9 RS Roller Chain Checkpoints Chain life is generally considered to have expired when the chain does not engage properly with the sprocket due to elongation or damage of its parts. When this occurs, it is usually necessary to replace the chain. A long, trouble-free working life can be achieved if chain is properly selected for the conditions of its application. To help prevent damage or premature wear, inspect the chain and sprockets for:
1. Abnormal noise 2. Chain vibration 3. Chain rising on the sprocket 4. Chain winding around the sprocket 5. Kinks or stiff bending of chain 6. Amount and state of lubrication 7. Contact between chain and case
8. Chain appearance. Check for dirt, corrosion, damage on the outside surface of the roller, contact marks, etc. Also check the inside edge and surfaces of the link plates and the surface edges of the pins 9. Damage on the sprocket tooth surfaces and side surface teeth and engaging areas 10. Abrasive stretch of the chain 11. Bending of chain and rotation of roller
Checkpoints 1. Lubrication
While the chain is in operation, check that the lubricating oil moves toward the link plates and that the chain or rotating disc is immersed in the oil bath. When the chain is stopped, check for dirt or abrasive particles produced by improper lubrication. When the chain is removed, the connecting link pin and the inside edge of the bushing should be checked. Damage or a red or reddish-brown color signal improper or insufficient lubrication. 2. Link Plate Chain exposed to repeated loads over the allowable load can develop fatigue breaks in the link plate. Fatigue breaks are difficult to anticipate until they produce a crack. Cracks usually develop at the edge of a hole or at the side of the link plate as shown in Figures 9-1 and 9-2. Check link plates often for cracks to prevent accidents.
Figure 9-1: Positions where Cracks are Likely to Develop
Figure 9-2: Example of an Expanding Crack
16 I NSTALLATION & M AINTENANCE
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