Pilot Pressure System - Sunrise Medical DeVilbiss 505DZ Service Manual

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
8. Carefully push sleeve into valve body (turning it slightly) so
you do not cut or nick the o-rings.To ensure proper
placement of sleeve, use the spring retaining spacer and
push the sleeve and spacer in until the spacer is flush with
the end cap mounting surface.
9. Reassemble remaining parts of valve in reverse order.
To replace purge valve:
1. Align valve body and gasket on manifold. Ensure that gasket
is aligned properly. Secure with two allen head screws.
2. Attach pilot pressure tubing to purge.
3. Reconnect the two wires on terminals of pilot valve.

Pilot Pressure System

The compressed air in the pilot pressure system is used to acti-
vate the four-way and purge valves.This compressed air
(approximately 22-28 PSI or 125-200 kPa) is stored in the pilot
accumulator cavity within the manifold. An internal check valve
on the inlet side allows compressed air to enter and prevents it
from escaping.The outlet end of the cavity is connected to the
pilot valves on the purge and four-way by an externally mount-
ed "T" fitting and 1/16" tubing.
A defective check valve in the pilot accumulator or leak in the
pilot pressure tubing would result in lower pilot pressure.This,
in turn, could cause a malfunction of the four-way and/or purge
valve or low oxygen concentration.
Four-way
valve
Pressure
vacuum
gauge
1/16"
I.D. hose
Figure 43
Pilot valve
Pressure test
assembly
To test pilot pressure:
1. Remove the front cabinet.
2. Remove the pilot pressure hose from the pilot valve on
the four-way or purge.
3. Attach the pilot pressure hose to the barbed fitting on one
end of the pressure test assembly that is included in the
service kit.
4. Attach the 1/16" hose on the other end of the test
assembly to the fitting on the pilot valve.
5. Install a pressure gauge on the test assembly.
6. With the unit operating, pilot pressure readings should be
alternating from 22-28 PSI (125-200 kPa).This pressure
range may vary slightly from one unit to another.This is
essentially the same pressure as that being exhausted by
the compressor.Therefore, it can also be used to help
determine if the compressor is working properly.
7. If pilot pressure is low, check sieve bed pressure.
8. If sieve bed pressures are normal, check for leaks in the
pilot pressure system. If no leaks are found, then the check
valve in the pilot accumulator may be leaking internally and
the manifold base must be replaced (see Figure 44).
9. If sieve bed pressures are low or rising slowly, then:
a. One or more of unit filters may be occluded.
b. There is a severe leak in system.
c. Compressor reed valves,Teflon ring, or the
compressor itself may be defective.
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