What is it and what to do about it?
Three causes of chain stretch and how to prevent it
What is chain stretch?
Although chains are frequently described as having stretched due to wear and use, the term 'chain stretch' is slightly misleading. A more proper term is 'chain elongation', since the chain links themselves are actually not getting longer. In the case of roller chains, it refers to deformation of one or more of the separate pieces that make up a chain.
Roller chains are the most commonly-used style of chain in production and assembly environments. There are various kinds of roller chains, including single (simplex), double (duplex), and triple (triplex). The more load a chain must transport, the more strands it will contain.
Roller chains consist of the following pieces:
Over time, the forces of friction, weight, contamination and heat can have multiple harmful effects on the parts of a roller chain. The pins (#3) are most prone to damage. To be precise, these pins are not elongating, but are undergoing one of a few possible effects:
• They may be bent to a certain degree
• They may lose material from friction, resulting in a change in their dimensions
• There may be a slight widening of the holes in the plates through which pins are inserted.
Signs of chain stretch
Chances are that you will see signs of chain stretch long before a chain breaks. In fact, breakage is very rare with modern chains. More common are one or more of the following symptoms:
• Excessive rattling, grinding, or other unusual noises coming from the chain drive
• Wear on the teeth of sprockets, often in a characteristic hook shape
• In the case of timing belts, a variation in timing as seen with a timing light
• If a tensioner is being used, the movement of the tensioner can be monitored to see if the required amount of tension has increased
Chain stretch can also be determined through a mathematical formula:
% = ((M-(S*P))/(S*P))*100
Where:
• M is the length of the links measured
• S is the number of links measured
• P is the pitch, or the distance between links
Example calculation:
A chain of 20 links (S) with a pitch of 1 inch (P) measures 20.5 inches (M).
Fill in the values to calculate the percentage of elongation:
-> ((20.5-(20*1))/(20*1)*100 = %
-> (.5/20)*100 = %
-> .025*100 = %
-> 2.5%
In this calculation, the percentage of elongation is 2.5%. In this situation, Interflon would recommend regular checking of the chain with a measurement tool until the maximum allowable elongation according to OEM specification has been reached.
The most common way to measure chain stretch is through use of a ruler or tape measure. You can also make use of various simple tools that fit into the spaces between pins. Often these will be provided by the manufacturer.
How to prevent chain stretch
The most important factor in preventing chain stretch is lubrication. If roller chains are poorly lubricated, stretching will take place very quickly. When a chain has elongated too much according to OEM specifications, it must be replaced. Replacement is expensive, can create hazardous situations and can be time-consuming. It necessarily involves shutdowns of production, so obviously a business wants to get as much life out of its chains as possible.
This is where Interflon excels. We save businesses time and money by providing them with high-quality lubricants specifically formulated to prolong the life of chains, as well as other types of production equipment requiring lubrication. Interflon lubricants last much longer than ordinary industrial lubricants, thanks to MicPol®, our unique technology that contains micronized, polarized particles and a polarized base oil.
Interflon lubricants with MicPol® stay much cleaner than wet lubricants, and will not form an abrasive paste of oil and dirt.
MicPol® particles are extremely small. This gives our lubricants excellent creeping and penetrating abilities, enabling them to get into the tiny spaces between pins, rollers, bushings, and plates.
MicPol® particles and a part of a specialized base oil are also polarized. This means they can bond to the positive particles on a metal surface. As a result, Interflon lubricants with MicPol® often last up to ten times as long as traditional industrial lubricants
Learn more about our MicPol® technology
Another highly significant factor in chain stretch is the accumulation of dirt particles between parts of a chain. These particles form a paste with existing traditional industrial lubricants, and they will cause pins, rollers, and bushings to lose material rapidly, again resulting in an overall elongation of the whole chain. Interflon products are particularly good at preventing this type of wear, because they create a dry film rather than a viscous layer. Whereas sticky oils and greases only accumulate soil, rust particles, and other types of airborne particles that ultimately form the aforementioned abrasive paste, Interflon products do not accumulate particles at all. Instead, they form a dry layer that gives particles nothing to adhere to. With no abrasive paste, there is no excessive wear, and chain life is prolonged significantly.
A pragmatic or preventive maintenance regime, rather than a calendar-based replacement system, is the key to getting the most out of your chain.
Proper lubrication technique of new chains
When new chains arrive from the factory, they are often coated in wax or another layer of preservative to protect them during storage and transport. It’s important to note that this layer is not intended to serve as chain lubrication, but is applied only for storage and shipping purposes. Furthermore, if this layer is not removed, it will prevent lubrication from reaching the inner workings of the chain, such as between the pins and bushings, or between the bushings and the links.
To effectively remove this protective layer, Interflon recommends immersing the chain in Interflon EM30+ degreaser or Interflon ECO EM100+ degreaser for a period of 15 minutes, followed by air-drying with a high-pressure air gun or air hose. Once all degreaser has been removed, lubricate the chain properly. Depending on the type of chain the following products can be used as chain lubricant:
- Interflon Lube TF
- Interflon Lube EP+
- Interflon Food Lube (NSF-H1, ISO21469, Kosher and Halal certified)
- Interflon Food Lube AL (NSF-H1, ISO21469, Kosher and Halal certified)
- Interflon Food Lube G series (NSF-H1, ISO21469, Kosher and Halal certified)
In case a grease needs to be used, Interflon offers a high penetrating NLGI 0 grease with load capacity, that is extremely water resistant and capable of repelling airborne particles.
