HELIX CTI-CRYOGENICS CRYO-TORR 100 Installation, Operation And Servicing Instructions page 34

7.3 Cleaning the Cryopump
AWARNING
If the cryopump has been used
to
pump toxic or
dangerous materials, you must take adequate pre-
cautions to safeguard personnel.
The arrays or other interior surfaces of the cryopump
vacuum vessel seldom require cleaning because dust
buildup does not affect performance, and the special
alloy copper cryo-condensing arrays are nickel plated for
corrosion resistance. Cryopump performance in most
cases can be recovered by regeneration. In case of a
system malfunction, (i.e., backstreaming of a rough
pump oil or "dumping" of a process chamber) saturation
or contamination of the 15K cryo-adsorbing array
(charcoal) may require more than regeneration. The
charcoal array, if not severely contaminated, may be
recovered by folIowing the vacuum baking procedures in
this section.
If you wish to clean the arrays and other interior
surfaces, follow the procedures below. Refer to
Appendix B, Illustrated Parts Breakdown while perform-
ing these disassembly and reassembly procedures.
1. Confirm that an adequate supply of indium gasket
material, PIN 3543738POO1, is available.
2. CarefulIy disassemble the components in the
vacuum vessel.
3. Clean the components as folIows:
ACAUTION
Do not clean the 15K cryo-adsorbing array (charcoal)
because you will contaminate it in the cleaning process.
Use the vacuum baking procedure to recover a 15K
cryo-adsorbing array that is not severely contaminated.
a. Wash each item in strong soap or detergent
solution and hot water.
b. Rinse the items in clean hot water.
c. Air or oven dry at 150°F (66°C) maximum.
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HELIX TECHNOLOGY CORPORATION
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4. To clean a 15K cryo-adsorbing array (charcoal)
that is not severely contaminated by oil backstream-
ing or dust particles covering its surfaces, vacuum
bake it at a temperature of 150"F (66°C) for at
least 2 hours.
Note:
It is good practice to perform tllis vacuum
baking procedure on the 15K array on a
regular basis to insure continued efficient
cryopump operation.
5. Ifthe 15K cryo-adsorbing array does not require
vacuum baking, the array surfaces may be dusted
using a lint-free cloth lightly moistened with
denatured alcohol. Allow the array to air dry before
assembly.
6. Wearing lint-free gloves, reassemble the cryopump.
Replace any indium gasket damaged during dis-
assembly.
7. Hold the torque on all screws that compress indium
gaskets for a minimum of 5 seconds to allow proper
gasket seating.
SCREW THREAD
TORQUE (INCH-POUNDS)
No. 4-40
11
No. 6-32 20
No. 10-32
30
7.4 Adding Helium Gas
ACAUTION
If the compressor helium pressure gauge reads less
than 30, decontamination is required. Refer to decon-
tamination procedures on page 7-4 or contact the
Product Service Department.
There are two conditions that require the addition of
helium gas:
1. Compressor not operating; helium pressure gauge
reads 245 psig (1690 kPa), or below.
2. Compressor operating; helium pressure reads
below that specified in the following Table.
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