model and specification? For example, if there are 10 valves of one model, how many sand holes are allowed? Is there a relevant standard code for this? Generally, only 1 or 2 out of 100 units are defective; otherwise, the pass rate would be too low.
Regarding the second point, I can check if there are any relevant standards. Thank you
It’s clearly stated in both the MSS SP55 and ASME B16.34 standards
The defects for which repair welding is generally permitted do not cause any issues affecting the performance or service life of the originally cast part~~As for the second question, it can be found in the \"Technical Standards and Acceptance Criteria for Cast Iron Castings\"~~
1. Qualified weld repairs carried out in accordance with the weld evaluation procedure generally pose no subsequent hazards. 2. The number of defective items with sand holes is zero tolerance according to the acceptance requirements. This generally refers to leaks detected through sand holes in the valve body during pressure testing. However, the small pits found on the surface of cast valves fall within the range permitted by standards, and they cannot be considered sand holes.
During the overall testing of the valve, if sand inclusions are detected, after they are removed and the valve passes the tests, can it still be shipped?
What if it’s a die-cast valve? If, during the pressure testing, it is found that there is seepage through small holes in the valve body, can it still be shipped out after being repaired by welding? Thank you