Continuous operation

As a leading supplier of cereals and cereal bars to major supermarkets, UK-based manufacturer Dailycer must meet demanding production schedules. Of equal or greater importance is the need to maintain high levels of operator safety. Establishing the optimum balance between the two is often a challenge, yet Dailycer feels it has solved the conundrum by implementing a safety solution for its critical mixing vessels.

The new mechanical system, based on Allen-Bradley Guardmaster trapped key interlock switches, allows ingredients to be added while the mixing operation is in progress, while preventing contact between operators and the moving agitators and shaft.

The two large syrup-mixing vessels are central to Dailycer's operations. Entry points on top of each vessel allow operators access in order to add extra ingredients - such as sugar - to the mixture. Ideally, these extra ingredients need to be added while the mixer is in operation. This prevents them from settling to the bottom of the vessel where they do not always dissolve properly, which could result in quality problems with the finished product.

Until recently, safety issues prevented ingredients from being added during machine operation: the rotating agitators and shaft within the mixing vessel were exposed to the limbs of any operators adding ingredients. Dailycer Engineering Manager Gwilym Jones was charged with the job of finding a solution.

"Any solution had to be simple because, in our experience, factory personnel bypass complicated guarding systems very quickly."

"We were fully aware from the outset of this project that by finding an answer to the safety problem we could also improve our production," says Jones. "The problem was finding a balance between the two. Any solution had to be simple because, in our experience, factory personnel bypass complicated guarding systems very quickly."

A second major consideration was the local environment. As the atmosphere around the mixing vessels is steamy because of the boiling of syrups, Dailycer wanted to avoid using any safety system that was electrically based or susceptible to corrosion.

"The solution we came up with takes into account all these considerations," said Jones, who explained that Dailycer designed a protective basket that allowed ingredients to be added with no possibility of catching or trapping hands or arms. The basket is connected to an Allen-Bradley Guardmaster single key chain interlock system that prevents it from being removed unless the agitator has been isolated.

When the basket is in place, an actuator bolt (connected to it via a chain), is inserted into the main body of the interlock switch mounted on the outside of the vessel. Only then, with the bolt inserted, can the trapped key within the key interlock switch be released and inserted into the isolator that allows the mixing vessels to start. If the key is removed from the isolator at any time the mixing operation stops.

"We installed the system ourselves and it is working really well," says Jones. "The Allen-Bradley Guardmaster trapped key interlock system has proved to be the ideal choice for the application."

The system provides robust mechanical operation, avoiding the use of electronics; in addition, its stainless steel construction is ideal for the steamy environment. Importantly, replacement coded keys are available in the event of one being lost.

"Overall, I think the success of combining our simple design with this safety interlock system can be summed up simply as offering the best of both worlds," says Jones. "Enhanced levels of safety and uninterrupted levels of production."