First let's start with some useful background info on rollers.
Scanner rollers that pull paper into document scanners are a consumable part (i.e. they wear out over time). They need to be replaced at the scanner owner's expense.
Rollers that are worn will often slip on the paper being scanned resulting in paper jams, significant pauses during paper feeding, slower scanning speed, and large black edges being displayed on the top edge of scanned images.
There are typically 3 consumable rollers that are designated as being user serviceable/changeable parts.
Scanners that pull paper in from the top of the ADF stack of paper will have one roller on the bottom of the scanner throat, and a pair of rollers (2) on the top section of the scanner throat.
Scanners that pull paper in from the bottom of the ADF stack of paper will have a pair of rollers (2) on the bottom of the scanner throat, and 1 roller on the top section of the scanner throat.
The pair of rollers (2) are usually known as the pick roller and the feed roller. The job of the pick roller is to grab the next page from the stack of pages in the ADF. The feed rollers job is to grab the page fed in by the pick roller and move it deeper into the throat of the scanner. The pick roller and feed roller are both driven by a motor via geared teeth.
The 1 single roller is normally known as the brake roller. The purpose of the break roller is to inhibit the scanner from picking up an extra sheet of paper during scanning. The brake roller is not driven by a motor. It's usually fixed in place, doesn't spin, or is difficult to rotate. A worn or faulty brake roller will often causes paper jams to occur, with more than 1 sheet of paper being pulled into the scanner
Now that you know what the rollers do, there are several easy ways to tell when the rollers should be replaced.
Simply look closely at them. Just like a car tyre, scanner rollers often have a tread pattern cut into the roller. Sometimes the tread pattern goes vertically round the roller and other times it just horizontal grooves across the width of the roller. As the roller scans the tread pattern or grooves slowly begin to wear out becoming harder to see.
At about 100,000 pages scanned many consumable rollers are no longer in good condition..Just like with car wheels, the rollers can have low to no tread pattern visible, wear unevenly forming bald spots on one edge and even flat spots on the roller.
Some scanners provide a software scanner management tool that allows you to see how many pages a set of rollers have scanned (e.g. Fujitsu SOP, Kodak Alaris SVT) or even alerts you that the rollers need changing (e.g. Fujitsu Scanner)
4. Some scanners provide access to the roller counters from the front panel of the scanner itself (e.g. Canon scanners)).
Most production scanners (high volume, high speed, higher cost) have other fixed rollers (that are not user-serviceable parts) and they are typically good for scanning up to 1.5Million pages before a factory service is required. A properly maintained high-volume production scanner is capable of scanning millions and millions of pages.
Remember to keep your scanners clean. They should be cleaned every day of use and the paper input tray, scanner throat and output tray should be carefully vacuumed to remove unwanted paper dust buildup.
We've seen many times a good scanner discarded because the customers think they are faulty when it's really just a case of replacing the rollers, giving them a good clean and returning them back into Service.
We hope you found this information useful.