A sheave gauge is an extremely useful tool for use in crane inspection and can be used in the following ways:
To accurately assess the sheave groove contour at the root
To assess the amount of wear of the groove wall
To verify that the wire rope size of the hoist
Groove Root Wear
Wire rope tends to wear the bottom of the sheave groove to a radius smaller than the radius of the sheave. This phenomenon is likely best explained by the fact that wire rope is not round and because wire rope, under load, becomes smaller in diameter. Therefore, in the absence of a high fleet angle or side load, the groove will show wear at the bottom of the groove first. To detect wear, place the proper size gauge in the sheave and shine a light behind the gauge. Light should not be detected between the gauge and the root of the groove. If wear is evident, the sheave should be replaced.
Groove side wall wear
Excess fleet angle (angle exceeding 1 ½ - 2 degrees) or side pulls (load lines off vertical by 2 degrees or more) can result in sheave groove wall wear. The optimal arc of contact between the rope and the sheave groove is generally about 120 to 150 degrees, although arcs of 90 degrees can be quite acceptable and result in good wire rope life on overhead traveling cranes. The sheave gauge can be used to gauge this wear in the groove. Be mindful that some manufacturers use multi-sized sheaves for economical reasons on small power hoist applications.
Hoist rope size verification
When inspectors check the hoist, they often do not have the luxury of OEM manuals for reference purpose. This being the case, they do not always know the wire rope size the OEM specified for the particular hoist. To verify the rope size, the bottom block (and top block) sheaves cannot always be used. The drum is the most recommendable check point to verify wire rope size. Use the sheave gauge on an unworn section of the drum to verify the wire rope size the designer intended to be used on the hoist.