What is in the set?
The PL22 smooth roll set is a complete drive set for the smooth (reduction) passage of roller mills driven by 22-rib PL poly-V belts. It consists of:
- PL-22-200 and PL-22-250 pulleys: two 22-rib pulleys of 200 mm and 250 mm diameter. Their ratio (250/200 = 1.25) gives the low speed differential a smooth passage needs.
- 3030-70 taper bushes: fix the pulleys to the shafts. The 3030 series bush comes bored for a 70 mm shaft.
- Tensioner arm: keeps the belt at the right tension.
- Bearing and circlips: let the tensioner pulley rotate and hold it in place.
Why a 1.25 ratio?
On smooth rolls semolina is not cut but reduced by pressure. The differential between the rolls is kept low so the flour does not overheat and starch damage stays limited. On gear-driven mills this ratio comes from tooth counts; on belt-driven mills from pulley diameters.
Why replace the whole set
Replacing just one pulley is often not enough. A worn and a new pulley have different groove depths, the belt seats differently on each and starts to slip. A tired bearing in the tensioner pulley also causes belt vibration and noise. Replacing the set removes all these risks at once.
Fitting sequence
- Release the tensioner arm and remove the old belt.
- Fit the pulleys to the shafts with their taper bushes; tapered surfaces must be oil-free.
- Align the pulleys in one plane with a straight edge or laser.
- Fit the new belt and set the tension with the tensioner arm.
- After a short test run, re-check the bush screws and belt tension.
