Equipment Repair

1Q. Is there any general advice you can give me on the repair of machinery?

1A. Many things, but probably the most important is indicator readings on rotating parts. As the TIR (Total Indicator Reading) of a rotating member becomes greater than 1 mil (0.001 inch) so should your concern.

2Q. When repairing a shaft should I be concerned on where the weld is?

2A. We had a large extruder shaft which had sheared due to overload. When a new piece was machined we made the new section in such a way that the weld was out of the high bending stress zone where it had failed and in a low stress area. This provided the shaft with additional design margin. This can't always be done, but understanding what caused the failure and some thinking before machining and welding can result in a more reliable design.

3Q. What is considered straight for a shaft?

3A. It depends on the service, but for things like a pump shaft, checked between centers, straightening is usually in order when they are out more that 0.001 inch.