New system for control and monitoring of a helium liquefaction plant implemented in LabVIEW

Abstract: This master’s thesis report describes the development of a new system for control and monitoring of a helium liquefaction plant which has been carried out at Kryolab, Lund University. At the plant, helium gas is purified and then cooled in several steps until it condensates. The plant is very similar to the ones constructed today, but Kryolab wished to replace the outdated control system. The new system has been programmed in LabVIEW and is run on a CompactRIO from National Instruments. It replaces the original analogue boards and a complementary software based system. In the early stages of the project the behaviour of the process was studied. Programs for plotting and logging were implemented for this purpose and used along with other available resources such as manuals, drawings and collected data from the plant. The code has been developed iteratively and every part of it has been tested before it was used to control the real plant. To verify the program behaviour in different situations a user interface with the possibility to set sensor values manually has been developed. New functions have been tested and added successively. The new system presents more data and a better overview of the process than previously available. Increased possibility to manually control some valves and to adjust trigger and set points used in the control has also been added. A new alarm system has been implemented and the start and stop sequences have been further automated. The project has been very successful. The improved overview aids in identifying potential problems and their causes. It has proved possible to run the plant under more difficult circumstances with the extended ability to adjust the control system. The opportunity to supervise and control the plant from a computer or telephone outside Kryolab has reduced the need to go to Kryolab outside regular working hours and made it possible to avoid some emergency stops. The new system provides the operator with improved insight in how the control works. The aspiration is that this will facilitate further development and improvement of the system.