Holistic Safety – It’s all Connected
A holistic safety approach supported by new technology and global standards integrates every piece of your operation to help increase stability and profitability.
By Dan Hornbeck, Safety Market Development Manager, Rockwell Automation
Many of today’s legacy manufacturing systems were developed with a minimalist approach to safety. When a demand on the safety function was required, older technology usually forced machines to come to a full stop and be in a ‘safe state’ before repairs or maintenance work could be performed. Due to time required to stop and restart the machine, productivity often was impacted, and personnel often bypassed the safety equipment — a hazardous condition, to say the least.
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A ‘holistic’ approach to automation system design uses new safety standard, leverages rapidly changing technologies, and applies a risk management process to address the manufacturer and machine builder’s goals of boosting productivity and meeting overall cost and efficiency goals.
Functional standards
Two significant trends are occurring in the development of new functional safety standards. The first is recognition of global standards by many countries and, as a result, a trend towards adopting these standards as regional or local standards.
This is very helpful for global machine builders and multinational companies faced with implementing safety solutions around the world. They now have the benefit of being able to design one corporate solution that can be deployed worldwide.
The second trend is the recognition and acceptance of new methods and technologies that help manufacturers adopt a contemporary safety solution that meets the design and cost goals previously mentioned.
The role of a safety standard is to provide design guidance for systems to help ensure that machine safety requirements are met. Older standards use the concepts of structure such as redundancy, diversity and diagnostic principles, to achieve functional safety. But one important concept was missing from this approach: time.
Newer machinery functional safety standards, such as EN ISO 13849-1, adds the element of time – known as mean time to failure dangerous (MTTFd) – to build on the existing safety structure approach. The time element adds a performance factor that the safety system is going to correctly perform the safety function when a demand is placed on the system.
“A holistic strategy for machine safety isn’t just about increasing safety for its own sake, but about increasing value and productivity by emphasising global standards, lifecycle design considerations, risk management and using modern safeguarding equipment. The best of all possible worlds is increasing your productivity enough to pay for increasing your safety” |
Technological innovations
Traditional safety systems, using hardwired devices, can be difficult to troubleshoot because they provide minimal indication of why a system went into a safe state. The safety switches were ‘series-ed’ in long strings to a controlling device. The machine may have stopped in a ‘safe state’, but the reason and correction to return the machine to production was difficult to determine. When these unplanned events occurred during production, they could lead to machine alignment issues, material waste, longer restart times and possibly even equipment damage over time. These factors contribute to increased downtime resulting in lost production and higher operating costs, since the work in progress would need to be cleaned, removed, reset or scrapped, and the equipment reinitialised.
Fortunately, contemporary technology allows these safety switches to be wired directly into a safety I/O block, reducing field wiring cost. The safety I/O then connects via a safety-capable network, such as DeviceNet or EtherNet/IP, to the safety controller. This simplified and cost-effective design can provide diagnostic information, through a human-machine interface (HMI), that is helpful in determining the reason the machine stopped, identifying the faulty device and returning the machine to production in the least amount of time; all while maintaining the highest level of safety to the operator and those repairing the machine.
These new safety controllers employ technologies based on programmable automation controllers (PAC), where safety and automation control are tightly integrated into one controller. This platform uses one software development environment to provide the flexibility and design productivity required for today’s manufacturing challenges. Designers are free to focus on the application and safety requirements without being burdened by separate control and safety solutions.
In the past, when communication networks were necessary, no single network could tie safety and automation control together, while also enabling data transport across several physical networks. Changes in network topology with the deployment of the Common Industrial Protocol (CIP) networking standard has eliminated this problem by providing for both standard and safety communications over networks such as DeviceNet and EtherNet/IP. Interconnecting all of the devices required for the standard and safety aspects of the application can now also be accomplished using the same networks you’re already familiar with and using.
These new contemporary technologies enable a holistic approach to the automation application. This holistic approach allows reduced design and implementation time and enhanced diagnostic capability, and lowers operating cost while improving the safety and productivity of the machine or line.
Risk management
So you might ask yourself, “How do I determine if an employee might be put into a hazardous situation and if so, how do I take advantage of these contemporary methods to protect that employee from the hazards?” The answer is an effective risk management programme.
A risk management programme is key for manufacturers to ensure safety in the workplace without decreasing productivity and driving up cost. Risk assessments are critical to this process.
Risk assessment gives a company a methodology to practice due diligence and good engineering practices while providing the appropriate amount of safeguarding in the work environment.
An effective risk assessment process must include identifying machine hazards, quantifying the level of risk those hazards present to employees, and evaluating methodologies that can help mitigate the risks to an acceptable level. A properly performed risk assessment allows the manufacturer to define the appropriate amount of safety for each machine or safety function and dedicate the resource required, whether financial, technical or procedural, in the most cost-effective manner.
Risk assessment requirements and methodologies are included in many regional and international functional safety standards.
So how do you meet the challenges we all face in manufacturing? How can you provide a safe place to work while reducing overall costs and increasing productivity? How do you design a machine that is accepted anywhere in the world?
The answer is that you want to use the latest functional safety standards, leverage advancements in technology and adopt a risk assessment-based approach to your risk management policies, so that your company can have a truly holistic approach to automation safety.
For more information, please e-mail us at: info_at@ra.rockwell.com with ref: Holistic Safety
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