Interlaboratory “Pilot Run” Study of Small Heat-Flow-Meter Apparatus for ASTM C 518

Thermal conductivity measurements of a high-density glass-fiber thermal insulation material near 24°C are presented for the determination of the precision and bias of ASTM Test Method C 518. The measurements have been conducted by 13 laboratories using small (305 by 305-mm) heat-flow-meter apparatus on three specimens of high-density glass-fiber thermal insulation material that were circulated among the laboratories. Test results are analyzed using ASTM Practice E 691 and subsequently compared to measurements of the same specimens conducted in a guarded-hot-plate apparatus using ASTM Test Method C 177. The 95% repeatability and reproducibility indexes for precision have been determined to be no worse than 1.1 and 4.0%, respectively. A method for estimating bias is presented.