Cryogenic Laboratory

The Institute disposes of one of the oldest cryogenic laboratory among the native Scientific Research Institutes. Three helium liquefiers (G-3, G-5 and G-4 which have the production 35 to 100 liters per hour) with the reciprocating expansion engines provide with liquid helium for all of the low-temperature experimental institute studies, liquefying to 2000 - 2500 liters during a month.

The IPP helium liquefiers are the prototypes of the first native commercial cryogenic engine helium plants (G-45, CHU-150/4.5), going today by CHU-600/15-150/4.5-40. The majority of the former SU Scientific Research Institute cryogenic laboratories have these units.

The works on the G-4 liquefier automatic control were performed during 1995 - 1997 years. The liquefier automatic control system (ACS) principle objectives were not only the automatic stabilization of the liquefaction regime and also the automatic setting in motion and stopping, the liquefaction mode optimization and ACS dialogue regime with the training functions.

The created ACS realizes the following functions:

• scanning and adaptation of the active liquefier information
• the operative information indicating on the mnemoscheme and in the histogram
• the colour indication of the controlled parameters leaving the working region
• the stabilization of the optimum liquefier's parameters and the automatic filling of the liquid helium vessels
• the automatic setting in motion and stopping
• the optimization of the liquefaction mode, including the optimization of the admission valve opening time for the expansion engine efficiency and the optimization of the engine inlet temperature for the fraction liquefied.

Furthermore the operator can: manual control a liquefier, change control parameters dates, during manual control connect the separate automatic control loops. The training function occurs by displaying the controlled mode operation sequence on a monitor screen during manual control. The program facilities have program simulator reproducing the mode operations sequence without liquefier natural start.

The Automatic Control System is based on the IBM PC AT - compatible with information-management functional modules that can be plugged into free PC slots.

ACS includes:

• IBM PC AT - compatible computer
• ADC (Analogue-Digital Conversion) module: 16 10-bit inputs
• PWM (Pulse-Width Modulation) module: 10 dry contact outputs
• DIO (Digital I/O) module: 10 dry contact outputs
• Detector signals Standardizing Unit with possibility of working with individual scale temperature detectors
• Amplifying modules.

As a pressure, temperature and liquid's helium level detectors, standard detectors like "Sappfire-22", TPK and TSP thermoresistors, "Krus" superconductive liquid's level detectors "SPO-39V 1" precision varistors are used. Executive mechanism are made on the base of the standard "RD-09" reversible drive. ACS includes the Software Tools (program package) which provide tuning and debugging without participation of specialist in programming.

Liquefier's G-4 ACS can be used for the commercial liquefiers "CHU-600/15-150/4.5-40" modes and another reciprocating expansion engines liquefiers practically without alternation.

Tel. (7-095)137-61-74, Fax. (7-095)938-20-30
e-mail: butkevit@kapitza.ras.ru

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