Julabo F12 - Cleanliness During Assembly; Leak Detection and Elimination

General safety recommendations and repair instructions
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6.3. Cleanliness during assembly
The greatest dangers to hermetically sealed compressors are dirt and moisture.
Particular care is therefore required when assembling such units:
 Use only cooling coils (evaporators), condensers and tubing that are clean and dry on the
inside and have been delivered airtight.
 Use only suitable refrigerant or nitrogen for pressure tests of those components.
 Open the connections immediately before assembly, and never leave the tubing open longer
than necessary!
 After cutting and deburring the tubing, carefully remove all metal shaving. Never use
compressed air.
 Dry all components that have been exposed to air by heating and simultaneously evacuating
them, fill with inert gas and close.
 Use a filter dryer not too small that has a close-meshed filter.
6.4. Leak detection and elimination
Wear a protecting mask to prevent poisoning by rests of gas!
Leak detection:
 Measure the stand-still pressure using a manometer that is connected to the filling connector
(7/16").
 Traces of the refrigerant in the system may be detected using an industry-standard electronic
leak detector.
 In persistent cases, the refrigerant must be pumped out to a residual pressure of approx.
2 bar. The circuit is then to be subjected with dry nitrogen (humidity <2 v.p.m.) at a test
pressure of about 20 bar.
After leak detection has been completed, this mixture must again be pumped out from the
system.
Elimination:
 Remove first the Schrader valve insert using a special tool.
 To prevent moisture entering the system and scale formation during soldering, circulate a
forming gas (95 % nitrogen + 5 % hydrogen) through the system via the open filling connector
under moderate pressure.
 Remove the filter dryer.
 Solder the leak (using a soldering torch and silver solder S15). Wait until the soldering joint
has cooled down with the help of the circulating forming gas.
 Insert a new filter dryer in the end of the capillary tubing and solder under the same conditions.
 Perform a seal test of the refrigerant circuit. This means, the circuit is to be subjected with
nitrogen or refrigerant at pressure to detect leaks.
 Screw in Schrader valve insert.
 Evacuate the refrigerant circuit using a vacuum pump and a filling device for at least one hour.
 Refill refrigerant.