Machine guarding is about to be turned on its head, with machinery avoiding workers rather than workers avoiding machinery. It is a simple concept but one that will change the way we interact with machinery and even the way factories look.
Put simply, a high speed, dual CPU, image analysis computer and safety PLC fed images by three cameras analyses the area around hazardous machinery, responding whenever activity inside its boundaries is sensed, by slowing or stopping the machine.
Pilz 's SafetyEYE is a machine safety system and when it was first demonstrated guarding a robot at National Manufacturing Week. A robot worked unhindered in the centre of a wide-open space with no obvious guards in place. The clues to SafetyEYE's presence were dotted boundary lines and flashing lights indicating the status of the system.
The SafetyEYE remains safe, even if it does develop a fault, reducing risk so far as is practicable, just as occupational health and safety laws mandate.
These systems remove any element of human error. People can and do cheat safety fencing. It happens in every industry and it is done with better intentions but it is potentially disastrous.
While training does help to reduce these incidents, any measure that helps to reduce the reliance on safe behaviour by engineering out a hazard is a step forward and in line with the hierarchy of controls defined by law.
So, with no need for safe behaviour and no fences, even if the SafetyEYE fails, the machine will be halted. In the case of SafetyEYE, this means two things: there are redundant systems in place and the system allows the machine to operate when it is functioning properly.
Redundancy is called for by Australia's principal machine safety standard, AS4024.1, to control Category 3 and 4 hazards. Under the standard, a single fault must not lead to loss of safety function and the fault is detected. To achieve this, signals from SafetyEYE's cameras – at a rate of 20 per second – are analysed by two separate image processing systems running on the analysis unit’s two computers, each of which have different operating systems.
The outputs from the image processing system are then compared by the SIL 3, Category 4 programmable safety system, which equates to a dual-channel input being fed to the dual-redundant programmable safety unit. If a breach of the zones is detected by the three-camera system, an appropriate output is issued by the analysis unit to signal an alarm, reduce the speed of operation or halt the process, for example.
This redundancy and fault detection makes SafetyEYE a Category 3 control system under AS4024.1 similar to safety laser scanners that are in use. This means that it is suitable to control hazards that can cause an irreversible injury when either the exposure is infrequent or of short duration and the possibility of avoidance is low, or the exposure is frequent and it is possible to avoid.
The near future holds even greater possibilities for this new generation of machine guarding, which promises to be able to differentiate between humans and other moving objects, such as the material being processed (car bodies or pallets, for example).
Of course, when it comes to guarding against hazards such as heat, spills and flashes, it is hard to imagine anything could take the place of a physical barrier. For many of Australia's workplaces, however, the vision of an environment that safeguards, rather than endangers, workers is soon to become a reality.