DENSO CORPORATION CLASSIC PLUS 26 - Manual (Page 41)

TROUBLESHOOTING AND REPAIR
33
• BRAZED FITTING AND ITS CLEARANCE
In general, the strength of brazing filler metal
is lower than that of the base metal. So, the
shape and clearance of the brazed fitting are
quite important. As for the shape of the
brazed fitting, it is necessary to maximize its
adhesive area. The clearance of the brazed
fitting must be minimized to facilitate brazing
filler metal to flow into it by capillary action.
• CLEANING OF BRAZING FILLER METAL
AND PIPE
When the refrigerant system has been
opened up, exposure to heat may have
caused brazing filler metal to stick to the
inside and outside of the pipe. Brazing filler
metal may also be compounded with oxygen
in the air to form oxide film. Fats and oils
may stick to the pipe from handling. All these
factors will reduce effectiveness of brazing. It
is necessary to eliminate excess brazing filler
metal using sand paper and by cleaning
thoroughly with a solvent such as Trichlene.
• USE OF DRY NITROGEN GAS
During brazing, the inside of the pipe under-
goes an oxidative reaction due to the brazing
flame. Introduce dry nitrogen gas (1 liter/
min.; adjust with the flow regulator) through
the pinch-off tube of the refrigerant cycle to
prevent oxidation.
NOTE: Take care not to allow dirt, water, oil, etc. to
enter into the pipe
• VERTICAL JOINT
Heat the whole brazed fitting to a proper
brazing temperature. Bring the brazing filler
metal into contact with the fitting so that the
brazing filler metal starts flowing by itself.
Stop heating the fitting as soon as the
brazing filler metal has flown into the clear-
ance. Since the brazing filler metal flows
easily into the portion heated to a proper
temperature, it is essential to keep the whole
fitting at a proper brazing temperature.
Brazed Fitting and Clearance
Vertical Down Joint
Vertical Up Joint