13
IV.
Calibration and Testing:
MEASURING SYSTEM RESILIENCY / BLEED-BACK
When under pressure all closed piping systems exhibit an elastic response that will force fuel from the
line if an opening is provided. The volume of fuel forced from the line is dependent on a number of factors
and must be measured for each installation.
The following statements outline a procedure for measuring the expelled volume, which is referred to as
resiliency or bleed-back. This procedure assumes the use of the Vaporless Model LDT-890 Leak Detector
Tester to perform this task.
The following procedure assumes no knowledge of the operation of the LDT-890 and therefore details
each step of the process. The operation manual supplied with the LDT-890 provides additional information
and should be consulted by the technician.
The following procedure measures the bleed-back for a single product. If the site contains multiple
products, this procedure must be repeated for each product.
CAUTION: Eye protection required during the calibration and testing process.
1. Disable ISM Repressure Cycle
With power applied to the ISM, disable repressurization function by setting REPRESSURE DISABLE
TIME from 00 to 23.
2. Power Off
Turn off the circuit breaker providing power to the product under test. This is done to prevent the
accidental starting of the pump while the line is open in the following steps. Power may remain on the
ISM-4080. However, it is acceptable if power is also disconnected from the module.
3. Install LDT-890 Test Unit
WARNING – THE FOLLOWING ASSUMES THE LINE HAS BEEN PURGED BEFORE THE
LDT-890 IS INSTALLED! IF THE LINE HAS NOT BEEN PURGED, DO SO FIRST BEFORE
INSTALLING THE LDT-890.
Select the dispenser at the highest point of the delivery system for the selected product. If there is no
elevation difference, select the dispenser furthest from the pump.
4.
Set the test unit selector to the PRESSURE STEP TEST position.
5. Power On
Turn on the circuit breaker for the product under test. If power had been disconnected from the ISM,
restore power to the module.
Summary of Contents for ISM-4080
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