The weight of the product that is being conveyed produces a resisting force which will fight against the forward motion of the conveyor belt, therefore providing additional belt tension to the conveyor system. The amount of tension produced by the conveyed product is dependent on the amount, size, and type of the product being conveyed, as well as how the belt is supported on the loaded side, considering the variance in coefficient of friction between slider and roller bed conveyor systems.
The mechanism designed to support the weight of the conveyor belt in the return section of a conveyor will impact the amount of tension experienced by the pulleys. This type of belt tension is produced by catenary load which is a byproduct of the level of catenary sag existing in a conveyor belt. If the conveyor belt is under-supported on its return side, the weight of the belt in that section is supported by the pulleys as a catenary load, and greater belt tension is needed to prevent excessive sagging. Belt return support rollers should be spaced so that the belt does not sag excessively between each roller. The schematics below illustrate the concept of catenary load:
The amount of belt tension on a conveyor system may require belt slack adjustment during installation procedures, during normal operation for belt tracking purposes, or for disassembly purposes during maintenance procedures. The term Take-Up refers to a variety of devices that are used to provide adjustment in the amount of belt tension on a conveyor system.
Since many of these devices require manual calibration, adjustment of belt tension with a take-up mechanism requires training and an understanding of how belt tension affects conveyor load. If not adjusted accurately, the take-up device can easily supply excessive belt tension which results in unanticipated loads on the conveyor components, particularly the pulleys and the belt.