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6.2.10 CCR
Maintenance
This section provides instructions on maintaining the CCR.
6.2.10.1 Charging the CCR Compressor Helium Gas
Charge the CCR compressor helium gas if the pressure indication on the supply
pressure is lower than the value specified in section 3.3.8.1. Note that the supply
pressure is dependent on both the cold head temperature and the ambient
temperature. Wait until the cold head is at ambient room temperature to make an
accurate reading of the supply pressure. If the ambient temperature of the room is
unusually lower or higher than normal for your facility, then the supply pressure may
also read low or high, respectively. It is best to wait until the ambient room
temperature is representative of normal operating conditions prior to charging the
helium gas. Refer to the HC-4E1 Helium Compressor Technical Manual for specific
instructions on charging the helium gas.
6.2.10.2 CCR Cold Head 10,000 Hour Maintenance
The moving parts within the CCR cold head require service after approximately
10,000 h of operation. If your Model CRX-6.5K probe station is approaching the
10,000 h operation point, you will need to return the CCR cold head to Lake Shore for
service; contact Lake Shore or your local representative to schedule this service.
6.2.10.3 CCR Compressor Oil Mist Adsorber 30,000 Hour Maintenance
The oil mist adsorber inside the CCR compressor should be changed after
approximately 30,000 h of operation to ensure the purity of the helium gas in the CCR
cold head. You may contact SHI directly to obtain the replacement adsorber, or
contact Lake Shore or your local representative to obtain a replacement adsorber.
Refer to the HC-4E1 Compressor Unit Technical Instruction for the manufacturer’s
part number and specific instructions on changing the adsorber.
6.2.11 Vacuum Pump
Maintenance
It is difficult to give specific instructions for all possible combinations of pumps that
may be used with the Model CRX-6.5K. Refer to the information included with your
selected vacuum pump for specific maintenance instructions, and add them to the
preventive maintenance schedule in section 6.2.1 of this manual. Some general
guidelines on vacuum pump maintenance follow.
6.2.11.1 Turbo Pumps
Turbo pumps are generally considered maintenance-free, and contain no user-
serviceable parts or maintenance items. Operate them according to manufacturer’s
instructions for the longest possible service life.
6.2.11.2 Scroll Pumps
Scroll pumps are frequently used because the fore pump for the turbo pump has
replaceable seals called tips that wear with use. As the tips wear, pump performance
degrades, but this seldom causes pump failure. The tips should be replaced when the
pump no longer performs adequately. Some manufacturers recommend replacing
the tips every year (depending on use) to keep the pump operating to specification.
However, a scroll pump can still be adequate for use as a fore pump even when it is
performing well below its specification.
6.2.11.3 Oil Mist Eliminators
The exhaust of a rotary-vane pump is often fitted with an oil mist eliminator (filter).
There are a variety of oil mist eliminators that may or may not include an inspection
view port or replaceable filter element. If the eliminator is not serviced or replaced
regularly, oil will exhaust from the pump. Consider scheduling service or replacement
of the oil mist eliminator when the pump oil is changed.