Safety Rules; Maintenance - TECNA 7900 Bedienungsanleitung

The value should be set according to the thickness of sheets to
be welded; it may be selected on the basis of personal
experience and the welding tables (see tab. 2).
The values in the force indicator scale refer to arms with a
length of L=125 mm. When using other arms either consult
table 1 or multiply the set force by the value in the following
table to deduce the force value obtained:
Arms length 125
Multiply by 1
Until there is no change greater than 1mm in the thicknesses to
be welded, or wear or electrodes (A) displacement, the setting
to zero is valid. To change the force, it is enough to adjust, by
means of screw (18), the index (17) to the required value.
Welding parameters adjustment
It is possible to adjust the welding time by the knob 56. Table 2
shows the times and setting for various types of welding. The
timer has a compensation circuit which calculates the actual
welding time needed even when paint, rust or dirt obstruct the
passage of welding current, thus the timer only ends the cycle
when a perfect complete weld has been obtained.
ITEMS 7902-7903 ONLY:
Welding current can be adjusted from 40% to 100% by
means of knob 47. We recommend to always use the highest
value except for: very thin thickness, rods with reduced  (1-
3 mm), stainless steel sheets.
Another advantage offered by current adjustment is the
possibility of reducing the power absorption when this is too
high for the mains on which the welder is used (of course, you
have to increase the welding time and check the welds
quality).
All versions P of these welders are equipped with pulse
function, which is selected by means of selector P. The data
in table 2 refers to the "timer" position. The "pulse" position
requires longer welding times.
WELDING EXAMPLES
Mild steel sheet mm 0.8 + 0.8 to be welded with 125 mm arms,
spot welder item 7900. Table 2 suggests:
Electrodes tip diameter 4 mm.
Welding time 9 cycles (knob 56).
Force on electrodes 75 daN (adjust as previously described).
Max, working rating 6 spots per minute (table 4).
Mild steel sheet mm 1 + 1 to be welded with 250 mm arms with
spot welder item 7902. Table 2 suggests:
Electrodes tip diameter 4.5 mm
Welding time 25 cycles (knob 56)
Current 4/4 (adjust with knob 47)
Force on electrodes 70 daN (set indicator 17 on 120daN to
balance the arms increased length).
Max. working rating 5 spots per minute (table 4).

SAFETY RULES

For a safe welder use, the installation must be carried out by
qualified personnel only; the welder maintenance must be
carefully carried out by following all the safety instructions stated
in the "MAINTENANCE" paragraph. In particular, notice that the
electrodes maintenance must be carried out with the welder
switched off. The welder must be used in a place fulfilling the
following features:
 In an inner place. The welder has not been designed for being
used outdoors.
 Room temperature should be between 0 and 40 °C (If water is
removed, storage is allowed down to 20°C below 0); 1000 m.
maximum altitudes.
 In a well ventilated area, free from dust, steam, and acid
exhalation.
"РУТЕКТОР" - сертифицированный дистрибьютор TECNA S.p.A. на территории РФ. rutector.ru info@rutector.ru 8 800 100 00 69
150 250 350 500
0.88 0.57 0.42 0.31
 The work place must be free from inflammable materials
because the working process can produce spatter of molten
metal.
If the welder is used to carry out welding processes which can
cause fumes, a proper aspirator must be installed.
In case of water entering the welder, immediately stop the
electrical supply.
Notice that these types of machines generate
strong magnetic fields attracting metals (metal
prosthesis included) and damaging watches,
magnetic cards and magnetic data storage media. Since
these magnetic fields can affect pace-makers, metal
prosthesis, hearing aids and all other electrical medical
devices, the wearers must consult their doctor before
approaching to the welding area.
The welded pieces may reach high temperatures.
Even some parts of the machine (electrodes, arms
and parts connected to the former ones) may
excessively heat up if the cooling water is not enough
or if the machine is used for a too high rating. Analyse the
working conditions and use, if necessary, suitable individual
protection devices (gloves, aprons and other clothes).
Personnel must wear both safety glasses and gloves. Avoid
wearing rings, metal watches and clothes with either metal
accessories or components.
working, high thickness and pieces with a difficult
coupling, wear safety shoes and aprons, and use protection
screens to protect the operator from possible spatter of
molten materials.
The safety shoes must be worn each time the pieces, because
of their shape or weight, bear risks requiring them.
Keep the area surrounding the welder free from inflammable
materials as the work may produce projections of melted metal
particles. It is forbidden to use the machine in explosive
atmosphere environments or involving fire risks.
Never carry the welder by its cable or yank it to take it off from
the socket. Keep the cable away from heat, oil and sharp edges.
If, while working, the cable is damaged, unplug the machine
from the mains. Do not use the machine if the cable is
damaged.
In case of fire do not use water but proper fire extinguishers.
In addition to the information stated in this chapter, always
operate in accordance with all the relevant laws in force.

MAINTENANCE

The maintenance operations must be carried out by
specialised personnel only, trained to accomplish them
under safety conditions. When possible, the welder must be
disconnected from electrical supply.
GENERAL MAINTENANCE
GENERAL WARNINGS
 Always check that the screws of electrodes, electrode-
holders, arms, and arm-holders (10), as well as the rigid (64-
75) and flexible (23) connection are well tightened.
 Remove oxide traces on the secondary circuit with fine sand
paper.
 Periodically oil axes 16-16-24-68.
 Keep the spot gun free from dust and metal particles attracted
by the magnetic field formed by the welder when in use.
 Neither washing the welding unit with jets of water which
could enter it, nor use strong solvents, thinners, nor benzine
that could damage either painting or the machine plastic
components.
When operating heavy