Upgradation of liquid nitrogen distribution lines of large thermal vacuum chamber at SAC, Ahmedabad

A 5.5m Dia. Thermal vacuum chamber was commissioned in 2002 to cater to the test requirements of electro - optical payloads developed at SAC, Ahmedabad. About 550 meter LN₂ transfer lines were installed for supply and distribution of LN₂ to various system elements. Out of this about 320 meter lines run in the clean room which were Superinsulated one and rest 230 meter located within the plant room and LN₂ yard area were PUF insulated one. Over a period, PUF insulation efficiency got deteriorated and vapor barriers no longer effective. This paper describes the upgrade task accomplished to improve overall loss rate of LN₂ lines and overall LN₂ consumption. It also describes the technical efforts and experiences gained during up-gradation of PUF insulated lines with S.I. lines ensuring minimum system down time and quality tests performed at segment level and assembly level for these lines.