Posted to News on 23rd Apr 2025, 15:00
Contrinex safety light guards speed up access-control for rotating drum mixer
To improve access for loading and unloading a large rotating mixing drum, a safety sensor solution was sought to replace unwieldy guards and doors. The safety system had to be rugged and mounted in front of each drum, so that the drum would stop rotating immediately if it detects any body part or person in the working area. Contrinex offered a solution.
Rotating drum mixers and drum driers feature a large metal drum surrounded by safety guards, typically steel-mesh panels, to prevent people from coming into contact with the moving parts, either the rotating drum or its drive components.
Previously, at the end of the machine's cycle, interlocks on safety guard doors at the front of the drum opened, enabling the doors to be opened for an operator to be able to unload and load the drum.
The machines are large, at over 2m tall and 2.5m wide, and so the doors were large and cumbersome to use, and projected into the gangway when open. They were considered to present a potential hazard when open, and the process of opening and closing them frustrated the operators and slowed the operating cycle of the machine.
The factory looked for an alternative safety guard mechanism to replace the doors, that maintained safe operation, was space efficient and provided unobstructed loading and unloading. It must be simple, space-saving and operate reliably in the production environment. The new safety mechanism needs to be robust to withstand the factory's manufacturing environment.
Contrinex's YCA-50K4-3500-G012 safety light guards were selected as non-contact access-control barriers at the highest safety categories of EN ISO13849-1 (Category 4, PL e) and IEC 64196-1 and -2 (Type 4). Their rugged aluminium housings were a key criterion alongside price in their selection. The speed and cost of fitting the system were improved by the guard's use of M12-5 pin connections, from which standard cables fed into a Contrinex's YRB-0131-241 safety relay.
If a person enters whilst the machine is operating, the system brings the drum to an immediate halt. Either an automatic or manual restart is possible once the area is clear. A protected height of 1032mm provided by the 3-beam unit was considered appropriate, but a maximum of 1532mm provided by a 6-beam unit could have been selected.
The new sensors take up much less space than the mechanical guards they replaced, improving workplace ergonomics. Loading and unloading is no longer impeded, increasing productivity while maintaining safety standards. Additionally, removing the mesh doors allows an unobstructed view of the machine during operation.
