The UL Product Safety Audit: Inside the Process

William D. Webb

Being prepared for an unannounced UL audit is key to maintaining UL certification and using the UL mark.

Getting the UL mark is a rigorous process. Once a manufacturer has earned the right to place the UL mark on a product, it is equally important to maintain its UL product report to ensure its continued UL listing.

To verify compliance, UL uses a Follow-Up Services Procedure. This procedure includes unannounced and nearly unrestricted access to a manufacturer's production facility where listed products are fabricated, assembled, tested, stored, and shipped. As part of the procedure, a detailed description of the product (the UL report) is used as a point of comparison during these unannounced examinations of a listed product.

Under this program, UL field representatives conduct unscheduled quarterly audits in an assigned territory, setting up and coordinating each audit. Because the audits are not announced to the manufacturers, this task can be challenging. Auditors must be flexible, creative, and sometimes lucky to make the whole process work. This article presents an overview of the UL audit process, including how to prepare for it and how to implement precautionary measures. It also presents a case study of an actual UL audit.

Preparing for an Audit

Update UL Product Report. To prepare for an audit, the first order of business is to verify that all UL file changes and report updates, if applicable, have been added to the manufacturer's UL product report. These changes include component substitutions, additions, or deletions requested by the manufacturer. Such design changes are generally triggered by product upgrades, obsolete parts, performance improvements, and cost considerations.

When a manufacturer requests a change, UL will review the change, update its report, and send a copy of the updated report's affected pages (with implementation instructions) to both the manufacturer and the UL representative. If the manufacturer has not implemented report updates before an unannounced audit, the UL representative generally allows time to implement such updates before continuing with the audit.

The Audit Process

On the day of an unscheduled facility visit, the UL representative may arrive at any time to perform the product safety audit (see Figure 1). The cognizant compliance person (compliance or agency engineer or other person responsible for product safety compliance issues) gets the call from the switchboard. The compliance person should be ready at all times and be in a position to set aside other tasks to focus on the audit process and the UL representative. Together, they determine an appropriate action plan that will allow the auditor to review the selected product. The size, complexity, number of problems encountered, and number of UL-listed products due for inspection dictate the amount of time required for the audit.

Although the UL representative may have a specific product in mind for review and audit, extenuating circumstances can preclude an audit of the selected product. One problem with an unannounced audit is that the chosen product may not be in production at the time of the visit. In this case, a product that is in production could be substituted, provided that product is also UL listed. To continue, however, the UL representative must have on hand the UL report for the alternate product; otherwise, the audit is over. The auditor usually returns within a few weeks.

Once a UL representative becomes familiar with a manufacturer's production cycles, audit rescheduling becomes less frequent and eventually unnecessary. As a remedy for this anomaly, however, UL plans to institute two new procedures in 2002. The first calls for the UL representative to contact the manufacturing facility to identify anticipated production dates. The second, called production ready audit, involves checking a manufacturer's readiness for a UL audit. Under the new program, when a product to be audited is not in production, the UL representative will instead perform a production ready audit. The new procedures are expected to minimize the number of rescheduled audits.

Verifying Compliance. The UL representative conducts the audit using UL's Follow-Up Services Procedure, which prescribes required actions and specific responsibilities. Manufacturers should be ready to present well-documented agency reports.¹

Most audits take place on the production floor, or wherever the audited product is assembled and tested. Most UL auditors follow the flow of the report (see Figure 2). At this stage, the UL representative verifies compliance of the product and its components and assemblies based on the information given in the UL report. The report includes photos of both external and internal portions of the product and a detailed description of relevant components. Each listed item is identified with a numbered balloon and an arrow or line indicating its location on the photo (see Figure 3). For each numbered balloon, a corresponding item number and descriptive paragraph details component specifications as well as any agency (UL, CSA, etc.) recognition, listing, or certification.

Figure 2. UL safety basic audit sequence.

Figure 3. Representation of a picture with balloon numbering system typically used in a UL report.

Plastic Parts. Plastic components such as line cords, panels, bezels, meter housings, consoles, and touch panels are often shipped in bulk to a warehouse or stockroom and therefore must be audited to ensure that the appropriate markings appear on each item. To verify compliance for such parts, the UL representative makes special arrangements to view them.

Controlling compliance of polymeric components involves instituting a set of procedures that includes vendor cooperation. It is the manufacturer's responsibility to provide verification of compliance to the UL standard. For example, if the UL representative is unable to verify line-cord compliance locally, the vendor for that cord must be contacted and asked to verify compliance in writing. Verification usually entails providing a copy of the UL yellow card or similar document. The document can be faxed or e-mailed to satisfy the audit process. This yellow card (or reference page) comes from a listing of all UL-recognized and -listed parts. The list is available in book form, and on UL's Web site (http://www.ul.com).

Noncompliance issues are not limited to obvious technical problems, such as the use of a component that does not appear in the product's UL report. Other problems can arise, and they must all be addressed quickly. It is important to note that if a problem is identified, manufacturers should take the time to correct it completely. Many labor-hours can be wasted if the same issues must be addressed repeatedly. Closure is essential in any audit process.

Case Study

For this audit, the product selected —a tabletop centrifuge—was in production. However, as a precaution, the UL representative brought UL reports for all products listed for the company. The centrifuge was listed to UL standard 3101. The auditor's primary task was to compare the component data listed in the report with the actual components and assemblies being used in production.

The product went through the first few sections of the report with all descriptions, mechanical measurements, and primary components (power input cords, power entry modules, circuit breakers, power transformers) matching the product as listed in the report. Similarly, all secondary components (relays, sensors, printed circuit components) matched the report with no discrepancies.

The UL representative, however, noticed that one printed circuit board (PCB) was not labeled with a flame rating (see sidebar). The PCB part number was in place and correct but there was no indication, as required by UL, of the material's flame rating. Although some sort of marking was visible on the PCB, it could not be identified as either a rating or a logo, even under magnification. The company contacted the manufacturer to resolve the problem, and thus complete the audit and avoid a variation notice. Upon investigation, the PCB manufacturer found that the logo was on the product, but it had been photographically reduced so much that it became unrecognizable. The PCB manufacturer was able to confirm compliance in writing. In addition, the PCB manufacturer took responsibility to correct the problem.

Because the centrifuge manufacturer was able to reconcile the compliance issue while the UL representative was at the site, no variation notice was issued. This concluded the audit.

Variation Notices

If the compliance of all questionable components could not have been verified in writing (or otherwise confirmed) while the UL representative was at the facility, a variation notice would have been issued. Once such a notice is issued, a UL program engineer reviews the circumstances to determine whether to allow the manufacturer to continue to use the UL mark. Continued use requires that a manufacturer provide proof of compliance within 15 days (at the discretion of the services engineer).

The UL Flame Rating Printed circuit board (PCB) material (e.g., G10) is a polymeric, and it must be labeled with a flame rating to satisfy UL requirements. The flame rating per UL 94 defines a polymeric part's resistance to fire. Typical ratings for PCB material are 94V-1 or better. The lower the number, the higher the flame rating (e.g., 94V-0 has a higher rating than 94V-1). The flame rating is indicated in one of two ways. The flame rating itself is printed, in clad, on the PCB (94V-1 etc.) or the PCB manufacturer's logo is printed, in clad, on the board. If a PCB manufacturer is UL authorized, its company logo can be traced back to UL's authorized PCB manufacturers list. To be authorized in this category, a PCB manufacturer is subject to independent UL inspections of its manufacturing process and materials. All polymeric components must be flame rated and the rating must be verifiable.

Alternatively, use of the UL mark could be delayed until UL verifies that the product is in compliance. If compliance cannot be verified after an agreed-upon time and no compromise can be reached, the UL listing for that product could be terminated. It could be reinstated if a resolution were reached between UL and the manufacturer. The noncompliant component or assembly type and its effect on the product's overall safety often dictate the consequences of a nonconformance.

Conclusion