Press belts in double belt presses have a tendency to deform into a convex shape in relation to belt supports such as press and heating platens and roller chains.
A deformed belt has the following disadvantages:
- Unequal pressure is applied to the product
- Tracking problems are caused in the press
- Belt is exposed to unnecessarily high stresses
- Risk of accidental damage to belt edge increases
Portable shot peening unit
A blasting head travels across the belt at one terminal drum – while the press is still running – and ‘shoots’ special balls at high pressure across the width of the belt. Air pressure, belt speed and the type of balls can be varied to achieve the best result.
This technique provides a number of clear advantages:
- No costly dismantling of belts
- No need for tricky joint welding and running-in procedures
- No plant stoppage: no loss of production
- Fast and effective: 6–24 hours per belt once the unit has been mounted (depending on belt length, width and degree of deformation)
- Process can be repeated during the life time of the belt
Installation of the shot peening unit at a plant involves building a simple frame to fit a rail which guides the shot peener heads across the width of the belt. This frame can be stored and used again on the next occasion.
There is also a need for air pressure. This is rarely if ever a problem as most plants have their own air pressure supplies with suitable pressure; if not, compressors can be hired in.