Workplace safety through machine design

GETTING things right 99% of the time isn’t enough when it only takes one error for someone to sustain a serious injury. If not flawlessly applied, administrative controls – regulations that rely on workers to consistently follow procedure in hazardous areas – can have serious consequences for safety on the factory floor.

Frank Schrever, MD of Pilz Safe Automation, regularly trains WorkCover inspectors in machine safety and claims that true safety is achieved not just by regulations, but through a machine design that anticipates human error.

“Humans are inherently unreliable; on average, they get something right 99 times out of 100, but the 100th time is enough to cause an injury.

“That’s why the law has an imperative that you must minimise risk through design, so that you are not dependent on human error,” said Schrever.

Research conducted in 2003 by the National Occupational Health and Safety Commission (NOHSC) highlights the role machine design plays over administrative control in minimising risk in the workplace. Analysing the cause of fatalities from 2000 onwards, the study found that 95% of deaths involving machinery and fixed plant were due, at least in part, to design issues.

Although the statistics are from three years ago, Schrever believes that the NOHSC’s findings still serve as a relevant warning for industry today.

As part of a drive to constantly improve levels of safety for workers on the factory floor, there is increasing pressure for machine designers to more strictly adhere to safety principles. AS4024.1, which outlines safety requirements for machinery and plant equipment, has recently undergone revision and is raising the bar for safety engineers in Australia.

“It’s now a much broader standard and aligns Australia completely with the European approach, which is of the highest level. We have a comprehensive standard now, covering everything from fundamental principles and risk assessments, through to details on circuit design for safety and ergonomic principles,” said Schrever.

Lost in translation

AS4024.1, consisting of 26 parts and approximately three times the size of the 1996 document, can be difficult to translate into practical steps. Although companies are legally required to conduct a risk assessment to arrive at a suitable safe engineering design, the challenge is applying the hefty AS4024.1 to the situation at hand.

“You have a document that says, ‘this is a high risk’, but what do engineers do with that? They have no clues as to how they’re meant to deal with it. The problem is that they have to understand AS4024.1, and that requires interpretation,” Schrever told Manufacturers’ Monthly.

The issue of translating machine safety standards highlights a larger problem of safety training in Australian industry.

According to Schrever, there is currently a lack of machine training for engineers, electricians and other technical workers in machine safety design principles.

Although efforts have been made (Swinburne University of Technology has recently started running short courses on machine safety design) there is still more education needed; not only in engineering and design, but also in machine maintenance and usage.

Emergency stop buttons

The consequence of insufficient education is that safety equipment is not properly used on the factory floor, resulting in a higher incidence of work related injuries.

One issue at hand is the proper use and installation of emergency stop devices. On the 1st August 2000, a worker caught his hand in the rollers of a winding machine and sustained serious injuries, resulting in the amputation of two of his fingers. He was unable to stop the machine because there was no emergency stop device.

Australian Safety Guarding discovered that a common occurrence in manufacturing plants is the lack of use of emergency stop buttons that comply with the Australian standard.

Peter Papas, design engineer of Australian Safety Guarding, claims that while AS4024.1 requires push-buttons to be the mushroom head latch-in or lock-in manual reset type, many emergency stop buttons in factories are not dual redundant and monitored. The buttons are also not located in the correct positions for workers and are being used at inappropriate times.

“Incorrectly installed emergency stops in factories are causing the machines to operate upon release or resetting, creating hazards.

“We also observed that a large percentage of plants are using emergency stop buttons as mere stops when going on tea breaks. Emergency stops should only be used in the event of a hazardous situation, with the exception of testing.

“Not maintaining or correctly arranging emergency stops designed according to AS4024.1 can have serious repercussions on worker safety in the factory,” said Papas.

New developments

Although adhering to safety standards is crucial, machines need to be workable as well as safe. According to Schrever, an effective safety design should not compromise productivity.

“Previous approaches to safety may have been a series of human error checks, whereas if a design is effective, you can grab the gates of a machine, pull it open and the machine is completely safe. A bad design would be where you have to stand and wait for three minutes,” said Schrever.

One of the current developments on the market is safety networking through field buses, where all the safety devices such as switches, emergency stops, light curtains within a factory such as are interconnected. Such systems are not only more reliant, but efficient from a production point of view due to its fast installation and quick diagnostics.

“Other future technologies that are coming include vision based systems where a safe camera can look at a work area, detect human ingress into danger zones and either slow down or stop the machine in question,” said Schrever.

Although not all factory applications require an intricate safety system, it’s important for a safety solution to be workable as well as adequately safe.

Translating the current AS4024 standards into practical and pre-emptive machine equipment is a positive step towards further ensuring worker safety on the factory floor.

Australian Safety Guarding 03 9569 4506.

Pilz Safe Automation 03 9544 6300.