Looking at functional safety from the proverbial 30,000-foot view, making a supply chain compliant with functional safety requirements requires that each component in the chain meets the criteria for functional safety demanded by its application. While the concept is simple enough to easily grasp, implementation is challenging.
From a risk management perspective, many manufacturers are looking to defer risk downstream in the supply chain. When you build an automation system, you have relatively little control other than the choice of vendor for the different components purchased for the system. How will these choices affect the functional safety status of the system being built?
By certifying the functional safety performance of components used in specific applications, UL’s functional safety component recognition program makes choosing components easier, more confident, and consistent across the supply chain.
“The whole idea is that the end user doesn’t have to bear all the costs associated with risk management through the supply chain, certification of the components, and so on,” says Anura Fernando, research engineer at Underwriters Laboratories. “Having the products they choose pre-certified, with very specifically constrained conditions of use, allows them to quickly integrate them while minimizing time and cost investment.”
UL Functional Safety Component Recognition
UL’s functional safety component recognition service covers the evaluation of components or materials intended for use in an end product functional safety certification. A recognized component is one whose complete safety in its application cannot be evaluated by looking at the component alone, and so conditions of acceptability are placed around its use—so that it has to be used in that specific context in order for it to satisfy the functional safety requirements.
Because UL Recognized Components are intended for specific applications, the well-known symbol of a UL in a circle can never be used in connection with the advertising or promotion of products that are UL Recognized Components. The appropriate symbol for promoting UL Functional Safety Component Recognition is the UL Functional Safety Recognized Component Mark.
Coordinating the outputs of functional safety evaluations so that one has the right safety integrity levels or performance levels— and also the right conditions of use and right safety functions— ties together during system integration: this supply chain coordination is the element that UL brings to the market.
“With its Component Recognition program, UL has a long tradition for certifying components for incorporation into products that then more easily and cost effectively achieve UL Listing,” says Thomas Maier, principal engineer, functional safety, at Underwriters Laboratories.
“We have therefore introduced a functional safety recognized component mark, which looks different from the functional safety listing mark for consistency with existing product marking,” continues Maier. “It clearly indicates that additional considerations need to be looked at when that device is being integrated into a product — and that’s an important part of the value proposition that UL’s functional safety component recognition program brings to the supply chain.”
The UL functional safety marks, both listing and recognized, are associated with specific safety functions and parameters that are briefly identified on the markings but refer back to the installation and product manuals, so that the information in those manuals can be properly used to integrate these components and ultimately end up with a system that meets functional safety requirements across the supply chain. In a way, this mirrors the structure of the standards themselves, where an application standard like ISO 10218-1 (robotics) is fed into by a component standard like 61800-5-2 (motor drives).
To understand the importance of this, consider changing the spark plugs in your car.
You go to the auto parts store and say “I need a set of spark plugs for the car,” and you give them the make and model of the car; and they sell you a set of appropriate plugs. But when you get home, you still need to look in the manual to see what the spark gap setting is. Otherwise it’s not going to fire when you ignite it. So you take out your feeler gauge and make sure that the gap is correct. Then you put it in and check the torque specifications to make sure you don’t break it off. All of these are critical elements in making sure the spark plugs are properly integrated into your engine.
It is the same concept that UL provides or ensures through its functional safety component recognition— it makes certain that essential pieces of information are in the manuals throughout the supply chain as it does its certification of individual components.
If your car had not had the proper certifications to make sure that the spark gap setting comes with the manual, you would purchase a set of plugs but you wouldn’t be able to start your car.
It is a System After All
The functional safety system is only as strong as its weakest link. System integrators need to consider functional safety throughout the supply chain, or else risk compromising the safety integrity of the entire system.
When system integrators are specifying parts for a safety system, if there are 20 components in the system, and 19 are SIL-3 rated, the highest level, and one is SIL-1 rated, the lowest level, then the system itself is rated SIL-1. This is why it is critical for integrators to ensure that all of their component pieces meet the SIL or PL level they want the system to meet.
“The very principal of functional safety is that functional safety is always a substance of the entire system or the application which runs safely,” says Maier. “Whether it is a safety monitoring relay or a motor drive—or a tiny but immensely complex component like a processor— as soon as it has the functional safety mark it will ease the task for designers to establish safety for the overall system or overall application.”
For more information on UL’s functional safety component recognition program or how to better integrate your supply chain to meet functional safety standards, please contact:
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