Operation
7-2
2) Set Opening of the Needle Valve
a. The needle valve on the helium vapor line in Figure A-2 is used to control
the natural convection flow within the Helium Re-liquefier.
b. Cryomech recommends that the needle valve is opened 2½ to 3 turns
from the fully closed position. Cryomech has preset it for optimum
performance with our test cryostat when there is liquid in the system.
Minor adjustments might increase the liquefaction rate for your
installation.
c. If ice forms on your vapor return line contact Cryomech for directions
3) Switch on the compressor package power at the MAIN circuit breaker. The RED OFF
light will illuminate. After a few seconds the display will read J-mobile and the system
will start to boot up, approximately a minute later the “Main Screen” will appear.
4) The compressor may be started by pushing the green “Compressor On” button, and
stopped by pushing the black “Compressor Off” button.
5) If the front panel display indicates “3 Phase Power Improperly Wired” after pushing
the “Compressor On” button, follow the instructions below.
6) Perform the following steps to correct the phase error in the compressor package:
a. Switch off the circuit breaker on the front panel of the compressor package.
b. Turn off the dedicated circuit breaker to disconnect the system from power at the
source (to prevent electrical shock).
c. Examine the power cord and wire colors at the panel circuit breaker. Re-wire the
input to the compressor by switching any 2 of the 3 input power wires.
d. Energize the breakers and press the “Compressor On” button. The compressor
package should now operate properly.
7.2 Normal operation behavior
7.2.1 Normal Compressor pressures
On start up a pressure differential should be noticed immediately between the high and
low pressure gauges. This differential will decrease as the cold head cools down.
The typical pressure differential is approximately 220 to 250 PSI (15.2 to 17.2 bar / 1520
to 1720 kilopascals) with a 5 to 10 PSI (.34 to .7 bar / 34 to 70 kilopascals) bounce on the
pressure gauge needles.
Actual operating pressures at various cold head temperatures are recorded on the Cold
Head Performance Table that is included with the cold head.
7.2.2 Normal sounds
When operating properly, the cryorefrigerator will emit a rhythmic squeak or chirp. This
noise is an indication of the proper flow of helium gas within the system.
7.2.3 Cool Down Time
The Helium Re-liquefier will cool down to 4.2K from room temperature and begin
condensing helium in approximately 4 hours
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