One of the main causes of delays in a project is safety critical component approval, so it is very important you understand what these are, why we need this data and, most importantly, what can or cannot be accepted.
In this video, Dennis answers some of the key questions relating to critical components, starting with ‘What makes a component critical?’.
For support with Electrical Safety Testing of your critical components, contact us today or view our Electrical Safety Testing solutions.
Hello. My name is Dennis Butcher and I am a senior engineer with TÜV SÜD in the UK and Ireland. I'm responsible for technical support for TÜV SÜD engineers and supporting customers' needs, including training. My aim is to transfer knowledge to help others to achieve their goals as seamlessly as possible, and to do this I strive to keep my knowledge current in a very changeable environment.
When the design for the product is such that a determined component in case of failure can compromise the safety aspect, this component is defined as "safety critical".
Components, which have specific requirements in the applied end product standards - Some common examples of these are mains input fuses, safety capacitors and fire enclosures.
Components, which have requirements in the National Standards included in the evaluation - Some countries or regions have different or additional requirements for safety critical components.
Materials, which are critical to maintain compliance with the standard (such as corrosion requirements, flammability) - Plastics, for instance, need a certain flammability rating depending on whether they form a fire enclosure or barrier. All plastic components and parts need a minimum level of flammability unless they can be exempted by size or mass.
Terminals and screws - For some purposes they must be protected from corrosion so may need plating or to be made of specific materials.
Electrical insulation must be adequate for the working voltages within the end product.
Professional judgment of the CBTL/NCB. This would usually be something that was relied on as a safeguard, but isn't specifically mentioned in the standard, eg the components comprising a battery protection circuit.
Simple answer: when the standard requires third party evidence of compliance (certification and or an accredited test report). In general, IEC covers most of the world. EN covers EU requirements, NRTL covers North American requirements.
Well, labels carrying essential safety information need to be suitable for application for the surface they're attached to, and the printing must be durable enough to withstand normal usage, including cleaning.
It should be adequately certified to an appropriate standard as determined in the end product standard. If it is not or cannot be certified separately, it can sometimes be evaluated as part of the end product. It is then controlled using minimum or maximum ratings to ensure that the required level is met. Operational document OD-G-2060 specifies guidelines for interchangeability of components in some constructions.
In some constructions, yes. In low voltage, low power products it might not be a concern, but in higher voltage and power products, such as AC DC power supplies, the inner layers may be carrying significant levels of power and hazardous voltages.
So, in conclusion, safety critical components must be used within their specifications to guarantee safe and controlled interruption, (for example, no fire and explosion phenomena) during abnormal or single fault conditions in the end products. This can be determined from data sheets and component certificates, but in all cases they are evaluated in the end products to ensure that they are suitable in that application.
During abnormal and single faults testing, some components become safety critical because they have a characteristic that limits hazardous energy to a safe level.
If you need support with electrical safety testing of your products, please contact us and we'll be happy to help.
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