subject: Important Factors To Consider While Selecting The Conveyor Chain Most Appropriate To Your Applicatio [print this page] The universality of the conveyor chain in various applications from moving vehicles down the line in auto production to the movement of sprinklers in agriculture can be seen around the world. Whenever something must be moved from point "A" to point "B" continuously no matter if it is to be assembled, washed, painted, inspected or heading for storage, you will undoubtedly find a conveyor as the basis of the system.
There are four critical criteria required for maximum performance of a conveyor chain. They are ultimate strength, wearability, fatigue resistance and impact resistance.
The weight in pounds required to break the chain on a linear plane is the measurement that determines the ultimate strength of the chain. The usual method of testing is by use of a tensile testing machine. The minimum strength values for each size of chain are dictated by ANSI. The material of which the chain is made, its manufacturing process, and hardening specifications used in making its components consisting of center link, side link, and pin are controlled by the manufacturer and determines the strength of the chain.
The ultimate strength of a chain is determined by the integrity of the material at a specific hardness. Although a high ultimate value will not of necessity make it fail-proof. The ultimate strength value determines what type or size of conveyor chain will be used for a variety of loads and is used mainly for application engineering.
The durability of a chain depends on a number of outside factors and is a somewhat imprecise value to use when comparing chains. A chains durability is affected by lubrication, loads, chain speed, system design as well as many other factors. Hardness is the only value that is controlled by the manufacturer that impacts wearability, and hardness has a huge impact on the other three criteria. A harder chain is the more durable chain but this very hardness causes the chain to be less fatigue and impact resistant. The harder the chain the less the resistance to fatigue and impact.
There are options in base materials that take the above into consideration. Standard SAE 1045 steel with a hardness of 370 offers good impact and fatigue resistance, a reasonable level of durability as well as meeting minimum ANSI strength requirements. A hardness of 420 BHN of the same material improves its durability and strength but at the same time loses a bit of its impact and fatigue resistance. Microtuff-15 micro alloy steel also has good wearability, higher strength value, and top impact and fatigue resistance for the same cost as the SAE 1045.
Fatigue resistance is the material's ability to withstand continuous bending, twisting, etc. without fracturing. It is perhaps the conveyor chain's most important asset or liability. Fatigue is not easily measurable until the material shows signs of fracture. In today's world of higher production rates, heavier overall chain loads, more intricate chain paths, with tighter radius turns, the chain is subject to more subtle bending and twisting than ever before.
As the conveyor chain travels around horizontal turns, the side load between the chain and the rollers or traction wheel creates a slight bending motion in the center link of the chain. This bending motion is the catalyst for fatigue. If fatigue is not recognized and the chain is not replaced immediately, the frequency of failures is sure to increase at a geometric rate. For this reason it is not recommended to use harder, more wearable, alloy chain on heavily loaded systems with multiple turns and high chain speeds. Alloy chain may be well suited for straight line over and under conveyors or slower lighter loaded conveyors in abrasive surroundings such as foundry cooling lines or incinerator draglines.
The impact resistance measure of a conveyor determines it's ability to absorb shock without breaking apart. The harder the material is, the less it is impact resistance. However, there are different materials having the same hardness with variable capabilities of absorbing impact and remaining intact. A chain's resistance to impact is a factor in many power and free systems.
With loads being stopped and started frequently, the chain, especially the pusher dog, is susceptible to impact failure if it is not manufactured from an impact resistant material. Other potential impact points on a conveyor are the loading and unloading stations. Impact failures, similar to fatigue failures, occur without warning, but unlike fatigue failures, they don't necessarily multiply.
When choosing a conveyor chain, it is important to consider the above criteria to achieve maximum performance. Using the correct chain for a specific application increases the life of the system, while preventing failure
