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Issue
Date: August 30, 2007
Revision Date: June 27, 2011
Western Fiberglass, Inc.
Co-Flow
Hydraulic Interstitial Monitoring System
Propylene Glycol Filled Pressurized Interstitial Space
CONTINUOUS
INTERSTITIAL LINE MONITORING METHOD (LIQUID FILLED)
Certification:
Certified as a continuous, liquid-filled interstitial
space leak detection system for use only with Western Fiberglass,
Inc., double-walled/coaxial flexible pipelines.
Maximum length is 200 feet.
No restrictions on pipeline diameter.
Operating Principle:
Similar to the methodology that has been applied
to liquid-filled interstitial double-walled tanks.
A pressurized reservoir is attached to the piping interstice
and filled with propylene glycol.
A pressurized cylinder is used to maintain pressure in the
reservoir. Pressure is normally adjusted to 50 psig for a
typical service station. The cylinder contains nitrogen or
air and a pressure switch to monitor pressure in the reservoir
(low pressure alarm is typically set at 35 psig).
The reservoir contains a dual-point level sensor that monitors
the liquid level and provides an alarm if the liquid level
is either too high (ingress of liquid) or too low (egress
of liquid).
Once the liquid leaks out of the system, the leak becomes
an air leak. Pressure drops are rapid and a pressure loss
alarm is produced.
The method must be used with a dual-point sensor system that
will properly fit into the reservoir, is compatible with the
interstitial liquid, and is on the NWGLDE list.
Sensors can be used to shut down the turbine system and/or
alert the operator that a potential problem exists.
Alarm Conditions:
Average
Liquid Level Required to Alarm* |
|
Time
to Alarm in Hours, as a Function of Leak Rate |
Lower
Level Alarm (in) |
High
Level Alarm (in) |
|
Leak
Rate (gph) |
For
3 inch Dia Reservoir (hours) |
3.2 |
15.1 |
|
3.0 |
0.1 |
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0.2 |
1.3 |
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0.1 |
2.6 |
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0.005 |
51.5 |
*The
liquid level required to alarm is controlled by the level of
liquid in the reservoir. This level is determined by the operator
when filling the reservoir. The reservoir is filled to a level
where the dual point sensor is floating midway between the low
and high level alarm.
Previously conducted theoretical calculations and laboratory
measurements confirm that dilution of the propylene glycol used
in the interstice of the WFG system will produce a significant
reduction in the alarm time. The use of diluted propylene glycol
(from100% to 50%) will reduce the alarm time by a factor of
approximately 7.2. For example, an alarm time of 80 minutes
would be reduced to around 11 minutes.
Applicability:
Western Fiberglass, Inc. underground double-walled/coaxial flexible pipelines containing gasoline, gasohol, diesel, heating oil #2, kerosene, aviation fuel, or motor oil. Other liquids may be stored after consultation with the manufacturer. Calibration:
Equipment requires no calibration other than
to ensure the reservoir is at a level where the dual point
sensor is floating midway between the low and high level alarm.
The electronics must be calibrated and maintained in accordance
with the sensor/monitoring equipment instructions.
Comments:
Pipeline fittings with interstitial communication
tubing must only be located in sumps or pump pits – direct
burial is not permitted.
The interstice must be filled from the low point in the pipeline
to minimize trapped air.
The evaluation was conducted in a Western Fiberglass, Inc.
double walled/coaxial flexible pipeline with an interstitial
capacity of 1.64 gallons, an inside diameter of 1.5 inches,
and a length of 200 feet.
Installers must be certified by both the piping and sensor
manufacturer.
Evaluation was conducted with an interstitial pressure of
50 psig.
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Western
Fiberglass, Inc.
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Evaluator:
Ken Wilcox Associates
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1555
Copperhill Parkway
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Tel:
(816) 443-2494
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Santa
Rosa, CA 95403
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Date
of Evaluation: 02/23/07
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Tel:
(707) 523-2050
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E-Mail:
sales@westernfg.com
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URL:
www.westernfg.com
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