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Restoring Dished Head knuckle thickness

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SJmetallurgist

SJmetallurgist

Mechanical
Joined
Apr 8, 2006
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47
Location
IN
As per UW-42, is it permissible to restore a dished head thickness falling below the minimum required thickness?
One of my fabricator has deposited the welding as per UW-42 onknucle of an ellipsoidal head The min req. thickness was 10mm, but observed was 9.6mm.

Any input would be highly appreciated.

Thanks
 
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<<<< The min req. thickness was 10mm >>>>
Is there a tolerance on the 10mm ? +/- .5mm, if you are lucky.
 
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Can you post pictures or show sketches revealing the extent of degradation ??

MJCronin
Sr. Process Engineer
 
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There is nothing in Section VIII that prohibits restoration of base metal thickness in the KR by welding per UW-42. However customer approval should be received before doing it. If this is a seamless head supplied as materials, SA-20 requires customer approval.
 
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Thanks @Don56. However, as per UW42, such weld restoration is only allowed for strength and modification purpose. Therefore the confusion.

Construction in which deposits of weld metal are applied to the surface of base metal for the purpose of restoring the thickness of the base metal for strength consideration; or modifying the configuration of weld joints in order to provide the tapered transition requirements...

Whic one of these cases would my case fall under according to you?
 
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SJ Metallurgist
Your situation is restoration of thickness for strength consideration. When I made heads we did this multiple times successfully, always with the customer's approval as well as our AI's, even when the heads were seamless.
 
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Is customer approval to ward off any liability issue arising from cracks in the knuckle after restoring knuckle thickness with weld overlay. When I took my NB exam (in NYC twin towers) around early 1990 work on knuckle was not regarded as a safe procedure, so what changed as I have been out of that loop about 15 years.
 
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Chicopee, if the head is seamless it is being supplied as a material and the rules of SA-20 enter. See SA-20 9.2.1.2. There are also interpretations on this that confirm it is acceptable. Where in the Code does it say you can't repair a knuckle.
 
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Pull out the FEA tool and justify the condition.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."
 
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