Portable Microleak-Detection System

Langley Research Center, Hampton, Virginia

Thursday, November 01 2007 The control volume has a known size and is instrumented with pressure and temperature sensors. In use, the control volume is evacuated, then disconnected from the vacuum pump, and then the pressure and temperature are measured as the leaking gas flows into the control volume. By use of the ideal-gas law, the rate of leakage can be calculated from the temperature and measured rate of increase of pressure.

An unusual feature of this system is a heating/cooling subsystem that includes a tube embedded in the flexible adhesive seal. A heating or cooling liquid can be circulated through this tube to maintain the seal at or near room temperature, where it is most effective, regardless of the temperature of the test object or the environment. The heating/cooling subsystem is essential, for example, for maintaining an effective seal for testing a tank, pipe, valve, or other object that contains liquid hydrogen or other cryogenic fluid. The heated/cooled seal enables testing at temperatures from –455 to +350 °F (about –271 to +177 °C), even in the presence of distortions caused by mechanical and thermal loads applied to the test object.

This work was done by H. Kevin Rivers and Joseph G Sikora of Langley Research Center and Sankara N. Sankaran of Lockheed Martin Space Operations.