Maintenance
Gas Cleanup
These procedures are required if leaks in the factory charged gas lines, the cryopump or the
compressor have reduced the pressure to less than 140 kPa (20 psig). Parts that have lost
their pressure must not be assembled into the system until they have been cleaned, to avoid
contaminating the system with air and water vapor.
Gas Cleanup of the Gas Lines
See the procedure in the Maintenance section of the Gas Lines manual.
Gas Cleanup of the Cold Head
Tools required: Open end wrenches 1”, 1 1/8”, 1 3/16”
This procedure can be done only after the cryopump has warmed to room
temperature.
This procedure is required every time the cold head has been opened to the atmosphere, to
avoid contaminating the system with air and water vapor.
Some of the following steps may have already been performed. Skip them.
1. Stop the compressor. Do not disconnect the electrical power to the compressor.
2. Disconnect the gas lines from the supply and return couplings of the cold head.
3. Locate two adapter fittings, P/N 255919B2, optional accessories available from SCAI.
Omit Step 4 when the cold head has not been removed from the vacuum
enclosure.
4. Stand the cold head on a work surface, resting on its valve motor housing.
5. Connect an adapter fitting to the supply (red) coupling on the cold head.
6. Connect another adapter fitting to the return (green) coupling of the cold head.
7. Connect a charge line to the pressure regulator of a helium gas cylinder containing 99.995%
pure helium gas with a dew point less than -50° C (-58° F) at 2070 kPa (300 psig). Set the
regulator at 690 kPa (100 psig).
AVOID INJURY. Never use compressed helium gas from a cylinder without a
proper regulator. Overpressure can cause personal injury if the system
equipment ruptures. When handling pressurized gas lines and other pressurized
equipment, always wear eye protection. Never apply heat to a pressurized gas
line or other pressurized components.
8. While connecting the charge line to the adapter fitting installed on the supply coupling of the
cold head, thoroughly purge the charge line from the regulator. It is important to remove all
air contaminants to prevent them from entering the system.
To Next Page
Loading...