Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M3/00—Investigating fluid-tightness of structures
  • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
  • G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
  • G01M3/32—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators
  • G01M3/3236—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators by monitoring the interior space of the containers
  • G01M3/3245—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for containers, e.g. radiators by monitoring the interior space of the containers using a level monitoring device
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/0023—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm with a probe suspended by a wire or thread
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/20—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measurement of weight, e.g. to determine the level of stored liquefied gas
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
  • G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
  • G01F25/14—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters using a weighing apparatus

Definitions

• This invention relates to a highly sensitive method to determine the rate of leakage of liquid from a storage tank and is particularly directed to determining the leakage and rate of leakage of fuel hydrocarbons in installed underground storage tanks. Leakage into and out of the tank can be determined by the method of the invention.
• a sensor of appropriate design is inserted into the storage tank through the fillpipe or other access hole and is coupled to a sensing device to measure mass displacement over a period of time.
• the preferred sensor design is such as to compensate for changes due to vaporization of the liquid and changes occuring in density and the level of the liquid due to temperature variations.
• the sensing device is calibrated to determine the amount of liquid per unit of change and after a short period of time, usually only several minutes, the change in mass displacement due to the leak is noted. In this way the rate of liquid loss can be determined by simple calculation.
• Figure 1 is a broad overall view of an underground hydrocarbon storage tank with the sensor and detector device in position.
• Figure 2 is a detailed view of the detector system.
• FIGS 3 and 4 are detailed views of preferred sensors.
• Figures 5 and 6 show the insertion of a preferred sensor into a tank.
• Figures 7 and 8 show the removal of a preferred sensor from the tank.
• Figure 1 shows an underground filled hydrocarbon storage tank 11 with the sensor 12 in position in the liquid. The top of the sensor is above the liquid level and the bottom of the sensor is within about 1 to 2 inches (i.e., 2.54 to 5.0 centimeters) from the bottom of the tank.
• the sensor has a cap 13 and also a cup portion 14 (detailed in Figure 3) to which supports of wire or string 15 are attached which, in turn, are connected to line 16 which supports the sensor from the weighing arm 17 of a balance shown generally as 18.
• a coupler 22 may be used for convenience i ⁇ . connecting line 16 to the balance arms.
• the balance 18 may be supported on a box 19 which in turn is supported by a base 20 having leveling screws 21.
• the box 19 may also contain the desired instrumentation and/or be provided with input and output jacks for connection to appropriate devices which are discussed later.
• the balance may be shielded from wind by means of a cover 23 as shown.
• line 16 is attached to the balance beam 17 by a detachable coupler 22 and passes through a differential transformer (i.e. a displacement transducer) 24.
• a differential transformer i.e. a displacement transducer
• Attached to line 16 and between the coils of the transducer is a ferromagnetic material 25 whose movement changes the electromagnetic flux of the transducer which is detected by the elctronic circuitry shown at 26 powered by a power supply 27.
• the transducer need not necessarily be around the line 16 , but may be placed in any convenient position, the only requirement being that it is responsive to movement of the balance beam.
• a suitable transducer is described in U.S.3, 179, 193 where it is used in conjunction with a cantelever type support for a fuel tank to weigh fuel removed from the tank and fed to an internal combustion engine.
• the electronic circuitry 26 will also contain an amplifier to send an amplified signal to a digital readout device 28 which, if desired, may have a strip chart recorder or other printer 29 attached thereto for obtaining a printed record of the measurements.
• FIG 3 which is a section taken on line 3-3 of Figure 1, the preferred sensor having cap 13 and cup portion 14 is shown in detail.
• the sensor is filled with liquid from the tank and extends from above the top of the liquid 30 in fill-pipe 31 to just above the bottom of the storage tank 11.
• the inside diameter of the cup section 14 is essentially equal to the outside diameter of the sensor in order to obtain compensation for evaporation of the hydrocarbon in the tank.
• the entire sensor system is readily supported by line 16 by appropriate wires or strings 15 through coupling means 22.
• the effects of any change in temperature are minimized. This is because the sensor fluid temperature is essentially the same as the tank liquid temperature with the same gradient, if any. As indicated, it is desired that the system measure a change of about 0.05 gallons per hour (3.1 cc/min.) which is equivalent to about 200 cc per hour. Since the measurements made in accord with the invention are made within a few minutes it is unlikely that there will be a temperature change of more than a fraction of one degree.
• Calibration is then carried out by adding a known amount of liquid to the tank and observing the change in the recording instrument. Observation is then made to the recorder device to note changes.
• the pen With a strip chart recorder, which is preferred, the pen will trace a straight line if there are no leaks. If a leak is present, the pen will deflect and the angle of deflection is indicative of the leak rate. From the number of divisions on the chart paper that the pen has deflected, the time of the trace, and the deflection per unit of liquid obtained from the calibration step, the leak rate is readily calculated. Also, by starting the pen at the center of the paper and standardizing the direction of deflection, the leak can be determined to be into or out of the tank.
• the sensitivity of the sensor is dependent upon the liquid level in the tank and the shape of the tank. The smaller the area of liquid, the greater the response to change of the sensor. Thus, when the tank is filled with liquid in a riser section, the sensor is most sensitive. At mid-point of a cyclinderical tank where the area of liquid level is greater, sensitivity is lowest, and sensitivity will be between these extremes at other positions. Thus, when a partially filled tank is measured, a sensor with a relatively large displacement is desired to increase sensitivity. Also, a more sensitive balance may be used for increased sensitivity.
• the preferred sensor for less than a full tank system is shown in Figure 4 and may be in the shape of a flat board 32 with a dished out upper surface 33 and having supporting wires 34 and 35.
• the board 32 will be sufficiently narrow so as to pass through a pipe into the liquid in the tank.
• the sensor is suspended on the liquid surface in a horizontal attitude with some liquid in the dished out portion 33 and the cross-sectional area of the liquid in the dished out surface is essentially the same as the cross-sectional area in contact with the liquid in the tank. In this way the compensation for evaporation is accomplished in the same manner as described above.
• the means by which the narrow sensor is introduced into and removed from the tank is illustrated by Figures 4 through 8.
• the sensor is provided with means to enter the tank and enable it to funciton in a horizontal position on the surface of the liquid. These means must also enable the sensor to be removed from the tank through the same opening through which it was introduced.
• Such means shown generally as 48 in Figures 4 and 4a embodies a quick release mechanizm to enable the sensor to be easily removed.
• the release means comprises a solid cylindrical core member 36 surrounded by an outer cover 37 made of she et metal, plastic or other suitable material. An angular bore hole in the core member is fitted with a pushing spring 38 and push rod 39.
• the support line 16 passes through the center top of the outer cover 37 and is fixed to a small cylindrical fitting 40 with an annular groove 41 which is held in a fixed position within core 36 by a restraining set screw 42.
• the core also is fitted with a screw eye 43 or other device to which line 34 is attached.
• a conical spring 42 is positioned between the top of core 36 and the outer cover 37. .
• the outer cover is provided with a port 44 acts as a catch for a pin 45 with an annular groove 46 which is attached to line 35.
• the port 44 is about twice as long as the diameter of pin 45.
• Outer cover 37 also may be provided with limiting stubs 47 to hold the assembly together.
• the pin 45 Before introduction of the sensor into the tank, the pin 45 is inserted through port 44 against push rod 39 and the groove 46 in the pin is positioned at the catch edge 37a of the outer cover. The effect of spring 42 is to hold the outer cover in a fixed position and because of this and spring 38, the pin 45 remains firmly fixed in the catch 37a.
• the sensor is then placed in the tank through a fill pipe or other access hole as show in Figure 5. When it is completely through the pipe the sensor opens as show in Figure 6 and after dipping it in the liquid to place liquid in its tray portion it is allowed to rest on the surface of the liquid as shown in Figure 7. After the determination for leakage is made and it is desired to retrieve the sensor, a weight 50 surrounding line 16 is dropped down the fillpipe 31 onto the quick release system 48.
• the above described leak measuring system may be used in numerous applications for both above and below ground installations. Also numerous variations may be made to the system. For example, it is possible to replace the displacement transducer with other means for determining displacement; e.g. capacitance devices and the like. In another alternative embodiment the displacement of the sensor may be replaced by the technique of measuring the change in mass necessary to keep the balance at its null point. Since such a technique will require it will be more expensive to build the equipment and therefore it is not a preferred method. Another option is to use telemetering means so as to remotely measure any changes in mass. Other variations and embodiments will be obvious to the skilled art worker.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Examining Or Testing Airtightness (AREA)
• Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
• Debugging And Monitoring (AREA)
• Investigating Or Analysing Biological Materials (AREA)
• Optical Measuring Cells (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=22183697

Family Applications (1)

Country Status (24)

Families Citing this family (18)

Citations (3)

Family Cites Families (12)

• 1979
  • 1979-10-12 US US06/084,241 patent/US4300388A/en not_active Ceased
• 1980
  • 1980-09-30 IL IL61191A patent/IL61191A/xx unknown
  • 1980-09-30 IN IN1113/CAL/80A patent/IN152896B/en unknown
  • 1980-09-30 CA CA000361453A patent/CA1138670A/en not_active Expired
  • 1980-10-02 AU AU65707/80A patent/AU538558B2/en not_active Ceased
  • 1980-10-07 IT IT25173/80A patent/IT1133195B/it active
  • 1980-10-07 NZ NZ195183A patent/NZ195183A/en unknown
  • 1980-10-08 NL NL8020417A patent/NL8020417A/nl not_active Application Discontinuation
  • 1980-10-08 WO PCT/US1980/001332 patent/WO1981001054A1/en not_active Application Discontinuation
  • 1980-10-08 DE DE803049945A patent/DE3049945A1/de not_active Withdrawn
  • 1980-10-08 JP JP50258680A patent/JPS56501420A/ja active Pending
  • 1980-10-08 CH CH3811/81A patent/CH652864A5/de not_active IP Right Cessation
  • 1980-10-08 GB GB8115513A patent/GB2075203B/en not_active Expired
  • 1980-10-08 BR BR8008868A patent/BR8008868A/pt unknown
  • 1980-10-10 DD DD80224474A patent/DD153734A5/de unknown
  • 1980-10-10 GR GR63105A patent/GR70765B/el unknown
  • 1980-10-10 BE BE0/202417A patent/BE885644A/fr not_active IP Right Cessation
  • 1980-10-10 ES ES495823A patent/ES8107389A1/es not_active Expired
  • 1980-10-11 EG EG628/80A patent/EG14382A/xx active
  • 1980-10-13 ZA ZA00806291A patent/ZA806291B/xx unknown
• 1981
  • 1981-04-21 EP EP19800902207 patent/EP0038356A4/de not_active Withdrawn
  • 1981-06-02 NO NO811865A patent/NO811865L/no unknown
  • 1981-06-10 SE SE8103639A patent/SE8103639L/xx not_active Application Discontinuation
  • 1981-06-11 DK DK254381A patent/DK254381A/da not_active Application Discontinuation
• 1984
  • 1984-01-27 GB GB848402252A patent/GB8402252D0/en active Pending
  • 1984-03-01 GB GB08405418A patent/GB2136137B/en not_active Expired
• 1985
  • 1985-04-04 SE SE8501711A patent/SE8501711L/xx not_active Application Discontinuation

Patent Citations (3)

Also Published As

Similar Documents

Legal Events