Machinery Safety – Does Category 4 Alone Always Mean We Get the Best Solution?

Machinery Safety – Does Category 4 Alone Always Mean We Get the Best Solution?

By Ken Robertson.

Machine Safety is a technically challenging aspect of WHS, particularly if you’re not too sure where to start.

There is often a misconception that if we just choose Category (Cat) 4 (highest level), that we must have done a good job and covered everything off satisfactorily. Sadly, in my experience, nothing could be further from the truth in the world of machine safety.

While Cat 4 is indeed the highest level of the machine safety categories, this only relates to the physical structure of the safety control system and it’s possible to install a Cat 4 safety system that is not only wrong, but is actually dangerous, even though it meets the highest machine safety category level.

Like all WHS solutions, the foundation is always the risk assessment, even in the machine safety world. If we get the risk assessment right, then everything else falls into place pretty easily. This, of course, raises the question of “how can we get the risk assessment right when it’s a subjective assessment?” That’s an excellent question and, of course, there is no way to guarantee that we get the risk assessment 100% “right”, but by following the risk assessment process we stand a good chance of doing this. We also demonstrate our due diligence, so we should be confident of at least coming up with an appropriate solution.

One critical part of the risk assessment process in the machine world (let’s be honest, every part is critical to the overall success of the risk assessment) is fully understanding the machine operation and the operator interaction with the machine. But don’t be fooled into thinking that going by what the SOP (of course there’s an SOP for every machine, isn’t there?) tells us is sufficient, because it’s not. We also need to observe the machine operation to get an understanding of ALL the operator interactions – the ones they’re supposed to do, the ones that get the job done faster/more efficiently and the ones that are “the way we’ve always done that”.

Once we have a good understanding of the hazards and the process, we’re then in a position to establish what might be the best possible solution to make the machinery safer – and it always makes sense to discuss the proposed solution with the operators because that’s when they’ll tell you about the other dozen interactions they need to have with the machine to actually get the job done. Only now do we get a better idea of the full scope of the machine safety requirements.

Still, we have to be careful not to fall into the trap of selecting the “wrong” solution, even though it might give us the right safety category. Light curtains are a perfect example because, although they are high-tech and meet the highest category requirements (Cat 4), the one thing they can’t provide is a physical barrier so, if parts ejection is a possible hazard, a light curtain will provide absolutely no protection to an operator if there’s a possibility that something might be ejected from the machine unexpectedly – let’s just call it a missile so we’re clear about the potential harm.

So don’t be tricked by the safety category and risk skimping on the risk assessment. Get the foundation set right and the rest will follow much more easily. Sound familiar?


CLICK HERE to buy your ticket to the NSW Regional Safety Conference & Expo and get the chance to listen to Ken’s story for yourself.