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C O M P O N E N T T E S T I N G , R E P A I R & R E P L A C E M E N T
Molecular Sieve Beds
The two molecular sieve beds alternately remove the nitrogen from the air passing through them and provide the patient with a con-
stant supply of oxygen.
Sieve bed pressures can be read by attaching pressure-vacuum gauges to the test points located at the top of the manifold assembly.
Normal pressure observed will be approximately 26 PSI (180 kPa).While one bed is pressurized, the other will depressurize to approxi-
mately 2 PSI (15 kPa).
The efficiency of the molecular sieve material will be impaired if it becomes contaminated by moisture. Contamination causes the
molecular sieve material to lose its nitrogen adsorbing properties resulting in a decrease in oxygen concentration. Also, the pressure
within the sieve bed will increase faster due to contamination which results in a shorter cycle time. Once the cycle time reaches the
minimum preset cycle time, the patient alert system will sound due to a short cycle.
NOTE—The unit should run for a minimum of 20 minutes before turning "Off" to prevent problems associated with moisture cont-
amination in the system.
The following tools are needed to test sieve beds:
•
(2) Pressure-vacuum gauges (part #PVO2D-601)
•
(2) Pressure test fittings (part #303DZ-632)
To test the sieve beds (Figure 28):
1.
Remove the front and back cabinets.
2.
Remove the two 1/16" plugged pieces of tubing on the top corners of the manifold.
3.
Attach the 1/16" I.D. hose from the test fitting to one of the access fittings on the manifold. Attach one of the plugged pieces of
tubing to the 1/16" barbed fitting on the test fitting. Attach the second pressure test fitting to the other access fitting. Connect
the pressure-vacuum gauges to the test assemblies.Turn the unit on and observe the cycling.
4.
Take cycle times. Refer to specifications for typical cycle times at 5 LPM.
5.
After 20 minutes of operation, check the oxygen concentration levels. A combination of short cycle times and low oxygen
concentration indicates contaminated sieve beds.
Pressure-vacuum
gauge
Pressure test
assembly
Manifold base
Left sieve bed
Figure 28
32
Pressure-vacuum
gauge
Pressure test
assembly
Right sieve bed
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Troubleshooting
