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Comprehensive Guide to Product Safety Design Principles

Discover crucial elements of product safety design including insulation, component selection, labeling, wiring, and more to meet international standards and safeguard against hazards.

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Comprehensive Guide to Product Safety Design Principles

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  1. Fundamentals of Product Safety DesignBerri RemenickNARTE Certified Product Safety EngineerProduct Safety ManagerWashington Laboratories, Ltd.September 14, 2007Gaithersburg, MD

  2. Outline • Background • Insulation • Component Selection • Labeling • Documentation • Wiring • Resistance to Fire

  3. Product Safety Requirements • US/Canada: NRTL Listing (cULus, cTUVus, cCSAus) • Legal requirement, customer requirement, or to limit liability • Europe: CE Mark • Legal requirement • Others: CB Report To facilitate International Approvals.

  4. Product Safety Hazards • Electric Shock Hazards: Accessible parts over 30Vrms, 42.4Pk, or 60VDC. • Energy Hazards: Energy level over 240VA or 8A • Fire Hazards: Materials, Enclosure, Abnormal conditions • Mechanical Hazards: Moving parts, Sharp edges, Tipping, Handles • Radiation Hazards: Lasers, UV, Sonic • Thermal Hazards: External temps, component temps

  5. Product Safety Design Guidelines

  6. Design Requirements Protection against electric shock and energy hazards: • The OPERATORcan not touch bare or inadequately insulated parts at hazardous voltage or energy levels. • Hazardous Voltage Level is typically >30Vrms, 42.4Vpeak, or 60VDC. Hazardous energy is typically >240VA or 8A Protection may be provided via insulation, guarding or interlocking.

  7. What is Insulation? • Physical barrier between two parts (tape, plastic shield, wire insulation, enclosure, etc) • Separation between two parts through air or along a surface (creepage or clearance distance)

  8. Insulation Types • Functional / Operational Insulation (DC input to ground) • Basic Insulation (Primary to Ground, TNV to Ground, TNV to SELV) • Reinforced Insulation (Primary to Secondary)

  9. Reinforced Insulation Example

  10. Spacings (Creepage / Clearance) • Based on the required insulation for your circuit. • Based on the maximum working voltage for your circuit. • Based on the environment the product will be used in (Pollution Degree) • Based on the PCB material: Material Group - Comparitive Tracking Index (CTI)

  11. Creepage / Clearance

  12. Creepage / Clearance Creepage • Creepage = distance between two points along the surface • Creepage is measured on 1:1 artwork or on a blank board • Locations of circuits determined by reviewing schematics Clearance • Clearance = distance between two points through the air • Clearance is measured on a populated sample

  13. Component Selection • Safety Critical Components must have the appropriate approvals or additional evaluation will be required. • Safety Critical Components: • Devices in the AC path (inlets, fuses, switches, power supplies, transformers, etc.) • Motors, fans • Power conversion components (AC-DC or DC-DC Converters) • Any isolation component (Transformer, Bridging Capacitors, MOVs,) • Wiring • Batteries • Others depending on their application.

  14. Component Selection • For NRTL approvals, all components must be UL approved. • For CE Mark approvals, all components must have a European approval such as CE, TUV, VDE, etc. (exception: fuses and wiring can be UL approved) • For GS or CB Scheme approvals, all components must have a TUV, VDE, or other official European approval. CE Mark is not acceptable for these approvals. • Approval certificates required (TUV or VDE Cert, CE Declaration of Conformity, UL File number, etc.)

  15. Labeling and Marking • Rated voltage, current or power, frequency • Manufacturer’s name or registered trademark. • Model or type number. • Fuse replacement info (if applicable). • IEC symbols wherever possible. • Warnings and Cautions appropriate for the particular equipment.

  16. User Instructions • Installation Instructions - information regarding mounting, connection to the supply, ventilation, input ratings, etc. • All information regarding use, cleaning, maintenance (if necessary). • All safety warnings and cautions. • Rack Mount instructions. • Safety-related information to be in appropriate language of the country you are exporting to. • Some standards have entire sections of specific info that must be in manual.

  17. Wiring and connection to the supply – Protective Earth - • PE conductor must be green/yellow or bare insulation conductor • PE connections must be double secured so that both the wire and insulation are crimped • IEC PE symbol shall be marked adjacent to PE stud • PE conductor shall connect to chassis directly from input (inlet, terminal block, etc). • PE conductor must be secured with washer and locknut. • Additional PE conductors can be secured to PE stud with a second washer and locknut.

  18. PE Stud Example EMI FILTER CHASSIS TO OTHER CONNECTION GROUNDS MECHANICALLY SECURED GROUND: GREEN/YELLOW WIRE SAME GAUGE AS OR BIGGER THAN SUPPLY

  19. Wiring and connection to the supply – Primary Wiring - • All AC wires shall be double secured. Double securement can be met by: Double crimp connector or Single crimp connector and cable tie or Single crimp connector and shrink sleeving. • AC wiring shall be rated for the maximum working voltage and current. • AC wiring shall be isolated from low voltage wiring or low voltage parts, this can be accomplished by: Shrink sleeving the AC conductors or By routing the AC conductors away from low voltage wires and securing with cable ties or By using UL1015 Reinforced Insulation wire.

  20. Resistance to fire and control of fire spreading • Enclosures, components, and other parts shall be constructed such that propagation of fire is limited. Flammability of enclosure, internal, and external parts shall be adequate for the use of that part. • Flammability ratings • 5VA – Most fire resistant • 5VB • V0 • V1 • V2 • HB40 • HB75 - Least fire resistant • Foamed materials: • HF-1 • HF-2 • HBF

  21. Resistance to fire and control of spread of fire • 60950-1 • Fire enclosure openings shall be: • Top and side openings shall be: • less than 5mm in any dimension or • less than 1mm in width regardless of length or • meet the 5 projection rule. • There shall be no bottom openings (some exceptions allowed but difficult to meet)

  22. Methods for Meeting Fire Requirements in 61010-1 • Requirement: There shall be no spread of fire outside the equipment in Normal or Single Fault Conditions. • Methods of Compliance: • A: Testing in single fault conditions • B: Reducing sources of ignition within the equipment • C: Containing fire within the equipment should it occur

  23. Requirements for fire enclosure • - Components in primary circuit • - Components in secondary circuits that are not • supplied by LPS • - Components in secondary circuits supplied by LPS • but not on V-1 material • - Components with unenclosed arcing parts • - Insulated wiring

  24. Parts not requiring Fire Enclosure • - Motors • - Transformers • - Wiring and cabling insulated with PVC, TFE, PTFE, • FEP, neoprene or polymide • - Connectors in secondary circuits powered by less • than 15VA or LPS • - Components in secondary circuits supplied by LPS • and on V-1 material • - Components in secondary circuits supply by max • 15VA and on HB785 if <3mm or HB40 if >3mm.

  25. Plastic materials used for fire enclosure • Movable equipment <18kg: V-1 or pass A.2 HWI test (if <13mm from high temp parts) • Movable equipment >18kg or stationary equipment: • 5VB or pass A.1 HWI test (if <13mm from high temp parts) • Materials filling an opening in a fire enclosure: V-1 or pass A.2

  26. Plastic materials used inside a fire enclosure • Inside a fire enclosure: V-2 or HF-2 or pass A.2 • Exceptions: • Electronic components (IC’s, optos, etc.) mounted on V-1. • Wiring and connectors insulated with PVC, TFE, PTFE, FEP, neoprene, or polymide. • Clamps, cable ties. • Wire marked VW-1 or FT-1 or better. • Others….

  27. Plastic materials used outside a fire enclosure • Material outside fire enclosure: • HB75 if <3mm or HB40 if >3mm or HBF or Glow Wire test at 550C • Connectors: • V-2 or pass A.2 or mounted on V-1 and be small or be in secondary circuit with max 15VA • Exceptions: • Electronic components (IC’s, optos, etc.) mounted on V-1. • Wiring and connectors insulated with PVC, TFE, PTFE, FEP, neoprene, or polymide. • Clamps, cable ties. • Others….

  28. Washington Laboratories, Ltd. • Help you select the proper Directives and Standards to apply to your product. • Evaluate and test your product to the appropriate Safety Standard and offer solutions for non-compliances. • Provide product design assistance. • Obtain cTUVus, cCSAus, cULus, GS Mark, and other approvals. • WLL is a Partner Test Lab for TUV Rheinland for 60950-1, 61010-1, and 60065

  29. Washington Laboratories, Ltd. • Give us a call or send us info about your product - we’re here to help! • Berri Remenick • Product Safety Manager • Phone: 301-473-1255 • Fax: 301-473-1257 • E-mail: berrir@wll.com

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