Troubleshooting; System Operation; Normal Operating Sequence - Sunrise Medical DeVilbiss Serie Manual De Servicio

SYSTEM OPERATION

The DeVilbiss Oxygen Concentrator uses a pressure swing
adsorption system.The air is drawn into the unit through air
filters and into a double-head compressor.
A pneumatic diagram of the system is shown in Figure 14.
The compressed air passes through a rotary valve (Figure 5),
which is cycled at a pre-determined rate, and is directed into
one of two sieve beds.The sieve beds contain molecular sieve
material which is a synthetically-produced inorganic silicate. It is
very porous and has the unique ability to selectively adsorb
nitrogen from the air as it passes through the sieve bed.
As one bed is being pressurized, the other bed is quickly
depressurized.This allows the nitrogen that was adsorbed
during its pressurization cycle to be exhausted from the
sieve material.
The nitrogen is released through exhaust ports located on the
rotary valve assembly.The ports are connected to a single piece
of hose running from the valve to the exhaust muffler.
Also during each bed pressurization, a small amount of oxygen
flows through an orifice (Figure 9) from the pressurized bed
into the depressurizing bed.The orifice is clamped inside a long
piece of blue tubing connecting the outlets of the two sieve
beds.This helps purge the nitrogen from the depressurizing bed.
The beds will continue to be alternately pressurized and
depressurized as the unit operates.
Oxygen leaving the sieve beds is directed through a check
valve to the accumulator tank. A pressure regulator (Figure 9)
on the tank controls the oxygen pressure as it leaves the accu-
mulator and enters the flow meter.The flow meter allows the
oxygen flow to be controlled and adjusted to the level pre-
scribed by the patient's physician. From the flow meter the
oxygen passes through the final bacteria filter (Figure 8), a
check valve, and finally the oxygen outlet port to the patient.
The DeVilbiss Oxygen Concentrator operates on a timed
cycle.The cycling is controlled by the PC board.The PC board
will send voltage to the valve causing it to shift and alternately
pressurize the sieve beds.
The PC board also activates the electronic alarm system. A
high pressure condition will be indicated with a "popping" type
sound produced by release of pressure from a pressure relief
valve on the compressor head. Low flow and power failure are
indicated by audible and visible alarms.
The 515 OSD Models operating system incorporates "turn-
down" technology.The PC board constantly monitors the flow
rate and will decrease the cycle time whenever the flow rate
is less than 2.5 LPM.Therefore it "turns-down" the cycle based
on lower oxygen demand. As a result, the unit runs cooler
with less power consumption.
T R O U B L E S H O O T I N G

NORMAL OPERATING SEQUENCE

When the concentrator is turned "On," the following cycling
sequence can be observed by attaching pressure gauges to the
sieve bed test points.
1. The rotary valve is quickly cycled several times to relieve resid-
ual bed pressure preventing a static condition in the compres-
sor.This rapid cycling only happens on start-up and is clearly
heard as pressure is being quickly exhausted several times
through the exhaust muffler that is connected to the valve.
2. The PC board applies a short DC voltage signal to the valve.
The valve will stop for approximately 7 seconds causing the
right bed to pressurize first while the left bed depressurizes to
approximately 2 PSI (14 kPa).
3. Voltage is again applied to the valve for a short time.The valve
will stop for approximately 0.7 seconds. During this time the
sieve bed pressures are equalized.
4. A short DC voltage signal is again applied to the valve.The
valve will stop for approximately 7 seconds causing the left
bed to pressurize while the right bed depressurizes to approx-
imately 2 PSI (14 kPa).
5. A short DC voltage signal is again applied to the valve.The
valve will stop for approximately 0.7 seconds. During this time,
the sieve bed pressures are equalized.
6. The cycle then repeats with step 2.
NOTE: In the "turn-down" mode (OSD models only), the fixed
cycle time is decreased to approximately 3 seconds and the
bed pressure equalization time to approximately 0.3 seconds.
NOTE: High-end sieve bed pressure should not exceed 1/2 PSI
(4 kPa) above high-end accumulator pressures. Refer to
Specifications for normal pressures obtained during the cycle.
9 LT-1928