WORKPLACE SAFETY
testing, some components become safety critical because they limit hazardous energy to a safe level or prevent access to it. Safety critical components must be used within their specifications, to ensure reliable and repeatable operation during normal, abnormal or single fault conditions in the end product.
APPROVAL
Safety critical components should be approved to the relevant component standards (if any). They must also comply with any specific requirements in the end product standard, and must be used within its ratings (voltage, current or power, rated max. temperature etc.). In addition to an accredited test report, components approved to an IEC standard must also have a CB Certificate if that standard is included in the CB scheme. Other international or national approvals may sometimes be accepted in lieu of CB Certification and reports, provided that the standard applied is technically equivalent to the IEC component standard.
One example is to use standards with different prefixes where the number that follows is identical, as in this example:
“If a required standard for a safeguard component is IEC 61058-1 (for switches) then the Cenelec standard EN 61058-1 may be used instead, as the main body of the Cenelec version is technically equivalent to the IEC standard, including test and compliance criteria. Note that. the edition or date of publication may not be the same as the IEC standard, so this must be checked to ensure that it is the equivalent version.”
They will also ask you to supply consumables used during testing, such as labels for a label printer. Samples should be representative of final production. However, if there are any variances, such as 3D printed parts that will be replaced later or different coloured enclosures etc., these should be disclosed as early as possible. This ensures that any potential impact on testing can be determined to avoid unexpected cost and delays. The full assessment of a product combines physical inspection, dynamic tests, and documentation review. There are two overall parts to the laboratory testing work, inspection and dynamic tests.
INSPECTION
The inspection part of the assessment includes examination, measurement and verification. This includes a review of the product’s markings, such as ratings and warnings/cautions, and the instruction manual is also reviewed.
A product will be inspected for creepage and clearances, checking distances between hazardous parts and accessible parts of equipment. Safety- critical components are also tested to ensure they have adequate and current certification, and that they meet the requirements of the relevant standard. Also, any hazardous radiation sources (including lasers and visible light hazards) must meet their required approvals to ensure they are within safe levels in equipment.
DYNAMIC TESTS
Dynamic tests include input current checks, which verify that the full-load current or power does not exceed the marked ratings of the equipment. Thermal tests ensure that components operate within their limits. Single fault tests cover a broad range of conditions, including, but not limited to, short circuiting of functional insulation and components. A high voltage test (hipot, electric strength or withstand test, usually for mains products) is applied across insulation barriers to ensure that breakdown does not occur. Touch current measurements may also be conducted, which ensure that no hazardous leakage currents are accessible to users or operators. Tests must also be done to check that mechanical hazards are adequately safeguarded.
SAFETY CRITICAL COMPONENTS One of the main causes of project delays is component approval. So, it is very important to understand what these are, and what can or cannot be accepted. In general, a safety critical component is a component which, if changed, could compromise the safety of the end product. The IECEE Operational Document OD-2020 defines a safety critical component as: “When the design of the product is such that a determined component, in case of failure, can compromise the safety aspect, this component is defined as “safety critical. During abnormal and single fault condition (SFC)
Some components or modules might be previously approved to an end-product standard instead of a component standard. This is usually the case where there is no appropriate component standard, or where the ‘component’ is an end product in its own right e.g. motherboards, power supplies, pumps, battery packs. In this case, the approval must also be acceptable for the end-product standard being used and the same ‘rules’ apply for acceptance as for any other component (as above). Some components in this section may also need additional verification to ensure that tests and compliance criteria are sufficient to meet the requirements for the end product. It is essential that, in addition to certification, the full test reports are also available. Alternate national standards may be required for some countries or regions. Some common examples are North America, the European Union, United Kingdom, Japan, Australia/New Zealand. It is also worth noting that a manufacturer’s Declaration of Conformity or a self-issued Certificate of Conformance is not acceptable in lieu of third-party accredited testing and certification. In some cases, an end product standard may allow for some components to be assessed in the end-use application. This will usually require additional in-application testing. Electric shock, fire and other hazards related to the use of electronic products are the cause of thousands of injuries and even deaths around the world each year, whether because of poor design, inadequate maintenance, or unintended use. Evaluating and testing a product, and its safety critical components, is therefore essential to mitigate potential risks and ensure end-user safety.
TÜV SÜD
www.tuvsud.com/uk INDUSTRIAL COMPLIANCE |SUMMER 2025 15
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