Automating Helium Liquefaction

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"Thanks to the NI products, recovery yields increased continuously, which has provided significant cost savings for the university."

- Florin Cristian BEURAN, Université Pierre et Marie CURIE

The Challenge:
Ensuring continuous, remote automated and manual monitoring of helium storage in conjunction with the operation of a previous generation liquefier.

The Solution:
Establishing distributed intelligence with a network of NI CompactRIO systems communicating with each other to automate the operation and control of all of the helium liquefaction facilities.

Florin Cristian BEURAN - Université Pierre et Marie CURIE

University laboratories consume large amounts of liquid helium, which is generally used for cooling and superconducting magnets for experiments carried out at temperatures close toc absolute zero. Nuclear fusion reactions in the core of stars produce helium constantly. Helium represents 25 percent of the visible mass of the universe, but is rare on Earth and very expensive. The most economically and environmentally friendly way to use it is in a closed circuit in which the gas is generated by evaporation of the liquid. Then it can be collected and channeled to the atmospheric pressure to the center of liquefaction where it is compressed to be stored, purified, and liquefied again.

One of the Most Modern Liquefaction Centers in Europe

The helium liquefaction center at the Université Pierre et Marie Curie, created in 2010, currently has 40 laboratory users. It is one of the newest liquefaction centers in France, but also one of the most modern in Europe because of its equipment and automation control. The center features gas management to prevent helium loss, improper use of the expensive tools, and explosions.

Significant Constraints

We needed an autopilot because facility operation is ongoing, the operations are complex, and human error is always possible. We used several independent programmable logic controllers (PLCs) to exchange data because of the range of facilities we needed to control and the hundreds of entries and digital and analog outputs we needed to manage. We also changed the amount of PLC I/O to cope with future facility developments. In addition, we faced important security constraints and a need to rapidly change certain critical parameters.

The combination of the NI CompactRIO platform and the NI LabVIEW Real-Time Module emerged as an ideal solution. The communication between the PC display and the CompactRIO systems used for automaton is transparent and more reliable, which leaves the programmer free to concentrate on  development.

Hundreds of Analog and Digital I/O Points

The network currently includes 15 NI cRIO-9074 controllers, each at the heart of a control cabinet. These cabinets pilot about 200 pneumatic limit contact valves and three compressors. The analog signals received by 20 NI 9203 analog input modules come from 50 pressure sensors, 20 temperature sensors, two purity of helium analyzers, and two superconducting probes for measuring the level of liquid helium. The digital signals received by 32 NI 9421 sinking digital input modules and eight NI 9425 sinking digital input modules are from 40 signal compressors, 50 switches, 20 pulse generators used for calculating the volumetric meters of gas flow from 15 detectors, and 400 end-position contacts of the automatic valves.

Software embedded on each CompactRIO controller analyzes the local data and sends the values ​​to the PC and other controllers. The PC, at the center of this network, displays data in the form of graphs and instantaneous numeric values and ensures a continuous data backup. We also developed an application using LabVIEW that displays a playback of the archives in the form of curves, so we can quickly identify faults in our facilities.

One advantage of using LabVIEW is the ability to easily plot multiple curves and set the display windows manually or automatically. Compared to other development environments, LabVIEW offers many preprogrammed technical solutions that facilitate the design work, such as communication protocols, elements of building a GUI, and multitasking applications.

CompactRIO: An Extremely Reliable Control Platform

Using CompactRIO empowered us to distribute automation functions over several controllers that communicate with each other. Therefore, we created an architecture that ensures we can maintain control of all liquefaction center facilities even if a failure occurs. From our experience of more than three years, the CompactRIO system is reliable and has never failed.

We attended a three-day training on using the LabVIEW Real-Time Module and also experimented with three CompactRIO controller networks. We developed the first functional version of the software in six weeks. In the following six months, we produced a second, more sophisticated version that included GUIs and data backup. The software application progressed in parallel with the construction of the facilities and activity of the liquefaction center. Automation of the new facilities increased our efficiency and productivity. Thanks to the NI products, recovery yields increased continuously, which has provided significant cost savings for the university.

Future Changes

In the future, we plan to migrate the calculations being made on the controller CPU to the FPGA. Additional changes include strengthening the surveillance networks outside the center of liquefaction and reporting real-time helium handling errors in user laboratories and integrating those issues into the existing automation. We also plan to expand the existing pipelines by connecting more than 20 additional laboratories in the already functional networks. Lastly, we plan to organize several months of LabVIEW training with students in Brevet de Technicien Superieur (BTS) automation so we can then involve them in the development of applications.

Author Information:
Florin Cristian BEURAN
Université Pierre et Marie CURIE
4, place Jussieu
BP 70 - 75252 Paris Cedex 05
Tel: + 33 (0)1 44 27 44 28

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