Simple, solid approach to belt tension

Pit & Quarry, Jan, 2005 by Lyle Hettver

Ensuring proper belt tension is a vital issue in conveyor operation. It affects belt tracking, overall belt performance efficiency and the life of the belt itself. All conveyors use some form of take-up device to adjust belt tension to the optimal level, one that prevents slippage between the belt and the drive pulley, and guards against possible material spillage caused by too much belt sag between idlers.

Take-ups also compensate for belt shrinkage or stretch, and allow for extra belt length storage for making belt replacement splices. While take-ups can be either manual (mechanical-style) or automatic, manual take-ups are found in a majority of conveyor units, particularly those that are less than 150 ft. in length.

Although manual take-ups are practical and cost-effective in shorter, lighter conveyors, they present challenges. There are many types and styles of manual take-ups, and many means used to tighten them. But what they all have in common is this: Even if you know how much tension you need (measured by PIW or pounds per inch of width), with a mechanical-style take-up, it's difficult to determine just how to get there.

How do you judge if belt tension is too tight or too lax when using a manual take-up? For most operators it's often a matter of time-consuming trial and error. Consider this simple, solid rule of thumb: You should have no less than 1-in. and no more than 3-in. of belt sag between return idlers that are typically mounted at 10-ft. intervals, no matter what the belt size.

Next, try this simple trick to ensure that you are within the above requirements: Cut a piece of tape to 6-in. in length. Mark the center at zero and indicate 1-in., 2-in. and 3-in. marks to the right and left of zero. Center the tape and place it on your return idler roll. Now it is easy to measure the belt sag and adjust the tension until the belt sag is no greater than 3 in. (1 1/2 in. on each side of the zero); and is no less than 1 in. (1/2 in. on each side of the zero).

Proper belt tension is critical to efficient conveyor operation. Consult with your equipment dealer or manufacturer to choose the most effective, easy-to-operate take-up systems. With the stretching and wearing-in process involved in installing a new belt, tensioning can become an everyday task, so specifying the right take-up system is important. But after initial stretching, belt retensioning becomes just another facet of your scheduled routine maintenance program.

Lyle Hettver is a customer service and support technician for Superior Industries, a manufacturer of conveyor systems and components. Visit www.superior-ind.com.