Safety concept for mixer cleaning
Walter Gerätebau GmbH has already been in close contact with the manufacturers of concrete products and their statutory accident insurance and prevention associations for many years, in order to keep safety conditions concerning automatic mixer cleaning up to date.
For 20 years, the company has been developing automatic cleaning systems for the concrete industry and has established itself as global market leader in terms of quality in the field of automatic cleaning of concrete mixers. Market proximity and intensive contact to the concrete industry resulted in a new safety concept, enabling any plant to achieve the safety standard of Performance Level “d” (SIL 2).
Inspection flaps with safety switch
Walter Gerätebau is manufacturer of complete cleaning systems for automatic cleaning of concrete mixers, bucket conveyors, concrete distributors and truck mixers. The most important reasons for investing in an automatic mixer cleaning system include the fact that it significantly improves the workplace safety on mixing plants, besides increasing the productivity and reducing wear and tear of the mixer. Due to the automation of the mixer cleaning process, the Walter system makes an active contribution to minimizing severe accidents, which are associated with the mixer cleaning process. For this reason, BG RCI (German Statutory Accident Insurance and Prevention Association for raw materials and the chemicals industry) still promotes the upgrading with a Walter mixer cleaning with 20% of the investment amount.
The cleaning systems of Walter are independent systems, equipped with their own control panel, in order to ensure the safety required. Any adjustments to customer-specific requirements, such as cleaning times or processes, are made within the internal Walter control. This is integrated into the control system of the mixing plant via the universal interface. The most essential components of this interface are the safety-related signals.
During the automatic cleaning process – according to the result of a risk assessment – all covers of the mixer have to be closed and/or the cleaning process has to be interrupted immediately when opened. Whereas the mixer pan cover of compulsory mixers is protected by safe switches or key transfer systems as standard and opening initiates the mixer to stop, inspection flaps and portholes for cameras are often not secured. To avoid high-pressure water jets to escape from the plant during the automatic cleaning process, all maintenance and inspection flaps are also equipped with safety switches from the perspective of the mixer cleaning system. For this purpose, Walter offers an optional kit which is easy to retrofit and integrate into the Walter control system.
Intelligent safety concept
The automatic cleaning process is followed by an inspection of the mixer and the subsequent cleaning of the cleaning heads and adjacent spots in the mixer. It is an advantage that the powerful Walter high-pressure pump is available for these works allowing for cleaning with the hand lance. As the entire system is under pressure, every valve for the cleaning heads has to be closed safely. An unintentional activation of a cleaning head, when opening the cover, has to be prevented by 100%, in order to exclude any hazard for the worker caused by the water jet. The risk assessment showed that the control configuration achieved the Performance Level “d” (SIL 2) for this proc-ess, thus providing protection against irreversible injuries. For the implementation of these requirements in practice, Walter Gerätebau has developed a new intelligent safety concept. If a disturbance occurs, the system automatically locks through a safety PLC system, which sends a fault signal to the main control system.
