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Effective safe automation

Technology, global standards, and open systems, can all work to increase productivity and equipment effectiveness.

Contemporary manufacturers shoulder heavy responsibilities, including the core, overarching responsibility of operating a safe and productive plant.

To achieve these sometimes conflicting goals, it is essential that management is committed to programs to improve productivity while providing employee, environmental and equipment safety.

When deployed properly, using a holistic approach, today’s safety automation systems allow the best of both worlds – a safer environment for employees, reduced environmental impact, better processes and optimised productivity.

Technology now provides the means to pursue these dual goals using highly integrated safety automation systems. These leverage the intelligence and diagnostics of the automation system, safely operating the machine in the most productive and profitable manner, reducing downtime, and providing sustained output to meet customer demands.

Looking back

Many manufacturing applications still use features that were once considered advanced. Yet even with most machines incorporating some form of safety feature to protect people as they interact with them, accidents through mishandling or lack of design foresight have forced significant systems reviews.

Some system designs in the past were developed with a blind eye toward safety – relying only on the operator and maintenance technician to be alert to hazards.

Others were deployed with safety as an afterthought – in response to an accident or new industry standards; using a ‘black box’ approach to safety, with the safety solution being completely separate from the automation system.

Other systems were developed with safety in mind, but were improperly implemented, or lacked the required productivity – using a ‘trade off’ mentality that resulted in neither being fully optimised.

Typical approaches, with some still in use, required machines to come to a complete stop for repairs and/or maintenance to be undertaken. Unfortunately, as productivity declines due to downtime, operators and maintenance personnel often bypass safety systems to keep up with production schedules, risking their safety in the process.

Even when machines are developed with safety in mind, they are often implemented in ways that mean human interaction with the machine is not as efficient, or not as safe, as desired.

In many cases, these typical approaches are no longer acceptable due to progressive enforced global standards on safety, significant technological innovation and contemporary risk assessment and management techniques.

Major developments in safeguarding and control technologies – most notably the advent of new microprocessor-based technologies in lieu of electro-mechanical or hardwired control – and global safety standards that allow these to be incorporated into industrial safety systems have provided new opportunities to improve both safety and productivity.

Impact of standards

Functional safety standards have improved the way machine safety systems are designed. Historically, safety standards provided guidance on how to structure control systems to help ensure that safety requirements were met.

These standards used principles based on redundancy, diversities and diagnostics, and created levels of safety system ‘structures’ to help ensure the safety functions were performed.

However, no time factor was integrated into these standards.

A new approach to global standards adds a time element, known as ‘the probability of dangerous failure, and the mean time to dangerous failure’ adding confidence that the safety system is performing as designed.

ISO13849-1:2006 builds on the ‘categories’ of safety structure; and IEC62061 builds on the foundation of the structure, also known as ‘hardware fault tolerance’.

The added diagnostics offer a safety system designer more flexibility in achieving safety requirements. Having the three elements in the safety system yields a time-sensitive level of integrity.

Safety component suppliers have increasing responsibility when it comes to functional safety. Product design standards are being modified to define the criteria, testing requirements, and statistical tools used to determine the time to dangerous failure.

Once this is accomplished, months of testing are required to confirm that a certain safety level is achieved.

Expanding technology boundaries

The same technologies that have integrated standard control disciplines – sequential, motion, drive and process – now coexist with safety control platforms.

High-integrity safety communications networks are also available, incorporating message redundancy, cross-checking and stringent timing, allowing safety and standard messages and devices to coexist using common media.

Safety has traditionally been segregated from standard control systems, implemented with individual components (such as safety relays or safety contactors) or a dedicated safety controller, and requiring different hardware, software and corresponding engineering and maintenance skill sets.

However, the ability to implement safety control within an architecture that can also perform multidiscipline control tasks delivers major benefits.

Hardware, software, and support costs, are minimised with assets shared by both the standard and safety control systems, while operationally, the intelligence and diagnostics of the automation system improves equipment productivity and lifespan, and reduces downtime.

Traditional hardwired safety systems can be difficult to troubleshoot, lacking the range of diagnostics needed to indicate what went wrong during production. Without these diagnostics, troubleshooting and repair times can be extensive, resulting in significant loss of production.

Moreover, these events normally occur when a machine is in full production, increasing the potential for equipment damage or alignment problems, material waste, and prolonged restart times. These factors increase downtime, maintenance costs, and lost productivity.

By contrast, in more advanced systems, E-stops are wired into a safety input/output block and connected via a safety-capable network to the integrated safety automation system. Diagnostic information is provided to the controller and human-machine interface in a readily accessible format. The controller, an operator, or a maintenance employee, can then take appropriate action to rectify the situation.

Another example of the advantages of integrated safety is the lock-out/tag-out procedures used widely to remove all sources of energy from a machine, in order to gain maintenance access. This process can be very time-consuming, reducing machine availability.

Instead, manufacturers can now create ‘safety zones’ in the application that can be managed independently, for various operational and maintenance scenarios. This design flexibility helps reduce the time required to restore the machine to working order after maintenance, improving productivity. It also reduces the likelihood of the safety system being bypassed, improving worker safety.

Another technology advancement that enables these systems, is seamless communication using open protocols. Traditionally, no single network was able to integrate safety and standard control systems.

That has changed with the emergence of common industrial protocol (CIP) safety, a networking standard that allows safety-rated devices to be connected to the same communications network as standard control devices.

CIP Safety is based on the CIP standard, which is an open application protocol for industrial networking, independent of the physical network. CIP Safety improves the level of integration between standard and safety control functions and increases visibility of safety in the system.

The combination of fast responding, local safety cells and the inter-cell routing of safety data create applications with faster response time. Additional flexibility also helps speed up system configuration, testing and commissioning.

CIP Safety capabilities on DeviceNet and EtherNet/IP are Technischer ÜberwachungsVerein (TÜV)-approved, with products available on both networks from multiple vendors.

The CIP protocol can also be used to integrate safety data with other plant information. As safety data is made more readily available, the information system can provide management with information that includes diagnostic data, reasons for and frequency of demands on the safety system, statistical data for lean manufacturing improvements, production data, and security access.

Integrated safety automation systems accommodate all machine lifecycle tasks including design, start-up, operation and maintenance, reducing these costs and time to market, and improving performance.

Effective risk management

There is increased industry support for proactive risk analysis, using this holistic approach to safety. The definition of formal risk assessment processes, covering risk identification, risk quantification and risk mitigation, are now included in many international and regional standards such as IEC61508, ISO13849 and ANSI/B155.1 and RIA 15.08.

Risk assessment processes defined within these standards typically have a lifecycle approach in sharing how to implement an effective process to identify machinery related risks, and to quantify the level of risk in terms of severity, frequency of exposure and avoidance.

Risk assessments provide processes for identification of specific hazards on a machine, quantifying the risks these hazards present to employees, and evaluating practices that could help mitigate the risks.

In addition, the process specifies the most appropriate safety circuit architecture required to mitigate the initial risk-rating, as determined by the assessment team.

Once the risks are fully defined and understood, they must be designed or mitigated to the greatest extent possible. Risk mitigation measures the physical improvements done to the machine in order to reduce the potential of injury, environmental or property damage.

A formal risk assessment process also documents any identified risks, the protective measures and safeguards implemented to mitigate them, and the risk remaining when these mitigation methods have been deployed.

It’s important to provide appropriate training and supervision, ensuring operators understand all safety measures, including proper use of personal protective equipment. Operators must be trained to operate the machines efficiently as they perform their tasks.

As part of an overall sustainable manufacturing program, progressive manufacturers are focusing on safety automation solutions that keep their people safe, their machines working, and their bottom lines robust.

A holistic approach to safety automation – which emphasises global standards, innovative technologies, trained personnel and ongoing risk assessment, all working together – can help improve floor operations and productivity, while protecting workers, equipment and the environment.

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