User's Manual Rev B / February 2021 / M125 Helium Compressor
97-00020-000
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8.4
Unscheduled Maintenance
The following corrective maintenance activities may be necessary should the helium gas circuit of Model 125 compressor
becomes contaminated.
8.4.1
Adding Helium Gas
If a compressor unit needs to have helium gas added more than once every several months, check for leaks caused by
improperly connected self-sealing connections or incorrectly sealed charge valve. If the compressor unit is connected to its
load (cryopump, cold head, etc.), check for leaks in the load also.
Use only 99.999% pure helium gas.
1.
Remove the flare cap of the gas charge fitting on the rear of the compressor.
2.
Loosely attaching a charging line from the helium pressure regulator on the helium pressure bottle to the 1/4 inch
male flare fitting installed on the helium charge valve. A user-supplied helium charging line terminating in a 1/4
inch female flare fitting and a pressure regulator rated at 400 PSIG (27.58 Bar) delivery pressure is required.
3.
Set the helium pressure regulator to 10 to 25 PSIG (.69 – 1.72 Bar). Allow helium gas to flow through the charging
flare fitting for 30 seconds to purge the charging line of air. Then tighten the flare nut at the end of the charge line.
a.
If the compressor is running under normal operating conditions, set the helium pressure regulator to 325
PSIG (22.41 Bar) and slowly open the helium charge valve in the rear of the compressor. When the helium
supply pressure gauge rises to 250 to 260 PSIG (17.23 to 17.93 Bar), tightly close the charger valve.
b.
If the compressor is not running, set the helium pressure regulator to 250 PSIG (17.23 Bar) and slowly
open the helium charge valve. When the helium supply pressure gauge rises to 190 ± 5 PSIG (13.1 ± .35
Bar), tightly close the charge valve.
4.
Insure that the helium charge valve on the compressor is tightly closed. Then shut off the helium pressure
regulator on the helium bottle. Remove the charging line from the male flare fitting and reinstall the flare cap.
8.4.2
Removing Helium Gas
Helium contamination is usually indicated by irregular, noisy or intermittent operation (ratcheting), and sometimes seizure
of the cryopump drive mechanism. This is caused by accumulation of frozen contaminants within the compressor load and
resulting in interference. The source of the helium contamination is due to either
•
Inadvertent introduction of ambient air into the system
•
Use of helium with purity of less than 99.999%, such as helium gas used for leak detection and welding.
Steps to decontaminate the helium circuit:
•
Minor contamination can usually be removed by running the cold cryopump for several hours to trap contaminants in
the cryopump, then shut down the compressor and immediately remove the helium lines at the compressor. Allow the
cryopump to warm thoroughly, and then perform the cleanup procedure as outlined in the cryopump manual.
8.5
Cleaning Equipment
Stubborn contamination involving water vapor requires decontamination of the compressor. One effective method
involves supplying clean helium to the return side at appropriate pressure while venting a small amount of gas from the
supply side; while the compressor is running. This is referred to as a "running purge". Contact Trillium US Inc. if such a
procedure is needed (refer to Section 2.2).
Caution:
Do not use solvents to clean the connectors. The fittings should never be greased or oiled. Otherwise
the helium circuit could become contaminated.
8.6
Returning Equipment
Before returning any equipment, contact Trillium US Inc. to receive special instructions and to obtain a return authorization
(RMA) number. See contact information in Section 2.2
.
