Improving manufacturing performance through intelligent safety system design
Ask any production line manager about the importance of safety and they will most likely tell you about the critical role it plays in helping to protect personnel, reduce injuries and meet compliance demands. These are all valid objectives, but manufacturers and machine builders are missing opportunities if they only focus on avoiding negative consequences rather than striving for greater performance.
Historically, industry has viewed safety practices as punitive actions or compliance activities. These days, however, manufacturers understand that a well-designed safety system can help improve efficiency and productivity, and machine builders increasingly recognise how safety systems can improve both business and machine performance.
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To achieve a higher level of functional safety and experience the resulting benefits, system designers must have in-depth understanding of the manufacturing process, the machinery limits and functions and a thorough knowledge of the ways that people interact with the machinery. They also need to be willing to consider and apply new safety technologies and techniques.
The functional safety lifecycle – as defined by IEC 61508 and IEC 62061 – provides the foundation for this detailed, more systematic design process for machinery applications. A key objective of the safety lifecycle is addressing the cause of accidents. To do this, designers aim to create a system that helps reduce and minimise risks, meets appropriate technical requirements and helps assure personnel competency. Previous standards have relied on prescriptive measures defining specific safeguarding. The new functional standards are performance-based, which makes it easier for designers to quantify and justify the value of safety, giving users the ability to tailor the specific safety functions to the application. It helps reduce cost and complexity, improves machine sustainability and helps achieve a more optimum level of safety for each defined safety circuit or function.
Safety Lifecycle phases
A risk assessment is the first phase of the safety lifecycle as it provides the basis for the overall risk-reduction process, which involves the following steps:
• Help eliminate hazards by design using inherently safe design concepts
• Employ safeguarding and protective measures with hard guarding and safety devices
• Implement complementary safety measures including personal protective equipment (PPE)
• Help achieve safer working practice with procedures, training and supervision
When designing a safety system, a risk assessment helps determine what potential hazards exist, and which safety mechanisms should be implemented to help ensure adequate protection against them.
The functional lifecycle provides the framework for several highly effective “design-in” safety concepts. These include passive, configurable and lockable system designs.
Easier and More Intuitive
A passive approach aligns with the design philosophy that safety systems should be easy to use and not hinder production. An effective passive system design performs its function automatically help boost productivity.
For example, in many production operations, manufacturers often use light curtains to help prevent machine motion when an operator enters a hazardous area. Other approaches, such as a safety interlock gate, require operators to perform a task to initiate the safety function. Even if it only takes 10 seconds to open and close the gate for each cycle, that time accumulates over the course of a 200-cycle day. With a light curtain, the operator simply breaks the infrared barrier when entering hazardous areas and the operation comes to a safe stop. Over time, this passive design helps increase productivity and creates a positive return.
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For example, an operator may need to access a machine and still need some form of power. The initial risk assessment identifies and defines all the tasks, including these, that must be performed on the machine with or without power. The assessment offers insight to create a configurable design that meets global safety requirements, helps increase productivity and helps reduce the incentive to bypass the system. In most cases, inexpensive components, like push buttons, selector switches and lights, are all that is needed to achieve an acceptable level of safety.
Turning Safety into Productivity
Using a lockable system design to systematically reduce mean time to repair (MTTR) can help boost productivity. It allows operators to select a safety configuration then lock it in place at the point of entry. A lockable design also helps achieve higher productivity by using the safety system in lieu of lock-out/tag-out (LO/TO) for many routine maintenance and setup procedures.
For example, in a LO/TO situation, operators may need to use six locks to safely shut down a line. If the safety system meets the target safety level – and complies with standard ANSI Z244-1 – the safety system can be used to disable the hazards. In this case, LO/TO is not required. Instead of locking the disconnect switch, operators only lock the safety system. The potential cost savings associated with reducing the LO/TO downtime by even a few minutes often proves to be substantial.
The far-reaching economic benefits of a well-designed safety system are too significant to overlook. Using safety technology with excellent reliability and the rigorous approach defined in the Safety Lifecycle, manufacturers and machine builders can harness the inherent value of intelligent safety system designs to help drive productivity, reduce labour costs and ultimately increase the bottom line.
For more information, e-mail us at: info_at@ra.rockwell.com with ref: Intelligent Safety
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