Maintenance
The flat gasket in the face of the male coupling seals the joint. A leak at this gasket seal can be
detected only when a gas line is connected. A leak here can be caused by:
• the coupling not fully tightened
• a worn, damaged or missing gasket seal
• dirt on or under the gasket seal
• dirt on the female coupling’s mating surface
• damaged parts on either coupling which prevent proper mating or sealing
Gas Line Repair
Leaks in the helically corrugated metal tubing cannot be repaired. Discard the damaged gas
line and install a new one.
Leaks at welded joints require special skills to repair. Consult an SCAI Service Center.
Leaks at the self-sealing couplings can be repaired by replacing worn or damaged parts.
Vent the gas line before beginning to disassemble it except when replacing a gasket seal.
When couplings are frequently disconnected and reconnected, it is important to wipe the
mating parts (threads and faces) with a clean, lint-free tissue or cloth.
Venting
Tools required: Adapter fitting with valve, 8M Aeroquip, P/N SK8217A2.
Open-end wrenches
Adapter fittings are available as optional accessories from SCAI.
1. Disconnect the gas line from the system. Install a dust cap on each of the male couplings of
the compressor and cold head, or on the RF feedthroughs, if used in the system.
2. Be sure the valve on adapter fitting SK8217A2 is closed. If only one coupling on the gas
line is to be repaired, install the adapter fitting on the good coupling. Use two wrenches.
3. Slowly open the valve on the adapter fitting to vent the entire charge of helium gas.
4. Close the adapter fitting’s valve. Do not remove the adapter fitting. It will be used for gas
cleanup and recharging.
Gas cleanup and recharging of the gas line are always required if a coupling
has been repaired. Instead of venting the gas line to atmospheric pressure,
some operators prefer to connect an adapter fitting and a charge line to the
coupling not being repaired, to purge the gas line with helium during repair. Set
the helium gas regulator at 35 kPa (5 psig) or less to prevent air from entering
the gas line and contaminating it.
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