Machine & Operator Safety
Safeguarding machinery protects workers – but only if you do it right
June 16, 2009 by Gil Dominguez
Safeguarding machinery to protect workers is a vital step in the automation process, however, when talking about safeguarding, many questions arise. How should I approach machine safety? What do I need to meet regulatory requirements? How can I best use my budget to make machinery safe and easy to use? Answering these questions will help you implement machine safety in your organization.
In Canada, each province and territory establishes safe workplace regulations. Every employer is responsible to provide a safe work environment for employees. While the regulators may only cite against these regulations, they will look to recognized standards to define good practice for safeguarding specific machines.
Every safeguarding strategy should start with identifying the hazards and estimating risk. Consider the risk factors, potential degree of harm and the probability of occurrence of harm to measure risk levels. Then, evaluate this level to determine how much risk reduction is necessary to reach tolerable levels.
Refer to applicable recognized standards for the specific type of machine you may have. These standards are created by people who have a great deal of experience with their respective machines and define minimum safeguarding requirements. The machine builder applies the minimum safeguards. The end-user must apply additional safeguards to reduce the remaining residual risk to a level that will provide employees with a safe work environment.
At the design stage, consider these initial risk reduction methods:
• Eliminate hazards
• Substitute of a hazard with another hazard providing a potential for a lower severity of injury
• Redesign the machine to limit the harm by reducing the speed or energ
Next apply basic safeguarding technology to the remaining risk. Examples include:
• Fixed guarding
• Interlocked guarding
• Protective presence sensing devices
Provide for the control of hazardous energy (lockout) and alternative protective methods (APM) for minor servicing. If you need more information, refer to the CSA Z460-05 standard.
Remember to apply safety without inhibiting productivity. Most workers are conscientious about doing a good job. If a safeguard is obstructing productivity, the employee may be motivated to bypass it. Proper safeguarding is transparent to the worker and provides the “path of least resistance” in completing job functions.
You can also apply the concepts of lean manufacturing to safeguarding:
• Keep safeguarding simple
• Make safeguarding transparent to operators
• Be practical
• Reduce wasted time, space, material and effort
And, consider ways to apply new innovations:
• Safe vision
• Safe servo motion
• Motion monitoring
Applying a safe vision system and safe servo control can reveal new opportunities for applying the concepts of lean manufacturing. Imagine a machine that appears to be totally unguarded at the operator interface. The operator is free to approach the machine to find the fastest way to load and unload the machine. All the while, the machine safety control system senses the worker’s approach and makes the machine completely safe as it slows down during approach. It then comes to a safe standstill before the operator can access any hazardous motion. Once the employee leaves, it resumes automatically, slowly at first and then at full speed.
As safety control systems become more sophisticated, the reliability of safety functions becomes more critical. New rating systems have been introduced into the world of machine safeguarding. These ratings, Performance Levels (PL) and Safety Integrity Levels (SIL), predict failure rate of the safety function. The higher the risk, the higher the reliability must be to ensure that the machine will be safe at every demand on the safety function.
But the fact remains that companies have limited resources for these safety technologies. Consider using a qualified safety consulting group to help maximize your investment. Seek a consultant with strong experience in machinery and automation safeguarding, and choose a group capable of providing the full range of assistance including risk assessment, safety concept and design, safe guarding implementation and validation.
Gil Dominguez is a safety consultant at Pilz Automation Safety L.P. in Canton, Mich., where he performs safeguarding evaluation, risk assessment, safety circuit design review and CE Marking. He also actively participates in ANSI, RIA, ISO, CSA band B11 standards. For more information, e-mail Gil at email@example.com or visit www.pilz.com.
Doug Nix, Compliance InSight Consulting Inc., contributed to the Canadian standards information.