Which unit combination is used to express porosity limits in the PQ weld criteria?

• A. Inches are used for all measurements
• B. Millimeters for porosity and weld length (with inch equivalents in parentheses)
• C. Centimeters for all measurements
• D. Meters for all measurements

Answer: (B)

Porosity and the length over which porosity is evaluated are given in millimeters because the PQ criteria use metric units as the standard. Small flaws like porosity are measured with fine precision, and millimeters provide that level of detail better than centimeters or meters. The length of weld being checked also needs to be described in a precise, small-unit scale, which millimeters supply. Providing inch equivalents in parentheses helps inspectors who are more accustomed to imperial units to convert quickly, keeping communication clear in mixed teams or field work. This combination—millimeters for porosity size and weld length, with inch equivalents in parentheses—is the most practical and accurate approach.