14
6.
System Purge
Authorize the dispenser. The pump should start running. On the right-hand pressure gauge of the LDT-
890, watch for the pump to achieve operating pressure.
7.
Check all connections for leaks. Correct any fault conditions.
8.
With the large beaker (1000 ml) under the LDT-890 discharge port, set the selector to the DISPENSER
NOZZLE position. Purge the tester of air by allowing 800 to 1000 ml of fuel to flow into the beaker.
Continue until air spitting has stopped. After purging the LDT-890, set the selector back to the
PRESSURE STEP TEST position.
9. Bleed-Back Measurement
Remove the dispenser authorization. The pump should stop running. Unless there are fault conditions
such as a leak or significant thermal contraction, the line pressure should stabilize at 20 – 30 PSI for
fractional horsepower pumps, or 20 – 50 PSI for higher pressure pumps.
10.
With the large beaker under the LDT-890’s discharge port, carefully move the selector
counterclockwise until fuel begins to flow. Monitor the line pressure and when it falls to 14 PSI rapidly
return the selector to the PRESSURE STEP TEST position. For a more precise measurement, have
one tech monitor ISM display while another tech drains line pressure, when the display changes from
MONITOR to DELAY, stop flow.
11.
With the flow of fuel stopped, empty the collection beaker.
12.
With the small (250 ml) beaker under the LDT-890 discharge port, carefully move the selector to the
DISPENSER NOZZLE position. Fuel will begin to flow into the beaker. When fuel stops flowing,
return the selector to the PRESSURE STEP TEST position.
13.
Note the volume of fuel collected. This volume is referred to as bleed-back. Repeat the collection
process several times to confirm the bleed-back volume.
Note:
Depending upon the measured volume, the use of the large beaker may be needed. When
possible, the small beaker provides more accurate measurements. The
averaging of several
consecutive samples
is necessary to accurately determine the bleed-back volume. Enter resiliency
value into ISM-4080 controller (see page 10).
This completes the bleed-back measurement procedure and set-up of the ISM repressure cycle. To ensure
proper installation and system calibration, a 3 GPH leak test must be performed.
LEAK DETECTOR TEST AT 3 GPH
Whether the ISM is fitted to a new installation or retrofit to an existing site, a test of the leak detector must
be performed. This is done to ensure that the VMI Leak Detector is operating normally and that the
selected ISM delay time is long enough for the VMI Leak Detector to return to its reset position.
The following statements outline a procedure for testing the operation of the VMI Leak Detector. This
procedure assumes the use of the Vaporless Model LDT-890 Leak Detector Tester to perform this task.
Содержание ISM-4080
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