Doc. 12-4091 - r01 (9/12/12)
PG-27
SERVICE
GUIDE
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©
2002 DESIGN
(
2012)
POSITIVE PRESSURE TEST REPEATED (to check for
component integrity after reassembly)
1. Ensure all Breathing Loop components are con-
nected and properly tightened as described in the above
sections.
2. Rotate the
OVER-PRESSURE VALVE (OPV) (40)
body clockwise until it is fully closed.
3. Close the
DSV/BOV (1)
.
4. Using a
regulator first stage
and
Diluent LP QD
hose
attached to the
ADV/MANUAL DILUENT VALVE
(52)
, fill the
COUNTERLUNGS (30, 44)
with pure breath-
ing gas, until gas vents from the
OVER-PRESSURE
VALVE (OPV) (40)
. The
COUNTERLUNGS (30, 44)
should be full and firm to the touch.
5. Listen for any air escaping. Also look for any defla-
tion of the
COUNTERLUNGS (30, 44)
.
6. Let the unit stand for 5 minutes inflated. Look again
for any deflation or loss of
COUNTERLUNG (30, 44)
fullness.
7. Any escaping air or deflation means the breathing
loop has failed The Positive Pressure Test.
NOTE:
The Shearwater Secondary can be used
as a digital gauge to verify pressure loss. With
positive pressure applied and the DSV closed,
the Oxygen Sensor readings should raise to
about 0.22 ~ 0.23 PO
₂
. If the Oxygen Sensor
readings start to drop back to 0.21 PO
₂
after 1
minute, there is a positive pressure leak
8. If the unit passes step 7, open the
DSV/BOV (1)
.
There should be a rush of air released. If that is not the
case, the Breathing Loop has lost gas - failed the test.
NOTE:
Be aware that if the ambient temperature
and introduced gas temperature are not matched
the unit may falsely fail the Positive Pressure
Test. Avoid this by allowing the unit and breath-
ing gas supply tanks to reach room temperature
before performing the test.
9. If the Breathing Loop has failed this test, repair/
replace any leaking component found during this
test. Repeat the test as necessary to find the source
of failure.