CA1229500A - Underground storage tank detector - Google Patents
Underground storage tank detectorInfo
- Publication number
- CA1229500A CA1229500A CA000468543A CA468543A CA1229500A CA 1229500 A CA1229500 A CA 1229500A CA 000468543 A CA000468543 A CA 000468543A CA 468543 A CA468543 A CA 468543A CA 1229500 A CA1229500 A CA 1229500A
- Authority
- CA
- Canada
- Prior art keywords
- tank
- contact
- probe
- steel
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Abstract
Abstract of the Invention Disclosed is an apparatus and method for testing an underground storage tank to identify unlined steel underground gasoline storage tanks from tanks of other construction. The apparatus includes an indicator of a physical characteristic, an elongated probe for contacting the tank bottom, a contact for the upper portion of the tank, and a generator of the characteristic. Performing the test determines if the characteristic can travel from the probe contacting the tank bottom, around the tank wall, up to the contact which is associated with the probe and meter for indicating the characteristic. If the characteristic is detected, it indicates of which material the tank is constructed.
Description
- Field of the Invention This invention relates to an apparatus and method for testing underground tanks typically used for storage of refined hydrocarbon fuels. More particularly, it relates to the determination of the material of construction of the storage tanks, and more particularly the detection of the tanks which are constructed of unlined steel.
Background of the Invention In dispensing hydrocarbon fuel at the retail level, service stations maintain quantities of various fuels at a-multitude of locations. Each location requires a plurality of tanks which have been installed over the years by various companies and vendors. Typically, the records of such tank installations are sometimes sketchy or lacking altogether. The records of the material of tank construction are equally vague.
With the introduction of new fuels differing in composition from standard gasoline (premium, unleaded, regular, etc.), the tanks or their linings are in some cases unsuitable for containment of such fuels. If a diesel fuel is introduced into a tank having a polymer lining, the lining may be deformed or deteriorate to allow leaks of the diesel fuel out of the tank.
In addition to the economic loss of a valuable refined product, the damage to the underground and surface environment can be tremendous. Environmental regulation demands that such leaps are to be avoided.
Service stations, however, are not in the economic position to dig up, remove and replace each tank to which a new fuel is introduced. Therefore, it would be advantageous to determine the material of construction of the tanks without removing them and with accuracy such that new fuels may be stored with confidence.
Background of the Invention In dispensing hydrocarbon fuel at the retail level, service stations maintain quantities of various fuels at a-multitude of locations. Each location requires a plurality of tanks which have been installed over the years by various companies and vendors. Typically, the records of such tank installations are sometimes sketchy or lacking altogether. The records of the material of tank construction are equally vague.
With the introduction of new fuels differing in composition from standard gasoline (premium, unleaded, regular, etc.), the tanks or their linings are in some cases unsuitable for containment of such fuels. If a diesel fuel is introduced into a tank having a polymer lining, the lining may be deformed or deteriorate to allow leaks of the diesel fuel out of the tank.
In addition to the economic loss of a valuable refined product, the damage to the underground and surface environment can be tremendous. Environmental regulation demands that such leaps are to be avoided.
Service stations, however, are not in the economic position to dig up, remove and replace each tank to which a new fuel is introduced. Therefore, it would be advantageous to determine the material of construction of the tanks without removing them and with accuracy such that new fuels may be stored with confidence.
2 -by Methods of detecting various characteristics are illustrated by the pertinent references such as U. S. Patent No.
380,842, Williamson, et at., which discloses in Figure 2 an ore sample placed on a metal plate and a second electrode used to pass over the surface of the sample to determine conductivity. A
current source is provided by means of a battery, and any current flow between the plate and the brush is detected by an audible sound produced in a telephone.
Also included in pertinent art is U. S. Patent No.
1,567,728, Greens lade, which discloses a test arrangement for a boiler stability. The test device includes a probe that extends into an opening or bore in the bolt and contacts the bottom of the bolt. The other contact member is attached to the boiler itself Jo that, if the stability is in proper condition, the circuit will be completed between the two electrodes, indicating that the bolt is in solid electrical contact with the boiler. If a leak between the bolt and the boiler has occurred, deposits of minerals would normally build up in the opening in the bolt and electrical contact between the two metallic bodies would not be made, thereby indicating that a leak did exist.
Not disclosed in any of the pertinent references is a means of determining the material of construction of underground tanks and further identifying those tanks which are of unlined steel.
It is, therefore, an object of this invention to provide a method and apparatus for determining the suitability of a tank for a particular fuel service.
It is a further object of this invention to provide a means for determining which tanks, if any, at a service station location are of unlined steel.
5C~
Other buckwheats of this invention will be clear to one skilled in the art based upon the Specification.
In the accompanying drawing, while there is shown, for purposes of illustration only, certain embodiments of the invention, it should be understood that the drawing does not define the limits of the invention, as changes may be made in the construction and operation therein disclosed without departing from the spirit of the invention or scope of the appended claims.
_ of Description of the Drawing The invention of this application may be understood by reference to the accompanying drawing in which the figure is a schematic representation showing an apparatus for testing an underground tank for determination of the material of construction.
Summary of the Invention The apparatus of this invention for testing the condition of an underground storage tank includes the elements of a test probe adapted for insertion into the tank to make contact at a first point within the tank, a means for making contact at a second point on the tank, a means for indicating a physical characteristic associated with the probe and the contact means, and a means for providing the characteristic to the probe or the contact means, whereby an indication of the characteristic is indicative of the material of construction of the tank.
The method of this invention for testing the condition of an underground storage tank includes the steps of contacting a first point within the tank; contacting a second point on the tank; providing a physical characteristic to the first point;
determining the existence of the characteristic at the second point, whereby such determination is indicative of the material of construction of the tank.
Detailed Description of the Invention The present invention provides an apparatus and method for determining the material of construction of an underground storage tank. The invention may best be illustrated in accordance with the Figure, in which is shown one embodiment of the present invention. For purposes of the explanation of this embodiment, the first physical characteristic will be electric current which is measured with respect to resistivity, although it should be understood that other characteristics such as electric voltage or charge may be used, as well as sound waves.
The test apparatus generally illustrated as 11 consists of elongated probe 24, contact fastener 30, current indicator 32, and current generator 34.
A storage tank generally illustrated as 12 is located beneath the surface 13 of the earth 14. The tank 12 consists of inside or interior surface or wall 16 surrounding fluid-containing compartment 18, fill pipe 20, and cover receptor 22. The probe 24 is lowered into the compartment 18 until its lower end 26 makes contact with first point 28 on the lower portion of the wall 16.
The contact fastener 30 is attached to either the fill pipe 20 or the cover receptor 22. Prior to fastening the contact fastener 30 to the tank 12, it should be, if possible, determined whether the material on the inside of the fill pipe 20 is in electrical continuity with the cover receptor 22 and/or the exterior of fill pipe 20. If there is electrical continuity, the contact fastener 30 may be placed at any location on the interior or exterior of the fill pipe 20, as well as the cover receptor 22.
Lo The probe 24 is connected to the current generator 34 by line 36. The contact fastener 30 is connected to the current indicator 32 via line 40.
The probe 24 preferably consists of an elongated, nonconductive plastic tube provided with an axial bore (not shown) of relatively small diameter. The bore is axially fitted with a highly conductive material such as copper surrounded by an insulating material within the bore, both of which project from the lower end of the probe 24. Preferably, the projecting end of the conductive material may be seated against the wall 16 of tank 12 and deformed to cause the insulating material to surround the conductive material and to sealingly mate with the wall 16 so as to insulate the conductive material. This is occasionally necessary when the tank compartment contains conductive fluid such as water at the point where the probe 24 is to contact the tank 12, thereby eliminating the passage of the current along the wall 16 which is to be desirably tested. Preferably, however, the tank 12 is drained of all water or conductive fluids. More preferably, the probe 24 is formed to shield the conductive material from the conductive fluid.
At the upper end of probe 24, the conductive material within the probe is connected to line 36. Contact fastener 30 is adapted for temporary electrical connection with some portion of the fill pipe 20 or the cover receptor 22 as by means of a binding clamp, an alligator clip, or a prod.
The current generator 34 may consist of a dry cell battery or an alternating current-to-direct current converter and a source of alternating current. The current indicator 32 may be any suitable current indicator/ohm meter. Preferably, the indicator is approved for use in and around explosive gas mixtures. The current indicator 32 and current generator 34 may I
be combined into a single apparatus. The current indicator may serve as both indicator and generator when they are combined into one device.
In a preferred embodiment, a capacitance indicator is provided to measure electrical capacitance.
The probe 24 is preferably formed with a spade-type point to enable the tank inspector to move through any residue on the bottom of the tank, to scrape the bottom of the tank surface clear of any corrosion material, and to physically determine the type of tank bottom surface, i.e., corroded or smooth.
The operation of the testing apparatus described above is as follows:
A tank inspector determines whether the fill pipe 20 or cover receptor 22 are in electrical contact with the wall 16 of the tank 12. The inspector scrapes away corrosion or dirt to obtain good metal-to-metal contact between the contact fastener 30 and the fill pipe 20. The contact fastener 30 is attached to the tank 12. The inspector inserts the probe 24 into the compartment 18 and moves it to the limit of its movement therein such that the lower end 26 of the probe 24 makes electrical contact with a point on the wall 16. The current or loop is then closed and may be traced from the battery terminals of current generator 34 through line 36 to prove 24 and lower end 26 to the first point 28 on wall 16, to the fill pipe 20, to fastener contact 30, to line 40, measured by current indicator 32, to line 38, to the other battery terminal of current generator 34.
If the current indicator 32 indicates a complete circuit exists, such a reading is the result of an unlined steel tank; or if an ohm value is not indicated, that is, an open circuit, it is indicative of a lined steel tank or a fiberglass tank. In the latter case, a second physical characteristic such icky) as electrical capacitance may be measured. A high capacitance is indicative of a fiberglass tank and a relatively low capacitance is indicative of a lined steel tank.
Certain tanks, typical of fiberglass construction, are fitted with a gauge pole protector which is normally metallic.
This protector is usually fitted with a spring mount bottom plate against which the gauge pole for measuring depth of fuel is placed. The pole moves the protector downward to rest against the tank bottom to permit accurate tank product measurements. In the test method of the present invention, an inspector can determine the presence of a protector during insertion of the probe by making contact with the plate and feeling of the spring resistance as top probe is moved further downward. Use of the method of this invention is not preferred for tanks fitted with such protectors.
Variations on the specific embodiment disclosed are readily understood by one skilled in the art and these are intended to be part of the disclosed invention.
380,842, Williamson, et at., which discloses in Figure 2 an ore sample placed on a metal plate and a second electrode used to pass over the surface of the sample to determine conductivity. A
current source is provided by means of a battery, and any current flow between the plate and the brush is detected by an audible sound produced in a telephone.
Also included in pertinent art is U. S. Patent No.
1,567,728, Greens lade, which discloses a test arrangement for a boiler stability. The test device includes a probe that extends into an opening or bore in the bolt and contacts the bottom of the bolt. The other contact member is attached to the boiler itself Jo that, if the stability is in proper condition, the circuit will be completed between the two electrodes, indicating that the bolt is in solid electrical contact with the boiler. If a leak between the bolt and the boiler has occurred, deposits of minerals would normally build up in the opening in the bolt and electrical contact between the two metallic bodies would not be made, thereby indicating that a leak did exist.
Not disclosed in any of the pertinent references is a means of determining the material of construction of underground tanks and further identifying those tanks which are of unlined steel.
It is, therefore, an object of this invention to provide a method and apparatus for determining the suitability of a tank for a particular fuel service.
It is a further object of this invention to provide a means for determining which tanks, if any, at a service station location are of unlined steel.
5C~
Other buckwheats of this invention will be clear to one skilled in the art based upon the Specification.
In the accompanying drawing, while there is shown, for purposes of illustration only, certain embodiments of the invention, it should be understood that the drawing does not define the limits of the invention, as changes may be made in the construction and operation therein disclosed without departing from the spirit of the invention or scope of the appended claims.
_ of Description of the Drawing The invention of this application may be understood by reference to the accompanying drawing in which the figure is a schematic representation showing an apparatus for testing an underground tank for determination of the material of construction.
Summary of the Invention The apparatus of this invention for testing the condition of an underground storage tank includes the elements of a test probe adapted for insertion into the tank to make contact at a first point within the tank, a means for making contact at a second point on the tank, a means for indicating a physical characteristic associated with the probe and the contact means, and a means for providing the characteristic to the probe or the contact means, whereby an indication of the characteristic is indicative of the material of construction of the tank.
The method of this invention for testing the condition of an underground storage tank includes the steps of contacting a first point within the tank; contacting a second point on the tank; providing a physical characteristic to the first point;
determining the existence of the characteristic at the second point, whereby such determination is indicative of the material of construction of the tank.
Detailed Description of the Invention The present invention provides an apparatus and method for determining the material of construction of an underground storage tank. The invention may best be illustrated in accordance with the Figure, in which is shown one embodiment of the present invention. For purposes of the explanation of this embodiment, the first physical characteristic will be electric current which is measured with respect to resistivity, although it should be understood that other characteristics such as electric voltage or charge may be used, as well as sound waves.
The test apparatus generally illustrated as 11 consists of elongated probe 24, contact fastener 30, current indicator 32, and current generator 34.
A storage tank generally illustrated as 12 is located beneath the surface 13 of the earth 14. The tank 12 consists of inside or interior surface or wall 16 surrounding fluid-containing compartment 18, fill pipe 20, and cover receptor 22. The probe 24 is lowered into the compartment 18 until its lower end 26 makes contact with first point 28 on the lower portion of the wall 16.
The contact fastener 30 is attached to either the fill pipe 20 or the cover receptor 22. Prior to fastening the contact fastener 30 to the tank 12, it should be, if possible, determined whether the material on the inside of the fill pipe 20 is in electrical continuity with the cover receptor 22 and/or the exterior of fill pipe 20. If there is electrical continuity, the contact fastener 30 may be placed at any location on the interior or exterior of the fill pipe 20, as well as the cover receptor 22.
Lo The probe 24 is connected to the current generator 34 by line 36. The contact fastener 30 is connected to the current indicator 32 via line 40.
The probe 24 preferably consists of an elongated, nonconductive plastic tube provided with an axial bore (not shown) of relatively small diameter. The bore is axially fitted with a highly conductive material such as copper surrounded by an insulating material within the bore, both of which project from the lower end of the probe 24. Preferably, the projecting end of the conductive material may be seated against the wall 16 of tank 12 and deformed to cause the insulating material to surround the conductive material and to sealingly mate with the wall 16 so as to insulate the conductive material. This is occasionally necessary when the tank compartment contains conductive fluid such as water at the point where the probe 24 is to contact the tank 12, thereby eliminating the passage of the current along the wall 16 which is to be desirably tested. Preferably, however, the tank 12 is drained of all water or conductive fluids. More preferably, the probe 24 is formed to shield the conductive material from the conductive fluid.
At the upper end of probe 24, the conductive material within the probe is connected to line 36. Contact fastener 30 is adapted for temporary electrical connection with some portion of the fill pipe 20 or the cover receptor 22 as by means of a binding clamp, an alligator clip, or a prod.
The current generator 34 may consist of a dry cell battery or an alternating current-to-direct current converter and a source of alternating current. The current indicator 32 may be any suitable current indicator/ohm meter. Preferably, the indicator is approved for use in and around explosive gas mixtures. The current indicator 32 and current generator 34 may I
be combined into a single apparatus. The current indicator may serve as both indicator and generator when they are combined into one device.
In a preferred embodiment, a capacitance indicator is provided to measure electrical capacitance.
The probe 24 is preferably formed with a spade-type point to enable the tank inspector to move through any residue on the bottom of the tank, to scrape the bottom of the tank surface clear of any corrosion material, and to physically determine the type of tank bottom surface, i.e., corroded or smooth.
The operation of the testing apparatus described above is as follows:
A tank inspector determines whether the fill pipe 20 or cover receptor 22 are in electrical contact with the wall 16 of the tank 12. The inspector scrapes away corrosion or dirt to obtain good metal-to-metal contact between the contact fastener 30 and the fill pipe 20. The contact fastener 30 is attached to the tank 12. The inspector inserts the probe 24 into the compartment 18 and moves it to the limit of its movement therein such that the lower end 26 of the probe 24 makes electrical contact with a point on the wall 16. The current or loop is then closed and may be traced from the battery terminals of current generator 34 through line 36 to prove 24 and lower end 26 to the first point 28 on wall 16, to the fill pipe 20, to fastener contact 30, to line 40, measured by current indicator 32, to line 38, to the other battery terminal of current generator 34.
If the current indicator 32 indicates a complete circuit exists, such a reading is the result of an unlined steel tank; or if an ohm value is not indicated, that is, an open circuit, it is indicative of a lined steel tank or a fiberglass tank. In the latter case, a second physical characteristic such icky) as electrical capacitance may be measured. A high capacitance is indicative of a fiberglass tank and a relatively low capacitance is indicative of a lined steel tank.
Certain tanks, typical of fiberglass construction, are fitted with a gauge pole protector which is normally metallic.
This protector is usually fitted with a spring mount bottom plate against which the gauge pole for measuring depth of fuel is placed. The pole moves the protector downward to rest against the tank bottom to permit accurate tank product measurements. In the test method of the present invention, an inspector can determine the presence of a protector during insertion of the probe by making contact with the plate and feeling of the spring resistance as top probe is moved further downward. Use of the method of this invention is not preferred for tanks fitted with such protectors.
Variations on the specific embodiment disclosed are readily understood by one skilled in the art and these are intended to be part of the disclosed invention.
Claims (5)
1. An apparatus for testing an underground storage tank to determine whether the storage tank is unlined steel, lined steel, or a non-metallic material such as fiber-glass, said apparatus comprising an elongated test probe mem-ber adapted for insertion into said tank to make contact with an interior wall surface of said tank at a first point, a contact member for making contact with said tank at a second point on said tank, and a circuit including a source of elec-trical current connected between said probe member and said contact member, and a meter for measuring the flow of current between said probe member and said contact member when said probe member has been inserted into said tank in engagement with said interior wall surface to determine whether said tank is made of unlined steel or one of said lined steel or said non-metallic material, respectively.
2. The apparatus set forth in Claim 1 including:
means for indicating the capacitance of said circuit including said probe member, said contact member and said tank when said probe member and said contact member are engaged with said tank to determine whether said tank is made of lined steel or said non-metallic material.
means for indicating the capacitance of said circuit including said probe member, said contact member and said tank when said probe member and said contact member are engaged with said tank to determine whether said tank is made of lined steel or said non-metallic material.
3. A method for testing underground storage tanks to determine whether said tanks are made of unlined steel, lined steel, or a non-metallic material comprising the steps of:
providing an apparatus including an elongated probe member insertable into a storage tank and in contact with an interior wall surface of said storage tank, a contact member adapted to be in contact with another portion of said tank, a source of electrical current and means for indicating current flow or the lack thereof between said probe member and said contact member through said tank, inserting said probe member into said tank and in contact with said interior wall surface, connecting said contact member to said tank at a point spaced from the point of contact of said probe mem-ber, and reading the flow of current between said probe member and said contact member through said tank to indicate whether said tank is made of lined steel, unlined steel, or a non-metallic material.
providing an apparatus including an elongated probe member insertable into a storage tank and in contact with an interior wall surface of said storage tank, a contact member adapted to be in contact with another portion of said tank, a source of electrical current and means for indicating current flow or the lack thereof between said probe member and said contact member through said tank, inserting said probe member into said tank and in contact with said interior wall surface, connecting said contact member to said tank at a point spaced from the point of contact of said probe mem-ber, and reading the flow of current between said probe member and said contact member through said tank to indicate whether said tank is made of lined steel, unlined steel, or a non-metallic material.
4. The method set forth in claim 3 including the step of:
providing means for measuring the electrical cape-citance between said probe member and said contact member, and measuring said electrical capacitance to determine, in the absence of current flow, whether said tank is made of lined steel or a non-metallic material.
providing means for measuring the electrical cape-citance between said probe member and said contact member, and measuring said electrical capacitance to determine, in the absence of current flow, whether said tank is made of lined steel or a non-metallic material.
5. The method set forth in claim 3 including the step of shielding the point of contact of said probe member from electrically conductive fluids contained within said tank.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US55864683A | 1983-12-06 | 1983-12-06 | |
| US558,646 | 1983-12-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1229500A true CA1229500A (en) | 1987-11-24 |
Family
ID=24230372
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000468543A Expired CA1229500A (en) | 1983-12-06 | 1984-11-23 | Underground storage tank detector |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1229500A (en) |
-
1984
- 1984-11-23 CA CA000468543A patent/CA1229500A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20041124 |