Oil burners fuel unit
Oil burners fuel unit
Type A, AD
1- Applications
The DELTA aluminium fuel unit type A is an efficient and
modern oil burner pump, provided with bilateral delivery
ports. Hub and shaft sizes are manufactured to
international standards (EN 225), so it can be fitted to
every oil burner.
The pump type A is designed for pumping oil in high
pressure oil burners and transfer pump applications. Its
features allow an easy pump replacement with every
other type of oil pump: the same unit is provided with
nozzle port in both the left and right sides.
For the use with low viscosity fuel (lower than
2.5cSt, i.e. Kerosene) standard pump can be used
without exceeding 12 bar.
To pump biodiesel or fuel containing it in any
percentage, it is necessary the “B” version with
special seals. On request the pump can be provided
free of nonferrous metals.
This unit must not be used to pump water or acid.
2- Operation
The type A fuel unit consists of a pump, solenoid valve
(A type only), filter and pressure regulator. The pumping
action is obtained from two spur gears (2), one of which
is connected to the drive shaft (3). The aluminium pump
casting provides the various oil ways, for the suction (6),
return (5) and nozzle ports (9). Pressure (8) and vacuum
(7) gauge ports are also provided.
On start up, the rotating gears purge the air from the
suction chamber, through a vent groove in the piston to
the return line in two pipe version, and through the
nozzle line (after the solenoid valve opening) in one pipe
On initial commissioning, it is possible to bleed the air
more quickly, through the pressure gauge port.
Because a vacuum now exists oil, due to atmospheric
pressure, enters the suction chamber through the filter.
From the suction side, the gears pass the oil to the
pressure chamber, where it comes up against the head
of the piston. Due to the build up of pressure, the piston
is forced back against the pressure regulating spring.
In the A type the flow of pressurized oil is interrupted by
an incorporated solenoid valve (10), and can, therefore,
be opened following the start of the motor (pre-purge), or
interrupted before stopping the motor itself (instant shutoff of the flame preventing the nozzle dripping). The
excessive oil discharges to the return side (or by-passes
in the one pipe version). It will be realized of course that
the spring tension, which is varied by the regulating
screw (1), regulates the pressure of oil required.
The AD type does not have a built-in solenoid valve.
When the burner motor starts, the oil will be discharged
from delivery ports straight away.
If the AD pump is used to provide oil to the nozzle, a
shut-off valve must be fitted in the nozzle line.
The pump can be converted from the two pipe version to
the single pipe version, removing the bypass plug (4)
from the vacuum port.
When the unit is converted to the single pipe version, on
initial commissioning the air must be bled through the
pressure gauge port (in this case lift installation are not
The cartridge filter (11) located in the front side, allows
an easy cleaning without to dismount any part of the
3- Pump identification
Pump type
A = with built-in solenoid valve
AD = without solenoid valve
B prefix = biodiesel version
(explicit request for nonferrous metals absence)
Nozzle capacity
(see graph)
Rotation (seen from shaft end)
R = clockwise
L = counter clockwise
Pipes system
1 = one pipe
2 = two pipes
Coil type
F = NF84 (coil with connector plug)
Coil power supply
A = 230 VAC 50/60Hz
B = 110 VAC 50/60Hz
C = 24 VAC 50/60Hz
4- Technical specifications
Oil viscosity ………………………………….
1,2 ÷ 12 cSt
Oil temperature ……………………………... 60°C max.
Power consumption ………………………... See graphs
Nozzle capacity ……………………………... See graphs
Fine adjustable pressure …….................... 6 ÷ 20 bar
Minimum pressure ………………………….
2,5 bar (for oil transfer applications)
Suction line vacuum ……………………….. 0,5 bar max.
Suction line pressure ……………….……... 2 bar max.
Return line pressure ……………………….. 2 bar max.
Starting torque ………………………………
0,1 Nm max.
Rotation speed ……………..………….……. 3500 rpm max.
Standard strainer……….….………………... Stainless steel mesh 130µ, 11cm²
Dimensions (EN 225) ………………………. Hub Ø32, shaft Ø8
Connections (ISO 228/1) …………………... Inlet – Return : G1/4
Nozzle port : G1/8
Pressure – vacuum gauge : G1/8
Weight ……………………………………….. A = 720 g AD = 600 g
Standard factory settings ………………… Pressure setting:
10 ±0,3 bar
Standard coil:
230 VAC 50/60Hz
Standard cable set:
3 cores, 700 mm
5- Solenoid valve specifications (A type only)
Power absorbed .……………………………. 9 W
Voltage tolerance …………………………… -15% / +10%
Ambient temperature .……………………...
0°C / 60°C
Operating pressure ……………………….... 25 bar max.
Flow factor (VDI/VDE 2173) ……………….. 0,059 m3/h
Cut-off pressure …………………………….. 6 bar
Approval (EN 264) …………………………..
TÜV No. 5S102/09
6- Diagrams
Nozzle capacity
Power consumption
7- Overall dimensions
Pressure regulation
Shaft sealing
By pass
Vacuum gauge
8 Pressure gauge
9 Nozzle port
10 Solenoid valve
11 Cartridge filter
8- Bypass installation
To convert the A/AD fuel unit from the single pipe
version to the two pipe version, do the following:
Using a 6 mm Allen wrench, remove the 1/4" plug from
return port (Fig. 1).
Remove the 1/8" plug from vacuum port .
Using a 2.5 mm Allen wrench, insert and screw the
bypass plug in the vacuum gauge port (Fig. 2).
Screw back the 1/8" plug into vacuum port.
To convert the A/AD fuel unit from the two pipe version
to the single pipe version, do the following:
Remove the 1/8" plug from vacuum port .
Using a 2.5 mm Allen wrench, unscrew the bypass plug
from the vacuum gauge port (Fig. 2).
Screw back the 1/8" plug in the vacuum port
Insert and screw a 1/4" plug into the return port (Fig. 1).
In the single pipe version, the air is bled through the
nozzle line, after the solenoid valve opening.
In the two pipe version the air is bled through the return
port. After conversion, the air must be bled manually,
through the pressure gauge.
Make sure that the bypass plug is not used in a single
pipe installation, because the fuel unit will not function
properly and damage to the pump and burner motor
could result.
9- Installation and Maintenance
11- Nozzle Cut-Off Test (A type only)
1. Make sure that the bypass plug is not used in a single pipe
2. Do not use fuel with additives to avoid the possible formation
over time of compounds which may deposit between the gear
teeth, thus obstructing them.
3. After filling the tank, wait before starting the burner. This will
give any suspended impurities time to deposit on the bottom of
the tank, thus avoiding the possibility that they might be sucked
into the pump.
4. On initial commissioning a dry operation is foreseen for a
considerable length of time (for example, when there is a long
suction line to bleed). To avoid damages inject some lubrication
oil into the vacuum inlet.
5. Care must be token when installing the pump not to force the
pump shaft along its axis or laterally to avoid excessive wear on
the joint, noise and overloading the gears.
6. In the A type pump do not force the valve stem and do not
use it as lever. If the AD pump is used to provide oil to the
nozzle, a shut-off valve must be fitted in the nozzle line.
7. Pipes should not contain air pockets. The number of
junctions should be kept to a minimum as they are a possible
source of leakage.
8. Rapid attachment joint should therefore be avoided. Always
use O-Rings or mechanical seal (copper or aluminium gaskets)
junctions if possible.
9. Avoid overtightening: G1/815 Nm max.
G1/420 Nm max.
10. Do not use PTFE tape on the suction and return line pipes
to avoid the possibility that particles enter circulation. These
could deposit on the pump filter or the nozzle, reducing
11. When junction threads, elbow joints and couplings are
sealed with removable glue, avoid excessive quantities, which
could enter in the oil ways and damage to the pump could
12. To clean the filter, unscrew the plug using a 4 mm Allen
wrench. Remove the cartridge from the unit and extract the inox
mesh. When reassemble, cartridge must be oriented with the
radial hole toward the inlet port. It must be thoroughly cleaned
at least once in a season to ensure correct working of the fuel
unit. An external filter should always be installed in the suction
line upstream of the fuel unit.
13. Make sure the combustion chamber is free of oil or oil vapor
before operating the system.
Fuel oil is not compressible but air is. Air trapped in the nozzle
line, anywhere between the fuel units nozzle port and the
nozzle itself, will compress during burner operation. Following
burner shutdown, any trapped compressed air will expand
displacing the oil in the nozzle line, forcing continued oil flow
through the nozzle that will, in effect, falsely appear to be poor
fuel unit Cut-Off. This occurrence is particularly common with
low flow rate nozzles used in conjunction with long air tubes.
To verify positive nozzle Cut-Off after burner shutdown, do the
1. Remove the nozzle line and fitting from the nozzle port of the
fuel unit and connect a 1/8" pressure gauge to the nozzle port
(a gauge of 20 Bar or greater be used). It may be more
convenient to use a gauge fitted out with an extension nipple or
with a line and flare nut to connect directly to the fitting installed
into the nozzle port. If any type of extension is used between
the nozzle port and the gauge, it should be kept as short as
possible to minimize the amount of trapped air.
2. Start the burner motor, energize the solenoid valve and vent
all air from the fuel unit and connected suction line system.
3. Shut off the burner motor. Initially the pressure will drop and
then stabilize within a second or two. The pressure reading on
the gauge should stabilize at 6 Bar or greater and hold for at
least two minutes.
Turn off all power before servicing any part of the system.
10- Nozzle Pressure Test
Most nozzles ratings are based upon 100 PSIG (6,89 Bar)
delivered oil pressure. The flow rate at the desired pressure
must be estimated using the nozzle manufacturers data sheets.
To insure that oil is delivered to the burner nozzle at the desired
pressure, do the following:
1. Remove the 1/8" plug from the port marked "P" and connect
a pressure gauge to this port (use a gauge of 0 to 20 Bar or
greater). The "P" port (Pressure Gauge Test Port) has been
provided specifically for the connection of the pressure gauge
for measuring the nozzle pressure; however, when available, it
is also permissible to use the vent port for measuring nozzle
2. Start the burner motor, energize the solenoid valve and vent
all air from the fuel unit and connected suction line system.
3. Check the adjustable nozzle pressure range of the fuel unit,
using a 4 mm Allen wrench, turning the adjusting screw counter
clockwise to lower the nozzle pressure and clockwise to
increase the nozzle pressure.
Adjust the nozzle pressure in accordance with the burner
manufacturers specifications.
12- Vacuum Test
The vacuum test is necessary to verify the fuel unit's suction
ability, to evaluate the leak tight integrity of the entire fuel unit
and connected oil suction line piping system, to confirm that
there are no abnormal restrictions in the oil suction line system,
and, to confirm that the system vacuum is within the allowable
specification limits of the unit. Please watch in any case the
graphs for maximum suction line length depending on line
diameter, viscosity, difference in height of suction line and
pump or nozzle capacity. To perform the test, do the following:
1. Remove the 1/8" plug from the port marked "V" and connect
a vacuum gauge to this port.
2. Start the burner motor, energize the solenoid valve and vent
all air from the fuel unit and connected suction line system.
3. With the burner motor running, close the valve connected to
the inlet port. You will note that the vacuum as measured by the
vacuum gauge will increase. Allow the burner motor to continue
to run until the highest vacuum reading is achieved. A fully
primed fuel unit in good condition should be capable of pulling
at least 0,7 Bar. If not, before condemning the fuel unit, be sure
that all connections and plugs are tight and the valve is in good
working order.
4. De-energize the solenoid valve and shut off the burner motor.
Initially, the vacuum reading will drop and then stabilize within a
second or two. Once the vacuum reading stabilizes, record the
reading. If the fuel unit is free of leaks, this reading should hold
constant for at least 2 minutes. If the vacuum reading drops,
there is a leak that must be located and corrected.
5. When each leakage is removed and the valve onto suction
line is open, check to be sure that the actual operating vacuum
does not exceed 0,5 Bar.
Elettromeccanica Delta S.p.A.
31030 Arcade (TV) Italy
Tel. +39 0422 874068
Fax. +39 0422 874048
[email protected]
We reserves the right to update or make
technical changes without prior notice.
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