Designing For Safety A short guide to safety in electrical and electronic products
Who am I? Alastair McLaughlin Product Safety Specialist at TÜV SÜD Product Service Over 20 years experience in compliance management and product testing Worked for retail suppliers, major children s product manufacturers, and TÜV SÜD Product Service Email: Alastair.McLaughlin@TUV-SUD.co.uk Phone: +44 (0)1789 731155 TÜV SÜD Product Service Slide 2
Contents Basic Safety Principles Why safety? What hazards to consider Submitting for Safety Testing Selection of test standards Hints and tips to minimise failures Questions and answers TÜV SÜD Product Service Slide 3
Basic Safety Principles Why safety? What hazards to consider
Basic Safety Principles Why safety? We have a duty of care to our end-users to ensure products are safe Legislation lays out safety requirements in broad terms Low Voltage Directive (including as required by R&TTE) General Product Safety Directive TÜV SÜD Product Service Slide 5
Basic Safety Principles EU law (the Low Voltage Directive) requires that products: be made in such a way as to ensure that it can be safely and properly assembled and connected protect against hazards arising from the electrical equipment to ensure: that persons and domestic animals are adequately protected against the danger of physical injury or other harm which might be caused by direct or indirect contact that temperatures, arcs or radiation which would cause a danger, are not produced that the insulation must be suitable for foreseeable conditions protect against hazards which may be caused by external influences on the electrical equipment to ensure: that the electrical equipment meets the expected mechanical requirements in such a way that persons, domestic animals and property are not endangered that the electrical equipment shall be resistant to non-mechanical influences in expected environmental conditions, in such a way that persons, domestic animals and property are not endangered that the electrical equipment shall not endanger persons, domestic animals and property in foreseeable conditions of overload TÜV SÜD Product Service Slide 6
Basic Safety Principles Electric Shock Energy Hazards Fire Heat Hazards Mechanical Hazards Radiation Chemical Hazards Foreseeable Conditions all the above hazards must be avoided in normal conditions AND avoided under fault conditions TÜV SÜD Product Service Slide 7
Basic Safety Principles Electric shock Electric shock is due to current passing through the body It can cause: Perception < 0.5mA Reaction 0.5-5mA Inability to let go 5-10mA Ventricular fibrillation 20-30mA Cell damage > 30mA Burn hazard (high frequency) > 30mA TÜV SÜD Product Service Slide 8
Basic Safety Principles Electric shock Direct contact with parts at hazardous voltage: Secure covers to prevent access Breakdown of insulation between parts at hazardous voltage and accessible conductive parts: Double or reinforced insulation Earthed accessible conductive parts Leakage Current: Limit leakage current to a safe value Select the lowest practical EMC filtering capacitors TÜV SÜD Product Service Slide 9
Basic Safety Principles Electric shock Law requires that insulation is suitable for foreseeable conditions Test standards require two levels of protection against electric shock (i.e. equipment shall be safe under both normal AND single fault conditions) TÜV SÜD Product Service Slide 10
Basic Safety Principles Electric shock Differing risk for different equipment (or parts of equipment): Moveable Equipment: higher risk: supply cord rupture, broken earth conductor Handheld Equipment: wear and tear is higher Operator access areas Service access areas Restricted access locations (RAL) Permanently connected equipment TÜV SÜD Product Service Slide 11
Basic Safety Principles Energy hazard High levels of electrical energy present a risk of injury (burns) or fire (ejection of molten or incandescent material) Short-circuiting releases the energy very quickly Can happen in low-voltage circuits Protection can be provided by: limiting user accessibility providing interlocks and guarding against accidental service personnel contact TÜV SÜD Product Service Slide 12
Basic Safety Principles Fire hazard Fires may be caused by high temperatures resulting from: Overloads Component failures Insulation breakdown High contact resistance Loose connections Foreign bodies TÜV SÜD Product Service Slide 13
Basic Safety Principles Fire hazard Approach to limiting risk of propagation: Providing over-current / over-temperature protection Avoiding high temperatures Positioning combustible materials away from potential ignition sources Limiting quantity of combustible materials Using materials with low flammability Using enclosures / barriers TÜV SÜD Product Service Slide 14
Basic Safety Principles Heat Hazard High temperatures under normal operating conditions can result in: Burns due to contact with hot parts Degradation of insulation & safety critical components Ignition of flammable liquids TÜV SÜD Product Service Slide 15
Basic Safety Principles Heat Hazard To reduce heat related hazards: Avoid high temperatures Add cooling features fans or heatsinks Avoid temperatures above ignition points of flammable liquids Warning markings Restrict accessibility TÜV SÜD Product Service Slide 16
Basic Safety Principles Mechanical Hazard Injury due the physical and mechanical properties of the equipment equipment stability sharp edges and corners ejected parts moving parts Approaches to limiting mechanical risks include: Restricting accessibility Guards, interlocks Stability testing Rounding of sharp edges and corners Warning markings TÜV SÜD Product Service Slide 17
Basic Safety Principles Radiation Hazard Equipment operators and service personnel shall be protected from injurious levels of radiation emissions Types of radiation include: Laser (light) radiation IEC 60825-1 X-ray (e.g. CRTs) Radio frequency Ultraviolet (UV) light Provide barriers to radiation Limit radiation levels TÜV SÜD Product Service Slide 18
Basic Safety Principles Chemical Hazard Injuries may be caused by contact with or inhalation of chemicals, their vapours and fumes. Protection against chemical hazards can be provided by: Avoiding the use of chemicals likely to cause injury Limiting contact and inhalation Avoiding conditions likely to cause leakage or vaporisation Regular exchange of air to prevent vapour build-up Warning labels and instructions regarding precautions TÜV SÜD Product Service Slide 19
Basic Safety Principles Selection of Materials and Components Must be selected and arranged to perform over the expected life of the equipment without creating any hazard Compatible with other materials or chemicals used Reliable construction and arrangement in normal operation and fault conditions Used within their specified ratings Approved to relevant component safety standards TÜV SÜD Product Service Slide 20
Submitting for Safety Testing Selection of standards Hints and tips to minimise failures
Submitting for Testing Selection of standards IEC electrical safety standards EN standards for electrical safety are derived from IEC standard Similarly many UL standards are derived from IEC EN and UL standards include group and national differences Editions of the standard Harmonised standards in the EU give a presumption of conformity European Commission s Official Journal (OJ) lists the current harmonised standards IEC webstore gives latest editions and amendments of the IEC standards National differences Many European Standards impose Special National Conditions (SNCs) SNCs are mandatory when the product is supplied in those nations TÜV SÜD Product Service Slide 22
Submitting for Testing Regulations, directives and laws tell us products must be safe Technical standards give the means to prove safety IEC 60065 (AV equipment) IEC 60335 (household appliances) IEC 60950 (office and IT equipment) IEC 61010 (lab and control equipment) etc (specialist standards for other safety requirements) TÜV SÜD Product Service Slide 23
Submitting for Safety Testing Types of Safety Testing There are two approaches to safety testing Type testing: A one-off test on a sample of the product. Does not guarantee future product quality CE marking (for inclusion in technical file) CB Scheme (as basis for obtaining international acceptance & certification) Product certification: An ongoing partnership between manufacturer and certification body Initial testing of product Regular factory inspections where the product is made Certification mark permitted on the product Benefits of certification: Market access Consumer confidence Ongoing production quality Marketing advantage TÜV SÜD Product Service Slide 24
Submitting for Safety Testing Preparing in Advance: Design Stage Ensure design engineers are aware of safety requirements Seek advice from 3rd parties Enlist a consultant Consider a 3 rd party design review at an early stage of development Highlight any issues with the design Avoid re-design at a later stage Advice on component and material selection TÜV SÜD Product Service Slide 25
Submitting for Safety Testing Preparing in Advance: Design Stage Select pre-approved components and materials Reduce testing requirements Avoid potential failures Avoid having to change / re-source components Know your target markets UL and EN standards required for US and EU respectively TÜV SÜD Product Service Slide 26
Submitting for Safety Testing Requesting a Quotation Know your market Different test requirements for different markets Provide as much information as possible Product description / Brochures Photos / drawings Define power requirements Specify other facilities required (water, drainage, compressed air etc.) Fan speed control or air conditioning incorporated in the product Timescales required Budget constraints TÜV SÜD Product Service Slide 27
Submitting for Safety Testing Collate documentation before submitting Circuit diagrams & schematics Parts listings Mechanical & exploded drawings Critical component approvals information User and service manuals Rating label drawings List all accessories and parts required to be included with the product Define product families List all production facilities Ensure that the equipment is suitably configured for testing Worst case normal load conditions Prepare support equipment loads & cabling Provide clear operating instructions Write test software TÜV SÜD Product Service Slide 28
Submitting for Safety Testing Find out how many samples are required Complete product Power supplies Fuses, thermal cut-outs and other components Plastic parts On-site testing can often be the most efficient way of testing 100% of our engineers attention All your support facilities available Issues can be resolved face to face Fix your problems and clear non-compliances in parallel with the testing TÜV SÜD Product Service Slide 29
Submitting for Safety Testing Safety Critical Components & Materials Which Components are Safety Critical? Mains components: Mains plugs and cords Appliance couplers Fuse and fuseholders Wiring Power supplies X and Y-capacitors Transformers Other components: DC-DC converters Fans Enclosure materials Connectors PCB material Thermistors and PTCs TÜV SÜD Product Service Slide 30
Submitting for Safety Testing Safety Critical Components & Materials Component approvals IEC and EN investigations Current test certificate / report Note - some certificates have expiry dates Relevant IEC / EN standard In English From a CB, CCA or LVD accredited test laboratory (e.g. TÜV SÜD Product Service, VDE) Must include all relevant information some certificates are made up of many pages, all should be supplied If the test certificate does not give all of the required details then a copy of the test report may be required e.g.: power supply units more detailed information is required i.e. maximum rated ambient, classification of outputs, method of mains isolation TÜV SÜD Product Service Slide 31
Submitting for Safety Testing Safety Critical Components & Materials Self-declaration may also be accepted A certificate of conformity (CofC), manufacturer s declaration You remain responsible that the component is suitably approved This will be stated in any test report issued For a Third Party Certification, self-declaration is NOT acceptable 3rd party approved components MUST be used (e.g. TÜV SÜD PS, UL, CB, VDE) Note: do not rely statements like designed to meet or complies with ENxxxx These are NOT evidence of suitable component approvals TÜV SÜD Product Service Slide 32
Submitting for Safety Testing Safety Critical Components & Materials Flammability of Materials Plastic or non-metallic materials Compliance may be based on testing, and/or suitable documentary evidence Applicable standards: UL 94, IEC 60695 To assess the suitability of the materials, the following information is required: Manufacturer name (eg: GE Plastics, 3M) Name and part number of the material (e.g. Lexan, LX437) Approval body s file number (e.g. UL E12345) Flammability rating (e.g. V-1, V-2, HB, HF2) Thickness of material used TÜV SÜD Product Service Slide 33
Submitting for Safety Testing US / Canadian Investigations All safety critical components and materials must have current NRTL (Nationally Recognized Test Laboratory) listing or recognition The following information is required: The name of the company that holds the NRTL approval The type or model number of the component The NRTL file number (e.g. UL E56789) Obtain a copy of the NRTL approval From the approval holder, or the manufacturer of the component/part or from the NRTL s website TÜV SÜD Product Service Slide 34
Submitting for Safety Testing US / Canadian Investigations Transformers with an insulation Class higher than Class A NRTL certification requires a NRTL Recognised insulation system (OBJY2) to be employed. A recognised insulation system is a combination of materials that have been tested together for suitability of use in prolonged high temperature conditions TÜV SÜD Product Service Slide 35
Submitting for Safety Testing UL Power Supply Listing Model number Ratings TÜV SÜD Product Service Slide 36
Submitting for Safety Testing Example of VDE listing Model number Ratings TÜV SÜD Product Service Slide 37
Submitting for Safety Testing CB Certificates Test report forms part of certificate Ratings Model number Test standard Number of pages TÜV SÜD Product Service Slide 38
Submitting for Safety Testing NRTL Certificates Ratings Model number Test standard Number of pages TÜV SÜD Product Service Slide 39
Submitting for Safety Testing On-Line Approvals Links TÜV SÜD Product Service https://www.tuev-sued.de/industry_and_consumer_products/certificates x ASTA and BEAB http://www.astabeab.com/buyers.htm x CSA http://directories.csa-international.org/ x ENEC http://www.enec.com/dev/recherche.php?soc=enec&s=2 x Intertek http://etlwhidirectory.etlsemko.com/webclients/its/dlp/products.nsf/$$search?openform x ÖVE http://www.ove.at/puz/reg/form.php x UL http://database.ul.com/cgi-bin/xyv/template/lisext/1frame/index.htm X VDE http://www.vde.de/vde_pi_en/zertifizierungsregister/detailsearch TÜV SÜD Product Service Slide 40
Submitting for Safety Testing Hints and Tips Ensure support is available during testing Select a nominated technical contact Attend on first day to assist with set up Respond to non-compliances as a package Advise when you are going to send new samples TÜV SÜD Product Service Slide 41
Summary Basic Safety Principles Why safety? What hazards to consider Submitting for Safety Testing Selection of test standards Hints and tips to minimise failures
Questions and Answers Thanks for listening! Any questions? TÜV SÜD Product Service Slide 43