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.
For optimum performance of a conveyor chain, four criteria are crucial – strength, durability, resistance to fatigue and resistance to impact.
The ultimate strength of a conveyor chain is typically measured in number of pounds required to break the chain on a linear plane. This test is typically conducted on a tensile testing machine and the minimum ultimate strength values for each size chain are dictated by ANSI. A manufacturer controls how strong their chain will be by the material, manufacturing processes, and hardening specifications used in the manufacture of the conveyor chain’s components (e.g., center link, side link, and pin).
The integrity of the material at a certain hardness determines the ultimate strength of the chain, but a high ultimate value does not by itself indicate that it is not subject to failure. This value rather is used for application engineering and in the decision as to what kind or size of conveyor chain should be used in various loads.
The Wearability of conveyor chain is probably the most nebulous value to document when comparing chains. Lubrication, loads, chain speed, system design, etc., are all outside factors that impact wearability. The only value that a manufacturer controls that would impact wearability is hardness. Unfortunately hardness has a major impact on the other three chain criteria. Obviously the harder a chain is the more wearable it would be but it also becomes less fatigue resistant and less impact resistant as the hardness increases.
There are different base materials that offer some options. For example, standard SAE 1045 steel at a hardness of 370 offers worthy impact and fatigue resistance, a good degree of durability, and meets minimum ANSI strength requirements. If the same material has a hardness of 420 BHN, its strength and durability would be enhanced but some of its resistance to fatigue and impact would be lost. As an alternative, microtuff-15 micro-alloy steel has good wearability and more strength along with excellent impact and fatigue resistance. It also costs the same as SAE 1045.
Fatigue resistance means that the material used is able to hold up under continuous bending, twisting, etc without breaking. It is quite possibly the conveyor chain’s most important asset or liability. Until the material shows signs of fracture, however, the fatigue level is not readily measurable. In today’s manufacturing world with its higher production rates, heavier loads, more convoluted chain paths with tighter radius turns, the chain is vulnerable to more subtle bending and twisting than ever.
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 term impact resistance defines the conveyor chain’s capability to absorb shock without breaking. Hardness and impact resistance have an inverse relationship, although there are many materials at the same hardness which have varying degrees of ability to absorb impact without fracture. A chain’s impact resistance is an important factor in many power and free operations.
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
For more information on Discount Conveyor Parts or Conveyor Components in general, please visit Blue Water Manufacturing.
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