Risk reduction processes can be shortened when diverse teams focus on verifying improvements throughout the design cycle.
Risk assessment has become a critical aspect of most industrial design programs, so it’s a process that should be constantly reevaluated to improve effectiveness. One aspect of any review should include validation, a step that ensures the value of actions taken to reduce risk.
Validation wraps up many elements of safe operations, including factors such as the performance of preventive technologies and techniques, documentation and the likelihood that safety features can be bypassed. It also looks at residual risks that remain after all steps have been taken and employees have been trained to avoid accidents.
Ensuring that risk assessment is validated and effective is a topic explored in a Webinar, Rethink Your Machine Risk Strategy: The Validation Process. Safe-T-Sense president and CEO Chris Gerges, who is also a TUV functional safety engineer, provides insights that can help those tasked with analyzing risks. One of the most important steps is to put together a team that includes as many involved groups as possible.
“You want to assemble a diverse team,” Gerges says. “The more diverse the team is, the more it is that they’ll see the risks. An operator might identify some tasks, while electricians see different issues. The more tasks you identify early in the process, the better.”
Diversity is important because the assessment must analyze problems that could arise anywhere in the machine’s life cycle, including setup and startup, inspecting, cleaning, maintenance and troubleshooting. Merely analyzing risks that occur during normal operations is not sufficient.
Gerges notes that creating inherently safe designs is the most important step in risk assessment because those concepts are the most likely to remain in effect over the machine’s lengthy lifetime. In contrast, it’s comparatively easy to work around or disconnect safeguarding measures like light curtains or other gear that is added later.
When companies are running through their risk reduction strategies, they need to focus on the number of dangerous faults their systems can detect, comparing that to the total of dangerous faults that can occur. That figure will help developers get statistics for Mean to Dangerous Failure.
Risk reduction is an iterative process – risks are removed or reduced in severity, then the analysis should be run again to see how the changes impact potential hazards. After risks are eliminated or mitigated, companies can establish administrative controls that further reduce the chance of injury. Handling these residual risks can include requiring personal protective equipment and training.
Verification and validation are also critical factors in the drive to ensure and prove that equipment is safe to operate. In order to properly implement your risk reduction measures, it’s very important to get manufacturer data from the equipment companies that supply contactors, drives, safety PLCs and light curtains, to name a few key components.
Collecting this data makes it possible to set fault exclusions for some system parameters. For fault exclusions, the designer can specify faults that won’t happen because important factors have been taken into account.
Gerges discussed a system in which designers might be concerned that a contactor in a system may have welding issues. Design teams can over size the contacts, using an 80 Amp contactor for a 40 Amp system, to make sure current passes through without problems. Filtering can also be added to handle transients. When companies use supplier data to show that a well-tried component is being used in this fashion, they can get a fault exemption, so they don’t have to prove that the design can handle that type of fault.
Using safety PLCs can also help reduce the time needed to handle risk analysis and assessment. However, testing still has to be done, for example by implementing short circuits to see whether the safety PLC detects faults and halts any motion that could be hazardous.
Designing and validating hardware is only one part of the task of proving that equipment meets safety requirements. Software has become a critical factor in system performance, so it’s an important factor in risk analysis. Programs pose a real challenge, since code can perform differently in response to many factors. It’s difficult to examine all the possible responses and prove that software meets risk level requirements.
Two standards, IEC 620261 and ISO-13849-1, address testing for functional blocks and test methodologies for software I/O handling. Proving that risk analysis plans are efficient and effective are challenges for design teams that need to get work done quickly without compromising the quality of the risk analysis. In many instances, designers should be sure to test software under fault conditions to ensure that responses yield the correct results.
When safety and risk analysis are considered from the outset of any design and development program, the likelihood of success rises exponentially. Creating a diverse team that examines many different aspects of ongoing operations can help companies get through the verification and validation processes with a minimum of issues while meeting design and cost guidelines.
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