The conveyor chain is a common sight in factories around the world and is seen in all types of situations from moving parts down the line in an automobile production plant to moving sprinklers around in an agricultural field. If something has to get from point “A” to point “B” on a continuous basis, whether for assembly, washing, painting, inspection or storage, you can be sure a conveyor chain is at the core 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.
Conveyor chain strength is normally measured in the quantity of pounds necessary to bust the chain on a linear plane. This is tested by a tensile testing machine and the values of the minimum ultimate strength for each size chain are dictated by ANSI. In the process of making the chain, the manufacturer controls its strength by the choice of material, manufacturing processes, and the hardening specs used in the components of the chain, which are its 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.
A conveyor chain’s durability value is the most subjective value to consider when comparing chains. Factors affecting it’s durability are lubrication, loads, chain speed, and system design among others. A manufacturer controls only the hardness factor that impacts the other three criteria. It is a fact that the harder the chain the higher its durability factor but along with this comes a lower resistance to fatigue and impact. The harder the chain the less resistance it becomes to fatigue and impact.
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.
While the chain moves around its horizontal turns, the side load between the chain and the rollers or traction wheel makes for a subtle bending motion in the center link of the conveyor chain. This particular movement is the catalyst for fatigue. Should the fatigue go unnoticed and therefore, the chain is not replaced at once, the instance of failure is diminished.
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.
In the case of loads that are often stopped and started, the chain, most particularly the pusher dog, is subject to impact failure if an impact resistant material was not used in its manufacture. Other possible points of impact on a conveyor are the loading and unloading sites. Similar to fatigue failures, impact failures happen with no warning, but they do not as a rule spread out as the fatigue failures do.
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
To learn more about Conveyor Take Ups or other Conveyor Chain Attachments please visit Blue Water Manufacturing.