Basics
Technology can help you reduce the coefficient of friction. Some of the newest chains (for example, low-friction top chain, engineered plastic roller chain, and bearing roller chain) can achieve low coefficients of friction with- out lubrication. Other chains would have to be lubricated to achieve these coefficients. In some instances, these new chains achieve dramatically lower coefficients of friction. That means you can save maintenance time, money, and energy at your facility. 2.3.2 Dynamic Tension of Starting and Stopping Conveyor chain accelerates when it changes from stop mode to operational speeds, and decelerates when it changes from operational speeds to stop modes. Therefore, a dynamic tension resulting from inertia affects the convey- or chain, and it is added to “the tension produced when conveyed objects are moving at fixed speed,” which is discussed in Basics Section 2.3.1. You must consider dynamic tension caused by inertia, especially in the following cases: 1. Starting and stopping chains frequently, such as intermittent use with indexing equipment. 2. Starting and stopping in very short time spans. 3. When chains in motion suddenly receive stationary objects to convey. The dynamic tension by inertia is calculated with this formula: T 1 = M 3 α = M 3 dv dt Where: M = total weight of conveying apparatus, including chain, attachments, product, etc., (kg) α = maximum acceleration (m/s 2 ) dv = change in speed (m/s) dt = time in which speed change occurs (s) For example: M = 5,000 kg, the total weight of chain, attachment, product, etc. f = 0.12, the dynamic coefficient of friction T = 5,000 3 9.8 3 0.12 = 5,880 N This assumes the conveyor is operating at constant speed. But when the chain starts, if the speed is increased to 20 m/min. in 0.2 seconds, then: dv = 20/60 = 0.33 m/s dt = 0.2 s T 1 = 5,000 3 0.33 = 8,250 N 0.2 Maximum tension = T + T 1 = 14,130 N If the chain is accelerated frequently in this manner, then select chains using T + T 1 .
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