There may be times when you want to replace a belt on a machine but no longer know the exact dimensions that are required. In this blog, I will explain how you can measure the length and the width of a conveyor belt without having to uninstall it from the machine. Although you may choose to remove the belt, replacement orders are usually made with the current belt still running in order to reduce unnecessary down time.
Before you begin measuring, it is a good idea to double-check the technical manual which you received from the manufacturer at the time of purchase. In some cases, the belt dimensions are specified in the list of items included.
It might seem easy to measure the size of a conveyor belt, but there can be serious consequences if you order a belt with the wrong dimensions. Conveyor belts are custom made and not all belts can be shortened or extended. In any case, it is best to avoid further changes which will accrue additional costs in manufacturing and extended downtime.
The width of the conveyor belt
The width is the easiest to determine because you can verify this information by measuring the old conveyor belt. Check if the belt edges are worn, which could significantly alter the width of the original belt. Also check that the belt width matches the width of the pulley. Find below the formula (from our Engineering Guide) which ensures that the conveyor belt has enough space to start tracking without running away from the pulley and thereby losing belt tension or being damaged as it runs against the side.
Pulley width recommendations:
|Belt width bo||Pulley width bo|
|bo ≤ 100 mm / 4 in||b = bo + 20 mm / 0.8 in|
|bo > 100 mm / 4 in||b = (1.08 ∙ bo) + 12 mm / 0.5 in|
The length of the conveyor belt
The most reliable way to determine the length is to place markings on the side of the conveyor belt. Measure the length at regular intervals until you return to the first mark. The total of these measurements is the length of the tensioned belt.
It is also important to deduct the pre-tensioned length (in most cases 0.3% is sufficient). This is regularly forgotten so that the belt is often delivered too long and cannot be adequately adjusted. Another possible but less accurate method is to measure the center-to-center distance between the head and tail pulley and to then note the corresponding diameters. Half of the circumference of the two pulleys and twice the center distance is the stretched length, but the pre-stress dimensions must also be deducted. With this method, you must ensure that there are no hidden loops (for example, a belt tensioner) which may require extra length.
The tensioning path must be checked for the total available length and the tensioner must then be adjusted accordingly. Depending on the position of the tensioner, the belt length can then be adjusted to best fit the conveyor. The total length of the tension path which we recommend for belts with a polyester tensile layer is 1.5% of the belt length, and for a belt with a nylon tensile layer, it is more than 2.5%.
The measuring accuracy will always depend on the design of the conveyor. A series of conveyors with only two pulleys should not touch each other. The belts cannot be too long or too short, or this will create gaps where the product can fall. In those cases, a middle drive is usually used in the return section. For long conveyors, it is customary to place the tension path behind the drive.
Call us if you need any on-site assistance with the measurement of a belt. We will be more than happy to help.