A safety system that will not negatively effect production

Wednesday, 14 June, 2006

A common complaint of today's machinery safeguarding requirements is their potential impact on production. Safety control methods are often found to have involved incorporating fencing around production lines so that either entry at any safe access point stops an entire line.

The hierarchy of controls stated in both codes of practice for plant and machinery safeguarding standards requires that where hazards or risks to operators cannot be eliminated through redesign or substituted with a lesser hazard, if not practicable then control methods in priority order should be engineering controls, isolation, administrative controls and personal protective equipment.

Regulations also provide that exclusive reliance on administrative controls and personal protective equipment must only occur where other measures have not been practicable.

Electrical safety control technology is well established, with pneumatic and hydraulic safety control technology now beginning to catch up. It has often been the lack of fluid power safety technology that has led to safety systems that slow processes due to the need of a safety system to shut down pumps or isolation procedures to be followed prior to operator access.

Combining the electrical safety control, new fluid power safety technologies and zoning a safety control system can have even further positives for the production process.

An example of this is a brick plant that identified several years ago the need to enhance operator safety at its brick dehacking and palletising machine. The result of integrating recent fluid power safety technology into a zoned safety system not only prevented the risks of operator injury, but has also led to improved productivity output levels.

Following the curing process, kiln cars deliver a load of bricks to the dehacker. A set of four adjacent rotational and sequenced heads hydraulically clamp a layer of 72 bricks each at approximately 60 pick up and drops per hour, delivering them in correct orientation to a conveyor, transfer, cardboard insertion, stacking, shuttling and palletising process. Processes had been engineered to minimise jammed, misaligned and broken bricks. These could not be entirely eliminated and frequent operator access to each section of the line is generally required.

As hazards exist right throughout the process, some designers may have taken the approach of guarding or fencing the machinery in such a way that if accessed, hydraulic pumps would shut down and thus the entire line come to a standstill. This would have had a very negative impact on production.

To maximise production a zoned safety system was integrated, which partitions each key section of the machinery as an individually guarded and safely controlled section. This was possible by combining guarding interlock systems with a programmable safety system and Fluidsentry hydraulic and pneumatic safety systems for each zone as applicable.

Guard access to each zone safely stops production only in that zone and allows downstream production to continue, while controlling upstream delivery where necessary. In the last six months of 2005, more bricks went through this particular plant than any previous six months in its history. This type of complete electrical and fluid power zoned safety solution is suited to many production processes and is becoming common in industry today. It enables manufacturers to comply with safety standards requirements and, most importantly, keep operators safe without negative impact on production.

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