Conveyor chain sprocket design

FB manufacture conveyor chain sprockets in a number of styles. These include conveyor chain sprockets made as platewheels or with normal or split hubs fitted on one or both sides. FB conveyor chain wheels can be manufactured in a variety of special materials with hardened teeth where necessary.

How to extend conveyor chain sprocket and chain wear life

The last thirty years have seen numerous innovations in conveyor technology that have brought greater safety and efficiency. However, change in this field has not always been necessarily for the better.

One innovation is the introduction of sprockets with an even number of teeth. It was thought that this would offer customers a greater choice when designing chain conveyor systems. However, sprockets with an even number of teeth are not recommended by experienced technical engineers.

If a sprocket has an even number of teeth, the same tooth will be engaged by the same rollers on each rotation, leading to uneven wear and decreased service life. A similar result will occur if the number of teeth in the smaller sprocket is a devisor of the number of pitches on the conveyor chain. Choosing a sprocket with an odd number of teeth, however, will offer you at least double the service life.

Double pitch conveyor chain sprockets are often overlooked nowadays but are ideal for saving on space and have a longer wear life than standard sprockets. Suitable for long pitch chain, double pitch sprockets possess more teeth than a standard sprocket of the same pitch circle diameter and distribute wear evenly across the teeth. If your conveyor chain is compatible, double pitch sprockets are definitely worth considering.

Many of today’s conveyors include electronic load monitoring in the control system. While this is a useful safety feature, technical engineers recommend that these are used in conjunction with shear pin sprockets.

Electronic sensing is ideal where there is a slow increase in load (due to damaged bearings or dirt contamination, for example) as there is time to stop the drive before any damage can occur. In the case of a mis-feed or mechanical breakage, however, where the load increase is sudden, the sensor will not automatically break the connection between the motor and the driven load and extensive damage can be caused to the conveyor chain and attachments. This is why a shear pin sprocket is needed in addition.

Shear pin sprockets may be more expensive than standard sprockets at the outset but will limit downtime and save on replacement costs. If a conveyor becomes overloaded and potentially dangerous, the shear pin will break and stop the conveyor, thus limiting damage. Once the load or obstruction has been cleared, only the shear pin needs to be replaced and the conveyor can quickly start moving again.

In summary, older types of sprocket are often forgotten but offer considerable advantages including long service life, limited damage in case of conveyor breakdown and reduced replacement costs.

How to tell when a sprocket needs to be replaced

Once a sprocket has worn to a certain degree it can cause rapid chain wear and will need to be replaced at the next available opportunity. However, replace it too early and you’ll be incurring unnecessary costs. Here’s our guide to determining when a conveyor chain sprocket needs to be replaced.

If you examine the faces of the sprocket teeth you should be able to tell immediately whether a sprocket has worn or not. You will notice a shiny strip on each of the teeth about the pitch circle diameter. The diagram below shows that a sprocket will need to be replaced if the depth of wear, dimension x, has reached 10% of dimension Y.

It is worth noting at this point that a high quality sprocket will have seen several chains before it shows anything like the extent of wear in the diagram.

When sprockets are replaced it is essential that they are properly aligned with the shafts as misaligned sprockets are a common cause of premature chain wear. When shafts and sprocket tooth faces are accurately aligned, the load is distributed evenly across the entire chain width which helps to achieve maximum service life. A straight edge, nylon line or laser sight tool should be used across the machined faces of the sprockets in several positions to check for wobble. When sprockets have been correctly aligned, you should drive the keys home as a final check.