4. Welding (SGI-3)
4.1. Measuring errors in connection with welding
Examples of measuring errors in connection with welding include:
v
Leak in fittings or weld groove.
v
Oxygen diffusion-proof hoses have not been used.
v
Defective membrane in shielding gas tool.
v
Weld groove too large and/or skew.
v
Insufficient shielding gas flow - failure to flush area clean.
v
Excessive shielding gas flow - injector effect created, so that - for instance - air is
sucked into the weld groove.
4.2. Shielding gas measuring
In connection with shielding gas measuring we recommend the use of PBI-Dansensor’s
original groove probe (accessory), if the shielding gas tool does not have separate
measuring gas hose fittings.
4.3. Material corrosion resistance
To ensure maximum corrosion resistance in 18/8 steel (AISI 304) the oxygen content must
be below approx. 30 ppm during welding. However, an oxygen content of approx. 50 ppm
is permissible for acid-proof steel (AISI 316).
4.4. Shielding gas tools
The need to use shielding gas tools depends on the task in question.
The use of shielding gas tools is not in itself any guarantee of high-quality welding. This
sort of guarantee can only be achieved in connection with oxygen measurement and
control.
There are several commercially available shielding gas tools, each of which has its
particular advantages. However, there are also many "home made" tools, which fully meet
the demands of the user.
A good shielding gas tool meets the following demands
:
v
Low purchase price and maintenance costs.
v
Equipped with fittings for connection of measuring gas hose.
v
Easy to mount and dismount after welding.
v
Good flow conditions, gas inlet from both sides and measuring outlet right below
the weld groove.
v
Protected against pressure rise as the groove closes during welding.
SGI-3/OXI-3/OXI-3.1 User manual
PBI-Dansensor A/S
PBI-210247-H UK 07/11/2005
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