Metal Stitching of castings

By - Date 09-04-2001 19:49

In South Africa this term is used for a process whereby cracked castings are repaired through drilling and tapping the cracked sections and pulling them together with small studs. A rather intricate operation, which when done well will render a casting "leak proof" after the repair.

By its nature, it is not practiced widely anymore, due to the advancement of welding technology. I do believe however, that there will be some companies around that still do this. Personally I would try the welding route first. (But then, being a welding engineer, what else would you expect?)

Regards
Niekie

By MBSims

Date 09-21-2001 04:20

Metal stitching is still in use, but as you said not as widespread. I have seen it used to repair cracks in cast CrMoV turbine casings in steam plants. It requires a lot of machining on a turbine casing since they are several inches thick. A "dogbone" shape opening is machined in the casting, then a slightly smaller dogbone shape insert is heated to expand it thermally and pressed into the opening. Upon cooling, the tension in the insert pulls the crack shut.

Marty

By ScottVandenbos Date 09-18-2001 19:44

the problem of welding castings is that is it difficult to get to the 'end' of the crack. The thermal input has a tendency to pushthe croak out further making the repair useless. A combination strategy has however been effective. - Find the ends of the cracks, drill then out (so they don't get longer, THEN weld the joint instead of weave the joint.