The Diamond Chain Company says that roller chain drives are one of the primary systems used in industry to transmit power and convey products. Since roller chain drives are widely used, productivity is highly dependent on the performance of roller chain. Roller chain that suffers from premature elongation ("stretch") due to wear and needs to be replaced on a frequent basis will negatively impact productivity and significantly increase the cost of the operation.
Here are some quick tips from the Diamond Chain Company that will help you prolong and achieve maximum roller chain life:
Lubrication and maintenance
The importance of selecting a high quality roller chain and following proper lubrication and maintenance procedures during operation can’t be overstated. Close adherence to lubrication type and method, based on the drive’s specifications will not only reduce wear, but will produce other benefits, such as cushioning impact loads and heat dissipation. To maximize your drive’s service life, however, lubrication is only a part of the necessary process. Selecting a quality chain will be just as important.
A roller chain is a series of connected journal bearings that articulate as they enter and leave the sprockets. This articulation results in wear on the pins and bushings. As material is worn away from these surfaces, the roller chain will gradually elongate. Elongation due to wear is a normal phenomena during drive operation. The rate of wear is dependent on several factors, including proper lubrication, load and the frequency and degree of articulation between pins and bushings.
The manufacturing of the critical wear components, pins and bushings requires the strictest attention to detail. This starts with the proper selection of raw material, part fabrication and part preparation prior to and including assembly. All of these are critical elements in achieving maximum performance. If the wear components aren’t of the highest quality, the wear life of the roller chain will suffer regardless of other factors.
Wear elongation measurement
Wear measurements can be made to determine if the chain has elongated to a length where replacement is necessary. To ensure accurate results, length measurements on roller chain must be done when the chain is in tension. If the chain is measured while still on the sprockets, the system must be turned off and all safety procedures have to be followed. The tight span of the chain is the section that should be measured. If the chain has been removed from the sprockets, the ANSI-specified measuring load should be applied to the chain, so that the slack has been removed.
Measure as closely as possible from the centre of pin to the centre of another. The more pitches (pins) contained within the measurement increase the accuracy. If the measured value exceeds the nominal by more than the allowable percentage-the chain should be replaced. The maximum allowable wear elongation is approximately three percent for most industrial applications, based upon sprocket design.
The allowable chain wear in percent for large sprockets with 68 teeth or greater can be calculated using the relationship: 200/N, where N is the number of teeth in the large sprocket. This relationship is often useful since the normal maximum allowable chain wear elongation of three percent is valid only up to 67 teeth in the large sprocket. In drives having fixed centre distances, chains running in parallel or where smoother operation is required, wear should be limited to approximately 1.5 percent.
Example: if 12 pitches (12 pins) of a #80 chain were measured and the result was 12.360 inches or greater (using three percent as the maximum allowable wear), the chain should be replaced. Anything less than 12.360 inches would still be acceptable by most industrial standards.
This is an edited article provided by Indianapolis, IN-based the Diamond Chain Company. For more roller chain tips or product information, visit www.diamondchain.com.