Fuel delivery system having corrosive detection assembly

A fuel dispensing system includes a fuel tank adapted to contain a quantity of fuel. A fuel dispenser in is fluid communication with the fuel tank via piping. A pump is operative to transfer fuel from the fuel tank to the fuel dispenser. A corrosive detection assembly operative to identify presence of a corrosive substance in the fuel is also provided. The corrosive detection assembly has at least one thermoelectric detector positioned to be in contact with fuel vapor in the fuel dispensing system, the thermoelectric detector producing a detector signal indicating presence of the corrosive substance. Electronics are in electrical communication with the thermoelectric detector, the electronics being operative to interpret the detector signal and produce an output if the corrosive substance is present. The at least one thermoelectric detector may comprises a plurality of thermoelectric detectors at different locations in the fuel dispensing system.

BACKGROUND

The present invention relates generally to equipment used in fuel dispensing environments. More specifically, the present invention relates to a fuel delivery system having the capability of detecting the presence of corrosives that might lead to reliability and maintenance issues.

As is well known known, liquid fuel delivery systems typically include one or more fuel dispensers located in the forecourt area of a service station. The fuel dispensers are connected via piping with a source of the liquid fuel (e.g., a tank containing gasoline). Typically, the piping is located under the forecourt so as to feed the liquid fuel from an underground storage tank (UST). Multiple USTs may be provided for different types or grades of fuel. Fuel grades can be mixed as necessary or desired to yield still further grades of fuel.

Modern fueling environments may store liquid fuels which are mixtures of gasoline and ethanol in various ratios, rather than “pure” gasoline. For example, E10 is a liquid fuel comprising 90% gasoline and 10% ethanol. As small amounts of water enter the storage tank containing a gasoline/ethanol mixture, the ethanol absorbs the water. Alternative fuels such as low sulfur diesel and biodiesel are also becoming more common.

The introduction of various alternative and pollution reducing fuels (e.g., fuels with ethanol oxygenate) has created the potential for corrosion in fuel dispensing systems (especially when the fuel does not have a biological reducing inhibitor such as sulfur or includes a biologically supportive substance, such as ethanol). When it occurs, corrosion can result in an interruption of fueling operations, loss of sales, and possible damage.

SUMMARY

The present invention recognizes and addresses various considerations of prior art constructions and methods. According to one embodiment, the present invention provides a fuel dispensing system comprising a fuel tank adapted to contain a quantity of fuel. A fuel dispenser is in fluid communication with the fuel tank via piping. A pump is operative to transfer fuel from the fuel tank to the fuel dispenser. A corrosive detection assembly operative to identify presence of a corrosive substance in the fuel is also provided. The corrosive detection assembly has at least one thermoelectric detector positioned to be in contact with fuel vapor in the fuel dispensing system, the thermoelectric detector producing a detector signal indicating presence of the corrosive substance. Electronics are in electrical communication with the thermoelectric detector, the electronics being operative to interpret the detector signal and produce an output if the corrosive substance is present. The at least one thermoelectric detector may comprise a plurality of thermoelectric detectors at different locations in the fuel dispensing system.

In some exemplary embodiments, the thermoelectric detector is located in an upper portion of the fuel tank above a maximum fuel level. In some exemplary embodiments, the pump is a submersible turbine pump (STP) and the thermoelectric detector is located in an STP sump. In some exemplary embodiments, the thermoelectric detector is located in a fuel dispenser sump located below the fuel dispenser.

In some exemplary embodiments, the thermoelectric detector may comprise a sensing circuit having a pair of junctions formed by interconnection of dissimilar conductors, the pair of junctions being configured to experience a substantially equivalent ambient temperature. In some exemplary embodiments, one of the pair of junctions is in direct contact with the vapor environment and another of the pair of junctions is in indirect contact with the vapor environment via a media isolated assembly. The detector signal in such embodiments may originate at the another of the pair of junctions. A second sensing circuit having a pair of junctions formed by interconnection of dissimilar conductors may also be provided, one of the pair of junctions of the sensing circuit and one of the pair of junctions of the second sensing circuit being connected together.

Another aspect of the present invention provides a corrosive detection assembly for use in a fuel dispensing system. The corrosive detection assembly comprises at least one thermoelectric detector positioned to be in contact with fuel vapor in the fuel dispensing system, the thermoelectric detector producing a detector signal indicating presence of the corrosive substance. The thermoelectric detector includes a sensing circuit having a pair of junctions formed by interconnection of dissimilar conductors, the pair of junctions being configured to experience a substantially equivalent ambient temperature. Electronics in electrical communication with the thermoelectric detector are operative to interpret the detector signal and produce an output if the corrosive substance is present.

Another aspect of the present invention utilizes a thermoelectric detector having a plurality of sensing circuits each with a different detection response time. For example, junctions of each such sensing circuit may be made of progressively heavier gage wire such that each heavier gage sensing circuit has a slower response time than the next smaller gage sensing circuit. The difference in time to detection between the sensing circuits is indicative of and related to the severity of the corrosive condition of the environment. That is, shorter detection times indicate higher concentration levels of corrosive substances.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Certain fueling systems, particularly those that dispense fuel without a biological reducing inhibitor or fuel that includes a biologically supportive substance, may experience excessive or accelerated corrosion. The corrosion is often caused by the presence of bacteria that may be introduced into the fuel from the surrounding environment. For example, the bacteria may react with ethanol in the fuel to produce acid (e.g., acetic acid) that has a deleterious effect on equipment of the fuel dispensing system. Embodiments of this invention provides a corrosive detection assembly that can be used to detect presence of the corrosive substance so that remedial action can be taken.

In this regard,FIG. 1is a diagrammatic representation of a fuel dispensing system10in a retail service station environment according to an aspect of the present invention. In general, fuel may travel from an underground storage tank (UST)12via main fuel piping14, which may be a double-walled pipe having secondary containment as is well known, to fuel dispenser16and nozzle18for delivery. An exemplary underground fuel delivery system is illustrated in U.S. Pat. No. 6,435,204, hereby incorporated by reference in its entirety for all purposes.

More specifically, a submersible turbine pump (STP)20associated with the UST12is used to pump fuel to the fuel dispenser16. (In some embodiments, the fuel dispenser may be self-contained, meaning that fuel is drawn to the fuel dispenser by a pump unit positioned within the fuel dispenser housing.) STP20is comprised of a distribution head22containing power and control electronics that provide power through a riser24down to a boom26, eventually reaching a turbine pump contained inside an outer turbine pump housing28. STP20may preferably be the RED JACKET® submersible turbine pump, manufactured by the Veeder-Root Co. of Simsbury, Conn. There may be a plurality of USTs12and STPs20in a service station environment if more than one type or grade of fuel30is to be delivered by a fuel dispenser16.

The turbine pump operates to draw fuel30upward from the UST12into the boom26and riser24for delivery to the fuel dispenser16. After STP20draws the fuel30into the distribution head22, the fuel30is carried through STP sump32to main fuel piping14. Main fuel piping14carries fuel30through dispenser sump34to fuel dispenser16for eventual delivery. Dispenser sump34is adapted to capture any leaked fuel30that drains from fuel dispenser16and its fuel handling components so that fuel30is not leaked into the ground.

Main fuel piping14may then pass into housing36of fuel dispenser16through a shear valve38. As is well known, shear valve38is designed to close the fuel flow path in the event of an impact to fuel dispenser16. U.S. Pat. No. 8,291,928, hereby incorporated by reference in its entirety for all purposes, discloses an exemplary secondarily-contained shear valve adapted for use in service station environments. Shear valve38contains an internal fuel flow path to carry fuel30from main fuel piping14to internal fuel piping40.

After fuel30exits the outlet of shear valve38and enters into internal fuel piping40, it may encounter a flow control valve42positioned upstream of a flow meter44. (In some fuel dispensers, valve42may be positioned downstream of the flow meter44.) In one embodiment, valve42may be a proportional solenoid controlled valve, such as described in U.S. Pat. No. 5,954,080, hereby incorporated by reference in its entirety for all purposes.

Flow control valve42is under control of a control system46via a flow control valve signal line48. In this manner, control system46can control the opening and closing of flow control valve42to either allow fuel to flow or not flow through meter44and on to the hose50and nozzle18. Control system46may be any suitable electronics with associated memory and software programs running thereon whether referred to as a processor, microprocessor, controller, microcontroller, or the like (which are intended herein as equivalent terms). In a preferred embodiment, control system46may be comparable to the microprocessor-based control systems used in CRIND and TRIND type units sold by Gilbarco Inc. Control system46typically controls other aspects of fuel dispenser16, such as valves, displays, and the like as is well understood. For example, control system46typically instructs flow control valve42to open when a fueling transaction is authorized. In addition, control system46may be in electronic communication with a site controller52via a fuel dispenser communication network54. Communication network54may be any suitable link, such as two wire, RS 422, Ethernet, wireless, etc. as needed or desired. Site controller52communicates with control system46to control authorization of fueling transactions and other conventional forecourt control activities. For example, the site controller functions may be provided by the PASSPORT® point-of-sale system manufactured by Gilbarco Inc. or by a separate forecourt controller.

The memory of control system46(and other memories discussed herein) may be any suitable memory or computer-readable medium as long as it is capable of being accessed by the control system, including random access memory (RAM), read-only memory (ROM), erasable programmable ROM (EPROM), or electrically EPROM (EEPROM), CD-ROM, DVD, or other optical disk storage, solid-state drive (SSD), magnetic disc storage, including floppy or hard drives, any type of suitable non-volatile memories, such as secure digital (SD), flash memory, memory stick, or any other medium that may be used to carry or store computer program code in the form of computer-executable programs, instructions, or data. Control system46may also include a portion of memory accessible only to control system46.

Flow control valve42is contained below a vapor barrier56in a hydraulics compartment58of fuel dispenser16. Control system46is typically located in an electronics compartment60of fuel dispenser16above vapor barrier56. After fuel30exits flow control valve42, it typically flows through meter44, which preferably measures the flow rate of fuel30. In some embodiments, meter44may be capable of measuring the density and/or temperature of the flowing fuel. Flow meter44may be any suitable flow meter known to those of skill in the art, including positive displacement, inferential, and Coriolis mass flow meters, among others. Meter44typically comprises electronics62that communicate information representative of the flow rate, density, and/or temperature of fuel to control system46via a signal line64. For example, electronics62may typically include a pulser as known to those skilled in the art. In this manner, control system46can update the total gallons (or liters) dispensed and the price of the fuel dispensed on an information display of fuel dispenser16.

As fuel leaves flow meter44it enters a flow switch66. Flow switch66, which preferably comprises a one-way check valve that prevents rearward flow through fuel dispenser16, generates a flow switch communication signal via flow switch signal line68to control system46to communicate when fuel30is flowing through flow meter44. The flow switch communication signal indicates to control system46that fuel is actually flowing in the fuel delivery path and that subsequent signals from flow meter44are due to actual fuel flow.

After fuel30enters flow switch66, it exits through internal fuel piping40to be delivered to a blend manifold70. Blend manifold70receives fuels of varying octane levels from the various USTs and ensures that fuel of the octane level selected by the customer is delivered. After flowing through blend manifold70, fuel30passes through fuel hose50and nozzle18for delivery to the customer's vehicle.

UST12includes an automatic tank gauge (ATG) system to monitor level of fuel30. The gauging system includes a tank monitor72in electrical communication with a probe74(e.g., a magnetostrictive probe) such as via an appropriate signal line76. In turn, tank monitor72is in electrical communication with site controller52, such as via signal line78. Preferably, tank monitor72is a microprocessor-based system having suitable program instructions stored in memory to perform the desired functions. For example, tank monitor72may comprise the TLS-450 or TLS-350 systems manufactured by Veeder-Root Company.

Probe74includes a probe shaft80that extends through the interior of UST12, as shown. A water level float82and fuel level float84are able to slide along the shaft80as the liquid levels change. In particular, water level float82floats on the water-fuel interface so that the level of water in the bottom of UST12can be detected. If the water level exceeds a threshold (such as if it is too near the inlet of pump housing28), operation of STP20can be interrupted. Fuel level float84floats on top of fuel30so that the amount of fuel in UST12can be determined.

As shown, probe74includes an electronics head86at the end of probe shaft80, located external to UST12in a well88. Head86generates signals provided to tank monitor72that are indicative of the locations of floats82and84. In an example embodiment, probe74may comprise the Mag Plus magnetostrictive probe system manufactured by Veeder-Root Company.

Fuel dispensing system10further comprises a corrosive detection assembly that is operative to detect the presence of a corrosive substance that may otherwise lead to premature corrosion within the fuel dispensing system. As will be explained, the corrosive detection system preferably includes at least one thermoelectric detector90situated in an electrolytic vapor environment within the fuel dispensing system. In this regard, evaporation of liquid fuel produces fuel vapor at various locations in the fuel dispensing system. A corrosive substance in the fuel will also be present in the vapor, where it is detected by the thermoelectric detector90as described more fully below.

In the illustrated embodiment, for example, a first thermoelectric detector90ais located in the ullage92of UST12at a location above the highest expected level of fuel30. As is well known, hydrocarbon vapors produced by evaporation of fuel30will be located in ullage92. If a corrosive substance is present in the vapor, detector90aproduces a signal that can be detected by suitable circuitry such as suitably programmed circuitry of tank monitor72. Toward this end, detector90ais in electrical communication with tank monitor72via a corresponding signal line94. In addition, or in the alternative, one or more thermoelectric detectors may be situated in other locations in the fuel dispensing system. For example, the illustrated embodiment includes a thermoelectric detector90bin STP sump32and/or a thermoelectric detector90cin dispenser sump34.

Referring now toFIG. 2, certain additional details regarding an exemplary corrosive detection assembly100of the present invention can be most easily explained. As shown, thermoelectric detector90is situated in a vapor environment102, which will be electrolytic in the presence of the corrosive substance. As a result, a signal indicating presence of the corrosive substance will be produced by detector90. While analog processing is possible within the scope of the present invention, the analog output of detector90is sampled and converted to a digital signal in the illustrated embodiment via a suitable analog-to-digital (A/D) converter104. The output of A/D converter104is fed to comparator circuitry106, which in this embodiment includes a microprocessor108and associated memory110. Microprocessor108executes suitable program instructions to interpret the digitized signals from detector90. If presence of the corrosive is detected, a signal indicative thereof can be provided to indicator112which may be any suitable device, circuitry, computer program, or other indicator that can be used to act upon the presence of the corrosive substance. For example, indicator112may be a visual or audible indicator to inform an operator that the corrosive material is present. In addition or in the alternative, indicator112may comprise a computer program that continuously tracks the amount of corrosive substance and generates action at the appropriate time. As noted above, the circuitry of corrosive detection assembly100may be incorporated into tank monitor72. For example, tank monitor72can be programmed to perform the functions described in relation toFIG. 2in addition to other functions normally performed by tank monitor72.

Certain aspects of a preferred implementation of thermoelectric detector90can be explained with reference toFIG. 3. In this case, detector90utilizes the Seebeck effect in which a temperature dependent potential is generated by the formation of a bi-metal junction that is common to a class of temperature measuring sensors called thermocouples. The bi-metal junction is formed when two dissimilar metal wires are coupled by welding or other common connection methods. In a thermocouple, a temperature difference between the two ends of the connected wires produces a measurable voltage.

In this regard, voltage EAand resistance RArepresent one electrical conductor of material type A (e.g., a base metal such as iron or copper). Similarly, EBand RBrepresent another electrical conductor of material type B (e.g., a noble metal or alloy such as nickel/chromium, platinum, etc.). T2is the junction formed by coupling material type A to type B at one end, which in the case of a thermocouple would often be considered the “hot” junction. T1is the junction formed by coupling material types A and B to measuring instrumentation at the other end, which in the case of a thermocouple would often be considered the “cold” junction. V is a voltage measuring device (e.g., a sampler) and RSis a known large resistance intended to minimize the effects of RAand RB. In a thermocouple, the difference between EAand EBrepresents the magnitude of the temperature difference between T2and T1.

In accordance with embodiments of the present invention, the known temperature response of the bi-metal junction is not important. For example, junctions T1and T2may both be equally exposed to the vapor environment in a way that both will experience substantially the same ambient temperature. In the presence of the corrosive substance, a galvanically impressed voltage develops as the base metal is activated by contact with an electrolyte substance within the vapor environment. (The electrolyte dispersed by evaporation within the closed confines of the UST or the like is the same substance responsible for corrosion in the fuel delivery system.) With the base metal as the positive lead, the impressed voltage produced by formation of the galvanic circuit (represented by EA1) increases the overall voltage VABat T1. Because the voltages EAand EBare minimized (due to no temperature differential between T1and T2), EA1can be easily detected.

FIG. 4illustrates an alternative thermoelectric detector114in accordance with the present invention, which can be used in lieu of detector90. In this case, a pair of similar sensing circuits116aand116bare provided. Sensing circuits116aand116bare both arranged to experience the same ambient temperature (i.e., the temperature of the vapor environment), but only junction T2of sensing circuit116ais directly exposed to the vapor environment. In this regard, sensing circuit116band junction T1of sensing circuit116aare physically isolated from the vapor environment, such as by seals, covers, etc. As shown, for example, sensing circuit116band junction T1of sensing circuit116amay be contained in a media isolated assembly118which allows measurement of the same temperature as junction T2of sensing circuit116awithout exposure to the vapor. As a result, only sensing circuit116awill experience the galvanically impressed voltage EA1. A simple comparison of the output voltage VABof sensing circuits116aand116bcan be used to determine whether EA1is nonzero.

FIG. 5illustrates an alternative thermoelectric detector122in accordance with the present invention, which can be used in lieu of detector90. In this embodiment, a pair of similar sensing circuits124aand124bare connected to share a common junction T1. The common junction T1and junction T2of sensing circuit124bare contained in a media isolated assembly126. While only junction T2of sensing circuit124ais directly exposed to the vapor environment, all junctions experience substantially the same temperature. As will be appreciated, T1is nonzero in this embodiment only when the base metal lead of sensing circuit124ais in contact with the corrosive substance.

FIG. 6illustrates an alternative thermoelectric detector130in accordance with the present invention, which can be used in lieu of detector90. In this embodiment, a pair of similar sensing circuits132aand132bare connected together on their metal-type B sides. The voltage measuring device V and resistor RSare connected across the metal-type A sides of sensing circuits132aand132bto form a common junction T1. The common junction T1and junction T2of sensing circuit132bare contained in a media isolated assembly134. While only junction T2of sensing circuit132ais directly exposed to the vapor environment, all junctions experience substantially the same temperature. As will be appreciated, T1is nonzero in this embodiment only when the base metal lead of sensing circuit132ais in contact with the corrosive substance.

FIG. 7illustrates another embodiment of a thermoelectric detector140in accordance with the present invention. In this case, detector140comprises a plurality of sensing circuits90a,90b, and90c, each of which may be similar to detector90discussed above. In this regard, the sensing circuits90a-ceach have a respective bimetal junction T2exposed to the electrolytic vapor environment. Notably, however, wires forming the sensing circuits90a-chave progressively heavier gage, such that90bhas heavier gage wire than90a, and90chas heavier gage wire than90b. In the presence of a corrosive environment, each of the detection elements (sensing circuits) will experience corrosion at a detectably different rate. (Stated another way, the heavier gage wire has a slower detection response time than the lighter gage wire.) Because of the relationship between material mass and corrosive potential, for example the percentage of evaporated acetic acid, the time relationship between corrosion on each element provides a technique to evaluate the severity of the corrosive conditions.

In this embodiment, a microprocessor142is utilized to sample the outputs of sensing circuits90a-cvia a multiplexer (“MUX”)144. As one skilled in the art will appreciate from the above discussion, the functionality of microprocessor142and/or multiplexer144may in some cases be provided by suitable programming of tank monitor72.) Microprocessor142enables operation of multiplexer144via a signal provided by line146to the multiplexer's “ENABLE” input. The outputs of the respective sensing circuits90a-care selected by microprocessor142via selection lines collectively designated148. The signals on selection lines148(designated S1through SN, with N being dependent on the number of sensing circuits in detector140) inform multiplexer144which one of inputs C1through C3is active at any given time. The selected input is then provided at output D to microprocessor142, e.g., via signal line150. Inputs C1through C3are in electrical communication with the respective sensing circuits90athrough90c. Respective amplifiers (or buffers)152a,152b, and152cmay be situated along the lines connecting sensing circuits90a-cand their associated one of inputs C1through C3, if necessary or desired. In operation, microprocessor142samples the outputs of sensing circuits90a-cin rapid succession. The different detection readings of the sensing circuits90a-cduring any detection cycle, and the differences between the same sensing circuit90a-cfrom one cycle to the next, is indicative of the severity of the corrosion.

Referring now toFIG. 8, a method in accordance with the present invention of determining presence of a corrosive substance in a fuel dispensing system is illustrated. For example, the illustrated method may be practiced by program instructions running on the processor of tank monitor72. After the process starts (as indicated at160), detector signals (e.g., voltage signals from detector(s)90) are received (as indicated at162). This signal information is then compared against predetermined criteria (as indicated at164). If the comparison shows presence of a corrosive and/or the severity of the corrosive (as indicated at step166), an output is made to the indicator112(as shown at step168). Otherwise, the process loops back for another comparison. The process ends at step170.

It can thus be seen that embodiments of the present invention provide a fuel dispensing system with a novel corrosive detection assembly. While one or more preferred embodiments of the invention have been described above, it should be understood that any and all equivalent realizations of the present invention are included within the scope and spirit thereof. The embodiments depicted are presented by way of example only and are not intended as limitations upon the present invention. Thus, it should be understood by those of ordinary skill in this art that the present invention is not limited to these embodiments since modifications can be made. Therefore, it is contemplated that any and all such embodiments are included in the present invention as may fall within the scope and spirit thereof.