What the code means
- D: double-sided – both the inner and outer faces of the belt are ribbed.
- PL: rib profile (about 4.7 mm rib pitch).
- 22: number of ribs; the belt is about 103 mm wide.
- 1765: belt length in mm.
Why double-sided?
On a roller mill the two rolls must turn towards each other, i.e. in opposite directions. In a three-pulley layout with a double-sided belt, the inner face drives one roll pulley and the outer face drives the other. One belt both reverses the direction of rotation and delivers the speed differential set by the pulley diameters. This layout works with the PL22 triple sets.
Why the length must be exact
In a three-pulley layout the take-up is limited. If the belt is even a few millimetres too long the tensioner cannot give enough tension; too short and it cannot be fitted. When replacing, read the code on the old belt; if it is illegible, determine the correct length from the mill model.
When to replace
- Cracks or missing pieces on the rib crests,
- Glazed, hardened belt surfaces,
- Tensioner at the end of its adjustment,
- Slipping noise and a drop in roll speed in operation.
Storage and fitting
Store spare belts cool, dry and out of sunlight, without kinking. Do not force the belt onto the pulleys when fitting; release the tensioner, seat the belt and then set the tension.
