U.S. patent application number 17/695470 was filed with the patent office on 2022-06-30 for precision depth sensor.
The applicant listed for this patent is Gregory E. Young. Invention is credited to Gregory E. Young.
Application Number | 20220205413 17/695470 |
Document ID | / |
Family ID | 1000006198312 |
Filed Date | 2022-06-30 |
United States Patent
Application |
20220205413 |
Kind Code |
A1 |
Young; Gregory E. |
June 30, 2022 |
PRECISION DEPTH SENSOR
Abstract
A system and method for monitoring liquid tanks that includes a
submersible sensor within the tank below liquid surface. The system
may also include a secondary sensor to determine ambient
conditions, and a controller to determine when changes in liquid
level are due to ambient events, or potential breach of system. A
calibration rod may be used to monitor displacement of liquid in
the tank and calibrate system to determine changes in height of
liquid level.
Inventors: |
Young; Gregory E.; (Prescott
Valley, AZ) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Young; Gregory E. |
Prescott Valley |
AZ |
US |
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|
Family ID: |
1000006198312 |
Appl. No.: |
17/695470 |
Filed: |
March 15, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16666183 |
Oct 28, 2019 |
11274635 |
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17695470 |
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PCT/US2018/030020 |
Apr 27, 2018 |
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16666183 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 27/06 20130101;
G01N 33/2847 20130101; F02M 21/02 20130101; G01N 27/223
20130101 |
International
Class: |
F02M 21/02 20060101
F02M021/02; G01N 27/06 20060101 G01N027/06; G01N 33/28 20060101
G01N033/28 |
Claims
1. A method of determining the qualities of a liquid in a storage
tank with an embedded sensor submerged into the liquid, with the
embedded sensor along a bottom surface of the storage tank or not
more than a few inches above the bottom surface, said method
comprising the steps of measuring the initial pressure along a
specific point in the bottom of the tank; determining a weight of
the fuel based on the initial pressure reading; calibrating the
measurement via use of a submersible displacement rod via
suspending a rod of a set volume into the fuel; detecting a further
pressure; determining a change in the pressure as between the
initial pressure and the further pressure readings; setting the
pressure differential to determine a pressure to volume ratio; and
thereafter monitoring the pressure reading at the sensor.
2. The method for determining the qualities of a liquid in a
storage tank as set forth in claim 1, further comprising the step
of measuring an ambient condition via a secondary sensor.
3. A method such as in claim 2 whereby the embedded sensor
determines the properties of a stored liquid, and compares those
properties with the expected change of system conditions reported
by a simultaneous secondary sensor detecting ambient
conditions.
4. A method as set forth in claim 1 wherein the embedded sensor
rests on the bottom of a fuel storage tank.
5. A method as set forth in claim 1 wherein the embedded sensor
rests no more than one inch from the bottom of a fuel storage
tank.
6. A method such as in claim 1 whereby the embedded sensor
determines the conductivity or resistance of the liquid.
7. The method as set forth in claim 6 wherein the embedded sensor
compares conductivity or resistance with the expected change of
system conditions reported by a secondary sensor detecting ambient
conditions.
8. The method as set forth in claim 1 further comprising the step
of removing the displacement rod from the fuel, wherein said step
of monitoring comprises taking multiple further pressure readings
at a set time interval; and comparing the initial, further, and
multiple further pressure readings to determine a weight change of
the fuel (based on pressure change reading) to detect a leak.
9. A method according to claim 1 further comprising determining
conditions of a tank of fluid via the embedded sensor within the
fuel, and a secondary sensor for determining ambient conditions,
and utilizing a temperature compensated volume to determine if
differences of fluid level are due to natural ambient
conditions.
10. A system for monitoring the fuel level in a tank, and
determining when changes in the fuel are due to leakage, said
system comprising: a. an embedded sensor submerged either along a
bottom surface of the storage tank or not more than two inches
above the bottom surface and set below the fuel level within the
tank; b. said embedded sensor comprising a pressure transducer and
a power source; c. a controller determining pressure sensed by said
embedded sensor.
11. The system of claim 10 further comprising a solid displacement
rod moving between a position at least partially outside fuel in
tank, and a position at least more partially within fuel of
tank.
12. The system of claim 10 further comprising a secondary sensor
outside the liquid of the tank, said secondary sensor capable of
detecting ambient conditions of at least one of temperature,
pressure, humidity, and/or dew point.
13. The system of claim 12 whereby said secondary sensor is within
the tank, said embedded sensor and said secondary sensor connected
to a monitoring system.
14. The system of claim 12 whereby said secondary sensor is outside
the tank, said embedded sensor and said secondary sensor connected
to a monitoring system.
15. The system of claim 12 wherein said embedded sensor includes an
opening to expose the pressure transducer directly to the fuel
pressure.
16. The system of claim 12 wherein said embedded sensor comprises
an analog digital converter coupled to said pressure transducer,
said analog digital converter in communication with said
controller.
17. The system of claim 16 further comprising an interface box
housing said secondary sensor.
18. The system of claim 16 wherein said embedded sensor and said
secondary sensor are coupled via a connector that passes through a
vapor-proof bung cap.
19. The system of claim 10 wherein said embedded sensor is located
within or below a drop tube.
20. The system of claim 10 whereby the controller comprises memory
to record and store data, and the controller receives simultaneous
data from the submerged sensor and data from the secondary sensor.
Description
CLAIM OF PRIORITY
[0001] The present divisional application includes subject matter
disclosed in and claims priority to U.S. patent application Ser.
No. 16/666,183, filed Oct. 28, 2019, entitled "Precision Depth
Sensor" (now U.S. Pat. No. 11,274,635, issued Mar. 15, 2022); and
to PCT application entitled "Precision Depth Sensor" filed Apr. 27,
2018 and assigned Serial No. PCT/US18/030020, and provisional
application entitled "Precision Depth Sensor" filed Apr. 28, 2017
and assigned Ser. No. 62/491,882, all incorporated herein by
reference, describing inventions made by the present inventor.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention is directed to petroleum-based tank
sensors, and more particularly related to storage tank monitoring
and maintenance via testing for leaks in the system.
2. Description of Prior Art
[0003] In the retail petroleum industry, it is important to
identify and recognize that underground and aboveground petroleum
storage tanks, as well as other containers such as Under Dispenser
Containment ("UDC") and sumps (to retain leaking fuel, keep water
out, contain pumps, access to tank probes and sensors, etc.), are
not leaking. These tanks, sumps, and UDC's (generally referred to
as "tanks") are usually interconnected by pipe. This means that the
tanks, UDCs, and sumps are penetrated (e.g. by the pipe) at various
locations. These penetrations, along with above-identified used,
and the unused, tank top penetrations (bungs), as well as the fuel
vessel itself, need to be monitored and tested to ensure the tanks,
sumps, UDC's, pipe and other penetrations, as well as the above
describe fueling accessories, are not defective or leaking. Many of
the systems of concern are on-site and see relatively minimal use
(as compared to tanks at retail fueling stations).
Identifying Water/Phase Separation
[0004] Part of the United States Federal law concerning tank
monitoring requires the detection of ingress of water. As water
separates from the fuel (e.g. diesel), or water finds it way in
with a fuel delivery, or water leaks into the tank, this water
accumulates at the bottom of the tank. Floats specifically designed
to track water at the bottom of fuel tanks are common. These floats
can rise when the density of the fluid at the bottom of the
container is greater than that of fuel. However, the use of ethanol
in gasoline and biodiesel in diesel have changed the ability to
detect the ingress of water. These two components, ethanol and
biodiesel, both absorb water and mix (or dissolve) well with the
respective fuel--thereby modifying the density of the separated
liquid(s). The accumulation of water in these fuels has adverse
effects on both the fuel and the storage vessels. The ingress of
water is difficult to detect if it is being absorbed into the
fuel.
[0005] The accumulation of water in ethanol blends can reach a
saturation level, or maximum dissolved amount for a specific
temperature and ethanol content of the fuel. If the fuel
temperature falls due to a load of cool fuel, or temperature
equalization with the environment, or other event, the
ethanol/water (as a mixture that was previously in suspension) can
fall to the bottom of the tank. This is known as phase-separated
fuel. Immediately upon phase separation, the octane level changes
(falls) in the remaining fuel due to the loss of ethanol in the
fuel. This modified fuel can impair/degrade potential engine
performance, damaging the engine, and possibly ruining the engine.
The phase-separated fuel is more aggressive to the inside of the
tanks; steel, coated steel, or fiberglass. This phase-separated
fuel is also a feeding/breeding ground for biological and fungal
activity within the tank or elsewhere. The biologicals,
particularly the Acetobacter bacteria, propagate in this
environment. The Acetobacter excretion includes acetic acid. This
acid, and chemical stew, creates what was predicted and called a
"cauldron effect". The cauldron effect is a potentially aggressive
mixture that attacks bare steel, softens the gel/fiberglass coating
of steel tanks and of fiberglass lined steel tanks, and is known to
expose the mesh, weakening the structural integrity of a fiberglass
tank such that containment has failed on tanks, steel and
fiberglass.
[0006] The phase-separated fuel can build up on the bottom of the
tank until phase-separated fuel is close enough to the pump inlet
to enter the fuel distribution system and be dispensed into
vehicles.
[0007] Fuel in the fuel storage tank that is not phase-separated,
but is high in dissolved water content, can be pumped into an
automotive tank. The vehicles drive off, and some of the vehicles
may be stored indoors. Whether due to storing in cool areas (e.g.
A/C garage) or due to storage in outside areas that the temperature
cools diurnally, the temperature of the fuel tank falls to a point
to cause phase-separation inside the automotive fuel tank.
Phase-separated fuel begins degrading the fuel tank and components
in the fuel system.
[0008] Water also affects diesel fuels. The accumulation of water
in the bottom of a tank provides a fuel water interface that allows
microbes to rapidly propagate. This interface can grow significant
biomass plugging filters, a particular type of bacteria
(Acetobacter) can acidify fuel causing tank and equipment
degradation.
[0009] Most diesel fuel today is mixed with biodiesel to meet
Federal fuel guidelines. The Sulphur content is reduced in fuel
today. Biodiesel adds lubricity to the fuel, a desired addition due
to the reduction of sulfur that used to provide a higher level of
lubricity to diesel. Biodiesel absorbs water. Bacteria and molds
grow in the biodiesel fuel in part due to the water in the fuel.
The fuel is acidified by the acetic acid waste of the Acetobacter
bacteria growing in the fuel. Bacteria and debris fall to the
bottom of the tank. During a fuel delivery the debris and bacteria
are pushed around the tank, up to and including the edges of the
tank. As the particles are pushed together, chemists recognize
these groups as colonies. The colonies "slime" themselves,
protecting the colony. This protection increases the survivability
of the colony, protecting them from chemical means of killing
bacteria in the tank. These colonies excrete acid, concentrating
the acid next to the tank in a way that it is not easily dispersed,
damaging/destroying steel, softening/damaging the gel coat and
fiberglass. Tanks fail in many ways, and may compromise containment
of liquid (such as fuel, etc.) stored therein.
[0010] Prior art solutions include magnetostrictive level probes
for sensing changes in fuel level within tanks. Magnetostrictive
sensors provide high resolution level sensors via a
magnetostrictive stem float, or probe level sensor. This continuous
liquid level solution is able to determine level within only a few
millimeters. Magnetostrictive sensors work by using a ferromagnetic
metal, which aligns itself with magnetic fields. By creating two
competing magnetic fields, the magnetostrictive level sensor is
able to generate a signal denoting the liquid level.
[0011] A magnetostrictive probe is built by suspending a
ferromagnetic metal wire inside a long stem. Electronics at the top
of the stem generate an electrical pulse that travels down the
wire, at regular intervals. This creates the first magnetic field.
The second is created by a magnet inside a float that moves up and
down the stem with the liquid level. When the electrical pulse
reaches the float, and the two magnetic fields collide, the metal
wire inside the stem twists, and a vibration is sent back up the
wire to signal change in fuel level.
[0012] There currently exists a need for more careful monitoring,
adaptive dynamic monitoring, and monitoring systems that avoid
corrosion and other means of adding impurities to the fuel line.
Therefore, it is advantageous to have a small, robust, portable
test method that can perform precision tests to detect leaks.
Tanks, sumps and UDC's (Under Dispenser Containment) are designed
to prevent fuel from polluting the surrounding area. If the fuel
leaves these containments, the ground will become polluted,
potentially polluting groundwater, potentially polluting indoor
vapor-space by migrating through soils and entering buildings,
subways etc.
[0013] There is a need in several industries, but notably, the
petroleum and the chemical industry to provide a leak detection
method that provides the ability to integrate several test methods
that can report information in several formats, having the ability
to test multiple fluids in liquid form.
[0014] Therefore a PDS (Precision Depth Sensor) can provide a
compact, robust measurement device, part of a method to be sure
sumps and UDC's and the penetrations through them are not allowing
moisture/water to penetrate into or fuel out of the containment
devices.
[0015] It is therefore a primary object of the present invention to
provide monitoring of fuel conditions within a tank.
[0016] It is another object of the present invention to provide a
system to monitor fuel conditions within a tank.
[0017] These and other objects of the present invention will be
made clear in light of the further discussion below.
SUMMARY OF THE INVENTION
[0018] The present invention is directed to a method of determining
the qualities of a liquid in a storage tank with an embedded sensor
submerged into the liquid. Preferably, the embedded sensor is set
along a bottom surface of the storage tank, or not more than a two
or a few inches above the bottom surface of tank, preferably about
one-half to one-inch or less suspended above bottom of tank,
preferably near lowest portion of tank bottom. A displacement rod
may be used to calibrate the measurement via use of a submersion.
Conditions may be determined of the tank of fluid via coordinated
submerged sensor within the fuel, and a secondary sensor to
determine ambient conditions. An initial pressure may be measured
along a specific point in the bottom of the tank. The weight of the
fuel can then be determined based on an initial pressure reading,
often along with a measurement of fuel volume. Then one may
calibrate the measurement via use of a submersible displacement rod
via suspending a (preferably vertical cylindrical) rod of a set
volume into the fuel. When the rod is emplaced within the fuel at a
specific height and/or volume, one may detect a new further
pressure from the PDS embedded sensor. Thereby, one may determine a
change in the pressure as between the initial pressure and the
further pressure readings. By using a pressure differential to
determine a pressure to volume ratio, one may thereafter monitor
the pressure reading at the sensor. Concurrent ambient conditions
may be monitored simultaneously and in conjunction with readings in
embedded sensor, such readings to be correlated to determine if
ambient conditions change cause changes in embedded sensor readings
(e.g. as by expansion of fuel due to temperature). Concurrent
ambient readings may be made within tank (near top (in ullage)),
and/or at or near exposed surface above-ground, and/or shallowly
buried within ground surface, and/or along exterior surface of tank
below ground.
[0019] A TCV formula may be used to determine if differences of
fluid level over time are due to natural ambient conditions, or
system failure. The conditions within the fuel are determined by a
sunken probe. The probe may rest on the bottom of a fuel storage
tank, and/or the probe may rest just above (within an inch or
inches) of the bottom of a fuel storage tank. A probe may determine
the conductivity or resistance of the liquid, and may compare
resistance with the expected change of system conditions reported
by a simultaneous system or outside system sensor. A probe may
determine the properties of a stored liquid, and compare those
properties with the expected change of system conditions reported
by a simultaneous system or outside system sensor.
[0020] The present invention also includes a system for monitoring
the fuel level in a tank, and determining when changes in the fuel
are due to leakage. The system is a precision depth sensor that
includes a submerged sensor below the fuel level within the tank,
wherein the submerged sensor may include a pressure transducer and
a power source, or off-board power source connected via wireless or
wires. The system also includes a controller for determining or
monitoring pressure sensed by the submerged sensor and compare to
expected levels. A displacement rod may be used to calibrate the
system by moving between a position at least partially outside
liquid in tank, and a position at least more partially within fuel
of tank. Preferably, a secondary sensor outside the liquid of the
tank, either within tank (towards top, or outside tank may be used
to determine ambient conditions and help coordinate determination
of the expected fuel level.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The present invention will be described with greater
specificity and clarity with reference to the following drawings,
wherein like numerals designate like parts, and in which:
[0022] FIG. 1 demonstrates an underground storage tank with PDS and
calibration rod in alternate positions.
[0023] FIG. 2 demonstrates an underground storage tank with PDS and
secondary sensor in alternate positions.
[0024] FIG. 3 demonstrates an underground storage tank of prior art
with magnetostrictive sensor.
[0025] FIG. 4 demonstrates exploded view of PDS sensor.
[0026] FIG. 4A demonstrates a cross-section of top of PDS
sensor.
[0027] FIG. 4B demonstrates a cross-section of center of PDS
sensor.
[0028] FIG. 4C demonstrates a cross-section of bottom of PDS
sensor.
[0029] FIG. 5 demonstrates exploded view of PDS sensor.
[0030] FIG. 5A demonstrates a cross-section of top of PDS
sensor.
[0031] FIG. 5B demonstrates a cross-section of center of PDS
sensor.
[0032] FIG. 5C demonstrates a cross-section of bottom of PDS
sensor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] The nexus of the PDS was how to provide a means of
measurement of liquid for different applications, one that did not
have the same problems as prior art magnetostrictive probe. Prior
art probes typically have a short lifespan, the cables grow
bacteria or corrode, and the results lose accuracy while testing
sumps. Tanks, particularly tall tanks, provided very low resolution
due to tank size and mounting issues of the probes. The corrosion
and particulate issue of the prior art is a problem for the
magnetostrictive probe.
[0034] One application may include digitally provided a means of
line testing, recording the information electronically in real
time, without requiring a human to make readings by sight, entering
the info and then calculating the results.
[0035] The PDS, as presently described. Provides a higher
resolution, allows monitoring smaller liquid level movements, for
regular tank testing and sump testing. Technology has now advanced
with smaller, faster, portable computers and higher resolution ADC
devices, to allow the PDS device to become a viable technology.
[0036] A housing protects the electronics as the PDS sensor is
submersed. The PDS system provides a program to record appropriate
information and transmit it to provide calculations.
[0037] The use of a temperature-controlled volume to determine:
whether changes in volume of the fluid are impacted by ambient
conditions, and adjusting expectations accordingly.
[0038] The present application continues on the disclosure of U.S.
patent application Ser. No. 16/666,183, filed Oct. 28, 2019,
entitled "Precision Depth Sensor" (now U.S. Pat. No. 11,274,635,
issued Mar. 15, 2022), and the incorporated file wrapper, and
attachments included herewith, herein incorporated by
reference.
Measuring Leaks
[0039] The primary method to determine the integrity of the portion
of the tank holding liquid in retail fueling stations is via the
use of probes. These probes are combined with a
computer/controller/processor, a.k.a. monitoring system. The
computer processes signal information from the probe to establish
the liquid level height and fuel temperature inside the storage
tank. This liquid level information is compared to tank charts
(preferably stored in the computer) to establish the fuel volume in
the storage tank. The temperature information is used to calculate
the volume change of the fuel due to thermal expansion or
contraction as calculated Temperature Compensated Volume or
TCV:
Fuel volume.times.Temperature change.times.Coefficient of
expansion=TCV
Leak rates are calculated by the results of TCV and time. The
testing of the area of the tank that does not have liquid is tested
in other methods not addressed here.
[0040] The calculated change of fuel volume (fuel volume plus or
minus the fuel volume change from the change of temperature) is
compared to the measured fuel volume (height). If the equipment is
accurate, and the calculations are accurate, and the tank charts
are accurate, the TCV should equal the tank volume. Therefore, TCV
should accurately track and compensate for changes in liquid
temperature and/or volume. Changes in volume can also be caused by
leaks out of the tank, and/or due to the ingress of liquid (usually
water). It is also possible to compromise systems when the tank is
sitting in an area that retains liquid (such as clay), that
effectively makes a containment area (soil or substrate) that water
or fuel moves very slowly into and out of. This contained liquid
can move in and out of leaking tanks and compromise purity of
contained fuel.
[0041] Prior art solutions include magnetostrictive probes, as seen
in FIG. 3. A well-known issue with magnetostrictive probes is
stickage. Stickage is the effect of friction between the stick
portion and the float portion of the probe. This problem is
exacerbated if the probe is not straight up-and-down (vertical).
Stickage is a significant issue when sump testing is done with
magnetostrictive probes as the setup requires strict attention to
ensure the probes have the least amount of friction.
[0042] Another issue with tanks and magnetostrictive probes, is the
higher incidence of significant bacterial growth, including
bio-film. The bacterial growth (mostly the Acetobacter, but others
contribute to this problem) is increasing acidity (lowering pH) and
thereby destroying equipment (including tank surfaces) and
increasing friction. Biofilm contributes to stickage, fouling of
the stick/float interface.
[0043] Another issue identified with the increasing acidity of fuel
is the amount of particles in the fuel due to the corrosion
occurring inside the tank system. The corrosion is continually
"stirred" and lifted into the fuel every time the tank takes a
delivery. These particles are contributing to the float sticking
problems. The high acidity is eating up the containment of the
float sensors, rendering them less accurate or not functional. To
combat issues of acidity, the PDS uses 316 stainless steel (as is
known in the art) for wetted portions of the sensor, such as the
shell or cylinder and caps, and treatment for steel components
immersed in low PH fuel allowing long life in low PH fuels.
Calibration
[0044] It is important to have a Pretest or Diagnostic mode for
sump and other containment testing. Today, testing equipment has a
Pass/Fail method of reporting leaks. This is due, in part, that
there is no acceptable leak rate allowed if it is detected.
Currently, manufacturers use the mandated test threshold (such as
0.05 mph for tanks) or 1/8'' per hour (for sumps) as the reporting
threshold. Basically, any leaks below the threshold do not have to
be reported, therefore the equipment is not designed to report it
(either because it lacks sensitivity, or is programmed as such).
When a technician is testing a tank or sump and there is a fail,
failure could be due to one or multiple failure points below the
threshold of detection required. If there are multiple points of
failure, there is no tool to help the technician as to where these
levels or failure points are located. Such is the need for a
Diagnostic test, a tool that allows technicians to test levels of
containments to find out if it is leaking a proportional share of
the total leak.
[0045] In order for such a tool to be useful for Pretest or
Diagnostic Mode, the sensitivity must minimally meet the ability to
detect a proportional amount of the potential leak points. The PDS
and sump test software is sensitive enough to detect as small as
0.0000001''. As current sumps/containments do not normally exceed
10 penetrations, the PDS is such an appropriate tool. A variation
of the PDS can exceed even greater sensitivity as described below,
such as to detect 0.00005 gph or 0.000005 gph, depending on the
size of the sump/tank the PDS is testing in.
[0046] Such a tool must be sensitive enough to give accurate
information to detect leaks smaller than the aggregate of the leak
threshold. It is suggested that in order for such a tool to help
identify small leaks that could in total affect aggregate test
results, it should be able to identify small enough leaks such that
if each penetration was leaking a proportional amount, the test
equipment could identify each leak, allowing the successful repair
of the containment. Each leak could be repaired, in turn, while a
test is made after each fix, until no detectable leaks remain. The
Precision Depth Sensor combined with the appropriate software is
such a tool for the retail petroleum industry and the current US
EPA test thresholds as the penetrations in sumps that could
leak.
Calibration Feature Example
[0047] PDS is placed in a tube of a known depth, such as 2 ft. Fill
the tube to the top, such that excess liquid runs down the side
into a secondary container. The weight per distance (height) is
then determined. With weight of a predetermined height, we can now
know precise height/weight changes. This will allow us to measure
depths on fluids not in a pre-defined list or of an unknown
product.
[0048] Track the temperature change of the "unknown" fluid in the
same container. Weight per degree can be calculated so temperature
compensated volume testing and monitoring can be accomplished.
Ideally this would occur in real time so the testing and the
temperature change could be identified as the liquid level change
is recorded.
[0049] Additionally, where the fuel is in a container that allows
changes in volume and growth due to thermal expansion or thermal
contraction to be tracked, The COE (coefficient of expansion) could
be calculated in the field, parallel to the testing that is
ongoing. The addition of a calibration rod to this container is an
additional method to check the sensitivity and accuracy of the
information.
[0050] Due to equipment, pipes, plumbing, sensors, pumps, leak
detection equipment, etc. the surface area of a sump is not the
same as the surface area calculated of (empty) rectangles, squares,
or circles, the typical shapes of sumps. Therefore, a method that
allows an operator to calibrate the surface area allows the
operator to report leak rate as the depth changes and the surface
area allow the test system to report volumetric leak rate
changes.
[0051] PDS embedded sensor should be ai a fixed position in tank.
Sensor may be located in a fuel pipe (drop tube). The drop tube
being sealed at a top may only be affected by ambient conditions.
Ullage pressure and ambient pressure should be isolated (and may
differ), allowing for more accurate readings.
[0052] The sensor should be set in a fixed position (as in other
embodiments) and cannot be loosely suspended to allow random
movement of sensor that may affect readings (unless location
known). If material of sensor will move, or change size (as in a
metal that expands/contracts with temperature, etc., such
information is to be calibrated. The present system may include a
pressure temperature monitor over a predetermined time. Static
temperature within tank may be required to run tests. One may make
multiple readings over time to detect a leak. Once may compare
varied readings to determine a leak and leak rate. For instance,
consecutive readings may not be compared, but a staggered
comparison may be needed (e.g. comparing first and third reading
with second and fourth, third and fifth, etc.).
[0053] For example, if after the setup of the equipment, including
the deployment of a PDS in the bottom of a tank, a calibration mode
in the attached computer was entered, a solid displacement rod of a
known length/volume could be lowered into the tank liquid, as can
be seen in FIG. 1. The calibration reading finishes. The rod is
removed. This displacement of a known rod volume allows the surface
area to be calculated based upon the detected height level (weight)
change. Tank 1 is placed within substrate or soil or ground 2. Tank
1 includes fuel 6 with a top level 7. Sensor (PDS) 5 capsule, is
preferably a cylinder, or capsule, or other structure. Rod 3 may be
started at position 3 above level 7, and then lowered into fuel 6
at rod position 4. Both rods are shown for illustrative purposes of
the position of a single rod. The volume of rod immersed is
determined by the amount of fuel displaced and height of fuel, or
vice versa. Sensor 5 may record weight, pressure, or the like.
Sensor 5 may also determine temperate, electrical characteristics,
etc.
[0054] The lowering of the displacement rod into the product at
beginning of the test for calibration, then removing it, and
repeating the test at the end by lowering the calibration rod into
the liquid for a second calibration and removing it a second time
would provide a second data point for calibration sensitivity that
can be used to confirm the sensitivity, check if the values match,
and if not within a statistical valid range, indicate the surface
area has changed or some other variable has changed thus requiring
compensation of other variables or a retest.
[0055] The lowering of the displacement rod in the beginning of the
test to get a calibration and leaving it in the liquid during the
test, removing the calibration rod at the end of the test also
provides two data points to calculate surface area/volumetric
changes and provides a check to insure the quality of the data from
start to finish.
[0056] The parameters of the vessel such as shape and size affect
the rate of change. For example, in liquid level change detection,
if a vessel were larger on the bottom but the sides sloped inward
towards the top of the vessel, the rate of change would slow down
as the liquid left the vessel. The liquid level change per time
interval would be less for the same volume of fluid that leaves a
vessel with the described sloping walls verses a vessel that the
sides did not slope. A means of determining this change and
compensating for this type of variable would be beneficial to
reporting accurate rate results.
[0057] Similarly, the above-mentioned sloping walls change the
accuracy of volumetric reporting unless there is a method of
determining how the surface area of the tank is changing and
integrating that into the volumetric calculations or liquid level
rate reporting.
[0058] Entering a slope calculation mode would allow the use of a
displacement rod entered 3 times, once to establish a starting
surface area, the second would establish a slope, percent change of
a consistent slope, the third would either represent the
continuation of the same slope, or a different value would
represent either a leak, an ingress, or a change of the slope. The
time between Calibration 1 and 2 and 2 and 3 must be varied by at
least two times to differential slope and leak and slope
results.
[0059] Not all exercises test the same material. For example, one
system may have water as the test media, in another tank, diesel,
yet another premium gasoline. Additionally, there may be a
different exercise that tests for both water and hydrocarbon, but
only in the liquid phase and not as suspended particles as in
determining the volume or percentage of water suspended in a
hydrocarbon such as diesel fuel.
Calibrating an Unknown Liquid
[0060] A user can enter a precise measurement of the current liquid
depth. Using this information, we can back calculate the weight per
fluid unit at one temperature. A calibrated fluid can be used for
precision testing at one temperature. Without a coefficient of
expansion (COE) we can only approximate actual fluid depths during
temperature change. With several repeats of the current liquid
depth as above and a new/changing temperature it is possible to
closely approximate the COE for the temperature.
Dual Sensors
[0061] To ensure that the testing system is calibrated correctly,
dual sensors may be employed. As can be seen in FIG. 2, Tank 1
includes contact with surface 20, such as through a bung hole.
First PDS sensor position 5 may be at a location just above the
bottom of tank 1. Alternative position 8 for sensor, may be along
bottom of tank. A wire 11 may be used to power PDS or otherwise
transmit analog or digital signals to outside box (not shown). A
second sensor location 10 may be used to determine ambient
conditions, such as temperature, humidity, etc. A further
alternative location 9 for secondary sensor may also be used on
surface, or outside tank system. Both secondary sensors 9 and 10
may be used, or each may be used in isolation to support PDS
submerged sensor 5. Further alternative location 9 may include an
interface box, as described below. Connector wire 19 may pass
through bung cap 29 to electronically and communicatively connect
with embedded sensor.
[0062] For instance, weight, height, and/or volume, etc. of the
liquid in the tanks is monitored. At the same time, a separate
monitor of ambient conditions may be used to monitor the conditions
of the greater system (i.e. atmosphere and geographic location).
For instance, if as the test is running (or the system is being
monitored) the ambient atmospheric pressure may change (i.e.
barometric pressure, temperature, dew point, humidity, etc.) thus
resulting in a change to the properties of the liquid that may
impact one or more of the monitored variables. By correlating the
instantaneous data from a sensor within the liquid to another senor
outside the liquid (for instance in the ullage of the tank, above
ground, or elsewhere) changes in the fluid due to ambient
conditions can be controlled. Therefore, changes that exceed
expected response to ambient conditions may indicate a leak.
[0063] A first sensor may be placed to gauge atmospheric pressure
above ground or in the ullage. A second sensor may be submerged
within the liquid the tank (such as an underground storage tank, or
above-ground storage tank). Both sensors may be connected in
real-time to correct for sensor readings in the tank. Otherwise,
the readings can be matched up at a later time, or in the analysis,
to compare atmospheric pressure with readings in the tank to
eliminate false triggers or masked leaks (false negatives and false
positives).
[0064] Simultaneous data may be taken inside, and outside, the tank
to test the weight of the fluid and ensure that it meets standards.
Weight is determined by pressure on the submerged sensor. This data
is compared with tables for standard compliance, with the
additional data point of temperature.
[0065] Another embodiment of the present invention includes a test
to determine quantity of water diluted in the fuel. This will help
determine the risk--level that the water admixed in the fuel may
separate given a major or minor change in conditions. For instance,
if the water level mixed into the fuel is at the point whereby a
drop of ten degrees to forty degrees in temperature will often
cause phase separation (i.e. when dispensed into a vehicle fuel
tank which may then be garaged or left out overnight), the system
can indicate potential risk of future phase separation. Phase
separation can occur wherein water drops from diesel, or
ethanol/water mixtures drops or separates from ethanol modified
gasoline. Current systems using a second, lower float (as can be
seen in FIG. 3) may work between phase-separated diesel/water, but
may not work in gasoline or gasoline/ethanol mixtures. Such a test
may be conducted via determination of electrical resistance through
the fuel, for instance via a probe with two separated terminals and
running a voltage there between. Such an electrical sensor can also
determine if the sensor is sitting in phase-separated fuel--based
on the resistance between the terminals.
[0066] Use of electrical current to determine resistance, and thus
properties of the fuel, may be conducted via a permanently affixed
probe. This probe may determine the ongoing risk of phase
separation (such as with expected or potential temperature drops,
changes in conditions, or post-dispensation to vehicles. The probe,
or any electrical resistance measuring system, can determine the
amount of water in the fuel. The novelty of the present invention
is the use of such a probe in a working tank, including tanks and
an underground storage tank at, for instance, a retail fuel
dispensary (gas station).
[0067] PDS provides for a more accurate reporting of fluid depth in
tall/high tanks via use of multiple sensors. Finding level/leaks in
large above ground storage tanks is difficult, the resolution is
much greater if you are measuring tanks 15 ft. and under. One of
the issues is the scale or sensitivity of the measurement devices.
The same graduations are available in the devices used whether you
are measuring 15 ft. or 125 ft. While time may allow a means of
looking for change, it is impossible to achieve the same resolution
with the magnetostrictive or pressure sensitive instruments
currently used if you are having to expand the same scale you used
for resolution over 15 ft. and apply it to 125 ft. Because
Depth/pressure sensors/pressure transducers (magnetostrictive
probes also) have a resolution scale, the distance or weight that
sensors are used for (pressure or distance range that is to be
parsed) sets the precision that can be obtained. If multiple depth
or magnetostrictive sensors are used, say mounted on a rod or to
precision distances from each other, the precision of smaller set
depth/weight ranges could allow significantly higher precision
results, allowing almost any desirable precision by the
placement/scale chosen. Allowing a pressure overlap, a controller
could decide which sensor was read/reported. The overlap would be
to allow each sensor to work within its range and the desirable
sensitivity such that one is no longer read/reported as the
pressure range leaves the assigned parameters of the defined area
of the sensor above or below the specific pressure the intended
sensor is depended upon for accurate information.
[0068] PDS allows a system to be Diagnosed, not only Tested.
Diagnostic is different from Testing from a regulatory perspective
in that a Fail is an actionable item from a regulatory perspective.
A Diagnostic mode allows sumps and other containers to be checked
before a regulatory Test must be performed. An example would be the
need to repair a fitting or connector that has obviously failed,
then check the sump to see if your repair is "holding" or working
as desired. The repair may not be the top fitting, so the sump may
be tested at the level of the penetration, this is not Testing all
the penetrations. Additionally, a Diagnostic may be run after a
sump has failed. Detecting at what level the leak is located might
entail testing from the top down or bottom up, each penetration,
the effects of height (pressure) determining the use of each or
both methods of testing.
[0069] It is well known that determining the height of a fluid can
be obtained by measuring the weight of a fluid (from a point such
as the bottom of a vessel) given certain known parameters such as:
the fluid weight (density) at a specific temperature; temperature
of the fluid; pressure on the fluid--Such as barometric pressure,
etc. To determine change of fluid height it is important to: know
elapsed time from one reading to the next (or the time of a
Beginning/Ending Test cycle); know the temperature of the fluid at
the measurement intervals; know the pressure on the fluid when the
measurements are made (barometric or other); and compensate for
changing temperature and pressure on the fluid during
measurements
[0070] The PDS is a digital submersible pressure sensor, as can be
seen in FIG. 2. As can be seen in FIG. 4, the electronics and
sensors should be in enclosures that are water tight, except for
the opening of the sensor measuring pressure. The enclosures are
preferably round. The enclosure is preferably lowered to the bottom
of a tank or containment sump using its data cable. The sensor is
preferably powered by very low voltage. A battery may be used to
allow the PDS sensor to remain submerged without wiring required.
The PDS sensor could communicate via wireless to a receiver either
at top of tank (either along a second internal tank sensor, or near
the bung), or outside of tank system. Alternatively, the PDS
submerged sensor can be connected to the tank, and may receive
power via current in an electrically conduction along a metal tank
surface. Alternatively, the PDS sensor may be mounted onto a
specialized tank surface near bottom of tank, either along surface
of tank or a few inches above the surface and receive power there
through. While the term "along" herein denotes either adjacent
(such as resting on bottom surface of tank) or set just above the
bottom surface of the tank, the use of a multiple of sensors wither
resting along the bottom of the tank and/or set just above the
surface (and sunk/enveloped by liquid fuel) may be used wherein
each of the sensors is separated from another by a predetermined
distance (e.g., six inches to two feet). The array of sensors thus
deployed may provide alternate readings of pressure, useful for
instance, when a significant buildup of water or other precipitate
interferes with other sensors. In a tubular/cylindrical tank, the
array of sensors may be set along the lowest point, or more
preferably one at/above the lowest point, and other(s) along the
curvature slightly raised from the lowest point of the structure.
PDS sensor may sit at bottom of tank, or alternatively be suspended
floating at a known height within fuel. A thin wire may be used to
provide power to PDS sensor from outside tank system to provide
power from a small battery, and/or solar cell power source.
Preferably, a low-voltage supply is provided to PDS.
[0071] The PDS sensor enclosure (or PDS) is used to encapsulate the
buried sensors (within the fuel). The enclosure may include an
opening to allow the fuel weight to be on the transducer. The
transducer is soldered to the board within the sensor. The ADC
(Analog Digital Converter) is marked on the board. Preferably the
ADC is in very close proximity to the pressure sensor connect.
Preferably, the pressure sensor connects to the ADC, the ADC
through to the processor. The processor board may sit above the
PCB, the connections through the black ovals to the left and right
of the oblong area marked that the ADC and RS-485 is in.
[0072] While this is the current configuration, alternative
configurations may include circular boards that stack on top of
each other in several layers within sensor. In such an arrangement,
the pressure transducer in communication with the liquid in the
sump or vessel can be on one end. The transducer connected to the
ADC, to the processor and terminating with a liquid proof seal that
allows RS 485 communication to the interface box. The interface box
contains a means for the pressure sensor to read ambient air
pressure and communicate back to the processor in the liquid,
allowing compensation for weight of the air pressure pushing down
on the liquid we are testing. The interface box may also allow
multiple PDS's within the same tank, or networked tanks, or
multiple unrelated tanks, to communicate to the computer through a
USB connection. The interface box may be a USB hub for the sensors
and a means to provide pressure to the individual PDS sensors. It
also provides the "key" for the sensors to communicate with our
program.
[0073] The "Board or boards" are located in the PDS, mounted
longitudinally in the circular PDS. The PDS sensor may be connected
by tube/wire to a point at top/inside tank, or outside of tank
through bung. In sump deployments, the top may be open, so the
connection would be straight through to the interface box, to the
computer. Used to monitor a tank, the connector from the PDS would
pass through a bung that has a cap that allows the wire to pass
without allowing vapor out or liquid in to the tank. Such sealing
could be through already existing compression fittings, or through
a plug that is mounted in the cap with vapor barriers, that allow
connections to be made on both sides of the cap, passing the
appropriate information through said connector.
[0074] The PDS sensor, using pressure and temperature measurement,
can allow determination of a temperature compensated level and/or
TCV. Temperature may be measured from a sensor embedded in the
housing liquid path(s), and/or elsewhere within tank, and/or
outside of tank system. Free water 1'' in depth can be detected
with an intrinsically safe water detection circuit. Entrained water
in fuel can be detected with an intrinsically safe water detection
circuit.
[0075] All data conversions, filtering, and timed testing are
performed in the PDS, an advantage as the potential of passing data
that is corrupted by transmission errors or missed communications
at the receiving equipment is reduced. The PDS communicates to a
computer or controller over an intrinsically safe cable or through
intrinsically safe wireless communications. Level may be reported
to at least 0.0005 resolution. Temperature sensitive to 0.01-degree
F. The sensor should be able to pass through a 2'' NPT threaded
opening for temporary deployments. The unit may be able to be
calibrated to unknown liquid types.
[0076] Currently, no permanently installed or temporarily installed
liquid level sensor used in the petroleum industry can also report
entrained water levels (above ASTM standards for the liquid such as
ASTM D6304-07, reporting 500 ppm or more water in diesel fuel or
ASTM D6304-07 for gasoline, reporting 1,500 ppm water in gasoline).
The addition of finding and reporting free water levels as low as
1'' with entrained water, with a petroleum or other liquid level
depth sensor is also not currently available in the prior art.
[0077] The present invention also includes the optional use of
electrical conductivity, ohms or resistance, to determine the
amount of water in fuel. While this is a test performed in labs, no
one has combined it with a liquid level monitor to monitor fuel
level/volume and suspended water, and free water, especially via
two integrated methods of monitoring.
[0078] To determine the size or capacity of the tank, in tank
gauging, or in tank testing systems, different tank configurations
are resident such that an operator can enter length and width and
height measurements of common dimension tanks of various
configurations including square, oblong and round tanks that are
horizontal or vertical. The tables for round, square, horizontal
and vertical tanks show inches/volumes to account for changes of
volumes as the diameter of the tank changes. There are charts that
account for differences of the ends of tanks as fiberglass and
steel tanks have different volume changes as the ends of the tanks
are different. For instance, steel tanks have mostly flat ends and
fiberglass tanks have a significantly larger bell on the end.
Similarly, dimensions of a sump can be manually entered to
calculate surface area of a sump. Such methods are acceptable and
commonly used. However, there are more automated ways that are more
accurate and allow sumps that have difficult shapes or protrusions
to determine surface area.
[0079] If the vessel has pipes or equipment inside the area to be
tested, and the equipment or pipes are exposed. The volume of the
liquid in the sump is not easily calculated.
[0080] The present invention includes a test method with: [0081] a.
The ability to test a wide variety of vessels: vertical,
horizontal, round, oval, sumps, drums, transport tanks, etc. to
determine if there are leaks. The shape, dimensions and protrusions
of and in the tank affect accurate volumetric reporting. Due to
equipment, pipes, plumbing, sensors, pumps, leak detection
equipment, etc. the surface area of a sump may not be the same as
the surface area calculated of (empty) rectangles, squares, or
circles, the typical shapes of sumps. Protrusions in tanks
Therefore a method that adds or subtracts known volumes can be used
to "calibrate" a specific volume displacement to change in height
to determine the volume change in tanks that have irregular shapes
or protrusions such as pipes, pumps or other irregular shapes in
the tank at the height of the tank; [0082] b. in a vessel,
determining the height of a leak from the bottom of the vessel.
[0083] c. Testing can be such that level change in a given time is
the desired metric to evaluate an action point or a classification
such as Pass-Fail
[0084] It is well known that determining the height of a fluid can
be obtained by measuring the weight of a fluid from a point such as
the bottom of a vessel given certain known parameters such as:
[0085] The fluid weight (density) at a specific temperature [0086]
The temperature of the fluid [0087] The pressure on the fluid--such
as barometric pressure
[0088] To determine change of fluid height it is important to: know
elapsed time; know the change of the temperature of the fluid
during additional measurements; know the change of pressure when
subsequent measurements are made; and compensate for changing
temperature and pressure on the fluid during measurements.
[0089] Testing can also be such that a volumetric amount is the
desired result such as 0.1 gallon per hour. In order to report in
volumetric measures, the parameters of the vessel are important.
The shape, dimensions and protrusions of and in the tank affect
accurate volumetric reporting. Due to equipment, pipes, plumbing,
sensors, pumps, leak detection equipment, etc. the surface area of
a sump may not be the same as the surface area calculated of
(empty) rectangles, squares, or circles, the typical shapes of
sumps. Therefore, a method that adds or subtracts known volumes can
be used to "calibrate" a specific volume displacement to change in
height to determine the volume change in tanks that have irregular
shapes or protrusions such as pipes, pumps or other irregular
shapes in the tank at the height of the tank.
[0090] The placement of at least two sensors to measure fluid in a
container that is shifting up-and-down from the back-to-the-front.
Multiple instantaneous readings allow instant readings that can be
used to calculate more precise volume readings of tanks in vehicles
that are moving such as ships, planes, cars trucks. A more precise
volume measurement can be determined in a shorter time by including
multiple sensors, but four sensors can give four axis weight
distribution.
Field Testing
[0091] A PDS has been installed in a test site involving an
intermediate tank used to transfer fuel into hospital gensets and
boiler loop system. The 1000 gal. tank stores fuel for two
generators and when needed a back-up boiler loop. Fuel is routinely
used in by the gensets and when the replenishment level is met (70%
of tank level) fueling from main tank(s) is sent to refill the
intermediate tank to 90%. A routine test run on the system
includes; manually emptying the intermediate tank and initiating a
reset. Upon reset, as the tank control system reboots, detects the
low liquid level and initiates a refill to the correct height, 90%.
Detecting accurate tank levels both in normal operation and through
extensive manual test sequences has shown the PDS to be robust in
its function through climate extremes and a robust test
protocol.
PDS Operation
[0092] The pressure transducer is directly soldered to the printed
circuit board and immediately routed through the 24 bit analog to
digital processor. The A-to-D processor outputs directly to the 32
bit processor which does all the math and statistics to output the
depth and gallonage of the fluid the transducer is
testing/monitoring.
[0093] The interface box has the external pressure sensor and
communicates that to the PDS for real-time pressure
compensation.
[0094] This information from the PDS is passed to the PDS interface
box via RS 485 communication and from the interface box to a
computer that has the VMI PDS reporting software. The reporting
software may be in a laptop computer such that a tester may move
from site to site saving the information, transmitting the
information through such communications as the laptop is capable
of, or printing the information. The PDS may also be reporting to a
standalone computer at a site that is continuously monitoring tanks
and reporting Alarms by horn or light, or outputting an alarm to
tank monitoring equipment designed to communicate alarms
appropriately as the site has specified, or the PDS computer may be
connected to communication systems directly. Such direct connection
may allow remote monitoring and reporting of alarms as well as all
real-time data gathered, including passed test and alarm or
reporting level events. Such equipment can be configured to allow
modification of programs to accommodate upgrades or "bug"
fixes.
[0095] One such application is to allow information to be shared
with Building Management Systems that monitor important equipment
such as tank fuel level, line leak detection, overfill alarms,
security systems, oxygen delivery systems, heating and cooling
equipment, etc.
[0096] Such equipment can be connected with other VMI programs to
control pumps, valves, filtration, chemical injectors for bacteria
issues, etc.
[0097] Global Data Structure variables for calculation of fuel
properties include: [0098] Current [0099] Pressure; [0100] Pressure
depth [0101] Calculated actual depth [0102] Internal temperature
[0103] On chip temperature [0104] State [0105] Input [0106]
Calibrated ADC count/mbar [0107] IS Modules State [0108] Pressure
ADC Value [0109] Internal Temperature ADC value [0110] On Chip
Temperature ADC value
[0111] The PDS may also have a 24-bit fluid conductivity sensor to
allow determination of the water % in the fuel. The barometric
sensor has a 24-bit temperature sensor so TCV can also be very
accurate.
[0112] One may put the same pressure sensor in the external USB
sensor to give us current barometric pressure. Minus this value
from the absolute and we have actual fluid weight. A 1200 mBar
absolute SMT pressure sensor may mount on the PDS PCB. Adding the
two values together gives us absolute measure depth.
[0113] A 32-bit processor is preferably used and connected to PDS
senor pressure transducer. A 24-bit processor may be connected to
the processor to provide ADC. Preferably, these items are contained
in the PDS sensor item shown in FIGS. 4-5. The system may
communicate to a box via USB, or other, cable. The box may include
a standard computer that is protected from the elements.
Alternatively, a wireless signal may be emitted for control by a
management system further away from the tank. A wire, or wireless,
communication system may allow the PDS to communicate with a
computer, such as a laptop, that runs software capable of providing
output to a user. The computer may also include memory to record
and store data. The computer may also be configured to provide
reports, alarms, etc. Similarly, a power source (e.g., municipal
high-voltage line) may be led down into tank to power transducer
and other PDS equipment. Preferably, power is transformed to
low-voltage when entering the tank. The power line may be
transmitted along the cable or pole supporting PDS.
[0114] PDS sensor 30 is shown. Center cylinder 32 is preferably
hollow to contain circuit board and other onboard components. Top
cap 31 may be used to seal PDS, and bottom cap 33 may be similarly
used. Transducer may be exposed through PDS sensor surface to allow
measurements to be taken. A membrane 37 may expose the transducer
to local pressure conditions outside PDS within tank, the membrane
may be situated at the bottom or in the sidewall of the PDS shell,
or more preferably in the top cap 31 or bottom cap 33. Emanating
wires 36 may read electrical resistance in the fuel, emanating from
the sidewalls of the PDS shell. Additionally, wire may communicate
information and/or power to components in PDS sensor through shell
32 or top or bottom of PDS. Printed Circuit Board (PCB) 35 may be
included and shielded within PDS shell.
* * * * *