Preparation For Gas Welding; Piping Connection By Gas Welding; Refrigeration Circuit Leak Check - Panasonic MDF-DU702VH Service Manual

2.2 Preparation for gas welding

Preparation：Flameproof sheet, tools, nitrogen cylinder, charge hose, branching instrument
Procedure : Pull the welded part as far as possible from the product and cover the periphery
with a flameproof sheet as necessary.
In order to prevent oxide film of pipe inside during welding, a nitrogen cylinder is
connected to the low pressure side service valve (SVL)
Replace the nitrogen in the piping. (Nitrogen substitution: provided secondary
pressure is 0.5 to 0.7 MPa) At this time,
Remove the valve in the check valve. (Outlet of nitrogen)
Low pressure
service valve
SVL
Note：Insulation materials are easy to ignite, be sure to cover with fireproof sheets.
The flow rate of nitrogen may be small (to the extent that it feels a little with the skin).

2.3 Piping connection by gas welding

Preparation: gas welding machine, exclusive lighter, silver braze, flux piping tool
(Cutter, reamer, bender, flare tool, expander, wrench, mirror, light etc.)
Welding cooling product (water-filled container, waste etc.),
Weld protective product (leather gloves, goggles, flameproof sheets, steel plates,
etc.)
Procedure: Take care not melt the pipe, heat it so that a braze melts around the connection,
and then braze to it. Check the brazed state with a mirror, light, etc.
When using silver wax, apply flux to the place where you usually braze.
Note: Forced cooling immediately after brazing heating adversely affects the structure of
copper metal. Please leave it for about 2 minutes and then apply wet cloth.

2.4 Refrigeration circuit leak check

Preparations: Leak check spray (liquid detergent can also be substituted)
Procedure: Continue with nitrogen replacement as it is, install a valve in the check valve,
and perform a leak check of the entire unit circuit.
(Nitrogen replacement: provided that the secondary pressure is 0.5 to 0.7 MPa)
Note: Use a leak check spray to check the gas leak at the replacement (welding)
point.
Check valve
High pressure
service valve
-43-
Valve sate
open shut
○
SVL