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GALAXY 3000 GE MV VRD
EN
3.3.1. STANDARD MMA WELDING MODE - VRD MODE.
With selector switch A, we can select the VRD (S) working mode.
The selection must be made with a screwdriver, as this is a safety
system and the aim is to prevent the control from being activated
unintentionally.
In VRD(S) welding mode, the risk of electrical discharge onto the welder in the welding circuit is reduced, by
means of a voltage reducer device.
This safety element, which reduces the equipment voltage only during the striking phase, is recommended
for applications with a greater risk of electrical shock:
Welding in confined spaces, where the operator is in contact with the exposed live parts of a site. For example, the
construction of steel structures, the inside of pressure containers, storage tanks or repair in naval industry.
Welding in damp atmospheres. Especially with temperatures of below 32º C
Work at height, where a slight discharge, without consequences on the ground, may cause a loss of stability and falls
with serious consequences.
Welding in mining industry.
This safety system will modify the electrode ignition system on reducing the initial no-load voltage necessary
to establish the arc. In such a way that the correct arc striking will be carried out by forcing the contact of the
electrode with the plate, having 2 seconds after this to establish the arc.
The striking system used for coated electrode welding with VRD system will change from
scraping to initial contact scraping.
3.3.2. COATED ELECTRODE WELDING RECOMMENDATIONS.
5.
Respect the appropriate welding and power cable sections for the welding intensity (see chap. 2).
Bear in mind that there are welding voltage losses in the cables, which increase when:
- The longer the welding cables are.
- The smaller the welding cables section is.
We will observe that with fixed resistance values, the intensity and voltage are directly proportional and
therefore the increase or decrease of one of the values affects the other in the same direction.
6.
Preservation and use of the electrodes.
- The coating of the electrodes used must not have any defects and due to their high hygroscopic power
(they absorb and retain humidity) they must be submitted to a drying process, respecting the
manufacturer’s recommendations.
- The use of electrodes in unfavourable humidity conditions, will cause faulty striking, increase of porosity,
arc interruptions and the appearance of cracks in the cooling phase.
7.
Polarity type selection. The recommended polarity will be given on the electrode box. Straight polarity (-):
Electrode to negative pole / Reverse-polarity (+): Electrode to positive pole.
8.
Earth tap.
- An incorrect situation can cause magnetic blow-out, making it difficult to control the electric arc.
- A bad contact of the mass will cause this to heat up, the current passage will be interrupted and the arc
will disappear.
