DeVilbiss DeVO/MC44-90 - Flow Meter; Pressure Regulator

SECTION 7
SERVICE INSTRUCTIONS
Flow Meter
Each flow meter (5 Fig. 2) is calibrated to an
accuracy of + 5% of full scale and is non-
repairable in the field. The flow meter on the
DeVO/MC44 is designed for use at 8.5 PSI at
flow rates up to five liters per minute. To
check the accuracy of operation, do so only
with devices of certified accuracy and exercise
care in the connection to the test flow meter.
interconnecting hoses should be of large
diameter and as short as possible since seem-
ingly unimportant variations in piping and
back pressure may cause a noticeable differ-
ence in the indicated reading.
The flow meter is pressure compensated
which provides a more accurate reading.
To replace flow meter:
1. Unplug unit from wall outlet.
2. Refer to Service Instruction B to open
front cover.
3. Remove hose clamp and hose from each
end of flow meter (4 Fig. 12).
4. Remove the two nuts holding meter to
contro! panel.
5. Remove flow meter by pushing it through
front of control panel.
Install new flow meter in reverse order.
Close front cover and secure with cabinet
fasteners.
Pressure Regulator
The pressure regulator (10 Fig. 11) stabilizes
the oxygen flow to the patient and also puts a
back pressure on the system. It is pre-set at 8.5
PSI and should not have to be adjusted in the
field. To test the pressure regulator use a
pressure gauge (Part #444-591) and a fitting
suitable to fit on the oxygen outlet (7 Fig. 2)
or on a short piece of tubing connected to the
outlet. The flow meter should be set at 2 LPM
when testing the regulator. If adjustment is
necessary, turn the allen head set screw on
top of pressure regulator until the outlet
pressure reads 8.5 PSI (58.6 KPa) at 2 LPM (a
protective coating may have to be removed
from set screw before adjustment is made.)
A malfunction in the pressure regulator will
cause a loss or fluctuation in the oxygen liter
flow as shown on the flow meter. It may also
cause a decrease in oxygen concentration if
defective or out of adjustment.
10/87
To replace pressure regulator:
1. Unplug unit from wall outlet.
2. Refer to Service Instruction B to open cab-
inet covers.
3. Remove hose clamp and hose from pres-
sure regulator.
4. Unscrew regulator from accumulator
tank.
5. Install new regulator on accumulator
tank, attach hose, and secure with hose
clamp.
6. Close cabinet covers and secure with cabi-
net fasteners.
Manifold Check Valves
Two check valves located in the manifold
allow oxygen to enter the accumulator tank
(9 Fig. 11) when the sieve bed pressure
becomes greater than the accumulator
pressure. They also prevent reverse flow of
oxygen from the accumulator to the sieve
beds.
A defective check valve will result in a de-
crease in oxygen concentration and lower
accumulator pressures. To check accumulator
pressures, use pressure gauge (Part #444-591)
and the pressure test assembly (6 Fig. 8)
included in the DeVO Service Kit. Remove the
1/16” (1.6 mm) diameter hose (4 Fig. 24) from
the accumulator tank and attach it to the
barbed fitting on the pressure test assembly.
Attach the 1/16” (1.6 mm) hose on the other
end of the pressure test assembly to the
accumulator tank fitting (Point F Fig. 24).
Then install the gauge on the pressure test
assembly. Turn unit on with the liter flow set
at5 LPM.
Notice that during each cycle the pressure in
the accumulator will rise to approximately
25.5 PS! (176 KPa) at which point the four-way
and purge shift to start a new cycle. The
pressure will then decrease to as low as 19 PS!
(131 KPa) at 5 LPM. This minimum pressure
will vary according to liter flow. The higher
the liter flow, the lower the pressure will drop
in the accumulator tank. When the check
valve opens, allowing oxygen to flow into the
accumulator, pressure will start to increase
until maximum pressure is reached.
NOTE: A defective check valve will cause a
rapid drop in accumulator pressure as well as
pressures below 19 PSi (131 KPa) at 5 LPM.