BIRD MicroBlender 3800 - Page 9

The gas with the higher pressure will also flow
directly to the blender outlet port bypassing
the Balance and Proportioning Modules. The
gas is also directed to the bottom of the unit to
the reed alarm, thus creating an audible
warning. The oxygen concentration will be
that of the gas at the higher pressure. The
blender in the alarm/bypass mode will deliver
the oxygen (100%) or air (21%) until the
bypass mechanism resets when source gas
pressure is restored to a differential of ap-
proximately 6 PSI (0.42 kg/cm’).
Some characteristics of the alarm/bypass
system on the MicroBlender differ somewhat
from those of model 3300 and other model
blenders.
If the MicroBlender is set at 21% and the
OXYGEN source pressure is reduced suffi-
ciently to produce a 20 PSI (1.41 kg/cm?) or
greater differential, the unit will not alarm
because it will continue to deliver 21% con-
centration according to the setting. If the
control is moved slightly from the 21% setting,
the alarm will sound.
Similarly, if the MicroBlender is set to deliver
100% concentration and AIR source pressure
is reduced or lost, the unit will not alarm
because it will continue to deliver the selected
100% concentration.
The MicroBlender should be disconnected
when not being used. if left connected to
source gases while not being used (i.e. no
output flow or bleed flow), the unit will not
alarm if a 20 PSI (1.41 kg/cm?) or greater
pressure differential develops. It is felt that if
the blender is not in use, an alarm under
these conditions may be an unnecessary
distraction or nuisance.
E GAS OUTLETS (FIGURE 6)
The primary gas outlet is utilized for
unmetered high flow applications in the range
of 15-120 LPM. The flow of gas is automati-
cally initiated by an attachment of a pneumatic
device to the outlet port. A check valve is
unseated upon connection allowing the mixed
gases to flow through the primary outlet.
AUXILIARY
QUILET
Figure 6
The auxiliary outlet is located on the right
side of the MicroBlender and is designed to
deliver metered gas through a flowmeter.
Mixed gas may be delivered within speci-
fied accuracy tolerance from this outlet at 2
LPM and above. When a connection is
made to the auxiliary outlet a 10-12 LPM
bleed of mixed gas to the atmosphere is
activated. This bleed is essential to ensure
accuracy of concentration for applications
utilizing low flows down to 2 LPM.