The Importance Of Proper Tensioning In Power Transmission And Conveying Chains
Proper tensioning in silent chain systems is crucial for optimal performance and longevity.
When new chains are installed, they should have just enough tension to ensure satisfactory operation. Running a chain too tight or too loose can significantly shorten its lifespan. A chain that is too tight will experience additional load, leading to accelerated wear and increased noise. Conversely, a chain that is too loose will exhibit whipping and excessive movement, leading to premature wear.
Elongation Of Chains
As a chain wears, it elongates and wraps around in a larger pitch circle, resulting in a chain that is too loose. This excessive elongation and chain slack can lead to several hazards, including:
- The chain not smoothly engaging the sprockets, causing hesitation and surging
- The chain experiencing shock loads
- The chain skipping teeth
- The chain whipping around and hitting the sprockets with too much impact, potentially hitting the drive box
- Damage and wear to the sprocket
- Increased noise
- Accelerated chain wear and shortened useful chain life
Ways To Re-tension The Chain
Re-tensioning the chain is essential to eliminate problems caused by excess chain slack. Here are some ways to avoid downtime and maintain the chain tension:
- Proper Installation and Periodic Checks: Chains must be properly tensioned during installation and checked periodically to ensure they maintain the correct tension.
- Adjusting Shafts: Many chain systems are designed with shafts that can be moved in and out. This feature makes it possible to tighten the chain as it elongates.
- Using an Idler: In systems where the drive is fixed, an idler may be present to tension the chain. The idler can be moved in or out to provide the right tension on the chain. (See image, idler circled in red)
- Automatic Tensioning Devices: Devices, such as a spring arm, may be designed into a system to automatically and continuously tension a chain.
How Much Elongation Is Acceptable?
The size of the large sprocket will limit the allowable elongation of the chain. In general, a chain will not properly wrap sprockets when it has elongated by 200/N % where N = the number of teeth in the larger sprocket. If more than this occurs, replacing the chain is suggested. Other application-related considerations may further limit the amount of acceptable elongation.
Proper Tensioning Varies With Shaft Orientation
On drives where the line between shaft centers is horizontal or inclined as much as 60 degrees from horizontal, the chain should be tensioned to allow a sag in one strand equal to approximately two percent of the shaft center distance. The chain should be taut in vertical or fixed center drives, and on drives subject to shock loads, reversing, or dynamic braking.
Proper tensioning is indeed crucial for maintaining the performance and extending the lifespan of chain systems. If you have any questions about your application, whether it is for power transmission or conveying, feel free to contact Ramsey for expert advice and assistance.
