Instruction manual

MicroBlender Instruction Manual
4 L2965–101 Rev. D
Proportioning Module
From the balance module, the gases flow into the proportioning module and
mix according to the oxygen percentage selected with the MicroBlender
control knob. This module consists of a double-ended poppet positioned
between two valve seats.
One valve seat controls the passage of air and the other valve seat controls
the passage of oxygen into the MicroBlender outlets. At this point, the two
gases have been blended according to the oxygen percentage selected by the
control knob.
Alarm/Bypass
The alarm feature provides for an audible alarm if source pressures differ by 20
±2 PSI or more. The primary purpose of the alarm is to audibly warn the operator
of an excessive pressure drop or depletion of either source gas. The alarm will also
activate when there is an elevation of either source gas resulting in a 20 ±2 PSI
difference. Should both gas pressures (oxygen or medical air) increase or decrease
simultaneously, and a 20 ±2 PSI differential is not seen, there will not be an
audible alarm. If either source gas pressure drops, the output pressure of the
blender will drop similarly, since the source gases are always balanced to that of
the lower pressure.
The bypass function operates in unison with the alarm. The alarm bypass
poppet communicates directly with the air supply on one end and the oxygen
supply on the other.
When the two source gases are near equal in pressure, the alarm bypass
poppet is positioned over the bypass channel, blocking the flow of both gases.
The poppet will remain seated for unequal pressures up to 20 ±2 PSI. Once a 20
±2 PSI difference occurs, the higher gas pressure will overcome the spring force
and pressure of the poppet at its opposite end, thus creating a path (air or oxygen)
to flow into the alarm channel.
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 medical air
(21%) until the pressure has been restored to a differential of approximately 6
PSI.
If the blender is set at 21% and the OXYGEN source pressure is reduced enough
to produce a 20 ±2 PSI or greater differential, the unit may not alarm because
it will continue to deliver 21% concentration according to the setting. If the
control is moved slightly from the 21% setting, the alarm will sound.