Note: Descriptions are shown in the official language in which they were submitted.
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'APPLICATION UNDER THE PATENT COOPERATION TREATY
TITLE: METHOD AND APPARATUS FOR STORAGE TANK LEAK
DETECTION
INVENTORS: JIMMY WOLFORD, BERNIE WOLFORD, CLARK
LOCKERD, RICKY SLAUGHTER
CITATION TO PRIOR APPLICATION
This is a continuation-in-part application with respect to PCT Application
Serial No. PCT/US2004/021704, Filed 07 July 2004 from which priority is
claimed under 35 U.S.C. 120 and under provisions of the Patent
Cooperation Treaty.
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention is directed towards a method and apparatus for
providing a safe, precise, and cost-effective storage tank leak detection
system; and more particularly, to a method and apparatus wherein the
containment integrity of a storage. tank is determined by mass measurements
of the stored product.
2. Background Information.
Storage tanks play a vital role in today's economy. The economy, on a
global scale, depends on the proper function of these tanks as they are
prevalent in several industries and virtually every geographical region in the
world. In light of the vital role these storage tanks play, the integrity of
the
tanks is placed at a premium. That is, storage tank owners are willing to
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invest huge sums of money in both the maintenance and inspection of such
tanks.
These tanks come in all shapes and sizes, are found both below and
above ground, and are used to store a wide-range of materials. Storage tank
capacities range from hundreds to millions of gallons and are used to store a
staggering assortment of products; these storage tanks are commonly used to
store hazardous material.
As one could imagine, there is a wide range of problems associated
with maintaining storage tank integrity, particularly with above ground
storage
tanks. Given the enormous dimensions of above ground tanks, the corrosive
products contained within the tanks, the incredible mass of the stored
product,
and the extreme weather conditions the tanks are subjected to; it is plain to
see that above ground storage tank leaks are an all-to-common problem.
Using the United States Environmental Protection Agency leak detection
threshold criteria of .05 gallons per hour in a 10,000-gallon underground
tank,
that threshold would equate to a 15 gallon per hour detection level in an
80,000 barrel above ground tank. Given the limited number of systems
capable of meeting the EPA's underground storage tank leak detection
threshold and the added difficulties associated with above ground tanks, the
difficulty in protecting against and detecting leaks is easily seen.
However, the recognized difficulty in preventing storage tank leaks
does not mitigate the duties or liabilities imposed on responsible parties.
Tremendous environmental and economic consequences and the threat of
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litigation and clean up costs associated with storage tank leaks force
responsible parties to invest large sums of money in the maintenance and
inspection of the tanks. Tank inspections are costly with respect to the
amount of money spent, the danger presented to the inspectors and the
environment, and production downtime. In fact, these inspections often
remove a tank from service for more than one month. The threat of liability
also forces responsible parties to spend money unnecessarily for the
maintenance of these tanks. Moreover, liability does not end with litigation
and clean-up costs.
Currently, responsible parties are, in some countries, being
incarcerated as a direct result of storage tanks leaks. These leaks have
contaminated surrounding ground water, some of which serves as drinking
water for local residents. As such, the facilities associated with such
incidents
have been shutdown until compliance with emissions regulations can be
established beyond reasonable doubt. Such proof, in turn, is dependent on
proof of reliable and sufficiently accurate detection systems and methods for
proving such compliance. Each day the shuttered facilities remain inoperative
adds to an already tremendous amount of money lost.
Prior to the present invention (to be described in detail hereafter), there
are simply no known systems or methods by which the leak detection
requirements can be met. Presently available leak detection systems lack
detection thresholds low enough to detect leaks down to permissible upper
leakage limits for above ground storage tanks.
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Clearly, for the reasons set forth above, there is a dire and immediate
need for the ability to determine, with far more precision than presently
possible through use of presently available systems and methods, the
presence and degree of leakage from above ground storage tanks, at least to
the extent of proving compliance with applicable storage tank leakage
regulations or statutes.
Comparison with Known Technologies in the Field
Storage tank leak detection systems are known in the art; however,
these products are fraught with problems. The present systems are
imprecise, or provide erroneous data for any or all of reasons including: the
consistency of the soil acting as the tank's foundation, the temperature
stratification of the in-tank product, extraneous noise sources, thermal
expansion of the tank's contents, water table level, previous soil
contamination, and/or tank shell dynamics.
Further, some detection devices can only be used when the storage
tank is empty, and no known system or method ensures a comprehensive
inspection of the tank. The most common form of such a system is "vacuum
box testing;" however, this system is intended only for weld joints and is not
usually applied to the entire tank bottom. Magnetic flux floor scanning is
also
used, but is not effective at examining the area of the floor surface close to
the surface walls or where there are physical obstructions. Ultrasonic
detection is used, but this is only effective for small areas of the surface.
Gas
detection is also used, but the types of materials stored in the tank can
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obstruct this method.
Other common leak detection systems employ a level sensor.
However, even large volume changes produce only small level changes, as
the cross-sectional area of the liquid surface in these tanks is very large.
5 This, combined with differential expansion and temperature change of the
stored liquid and its vapor, make this type of detection system inconsistent
and very nearly worthless.
Finally, mass measurement detection systems are known in the art.
However, the presently available systems and associated methods are not
capable of the precision, which is indicated above as crucial at the present
time (and which, as described below, is afforded by the systems and methods
of the present invention). Present mass measurement leak detection systems
in the art are limited by tank shell variations resulting from temperature
effects
on tank shell plating. As such, known mass measurement detection systems
are only sensitive enough to be used in smaller tanks, typically underground
storage tanks. However, as will be seen in the specification to follow, the
present invention overcomes tank shell variations and other shortcomings of
presently known technology in this field through data collection and data
correction apparatus, techniques and interpretation.
In light of the severe consequences of failing to detect significant
storage tank leaks, presently not detectable through use of known systems or
methods, there is a compelling need for a system and method by which one
can detect very small leaks even in very large tanks, ideally in a safe and
cost
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effective manner.
It would well serve those who are responsible for maintaining storage
tank integrity to provide a safe, precise, and cost-effective detection system
that does not depend on independent variables such as fluid temperature,
fluid stratification, or tank stabilization, and may be used in an efficient
manner thereby preserving industrial and environmental resources.
SUMMARY OF INVENTION
1o In view of the foregoing, it is an object of the present invention to
provide a storage tank leak detection apparatus with a very low detection
threshold that may be used in an efficient manner thereby preserving
industrial and environmental resources.
It is another object of the present invention to provide an apparatus for
safe storage tank leak detection
It is another object of the present invention to provide an apparatus for
precise storage tank leak detection
It is another object of the present invention to provide an apparatus for
cost-effective storage tank leak detection
It is another object of the present invention to provide an apparatus for
non-intrusive storage tank leak detection
It is another object of the present invention to provide an apparatus for
storage tank leak detection where the contents of the storage tank do not
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have to be removed
It is another object of the present invention to provide an apparatus for
storage tank leak detection where no chemical additives are involved
It is another object of the present invention to provide an apparatus for
immediate storage tank leak detection
It is another object of the present invention to provide an apparatus for
conclusive storage tank leak detection
It is another object of the present invention to provide an apparatus for
quantitative storage tank leak detection
It is another object of the present invention to provide an apparatus for
storage tank leak detection that does not depend on fluid temperature
changes
It is another object of the present invention to provide an apparatus for
storage tank leak detection that does not depend on fluid stratification
It is another object of the present invention to provide an apparatus for
storage tank leak detection that does not require tank stabilization time
It is another object of the present invention to provide an apparatus for
storage tank leak detection that requires only minimal tank preparation
It is another object of the present invention to provide an apparatus for
storage tank leak detection that has been evaluated by an EPA-recognized,
independent third party laboratory
It is another object of the present invention to provide a method with a
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very low detection threshold that may be used in an efficient manner thereby
preserving industrial and environmental resources.
It is another object of the present invention to provide a method for safe
storage tank leak detection
It is another object of the present invention to provide a method for
precise storage tank leak detection
It is another object of the present invention to provide a method for
cost-effective storage tank leak detection
It is another object of the present invention to provide a method for
non-intrusive storage tank leak detection
It is another object of the present invention to provide an apparatus for
storage tank leak detection where the contents of the storage tank do not
have to be removed
It is another object of the present invention to provide a method for
storage tank leak detection where no chemical additives are involved
It is another object of the present invention to provide a method for
immediate storage tank leak detection
It is another object of the present invention to provide a method for
conclusive storage tank leak detection
It is another object of the present invention to provide a method for
quantitative storage tank leak detection
It is another object of the present invention to provide a method for
storage tank leak detection that does not depend on fluid temperature
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changes
It is another object of the present invention to provide a method for
storage tank leak detection that does not depend on fluid stratification
It is another object of the present invention to provide a method for
storage tank leak detection that does not require tank stabilization time
It is another object of the present invention to provide a method for
storage tank leak detection that requires only minimal tank preparation
It is yet another object of the present invention to provide a method for
storage tank leak detection that has been evaluated by an EPA-recognized,
independent third party laboratory.
The present invention provides a safe, extremely precise, and cost-
effective solution to the problems mentioned above. Test results associated
with the present invention provide an accurate determination of containment
integrity, and in the event of leakage, a precise volumetric leak rate. The
present invention is not restricted by fluid type, fluid temperature, fluid
level, or
tank size.
Distinguished from products known in the art, the present invention
provides an intrinsically safe detection system. The leak detection system of
the present invention uses a sufficiently low wattage (as established in the
National Electric Code) so that the components of the system may be placed
within the class I area of the tank. In fact, the present invention provides
for
leak detection system components to be placed within the storage tank. As
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will be described in the specification to follow, placement of leak detection
components in the tank used in combination with system control techniques
and data correction software, provide for precision not possible with products
known in the art.
5 Further, no physical inspection of the tanks is required for practice of
the present system. As such, there is no need to drain, clean, or enter the
tank. With no need for physical inspection, neither inspectors nor the
environment are exposed to the contents of the tank. With no need to drain
the storage tank, practice of the present invention does not produce
10 hazardous by-products associated with the draining/cleaning process, and
danger from transport and storage of the drained product is avoided. Finally,
the systems and methods of the present invention do not require chemical
additives to be mixed with the tank contents. As such, incidental spills and
leaks are avoided altogether.
Practice of the present invention is cost effective. Tank structure or the
foundation and surrounding soil are not disturbed, as such; set-up time and
capital investment costs are minimized. The present invention is non-intrusive
and does not require manual inspection of the tank. Therefore, operation of
the tank is not hindered, so there is no production downtime. There is no cost
related to the handling, transport, disposal, or storage of removed hazardous
material. Finally, testing can be accomplished simultaneously to further
reduce the total time involved and rapidly identify problem areas.
The determinative feature of mass measurement leak detection
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systems is the sensitivity of the apparatus. That is, the lower the leak
detection threshold level of a device, the more effective it wi1l be at
detecting
leaks. The present invention, by employing a combination of techniques and
components not known in the art, provides a leak detection threshold that is
much lower than any known device. Most importantly, the system of the
present invention provides for placing mass measuring components within the
actual storage tank, thereby eliminating extraneous noise associated with
bubbler units required by other products in the art. The system secures the
mass measuring components within a vacuum and holds the mass
measurement component's temperature constant during the entire
measurement process. Further, the system corrects errors in the data
attributed to storage tank shell dynamics and inherent imprecision in the mass
measurement devices. This data correction process will be discussed in
detail in the specification to follow.
As mentioned, tank shell variations limit the effectiveness of presently
known mass measurement detection systems. The systems and methods of
the present invention overcome tank shell variations through data collection
and data correction techniques. First, data is collected through use of a
quartz crystal type pressure transducer (the specifications and use of this
transducer will be explained in more detail in the Detailed Description of the
Preferred Embodiment). A connected to the pressure transducer , records
pressure data over a period of time (preferably one to five nights). The
atmospheric temperature and barometric pressure are recorded and precisely
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analyzed to calculate any changes in the mass of the fluid within the tank.
This data is regressed to give a line slope that is converted to a leak rate,
usually in gallons per hour.
Data generated by the transducer is collected on a 24-hour basis. Only
data containing a sufficiently low amount of extraneous noise is analyzed.
Such data is usually obtained at nighttime and during fair weather conditions.
Also, data correction software accounts for the coefficient of expansion for
any given storage tank. The nighttime data is corrected for atmospheric
conditions, and variations in the tank shell. These measurements and
corrections allow the system to repeatedly achieve the stated accuracy in real
world conditions on a routine basis.
For even greater precision, the leak detection system of the present
invention provides for an independent barometric measuring means to
constantly record the barometric pressure during the data collection process.
This independent barometric pressure measuring means, used in combination
with data correction software, corrects any zero drift associated with the
individual pressure transducer. That is, this system corrects for the inherent
error present in any transducer when that transducer deviates from its initial
.
Practice of the apparatus involves securing a combination of precise
mass measurement components, including a highly precise quartz crystal
type pressure transducer, in a vacuum-sealed canister. This canister is then
lowered to the bottom surface of a storage tank. A differential reference is
placed just above a liquid surface. The pressure, measured at the tank floor
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("tank bottom pressure") and atmospheric pressure measured just above the
liquid surface, is recorded by the above-referenced micro sensitive
differential
pressure transducer, recorded on a real time basis and post processed using
a data analysis routine to accurately calculate any changes in the mass of
fluid contained within the tank to determine if there is a loss. The present
system, using the specified transducer, and when used in the manner and
with the data interpretation described herein, is capable of detecting above
ground storage tank leaks at a threshold of less than .9 gallons per hour with
a probability of detection of 95% in a tank - far more accurate than possible
with any presently available quantitative leak detection system. This,
quantitatively, amounts to detecting pressure differentials equivalent to less
than 1/10,000th inch of water column pressure, a tolerance level necessary to
achieve such detection thresholds.
The method and apparatus of the present invention provides a safe
and effective way to detect very small leaks in very large tanks.
Particularly,
the present invention provides a tremendous improvement in accuracy and
leak detection threshold, allowing its users to achieve greater results than
presentiy thought possible.
Thus, in satisfaction of the above objects, an embodiment of the
present invention provides systems and methods for solving each of the
stated problems with presently available storage tank leak detection systems.
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BRIEF DESCRIPTION OF THE DRAWINGS
Annex A is a printout of the industrial controller program source code
referred to herein as the program.
Fig. 1 is a block diagram depicting the general layout of the present
leak detection system.
Fig. 2 is an elevational, sagital cross sectional view of the canister
("protective enclosure means") of the leak detection system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the drawings and the description that follows, referring to figure 1, a
preferred embodiment of a storage tank leak detection system according to
the present invention is generally designated as system 10. An embodiment
of the present invention is shown to include a vacuum-sealed canister 12,
which houses and protects a plurality of mass measurement components and
system control components. In the preferred embodiment, vacuum-sealed
canister 12 is made of a substantially non-corrosive metal (aluminum, for
example), however, any material that is corrosion resistant and offers
sufficient protection to the components enclosed is adequate for use with the
present invention. Canister 12 is directly immersed in storage tank 60 and
rests on storage tank bottom surface 62. Canister 12 further contains vacuum
seal nozzle 14 and transducer high side aperture 20. Vacuum seal nozzle 14
allows communication means to pass from the inside of the canister to the
outside of the canister while maintaining the integrity of the vacuum inside
the
canister. Vacuum nozzle 14 further contains barometric pressure measuring
means aperture 16 and transducer low side aperture .
At its proximate end canister hose 15 forms a fluid tight seal with
vacuum seal nozzle 14. Extending from vacuum seal nozzle 14, canister
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hose 15 passes through storage tank top surface recess to an area outside of
the class I region of storage tank 60 (class I region refers to the National
Electric Code designated hazardous areas in which only power wattage levels
of less than certain prescribed levels may be introduced). Canister hose 15
5 serves as a conduit for communication means extending though vacuum
nozzle 14 and as an atmospheric reference in its service as a barometric
pressure measuring means reference hose. Canister hose 15 allows
transducer low side aperture and barometric pressure measuring means
aperture 16 to be directly exposed to atmospheric pressure while maintaining
10 a fluid tight seal with vacuum seal nozzle 14 thereby preserving the
integrity of
the vacuum of canister 12.
Contained within vacuum-sealed canister 12 is differential pressure
transmitter 22. In the preferred embodiment, differential pressure transmitter
22 is comprised of a highly precise quartz crystal type pressure transducer 24
15 . Transducer 24 contains an oscillating quartz crystal and has a resolution
of
1x10-8, as known in the industry.
The differential pressure transmitter 22 consists of a pressure
transducer and a serial interface board, commands are sent and
measurement data are received via either an industry standard serial port.
Measurement data are provided directly in user-selectable engineering units
with a typical total accuracy of 0.01% or better over a wide temperature
range.
Pressure measurements are fully temperature compensated using a precision
quartz crystal temperature sensor. The unit is oil filled on the high pressure
side and features an oil filled buffer tube. The unit is rated for 0 to 15 psi
differential pressure."
The ultimate resolution achievable with a transducer is limited by its
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noise level. System 10 greatly reduces noise thereby increasing the
resolution of transmitter 24. In system 10, transmitter 22 has been modified
from its original configuration so that it may be directly immersed in storage
tank 60. This modification has eliminated dependence on any bubbler unit
(thereby eliminating noise associated with such units) as required by other
products. As will be further described in this section, transducer 24 is held
at
a constant temperature and secured in vacuum to further reduce noise.
Quartz crystal type pressure transducer 24 is further comprised of
transducer low side 26. Transducer low side 26 is a differential reference
that
receives the barometric pressure value at the liquid surface. Transducer low
side tube 28 forms an air tight seal at it proximate end with transducer low
side 26 and extends though the vacuum of canister 12 where it forms an air
tight seal at its distal end at transducer low side aperture of vacuum seal
nozzle 14. Transducer low side tube 28 allows transducer low side 26 to
receive the barometric pressure from the reference point at the liquid surface
while allowing canister 12 to remain in vacuum.
Quartz crystal type pressure transducer 24 is further comprised of
transducer high side 30. Quartz crystal type pressure transducer high side 30
is a pressure reference point, which measures the sum of the barometric and
hydrostatic pressure at tank bottom surface 62. Transducer high side 30
contains a protruding transducer high side tube 32. In the preferred
embodiment, transducer high side tube 32 is filled with a pressure-sensing
liquid and extends through transducer high side aperture 20 where it is ported
to the product contained in tank 60. Transducer high side tube 32 is
surrounded by tube fitting 34. In the preferred embodiment, tube fitting 34
slides along high side tube 32 and forms a fluid tight seal at high side
aperture
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20. Tube fitting 34 allows high side tube 32 to extend through high side
aperture 20 while maintaining the integrity of the vacuum of canister 12.
Transducer 24 transducer low side 26 and transducer high side
30 to arrive at the pressure exerted by the mass of the stored product.
Transmitter 22, communicating digitally, then sends this processed
information to 30. This data is transmitted along data transfer means 23. In
the preferred embodiment, data transfer means 23 is a standard bus
communications cable. However, one could easily envision a data transfer
means such as wireless communication that would work equally as well. Data
transfer means 23 extends from the output of differential pressure transmitter
22 through vacuum seal nozzle 14 and continues, separated from storage
tank's 60 contents by canister hose 15, to 30.
Also contained within canister 12 is 34. Data transfer means
39 extends from the output of transmitter 34 through vacuum seal nozzle 14
and continues, separated from storage tank's 60 contents by canister hose
15, to 30. In the preferred embodiment, data transfer means 39 is a standard
bus communications cable. However, one could easily envision a data
transfer means such as wireless communication that would work equally as
well.
serves as a part of a temperature regulation scheme used to keep the
contents of canister 12 at a constant temperature during the data gathering
process. This data is transmitted along data transfer means 23. In the
preferred embodiment, data transfer means 23 is a standard bus
communications cable. However, one could easily envision a data transfer
means such as wireless communication that would work equally as well.
While the above temperature regulating scheme has been described with
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reference to one embodiment, one could easily imagine other temperature
regulation schemes that would work equally as well.
The use of this temperature regulation scheme to hold
transmitter 22 at a constant temperature further increases the precision of
the
apparatus. The absolute temperature at which transmitter 22 is maintained is
not critical, rather constancy of temperature affects the integrity of the
subject
measurements. As a matter of practicality and economy, temperature of
transmitter 22 is maintained, according to the presently preferred mode of the
present invention, at a temperature of approximately F above the ambient
temperature of the product (oil or gasoline, for example) in tank 60. If, for
example, the product is at 500 F, transmitter 22 is maintained at 0 F, if the
product is at 90 F, transmitter 22 is maintained at F, and so forth.
Also contained within canister 12 is barometric pressure
measuring means 40. Barometric measuring means 40 serves as an
independent reference for true atmospheric pressure. In the preferred
embodiment, barometric pressure measuring means 40 may be any standard
barometer that sends signals to be processed by 30. Barometric measuring
means 40 is very useful for increasing the precision of system 10. The
present invention employs barometric measuring means 40 to serve as an
independent measure of true atmospheric pressure thereby allowing for data
correction over any extended period of time. As will be discussed in this
section, data correction using values taken from barometric pressure
measuring means 40 greatly increases the precision of the current invention.
Barometric measuring means tube 42 forms an air tight seal at
its proximate end with Barometric measuring means 40 and extends though
the vacuum of canister 12 where it forms an air tight seal at its distal end
at
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barometric measuring means aperture 16 of vacuum seal nozzle 14.
Barometric measuring means tube 42 allows barometric measuring means 40
to receive the barometric pressure from the reference point at the surface of
liquid within storage tank 60, while allowing the interior of canister 12
(with
transmitter 22 installed therein) to remain in vacuum so as to substantially
eliminate any environmentally-effected variations in instrument performance).
Data transfer means 43 extends from the output of barometric pressure
measuring means 40 through vacuum seal nozzle 14 and continues,
separated from storage tank's 60 contents by canister hose 15, to 30. In the
preferred embodiment, data transfer means 43 is a standard bus
communications cable. However, one could easily envision a data transfer
means such as wireless communication that would work equally as well.
Although not necessary, 30 are typically housed in a separate
enclosure, such as field unit 50. In accordance with the described routines to
follow and the exemplary computer code depicted in Annex A attached hereto
and incorporated herein by reference, processes data received from
transmitter 22, fluid temperature transmitter 34 and barometric pressure
measuring means 40. 30 communicates with 70 by data transfer means 72.
In the preferred embodiment, data transfer means 72 is a standard bus
communications cable. However, one could easily envision a data transfer
means such as wireless communication that would work equally as well.
The software commences operation with the initialization of data
collection at the tank bottom, along with the atmospheric and environmental
conditions. Data is automatically collected via industrial computer controlled
programming over some length of time, preferably 36 to 60 hours. The length
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of the test is dependent on tank size and site atmospheric conditions
As will be discussed and illustrated hereafter, remote computer
contains software that performs linear regressions . This regression detects
minuscule changes in the mass of the stored product, thereby indicating the
5 presence of the smallest of leaks. As the compilation of data grows, the
more
precise the regression becomes. The post processing module and software
of remote computer is independent of the
There are software programs or modules involved with the
storage tank leak detection system of the present invention: The program,
10 the local computer program and the linear regression program operated on
remote computer 80. The program is performed by 30 and is responsible for
obtaining (subroutine Measure) data from transmitter 22, controlling the
temperature of transmitter 22 (), obtaining transmitter 22 differential
pressure
and temperature (), . The data acquired by the program is stored within 30 in
15 non-volatile memory.
The primary purpose of the program is to interrogate an
intelligent differential pressure transmitter (transmitter 22) via a serial
connection. The pressure read from transmitter 22 is the difference in
pressure read from transducer low side 26 and transducer high side 30. That
20 pressure value is modified by two additional variables in order to improve
the
accuracy of the reading. The performs correction of barometric pressure; an
analog barometer (such as barometric pressure measuring means 40)
provides the signal that is sent to correct transmitter pressure for errors
due to
changes in barometric pressure, as measured at the upper surface of the
contents of storage tank 60. Also, the program monitors ambient temperature
compensation for changes in the tank diameter which otherwise would skew
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the data interpretation. This post processing is intended solely to detect
variations of contents of storage tank 60 due to leakage and eliminate
variations due to environmental changes. Any change in tank diameter is
accommodated in the calculations thus properly attributing substantially all
variations in differential pressure to variations in the content of storage
tank
60, such as through leakage.
The obtain pressure readings and transducer temperature readings
from transmitter 22. This performed every one minute.
The remaining recorded variables are also obtained on a one minute
time frame. .
Finally, the program is responsible for data storage. This is
accomplished in subroutine Record. One record per minute is stored. The
organization of the data is by date and time. The record for every minute will
include: (1) the differential pressure representing the hydrostatic pressure
produced by the fluid mass (as a floating-point number, IEEE 32 bit format),
(2) the barometric pressure (as a x-16 bit integer), (3) the ambient temperate
(as x100-16 bit integer), .
The software program of the storage tank leak detection system of the
claimed invention is the linear regression program. Remote computer
performs this program. Linear regression of logged data, is performed as
follows: - only nighttime data are typically used in order to minimize
extraneous noise in the analysis, a best linear fit is used for data points in
each data section - when the sections of data that represent durations of
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appropriately low noise level are included in the best fit data regression,
the
slope of the best fit line indicates the leak rate. Calculation of the linear
regression and best fit are straightforward and could be performed by
common software such as Microsoft Excel.
It is believed that, while safe and efficient, the present device will
obviate significant inconvenience and provide substantial utility to those who
wish to detect leaks in storage tanks. Specifically, the present device will
allow very small leaks to be detected in very large storage tanks in a
consistent and cost-effective manner.
Although the invention has been described with reference to specific
embodiments, this description is not meant to be construed in a limited sense.
Various modifications of the disclosed embodiments, as well as alternative
embodiments of the inventions will become apparent to person skilled in the
art upon the reference to the description of the invention. It is therefore
contemplated that the appended claims will cover such modification that fall
within the scope of the invention.
