Page 2 - Bio Pump M Series

M34DM-3 Bio Pump
To meet the needs of today’s fuel-
efficient, downsized and space
efficient burners, Webster’s
M34DM-3 incorporates improved
access to both the bleed valve and
bypass plug. Locating the bleed port
plug assembly on the side of the
fuel unit provides the service
technician with one visible and
accessible location to either bleed
the fuel unit or change the bypass
plug without removing the burner.
In addition to improved access the
M34DM-3 cleaner blade has been
thickend to provide a more robust
cleaning action. For maximum
protection, an additional line filter
should be used in accordance with
recommended standard
practice All of the
BUNA-N elastomers
have been replaced with
VITON to provide extended
life at critical locations within the
fuel unit.
The M34DM-3 retains all the industry
accepted, state-of-the-art features of
the M34DK-3 fuel unit. These include
faster fuel cut-off, improved priming
on single pipe installations. This unit
can easily replace your standard
M34D or A2VA residential pump.
The M34DM-3 is capable of
maintaining a three gallon per hour
fire size at up to 150 PSI throughout
its design life. The M34DM-3 is
factory preset to 100 PSI and is
adjustable to 150 PSI.
General Operation and Fuel Unit
Oil Flow
The compact M34DM-3 Fuel Unit is
engineered for efficient pumping of
Bio fuel. The cut-away view illustrates
the oil flow through an M34DM-3
operating in a one pipe system, with
a suction line and no return to the
storage tank.
A one pipe system is frequently used
when the storage tank is located
above the fuel unit, or when
automatic venting is not necessary.
Vacuum at the pump inlet should not
exceed 10” Hg. For this type of
installation to be reliable, the total
system must be completely airtight.
During installation or servicing of the
fuel unit, air may be manually bled
from the system through the side-
located bleed valve.
One Pipe System
Fuel enters the fuel unit through the
inlet port and is drawn into the front
cover chamber. A vacuum, created
by an inner and outer rotating gear
set, pulls oil through the rotary filter
and into the gears. As oil moves
around the gears, it is compressed,
creating a higher pressure. Oil
leaving the gear set branches into
two paths. One path leads to the
pressure regulating chamber. A
second path directs oil to the bleed
valve. Oil flowing into the pressure
regulating chamber branches into
two paths. Up to three gallons per
hour can flow out the nozzle port,
and the remaining oil by-passes the
pressure regulator, returning to the
front cover chamber.
The M34DM-3 will provide up to
Hg of inlet vacuum. The two
pipe system (shown below), with
both a suction and return line is
self-venting. This allows any air in
the system to escape and be
returned to the storage tank
through the return line.
Two Pipe System
The by-pass plug, inserted through
the bleed valve port, blocks the
surplus oil return to the front
chamber. This oil is directed to the
return port and back to the storage
For More Information on Bio Fuel
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Fuel subject to vacuum
Fuel at atomization pressure
Fuel at return pressure