The dimensional stability of polychlorotrifluoroethylene (PCTFE) valve seats used in gas cylinder regulator applications was evaluated by thermomechanical analysis (TMA). Testing focused on two commercial grades of PCTFE, Kel-F® 81 and Neoflon® CTFE M400H, and on actual PCTFE valve seats obtained from different manufacturers. The effects of resin grade, percent crystallinity, and process history on TMA deflection were evaluated. TMA results frequently showed low-temperature dimensional instability between 40 and 70 °C. The corresponding permanent height change resulting from brief cyclic heating of as-received material to 150 °C ranged from to +3.9 to -8.5 percent. Complementary differential scanning calorimetry data indicated the origin of the dimensional instability to be anomalous relaxation at or close to the glass transition. The data are discussed in the context of several proposed valve seat failure mechanisms: contaminant promotion, flow resonance, and flow friction. The combined data show significant property variations within the PCTFE resin family. Such property variations could have important implications for the use of PCTFE in valve seat applications.
Objectives-To address the causes and prevention of fire incidents involving aluminum bodied oxygen regulators used by firefighters or emergency medical technicians. Conclusion-Development of the ASTM standard and associated testing will be helpful to oxygen regulator designers to design safer oxygen regulator systems. As well, there are a number of additional safe handling procedures that firefighters and emergency medical technicians can follow to reduce the risk of a regulator fire. (Injury Prevention 2001;7(Suppl I):i34-37)
Methods-The
Adiabatic compression testing of components in gaseous oxygen is a test method that is utilized worldwide and is commonly required to qualify a component for ignition tolerance under its intended service. This testing is required by many industry standards organizations and government agencies. This paper traces the background of adiabatic compression testing in the oxygen community and discusses the thermodynamic and fluid dynamic processes that occur during rapid pressure surges. This paper is the first of several papers by the authors on the subject of adiabatic compression testing and is presented as a non-comprehensive background and introduction.
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