Fundamentals of Product Safety Design Berri Remenick NARTE Certified Product Safety Engineer Product

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

• Background
• Insulation
• Component Selection
• Labeling
• Documentation
• Wiring
• Resistance to Fire

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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.

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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

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Product Safety Design Guidelines
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Design Requirements

• Protection against electric shock and energy
  hazards
• The OPERATOR can 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.

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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)

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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)

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Reinforced Insulation Example
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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)

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Creepage / Clearance
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Creepage / Clearance

• Creepage
• Creepage distance between two points along the
  surface
• Creepage is measured on 11 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

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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.

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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.)

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Labeling and Marking

• Rated voltage current or power frequency
• Manufacturers 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.

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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.

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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.

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

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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

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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)
  

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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

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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

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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.

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Plastic materials used for fire enclosure

• Movable equipment
• V-1 or pass A.2
• HWI test (if
• Movable equipment 18kg or stationary equipment
  
• 5VB or pass A.1
• HWI test (if
• Materials filling an opening in a fire enclosure
  
• V-1 or pass A.2

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Plastic materials used inside a fire enclosure

• Inside a fire enclosure
• V-2 or HF-2 or pass A.2
• Exceptions
• Electronic components (ICs 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.

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Plastic materials used outside a fire enclosure

• Material outside fire enclosure
• HB75 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 (ICs optos etc.) mounted
  on V-1.
• Wiring and connectors insulated with PVC TFE
  PTFE FEP neoprene or polymide.
• Clamps cable ties.
• Others.

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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

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Washington Laboratories Ltd.

• Give us a call or send us info about your product
  - were here to help!
• Berri Remenick
• Product Safety Manager
• Phone [phone]
• Fax [phone]
• E-mail berrir_at_wll.com