12
Impulse Second Stage Service & Repair Manual
© 1997 U.S. Divers Co., Inc.
NOTE
: If an accurately calibrated airflow test bench is not
available, proceed to Subjective Tuning Procedures provided
on the following page.
SECOND STAGE AIR FLOW TEST
1.
With the regulator still connected to the test bench, pressurize
the system to 3000 psi (
±
100) and place the second-stage
mouthpiece over the mouthpiece adapter.
2.
Turn the second stage adjustment knob in clockwise between
1/2 - 3/4
turn, only until the airflow has stopped.
3.
Slowly turn the flowmeter control knob until the flow reaches
a minimum of 15 SCFM (425 liters per minute). The reading
on the Magnahelic gauge (inhalation / exhalation effort gauge)
should indicate no more than +6.O” H
2
O. If the reading
e6.0" H
2
O, refer to refer to Table 1 - Troubleshooting
for corrective guidelines and specific procedures.
SECOND STAGE OPENING EFFORT TEST
1.
With the second stage adjustment knob turned in clockwise
1/2 - 3/4 t
urn, turn the flowmeter control knob shut, and then
slowly reopen while watching both the Magnahelic gauge and
the intermediate pressure gauge.
2.
When the intermediate pressure gauge begins to drop below
the intermediate pressure “lockup,” the magnahelic gauge
should indicate an opening effort of +.6" of H
2
O to 1.0" of
H
2
O.
3.
Turn the second stage adjustment knob completely in clock-
wise, and repeat the above procedure to ensure that the open-
ing effort does not exceed 2.7" of H
2
O. If the opening effort is
not within these prescribed ranges, refer to Table 1 - Trouble-
shooting.
SECOND STAGE PURGE FLOW TEST
1.
Turn off the flowmeter control knob.
2.
While the second-stage is still mounted on the mouthpiece
adapter, watch the flowmeter gauge and fully depress the
purge cover. The flowmeter gauge must indicate a minimum
of +5.0 SCFM (142 L.P.M.). If the purge flow is less than
+5.0 SCFM, refer to Table 1 - Troubleshooting.
3.
When purge flow is correct, remove the second-stage from the
mouthpiece adapter on the flow test bench. Shut the valve of
the test bench, and purge the second stage to depressurize the
system. Remove the regulator.
EXTERNAL LEAK TEST
1.
After disconnecting the regulator from the flow bench, con-
nect to a scuba cylinder filled to approximately 3,000 psi.
Open the cylinder valve to repressurize the regulator, and
submerge the entire system in a test tank of clean water.
