Safety always partners productivity

"If safety ain't productive, it ain't safe."

This rather ungainly statement does in fact point to a profound truth in manufacturing environments.

The truth is that safety applied without reference to productivity of the workplace and the operability of the machines, plant and equipment, can lead to quite dangerous outcomes regardless of the technical and legal compliance of the safety solution.

How can this be? Let’s examine this in some more detail.

The law has long been exhorting us to eliminate risk and if that is not possible to minimise it by engineering means. Those engineering means are not described in legislation, except to the extent of expressing a guarding hierarchy which defines the guarding types and the order in which they should be examined and employed, so far as is reasonably practicable.

This hierarchy is central to many engineering solutions for risk minimisation of machines, and here the law has got it just about right.

If we can, says the law, (including the new harmonised laws now enacted by NSW, QLD the Territories and the Commonwealth) we must apply a permanently fixed (welded) physical guard. This, of course can only happen if access is never required for operation, maintenance or cleaning.

A guard which is not removable, isolates the hazard from us, thus reducing the probability side of the risk equation (risk = severity x probability) to a very low level regardless of the severity of the injury that might result if we were to come into contact with that hazard.

Job done? Not quite.

Most machines require that we do have to have access to the dangerous parts for operation maintenance or cleaning. In this case, says the law, we must have an interlocked physical guard.

What is that? An interlock is typically a switch which turns off the hazardous energy when we open the guard. It may even prevent us from opening the guard until the hazardous machine functions have stopped. So far so good.

But how do we design the interlocking system so that it is guaranteed to function, so that the switch and control system can’t fail and let us into a machine which is still running? The law has nothing to say about these things, but it does point us via the codes of practice to Australian standards, which do.

And the prime standard in this regard is AS 4024.1-2006 Safety of Machinery together with it’s suite of technical and machine specific standards.

This standard covers all the fundamental requirements of machine safety from risk assessment via safety control systems, interlocking, emergency stop, unexpected start, guarding design and to a complete set of ergonomic considerations.

It provides detailed guidance on how to design safety control systems which have decreasing probabilities of dangerous failure as the risk increases. So, knowing this, the job must be done now? Not quite.

Is it practicable to interlock every guard that has to come off a machine for operation, maintenance or cleaning? Absolutely not.  So where to from here?

Well, the law quite sensibly leaves this decision to you. If you decide that it is not reasonably practicable to weld or interlock a guard, then you can now use a guard that can only be removed with the use of tools, and the standard AS 4024 supports this further by saying that the tool should not normally be available to the operator.

Please be sure however that you really have your ducks in a row about the “not reasonably practicable” part of that, and can defend that decision if an incident were to occur. There are five tests for reasonable practicability, defined in the OH&S act (and in the harmonised act) and each one should be considered in the context of that risk.

Cost is at the bottom of that list, but can be a valid argument only if it can be clearly demonstrated that the cost is grossly disproportionate to the risk.

Many guards are rarely removed; for instance, the idler guards on a very long conveyor, and if that is the case, an argument may be legitimately raised to bolt these guards only. But in this case, we are now dependant on human behaviour to control the risk.

That is, the human must follow some administrative control like a lock out tag out and test procedure before removing the guard, to ensure there is no hazardous energy left in the machine and it cannot start unexpectedly.

There are five tests for reasonable practicability and each one should be considered in the context of the risk.Sadly, these approaches are often applied to guards that are removed frequently, and over time diligence wains, complacency creeps in and terrible injuries can result.

This is simply because humans are relatively unreliable when it comes to performing repetitive tasks and accidental, occasionally deliberate departures from procedure are made. i.e. guards are left off with the machine running.

This can of course happen even when guards are removed infrequently; thus the sensible approach in the legal hierarchy of risk control which tells us to minimise risk by engineering means first, before relying on human behaviour via administrative controls and PPE.

The clear message here is that the risk assessment team has to tread a careful line analysing the situation in detail, before deciding on bolted guards.

So, are we done now? Not yet.

Physical guards may not always be reasonably practicable. In these cases (and there are plenty of them) a presence sensing system can be used. These are devices like light curtains or pressure mats which detect people entering a hazardous area and shut the machine down.

Why is a presence sensing system at the bottom of the legal guarding hierarchy? Simply because many machines can eject objects at very high velocity, and a presence sensing system will not contain those hazards even though it may well detect the object moments before it strikes you.

Nevertheless, there are many instances, for example palletising machines, where presence sensing is the ideal solution. Goods can enter and exit the machine freely by careful muting of the presence sensing device.

However, if a human tries to enter such a machine (which can and do cause fatalities), the machine shuts down, controlled by an AS 4024 based control system matching the level of risk. Lots of important safety design considerations in such a system.

There we are. Are we? Sorry, no; the most important part is still to come.

If we simply, diligently follow the requirements described so far we could be ignoring the most dangerous and often subtle issue. That is, the tendency of humans to want to do things quickly and easily.

A safety system which has not taken this into account can, and frequently does motivate people to bypass or defeat the system which is slowing them down or making their job more difficult. They are not usually doing this with malicious intent, or to harm themselves, but with the laudable motive of maximising output.

That is, production. Often, safety designers with safety only in mind, cleverly attempt to make things extraordinarily difficult to defeat (which the law also asks of us) only to find that the defeater has been even more highly motivated to find even cleverer ways to get around it.

And all because the productivity and operability of the machine was not considered in the safety solution. 
A recent German study showed that around 40% of installed metal working machine safety systems were tampered with in some way. It is a global problem.

Tread carefully as there is no one-size-fits-all solution to the safety problem.Therefore, we must have the productivity and operation of the plant we are trying to make safe, at the forefront of our thinking.

We must discuss the possible safety solutions with the people who operate, maintain and clean the machines, solicit their input and arrive at clever solutions which not only make the machine safe by design, but do not make them harder to use and do not reduce the productivity of the process.

With this thinking incorporated, productivity can often be enhanced over that of the original machine, and with the key stakeholders involved, we have the double benefit of buy-in to a solution which is making their work safer, faster and easier.

There is no one-size-fits-all solution to this problem. Careful thinking must be done, often on a case by case basis to determine the optimum, safe and productive design.

Finally, after all this has been done, there is usually some residual risk left, elimination being rarely possible. As long as we have explored all the of the engineering based risk reduction solutions (so far as is reasonably practicable), then, and only then, can we apply administrative controls and personal protective equipment to control those final risks.

These controls can be essential in many environments (consider noise, falling objects, ejected substances), but we must recognise that they are totally reliant on the predictable behaviour of humans to be effective. This does require total focus from the management of the company and their OH&S teams, to re-enforce the training and the practice, on an ongoing basis, forever.

And that is subject of another story called behaviour based safety.

[Frank Schrever is Principal Consultant, Machine Safety By Design.]

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