Sizer rods: Does size matter, is big and slow the way to go?

Film size presses (i.e. SymSizer, OptiSizer) use rotating rods to control starch or coating film applied on the applicator roll. Rod diameter and surface type vary depending on the application.

Starch applicators normally use 10-15 mm diameter grooved rods, while coating applicators use larger 20-30 mm smooth rods. In order to improve rod life for starch applicators, some mills have switched to using large diameter grooved rods for starch as well.

Since larger diameter rods will tend to apply more starch to the paper, groove size and rod loading pressure may need to be tuned for optimum performance with large diameter rods.

One mill in particular of has increased its rod life significantly, much greater than the typical 30 days with small diameter rods.

Using large diameter rods allows the rod rotational speed to be lowered (~40-50 rpm) while the surface speed is similar to faster rpm small diameter rods. Since rotational speed has little effect on coat weight, a lower rod speed can help reduce rod and rod bed wear.

If large diameter rods are used, there may be a need for an additional support tube running at 2-3 psi to keep the rod securely mounted in the bed. Also, large diameter rods are heavier and stiffer than small diameter rods, requiring more people to change the rods.

The benefits of greater rod/bed life are a reduction in valuable machine downtime used to change them and a decrease in your rod/bed total operating cost.

With our applicator rods, whether you use Valmet Applicator Rod Grooved, Valmet Applicator Rod Smooth or Valmet Applicator Rod Smooth C (ceramic), you will achieve excellent coating/sizing and paper quality, maximum production capacity and optimized costs.

Our applicator rods are made to last. Increased rod lifetime means fewer rod changes and fewer rods used, resulting in savings in time and costs.

For more information on optimizing your sizer operation, contact your Valmet representative.