Conveyor Maintenance - Managing Catenary Sag

Modular belt conveyor tensioned with catenary sag sections.

Most production personnel do not place high priority on conveyor maintenance. Conveyors are often the last thing considered when planning a maintenance schedule.
This is a mistake.

You can run a conveyor for quite a while with little intervention, but in order to make sure your new conveyor operates efficiently and effectively for years, there are a few things that you need to watch for. 

One of the most important parts of modular and table top conveyor to watch is the catenary sag.

What is catenary sag? 

Catenary sag refers to the section of the belt that hangs down just after the drive sprocket on the underside of the conveyor on table top and modular belt conveyors. Some sag is good, even required, to keep your conveyor running smoothly. The weight of the sagging chain creates back tension on the rest of the belts, keeping the sprocket teeth engaged with the slats and keeping the conveyor in its wearstrip guides. 

Over time, however, modular belt links and table top slats will stretch. Not much per link, but even a fraction of an inch can add up to inches when you have thousands of links in a chain. Left unchecked for long enough and the catenary can sag several feet, enough to run into problems. If it is allowed to grow the chain can sag to the point where the individual slats can catch on other equipment, resulting in damaged chain, conveyor, guarding, and other equipment.

How to fix excessive catenary sag

To reduce the sag it is necessary to break the chain and remove links to take up the slack. Removing chain usually requires removal of the pins holding the slats or links together using either specialized tooling from the chain manufacture or other had tools such as a need nose pliers.

For complete instructions on chain link removal you should refer to the manufactures chain maintenance manual.

It’s a simple thing to do, but can be overlooked when there are more complicated pieces of equipment asking for your attention.


Conveyor Maintenance - Managing Catenary Sag was posted to Words in Motion - A blog created by Product Handling Concepts, your source for conveyor, conveyor equipment, and automation solutions.