Positioning Of Graphite Electrodes; Brazing Of Tubes - Virax Cobraz 28 Notice D'utilisation

Positioning of graphite electrodes:

Presentation of the electrodes
Rod type electrodes
Rod electrodes are mainly used for use in boxed locations where connections are difficult to
make, or in the case of a simultaneous brazing of a T-connection.
The purpose of the copper covering is to help electrical conduction between the electrodes'
support and the graphite.
Important:
The tube and the electrodes must come into contact only through the graphite, otherwise a short
circuit may occur.
Observation:
During prolonged use the electrodes turn red; this is not a malfunction.
Prismatic type electrodes
Prismatic electrodes are used principally for brazing of tubes and brazing to touch; they present
a large contact surface with the tube. They are also used for hard soldering (with silver) with the
Cobraz 54.
Observation:
In the case of prolonged use the electrodes turn red; this is not a malfunction.
Positioning of the electrodes on the supports
• Clean the supports and the electrodes using a metal brush.
• Position the electrodes on the supports.
• Tighten the nuts.
Change of electrode support
The electrode supports may be changed.
• Unscrew the supports.
• Clean the new supports using a metal brush to optimise contact.
• Clean the supports in position.
• Screw in the supports.
• Screw the electrodes on to the supports.
Important:
Cleaning the supports is an important procedure. It lets the contacts between the electrodes and
the supports be optimised.

Brazing of tubes

• Choose electrodes suited for the work to be undertaken.
• Fix the electrodes on to the supports.
• Connect the brazer to a 220 V socket which has been correctly earthed.
• Turn the machine on by throwing switch (3).
• Apply a fine layer of flux on the end of the tube to be brazed.
• Fit the connection inside and rotate both tubes to spread the flux well.
• Position the electrodes on the tube.
• The electrodes start to heat when they come into contact with the tube.
• The copper tube is hot when the flux has changed colour.
• Apply the braze at the joint.
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