Safe operator

Plant machinery punches above its weight when it comes to national casualty statistics.

About 13% of all of the reported major workplace injuries between 2012 and 2013 involved contact with moving machinery, according to the Heath and Safety Executive (HSE).

Across the whole of the manufacturing industry, the food production sector clocked up the highest number of major injuries, and almost twice that of the industry as a whole, adds the HSE.

Until recently, operator safety has been the core focus of those concerned with machine safety.

In the machine world, the demand rate for a safety function is very frequent because you are protecting personnel

David Collier

However, the goalposts are now shifting to also include those tasked with maintaining, upgrading and repairing the machine throughout its entire life cycle.

In May, global food producer Heinz was fined £50,000 for serious safety failings after an engineer had his hand severed when it became trapped in live, unguarded machinery at its Norfolk plant.

The engineer had been servicing a potato-peeling machine at the manufacturing plant during a maintenance shutdown.

As he tried to retrieve a dropped bolt, he climbed down from the peeling machine, which had been isolated, and put his hand into the slurry pump below, which operated and severed his right hand.

HSE’s investigation revealed that although the slurry pump appeared to be an integral part of the peeler, it was in fact a separate machine with its own power supply and isolation point.

Crucially, a protective grate bolted on top of the pump to prevent access was absent, enabling the incident to occur.

The potentially disastrous consequences of removing guards and safety interlocks are a common scenario in industrial settings.

However, changes in legislation and industry standards mean that these bad practices are now beginning to be addressed, says Dan Rossek, product marketing manager for sensor, vision & safety at Omron.

He identifies the corporate manslaughter act that came into force in 2008 as having made a major impact at the senior executive level because “top level management are personally liable for safety”.

Specifically relating to safety interlocks, there is a new standard called ISO14119 that will come into effect in May 2015.

“This completely revisits how we apply machine interlocking devices for access doors on machinery,” says Rossek, adding that this will make it more difficult for operators to bypass machine safeguards.

As to why operators seek to bypass safety features in the first place, Pilz Automation Technology business development manager David Collier says there are many reasons.

“It is generally not malicious, but someone trying to do their job under pressure or with a certain level of complacence,” he says.

Collier adds that there is increasing pressure on machine designers to make it technically more difficult to bypass safety controls, and reduce the motivation to do so by bolstering functionality.

While manufacturing machinery is one part of the equation, equipment used in processing presents a more complicated scenario, says Collier.

“In the machine world, the demand rate for a safety function is very frequent because you are protecting personnel, rather than preventing a process going out of control and blowing up the site,” he says.

“Whereas most safety functions in the process world are very rarely called up, so in order to know if it is running correctly safety systems must be tested periodically.”

He says Pilz is often involved in process applications that require a very high degree of safety, and it also designs equipment for situations where physical guarding cannot be easily applied.

One of these is a 3D safety camera system called Safety Eye, which is fitted to ceiling or to a wall so it can oversee a particular machine or robot and define safety limits around that system.

Another factor that can unwittingly result in unguarded machinery are upgrades to existing equipment, says Paul Laidler, business director for machinery safety at TÜV SÜD Product Service.

These are often undertaken to meet the demands of technological change and competitive market pressures.

However, Laidler warns that if substantial changes are made, any existing Declarations of Conformity under the Machinery Directive may become invalid.

This could mean that a new conformity assessment must be carried out, even if the machinery was originally compliant and CE marked when it was first purchased and put into service.

Another common oversight is that the functionality or performance of a machine can also be changed if it is interlinked with other equipment as part of an assembly.

This could be the result of a well-meaning maintenance engineer who tries to make things easier for the operator by modifying equipment, or adding a pneumatic system.

“I think a lot of operators opt to call in outside advice to determine whether or not process upgrades require CE marking or can simply be classified as a repair,” says Laidler.

“It can easily snowball from a small equipment upgrade to something far bigger, before they can put the machinery back into service.”

Automation is another area where machine safety is critical, especially as the use of robotics grows in popularity, says Rossek.

“Many companies in sectors such as food are looking at automating manual processes to boost efficiency, and introducing equipment for processes such as cutting, which can present many dangers,” he says.

“Because food production is largely organic in nature, it often needs some sort of interaction between humans and machinery, and this is where issues can arise.”

Safety was traditionally dealt with separately to automation, but now it is being integrated into that process, and we are seeing the development of integrated safety systems that include machine logic control, motion control and safety, he adds.

It because they are often placed near to workers, that safety is such a critical consideration for robots in manufacturing environments, says John Ralphs, senior controls engineer at Fanuc Robotics.

“We supply robots and robotic systems largely for pick and place applications for companies such as Heinz, Weetabix and GFK,” he says.

“From a robotics safety point of view, the first principle is whether you can stop the thing once it has started.”

Dual Check Safety (DCS) Position & Speed Check software is the package of safety features integrated into FANUC’s R30iA and R30iB robot controllers, ensuring safe monitoring of robot position and speed.

Ralphs says it allows safety zones to be quickly and easily designed, and removes the need for hardware such as limit switches and zone switches.