baltur BT 100 DSPG, Инструкция по техническому обслуживанию, эксплуатации и установке

Страница: 13 / 92

E
N
G
L
I
S
H
13 / 32
98319_200910
DESCRIPTION OF OPERATION WITH LIGHT OIL
(See BT 8714/2)
This is referred 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.
The burner’s control box (cyclic relay) is connected by operating
panel switch ( I ).
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.
The pressure of the air supplied by the fan must be sufficient to let
the relative pressure switch come into operation; on the contrary the
control box stops in block position . Oil from the pump reaches the
atomizer unit and is obliged to circulate within it because the passage
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 by strong which are situated
at the apposite 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 pres-
sure 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 manoeuvres:
the modulation motor’s opening stroke (45 seconds) +
pre-ventilation time foreseen by the control box (22,5 seconds) +
modulation motor’s closing stroke until ignition air position (about
40 seconds)
Therefore, altogether, the duration of the pre-ventilation and oil pre-
circulation phase is about 107 seconds.
Subsequently, the control box continues carrying out the ignition
programme by connecting the ignition transformer which, in turn,
feeds the electrodes with high voltage. High voltage between the
electrodes primes the electric spark for ignition of the fuel/air mix -
ture. 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 from 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
Control box &
relative Pro-
grammer
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
15
Control box specifications
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 photoresistance.
The programme proceeds and, after 5 seconds, surpasses the
“shut down” position, disconnects the ignition transformer, and then
connects the modulation circuit. The modulation motor commands
an increase in the delivery of fuel and combustion air at the same
time. The increase in fuel delivery is determined by a disk with a
varied profile which, by rotating, can determine a greater compres -
sion 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.
There should also be an adequate increase in combustion air to
meet the increase in fuel delivery. Adjustment can be carried out
at first regulation by operating the screws which vary the profile of
the command disc of the combustion air regulator.
Fuel and combustion air delivery both increase at the same time until
they reach maximum value (light oil pressure at the return pressure
regulator is equal to about 18 ÷ 20 bar if the pressure at the pump
is at the value of 20 ÷ 22 bar).
Fuel and combustion air delivery keeps its maximum value until
the temperature of the boiler (pressure if we have a steam boiler)
approaches the set value on the thermostat (or pressure switch) of
the second stage which determines the return of the delivery regu -
lation servomotor (fuel/air) in the apposite direction to the previous
movement thus gradually reducing the delivery of the gas oil and
of its combustion air to a minimum value.
If even with a minimum fuel and combustion air delivery a maximum
temperature is reached (pressure if we have a steam boiler), at the
set value the thermostat (pressure switch if we have a steam boiler)
determines the complete stop of the burner.
When the temperature lowers (pressure if we have a steam boiler)
below the value causing the activation of the stopping device, the
burner starts up again as described above. Under regular working
conditions, the 2nd stage thermostat (or pressure switch) detects
any variation, in the boiler load and automatically requires the
adjustment of the gas oil delivery and of its combustion air to the
delivery regulation servomotors (fuel/air).
Thus the delivery regulation system (fuel/air) reaches a balance
position corresponding to a fuel delivery and to its combustion air
delivery equal to the heat amount required by the boiler.
!
As an indication , it should be kept in mind that the field of
variation in output obtainable with a good quality fuel is from
1 to 1/3 of the maximum output given on the rating plate.