These guidelines cover the more common problems in product safety engineering.
Own the standard
- Obtain and maintain a current copy of all applicable product safety standards
- Read the standard
- Apply the standard during initial product design
Select proper components
- Use components that are properly third-party certified. NRTL-certified parts usually meet this requirement. CE Marking and CB-Certified components may require additional investigation and testing and special surveillance.
- Obtain conditions of acceptability for critical components
- Use components within their ratings
- If custom uncertified components must be used, have them assessed as early as possible
- Understand what is required of the enclosure: Does it need to provide mechanical protection? Electrical protection? Fire hazard protection?
- Select materials that can meet the tests required by the standard
- If polymeric material is used, know what characteristics are critical to its acceptability
- If conductive material is used, then consider spacing from circuits as well
Openings in products
- Keep openings to a minimum
- Design ventilation or other openings to not only meet your service requirements, but also to allow the product to maintain proper integrity and reduce risk of electrical shock, fire or mechanical hazard
- Avoid openings in the bottom. If not possible, then be aware of requirements and tests that may be necessary.
- Avoid openings in the top. If not possible, then be aware of requirements and tests that may be necessary.
- Know how each different circuit will be classified as to potential hazard: Is it mains? SELV? TNV? Other?
- Know what is required for physical distances, thickness of insulation, type and amount of insulation
- Intended altitude of use can affect selection of requirements
- Properly assess the nature of the voltage involved when assessing spacing requirements: Is the voltage sinusoidal? Is it direct current? Are there repetitive peaks such as those typical in a switched-mode power supply?
- Special requirements apply where conductive coatings may be used
Plastics and printed wiring boards
- Most plastics will be required to have at least a flame rating
- Know what is required for each plastic: HB? V0? 5V?
- Take into consideration the plastic’s use: Is it for the enclosure? Is it an insulator?
- Special requirements apply to use of conductive coatings
- Same thing applies to printed wiring board materials
- Additional requirements may apply for printed wiring boards supporting hazardous energy
- Products employing laser emitters are covered by the U.S. Code of Federal Regulations, Title 21, Part 1040, and the Canadian Radiation Emitting Devices Act, REDR C1370
- There is some harmonization with IEC 60825-1 classifications
- Products producing ionizing radiation are covered by the U.S. Code of Federal Regulations, Title 21, Part 1020, and the Canadian Radiation Emitting Devices Act, REDR C1370
- There are often additional requirements for products that produce ultraviolet emissions too.
- In the United States it is often necessary to apply the requirements of UL 50 and in Canada CSA C22.2 No. 94
- Additional requirements apply that are beyond IEC 60529 compliance declaration
- UL 50/CSA C22.2 No. 94 have requirements that include assessment of the plastics for UV exposure and of gaskets relied upon for ingress protection
- Where conductive coatings are used, additional requirements may apply
Product markings and documentation
- Identify all required markings. Place them on the product as intended or generate drawings showing the marking text and where it will be placed:
- Electrical ratings
- Model and manufacture or trademark
- Safety warnings
- Installation instructions & user/operating instructions
Preparing for surveillance
- Prepare for at least two factory surveillance visits per year
- Be prepared to show that the product being labeled remains compliant
- Production line testing may be required; this usually includes electric strength testing and earthing continuity testing
- When you get the descriptive test report, review it; this is what our inspectors use to conduct inspections