baltur GI 350 DSPG, Инструкция

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DESCRIPTION OF TWO STAGE PROGRESSIVE OPERATIONS
(See BT 8714/2)
This is referred to as a 2-stage progressive operation because the passage from the 1st flame to the 2nd flame
(from the minimum rate to the maximum pre-established rate) takes place gradually both as delivery of combustion
air and of fuel. The burner’s control box (cyclic relay) is connected by operating panel switch ( I ).
Control box specifications
The cyclic relay control box carries out the ignition programme by starting up the fan motor and thus the pump in
order to effect the pre-ventilation and light oil pre-circulation phases.
It is necessary that the air pressure supplied by the fan is sufficient to cause the intervention of the relative pres-
sure switch, if not, the control box will go to “shut down”.
Oil from the pump reaches the atomizer unit and circulates within it because the passages leading to the outward
and return nozzles are closed. This closure is carried out by “closing pins” applied to the ends of the rods.
These “pins” are pressed against their seats by strong springs which are situated at the opposite ends of the
rods.
The oil circulates, comes out of the atomizer unit return and arrives at the return pressure regulator.
It passes through this and reaches the pump return and from there it is discharged back into the return.
Oil circulation, as described above, should be carried out at a pressure value slightly higher (by some bar) than
the minimum pressure at which the return pressure regulator has been set (10 ÷ 12 bar).
Duration of the pre-ventilation and oil pre-circulation phase is not 22,5 seconds, as foreseen by the control box,
because it is effected when the air shutter is in an open position.
The pre-ventilation and pre-circulation time is calculated by summing together the times of the following manoe-
uvres:
- the delivery regulation servomotor’s opening stroke (fuel/air) (45 seconds) +
- preventilation time foreseen by the control box (22,5 seconds) +
- the closing stroke of the delivery regulation servomotor (fuel/air) until ignition air position (about 40 seconds).
Therefore, altogether, the duration of the pre-ventilation and oil pre-circulation phase is about 107,5 seconds.
Subsequently, the control box continues carrying out the ignition programme by connecting the ignition transformer
which feeds the electrodes with high voltage. The voltage between the electrodes primes the electric spark for
ignition of the fuel/air mixture. 2,5 seconds after the ignition spark appears, the control box carries voltage to the
magnet which, by means of appropriate levers, moves backwards the two rods which intercept the flow (outward
and return) of light oil to the nozzle.
This moving backwards of the rods also determines a closing of the passage (by-pass) inside the atomizer unit.
Consequently, the pump pressure is taken to the normal value of about 20 ÷ 22 bar.
Deviation of the two rods the closing seat, now permits the fuel to enter the nozzle at the pressure at which the
pump has been regulated at (20 ÷ 22 bar), and comes out of the nozzle adequately atomized.
The return pressure, which determines delivery to the furnace, is regulated by the return pressure regulator.
The value of the ignition flow rate (minimum delivery) should be about 10 ÷ 12 bar.
The atomized light oil which comes out of the nozzle is mixed with air supplied by the fan and is then ignited by
the spark of the electrodes. Flame presence is detected by the photoresistant cell.
The programme proceeds and, after 5 seconds, surpasses the “shut down” position, disconnects the ignition
transformer and by this point on the burner is operating at minimum output. If the boiler thermostat (or pressure
switch) of the 2nd stage allows it (regulated at a temperature or pressure value superior to that existing in the
boiler), the servomotor which regulates the delivery starts turning and determines a gradual increase in the fuel
delivery and in the relative combustion air until it reaches the maximum delivery value at which the burner has
been regulated.
The increase in fuel delivery is determined by a disk with a varied profile which, by rotating, can determine a greater
compression of the return pressure regulator spring and thus an increase in the pressure itself.
When the return pressure increases, there is also a corresponding increase in fuel delivery.
Control box
& relative
Programmer
LAL 1.25
Cyclic relay
Safety Time
in seconds
5
Pre-Ventilation & Oil
Pre-circulation Time
in seconds
22,5
Pre-ignition Time
in seconds
2,5
Post-ignition
Time
in seconds
5
Time between
1st flame & Start
of Modulation
in seconds
20