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SECTION 7
SERVICE INSTRUCTIONS
The opening and closing of the purge valve
can be observed by attaching pressure gauges
to the test points (1, Fig. 22) on the manifold.
When the purge is activated there will be a
sudden increase in pressure in one bed and a
sudden
decrease in the other as the cycle
changes. When the purge is deactivated the
pressures in the sieve beds will continue to
increase and decrease respectively. You will
hear the oxygen being transferred when the
purge is activated and the exhaust will also be
heard when the valve is deactivated.
A purge valve stuck in the activated position
will cause both sieve beds to pressurize simu!-
taneously and activate the alarm system. The
red long cycle and high pressure lights will be
illuminated. See Section 5, Alarm System.
If
the purge valve remains
in a deactivated
position,
the
alarm
system
will
not
be
activated but the following symptoms may be
noticed:
(1)
No sudden increase and decrease of sieve
bed pressures when
cycle changes. They
will go up and down gradually.
(2) Only the exhaust can be heard when unit
cycles.
(3) Possible drop in oxygen
concentration,
especially at the higher liter flows.
There are several reasons for the purge valve
to malfunction. The cause of failure must be
determined
before
the
proper
corrective
action can be taken. Some reasons for purge
failure are:
(1) Continuous or no voltage to pilot valve on
purge.
(2) Little or no pilot pressure.
(3) Foreign matter inside valve preventing
spool from shifting.
(4) Defective or damaged purge.
(5) O-rings
on
sleeve
may
be worn
pre-
venting the valve from shifting properly.
To test purge valve:
1.
Connect pressure gauges furnished in the
DeVO Service Kit to the test points (Fig.
22) located on the manifold.
2.
Turn
unit on
and
observe
the
green
indicator light (8 Fig. 12) labeled purge on
the
MC
board.
When
this
light
is
illuminated (approximately
1.0 seconds)
the purge should be activated and there
10/87
18
should be a sudden increase and decrease
of pressure in the respective sieve beds.
The absence of this purging action indi-
cates that the purge was not properly
activated. Refer to the normal
cycling
sequence on page 24.
3.
Place the test leads of a volt meter across
the terminals (See test position B, Fig. 16)
located
on
top
of the
pilot
valve.
Approximately
12-15
VDC
should
be
measured while the green purge indica-
tor light is illuminated
(voltage
will
be
supplied for approximately
1.0 seconds).
İf this reading
is not obtained, check for
loose or broken wires from
the
purge
valve to the MC
board.
If no loose
or
broken wires are found, replace the MC
board.
4.
Test
for
pilot
pressure.
See
Service
Instruction "J", Pilot Pressure System.
5.
If 12-15 VDC is medsured
at connecting
leads to purge
and
pilot
pressure
is
normal
then
the
purge
valve
is either
defective or foreign
matter
has gotten
inside valve causing it to malfunction.
In
either
case the
purge
valve
must
be
removed to clean or replace it.
To remove purge valve:
1.
Unplug unit from wall outlet.
2.
Refer to Service Instruction
B to open
cabinet covers.
3.
Disconnect the two wires from terminals
on pilot valve (4 Fig. 16).
4.
Remove the pilot pressure tubing
from
pilot valve (5 Fig. 16).
5.
Remove the two allen head
cap screws
from top of purge using an allen wrench.
The top or valve body and gasket can now
be removed.
NOTE:
Do
not remove
the
valve
manifold.
The valve manifold
will remain
on the
unit
whether you are cleaning or replacing the
valve.
To clean purge valve:
1.
Remove the two allen head screws from
the top of purge valve. The top of the
valve or valve body can now be removed
along
with
the
pilot valve. The
valve
manifold
will
remain
on the
unit.
A
rubber gasket
located
between
valve
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