Performance of cryogenic demountable indium seal at high pressures.

An essential challenge in seal design is to provide an ultra-low leak rate at cryogenic temperatures and high pressures. In this paper, the performance of demountable indium seals under a charging pressure of 8.5 MPa A and at cryogenic temperatures down to −190 °C was investigated. Three indium seal structures with a diameter of 30 mm were specifically designed and tested. All three structures went through both room temperature and cryogenic temperature tests in cycles with a pressure of up to 8.5 MPa A. In addition, leak rate experiments regarding the creep relaxation effect of the indium ring were conducted. The results showed that the leak rates of all three structures were lower than 1 × 10−10 Pa m3 s−1 at both room temperature and cryogenic temperature with the pressure up to 8.5 MPa A when the torque was 8 or 12 N m. It was concluded that the linear loads for achieving a successful indium seal were 163, 171, and 220 N mm−1 alongside its circumference for the 2 mm indium M-T structure, the 3 mm indium M-T structure, and the Z-shaped seal structure, respectively. Furthermore, although the torque slightly dropped after the assembly due to the creep relaxation effect, the leak rates of the structure were still lower than 1 × 10−10 Pa m3 s−1 three days after the assembly. The present work is helpful for designing ultra-low leak rate demountable indium seals at cryogenic temperatures and high pressures.