Maintenance Procedures
5-2
P/N 8040613
C
HELIX TECHNOLOGY CORPORATION
-
TI
CRYOGENICS
5. Reduce the pressure in the cold head to a level of 30 psig by using
the maintenance manifold. Reducing the pressure in the cold head
to below 30 psig (200 kPa) may introduce more contaminants into
the helium circuit.
If you only have the manual regeneration option, turn the cryopump
OFF and open the purge valve until the second stage temperature
reaches 290K.
6. Attach a two-stage regulator (0-3000/0-400 psig) and charging line
to a helium bottle (99.999% pure). DO NOT OPEN THE BOTTLE
VALVE AT THIS TIME. Purge the regulator and charging line as
introduced in steps a through d below. Do not use helium gas that is
less than 99.999% pure.
a. Open the regulator a small amount by turning the adjusting
knob clockwise until it contacts the diaphragm; then, turn
approximately 1/8 to 1/4 turn more, so that the regulator is
barely open.
b. Slowly open the bottle valve, and purge the regulator and
line for 10 to 15 seconds. Turn the regulator knob counter-
clockwise until the helium stops flowing.
c. Loosely connect the charge line to the 1/8-inch Hoke valve
on the maintenance manifold.
d. Purge the charge line again, as in step a, for 30 seconds, and
tighten the charge line flare fitting onto the Hoke valve
while the helium is flowing.
This procedure is required to ensure that both the regulator and the
charging line will be purged of air and that the air trapped in the
regulator will not diffuse back into the helium bottle. For best results,
CTI-CRYOGENICS suggests a dedicated helium bottle, regulator, and
line, which are never separated, for adding helium.
7. Perform in sequence:
a. Backfill the cold head with helium to a static charge pres-
sure of 195-205 psig (1345-1415 kPa) by adjusting the reg-
ulator to the required pressure, and opening the Hoke valve
on the manifold. Close the Hoke valve when the pressure is
correct.
b. Depressurize the cold head to 30 and 50 psig 200 and 330
kPa) by slowly opening the ball valve and allowing the
helium to bleed out slowly. Do not reduce the pressure to
less than 30 psig or the cold head may be further contami-
nated.
