Take a holistic approach to machinery safety

Taking a holistic approach to machinery safety means looking at many aspects of a company's operations, says Robert Sharrock.

It may shock you to read this, but some users of machinery still want to do only the bare minimum to comply with the assorted standards and regulations so that they will not be prosecuted by the HSE (Health and Safety Executive).

Such users are not truly concerned with the safety of their employees; rather they are trying to spend as little money as possible to avoid the threat of fines and prison sentences.

A better approach is to undertake a risk assessment, see where the unacceptable risks are, and then take appropriate action to reduce the risks to an acceptable level.

A similar approach can also be taken by machine builders.

Although this is certainly an improvement over doing little or nothing, the ideal is to take a truly holistic approach to machinery safety.

This includes everything from the design of the machinery to the education and training of everybody that is responsible for any aspect of it, regular safety audits and a corporate culture of safety-first.

Design is the phase in a machine's life where the greatest impact can be made in relation to safety.

The designer should ensure that the machine is safe to set up and operate, and also that it is safe to install and commission, safe to maintain and repair, and safe to decommission.

Although safe operation is usually at the forefront of a designer's mind, safe maintenance and repair should also be a high priority.

Around 50% of fatal accidents involving industrial equipment are associated with maintenance activities, and design is a contributory factor in some 32% of these fatalities.

The first hurdle to be overcome is the traditional attitude adopted by designers: "the machine has been designed so that it will not fail".

Unfortunately, machines do fail, so it is better to work on the assumption that unplanned maintenance and repairs will be required at some point.

Every time a maintenance technician needs to work on a machine, there is a possibility that he will be exposed to hazards, so the best thing a designer can do is aim to make the machine as reliable as reasonably practicable to minimise the maintenance requirement, scheduling long intervals between routine maintenance tasks.

But it is also important to design the machine and its control system so that maintenance can be carried out safely.

For example, hold-to-run controls can be installed that allow a machine to be run at a reduced speed, or removable toolholders can be used so that sharp blades can be replaced on a workbench instead of in an inaccessible position inside a machine.

In addition, operators and maintenance technicians must be discouraged from bypassing safety equipment.

Because safety components are often designed to interrupt processes in the event of a fault, they are bound to have a small impact on machine availability.

In order to minimise this effect - and the temptation to interfere with the safety circuits - high-reliability safety components should be specified so as to keep the number of nuisance trips at a minimum.

Designing safety into a new machine is relatively easy, but it has to be remembered that the vast majority of machines do not remain unaltered, with unchanged operating procedures, for their entire lifetime.

Modifications are almost inevitable, and working practices can evolve unchecked or be deliberately revised by managers in an attempt to improve throughput.

However, as soon as any change is made to the machine or the way it is operated, the original risk assessment is invalidated.

Research has shown that a significant number of industrial accidents result from uncontrolled changes, though it is usually via a complex sequence of out-of-the-ordinary events that a change leads to an accident.

Clearly it is necessary to ensure that machinery and operating procedures are fully documented.

And even if a machine and its associated safety systems are all properly designed and documented, it is essential that the situation is monitored during installation, commissioning and first-off production.

Invariably it is found necessary to make small changes during any or all of these stages, so it is vital that any proposed change is first subjected to a rigorous risk assessment, and any changes that are implemented must be fully documented.

After production has commenced, a further review should take place to make certain that no further changes have been introduced, especially concerning maintenance intervals.

Note also that "no further changes" also refers to the raw materials or components that are being processed by the machinery.

Finally, audits should be undertaken on a regular basis to check that the machine and operating procedures are still exactly as documented.

Furthermore, functional audits should also be carried out on the machinery safety-related circuits.

Often the components in a safety control system are only used in the event of an emergency, so there would not normally be any means of checking that they still function correctly; to only discover there is a problem when a safety circuit fails could be catastrophic.

Of course, this is one area where safety fieldbuses, such as AS-i Safety At Work (AsiSafe) and Profisafe can make a huge difference, with intelligent field devices able to perform self-monitoring functions and transmit diagnostic data to a central controller that can alert the machine operator prior to the failure becoming an unacceptable risk.

Another aspect of the holistic approach to machinery safety is education and training, which have become more important than ever, now that machinery is increasingly complex and there are new standards and regulations with which companies must comply.

For example, BS EN61508:2002, the series of standards relating to electrical/electronic/programmable electronic (E/E/PES) safety-related systems, recognises that companies require competent personnel and, importantly, must be able to demonstrate their competency.

Whereas on-the-job experience may have sufficed in the past, this is unlikely to be acceptable under the new regime being encouraged by the HSE.

Training for machine operatives and maintenance technicians is an obvious requirement, but there is also a greater need for more general education of the workforce and management in order to generate a safety-first corporate culture.

In today's economic climate and fiercely competitive markets, the pressure is on to increase throughput; but an industrial accident has multiple impacts throughout an organisation, the costs of which could far outweigh the value of any slight increase in throughput achieved by cutting corners on safety.

There is a strong argument in favour of taking a holistic approach to machinery safety, but such a philosophy can also have unexpected benefits.

For example, there has recently been a much-publicised campaign by the HSE referred to as "Making paper safely".

Thanks to this scheme, the papermaking industry has succeeded in cutting the number of fatalities and serious injuries by around 27% over a three-year period, which equates to 174 people being saved from death or serious injury.

However, an unexpected outcome is that many of the participating paper mills have also reported a significant improvement in quality and throughput.

It seems that the traditional working practices inadvertently led to unwarranted interference with the processes; now that there is less opportunity for manual intervention, the processes run more smoothly and consistently, leading directly to a financial benefit to the mill owners.

Taking a holistic approach to machinery safety means looking at many aspects of a company's operations.

In turn, however, improvements can be made to efficiencies so that any additional safety measures carry no cost penalty.

If companies need advice or assistance with any aspect of machinery safety, they can contact Siemens Automation and Drives, which has a team of engineers with the knowledge, experience and training to provide the necessary support.

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