Abstract:
The present discloses alternate constructions of water detector floats for fuel storage tanks. Embodiments show various techniques of altering the density of a sub-assembly floatation device while maintaining the system&#39;s efficient ability to detect water presence in conjunction with a Magnetostrictive probe. In the float&#39;s upward motion due to water presence or high density fuel in the tank, at some predetermined locations, its density is altered by way of strategically located free weights along its travel path.

Description:
PRIORITY CLAIM 
     The application described within claims the benefit of provisional application Ser. No. 61/602,154, filed Feb. 23, 2012. 
     FIELD OF THE INVENTION 
     This present invention is in relation to monitoring devices capable of determining the fuel level inside of a storage tank. It is intended to be utilized in conjunction with a Magnetostrictive probe where such a device is adapted to determine the level and quality of fuels. In this case, this invention coupled with the Magnetostrictive probe will facilitate the determination of water levels inside of the reservoir. 
     BACKGROUND OF INVENTION 
     Storage tanks used in fueling environments are usually located underground. Liquid fuels such as gasoline or diesel are stored in bulk until they are dispensed to customers by means of the station&#39;s fueling equipment. Environmental compliances require that monitoring systems be in place to determine inventory and leakage. Many types of equipment are used to perform this measurement. In this invention, we are going to focus on the use of a Magnetostrictive probe, which is the most commonly used detection apparatus employed in this industry. 
     Similar to its use in this application, the Magnetostrictive probe is fitted into a tank, and is comprised of a shaft that protrudes over the height of the entire tank. Detections and logic circuitries are located inside of a canister usually situated on top of the shaft. The probe and other accessories, like floats are introduced into the tank via a riser pipe connected to the tank. The means of ascertaining the levels, “fuel” and “water”, are commonly through the utilization of floating bodies each carrying a magnet. The floats are often constructed of materials such as Nitrophyl, Buna-N, Urethane and Stainless Steel. In the tank, floats are calibrated to have densities that are less than the fuel they are intended to monitor in order to float at the surface of said liquid; in this case gasoline products. Floats are allowed to sink into a fuel layer to stop at the interface of another fluid where the buoyant forces exerted by the combined fuels matches the density of the float in question. In this instance, the float remains at the interface of the two fuels. By this method, the systems are not limited to only two floats. A multiplicity of such floats could be adapted into a single probe intended to be used in a tank having various fluids of different densities. 
     The Magnetostrictive probe detection apparatus is set to locate the presence of a magnet along the shaft by means of an interaction between the permanent magnetic field emanating from the magnet and the circumferential field introduced into the Nichrome wire within the shaft by the application of a current pulse into that said wire. With the float slidably disposed along the probe&#39;s shaft and carrying the magnet that is intended to report its location, the system is able to locate the exact position of the float along the shaft. This is accomplished by means of the known propagation velocity of the twist resulting from the interaction between the two magnetic fields mentioned earlier. The delta time from when the current pulse was applied to the time a resulting twist is detected represents the time interval taken for the wave to propagate along the wire medium from its origin. When that time “T” is divided by the known propagation velocity in that wire, the magnet&#39;s exact location is then calculated by the system. 
     The intent of this invention is purely for fuel quality determination. With water capable of entering the tank by many means, such as a leaky tank, condensation, a poorly sealed tank, vent pipe etc. the possibility for water accumulation at the tank&#39;s bottom had always been a problem faced by this industry. However, previous to the time when ethanol was introduced as a means of controlling pollution, the water used to remain at the bottom of the tank where it would be accumulated and gets detected by the float that was designed to work in the interface of gasoline and water. Ethanol&#39;s affinity to absorb water creates a different problem that renders inoperative the current floats used in the industry. This invention&#39; sole intent is to help overcome this problem. 
     When water enters a tank containing 10% ethanol by volume, or E10, the water is absorbed by the alcohol content of the fuel and remains suspended in the gasoline until the water and ethanol ratio exceeds a threshold. When this state is reached, the combined solution precipitates out of the fuel and resides at the bottom of the tank. This solution has a density lower than that of water and the interface behaves very closely to that of gasoline, which confuses present water detection systems. 
     This newly formed aqueous solution is different than water in density, thus making it difficult for a float that was designed to work at the boundary of gasoline and water to have the right buoyant force necessary to lift it from the tank&#39;s bottom. In some instances, when the ratio of water in the solution is high enough, the float is lifted but it takes a considerable level of this solution to achieve this. In that case, the true height of this solution is not properly reported by the probe and jeopardizes the quality of the fuel dispensed and the integrity of the gas station&#39;s brand. 
     SUMMARY OF INVENTION 
     With this invention, a solution is offered to the problem of not detecting the presence of water in a tank. Current floats are not buoyant enough to perform in this newly formed aqueous liquid. By design, the industry&#39;s present floats are not supposed to perform well in the secondary fluid with densities lower than that of water. 
     The proposed interface float uses the technique of reducing the density of the water float to closely match that of the lowest water-ethanol mixture. By this approach, floats of any size can be adapted to take advantage of this technique. As a means of preventing the float from rising to the surface of the fuel in the event that the density of the fuel becomes very close to that of the float, trigger weights are strategically placed to stop the float from rising to the surface. Those trigger weights may be manufactured with any materials suitable to work in the fluid being measured. Their sizes depend on the mass needed and the space available to fit a given volume that will satisfy that mass. Triggers could range from just one to multiple points. 
     An embodiment of this design concept uses the Magnetostrictive probe to read the float&#39;s magnet via the Nichrome wire. This magnet is retrofitted into a floatation system that is made very buoyant, permitting it to respond to the lowest water-ethanol layer mixture that may have a density nearing 780 kg/m 3 . 
     Being so buoyant, the float does present the risk of being lifted to the tank&#39; surface in the event that the fuel density exceeds that of the calibrated float. To prevent this from happening, the float is guarded by a triggered weight that will prevent it from rising to the surface. This weight adds to the mass of the float, bringing it to a level that is exceeding the highest fuel density expected in the tank, while still allowing the float to rise in the presence of the lightest density water-ethanol mixture. 
     One other embodiment presents this invention with two trigger points. Used in this way, the float could be made to remain very sensitive to various water-ethanol densities while keeping the system from having large water offsets due to the added mass. The trigger points are separated by a distance that allows the float to travel upward along the probe for a predetermined distance before reaching the second trigger point. After the first trigger point, any upward travelling of the float will place the station in a dangerous situation where remedial actions should have been taken even before the float reaches the second point. 
     Yet in another embodiment, the first trigger point engages a telescopic assembly which carries the trigger weights, one on each leg of the telescope. This method offers a degree of stability to the float in its upward travel. In this approach, the upper weight is lifted first, while the second trigger point is where the telescopic tubes meet. 
     Another embodiment presents the trigger weights suspended by a flexible harness separating the weights. The weights are held in place by an anchor point strategically located above the float in such a way that the distance separating the top of the float to the first trigger point would be predetermined at the design phase. Upon making contact with the first trigger point, if the level of water continues to rise, the harness separating the weights will fold to accommodate the rise. The folding effect continues until the second trigger point is reached. 
     Yet another embodiment shows the weights carried by a fixture where one trigger point is located internal to the float and the other is externally situated at a predetermined distance above it. 
     Either single or multiple trigger points, whether they are located internally, above or below the float, the goal is to use weights to trigger variable densities in a float. This approach allows a low density float to be used thus stopping it from rising to the surface due to high density fuel by supplementing to its mass. The density of the fuel could rise because of low temperature, fuel tempering and other factors. Anyone skilled in the art will realize that other aspects of this invention not mentioned constitute other embodiments related to the spirit of the technique utilized and remain within the scope of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In  FIG. 1 , the concept driving this invention is illustrated where float  300  with an initial density of 775 kg/m3 is to be used for interface layer measurement. This initial concept makes use of a single density trigger point raising the float density to 810 kg/m3 by adding weight  308  to the assembly. This helps to resolve the problem of having the float rising to the surface of the tank. 
         FIG. 2  is a graphical representation of the performance of the single trigger point floatation system. It shows the float&#39;s response in relation to the trigger point in various density fuels. It also illustrates the severity regions encountered as the water level increases in the tank. 
       In  FIG. 3 , the concept driving this invention is illustrated where either floats  400 ,  500 ,  600 , 700  of initial density of 775 kg/m3 is to be used for interface layer measurement. This concept makes use of dual density trigger points raising the float&#39;s density incrementally to 790 kg/m3 as either weight  408 ,  508 ,  608 ,  708  is added to the initial float. Later as either weight  409 ,  509 ,  609 ,  709  is added to the previous combination, the density is raised to 810 kg/m3. This assembly will, as in the first case, contribute to resolve the problem of having the float rising to the surface of the tank. 
         FIG. 4  shows a graphical representation of the performance of the dual trigger points floatation system. It shows the float&#39;s response in relation to the trigger points in various water levels. It illustrates the severity regions encountered as that level of water increases in the tank. 
         FIGS. 5A-5C  are cross-sectional representations of the single trigger mode of the water float  300  in its various stages of operation. 
         FIGS. 6A-6E  are cross-sectional representations of the dual trigger mode of water float  400  in its various stages of operation. 
         FIGS. 7A-7B  are cross-sectional view of an alternate representation of the dual trigger mode of water float  500  seen in two different stages of operation. In this configuration the trigger weights  508  and  509  are carried by a telescopic assembly  503 . Trigger point  505  contacts weight  508  located on top of this arrangement. Trigger point  506  is therefore located below, being the end part of the first leg of the telescopic assembly  503 . Together they work in an identical fashion as any two trigger modes of operation. 
         FIG. 8  is a cross-sectional representation of an alternate mode of representing the dual trigger water float  600 . The weights  608  and  609  are suspended above the float and joined together by a flexible membrane  607  capable of folding to accommodate the rise of the water float. The anchor point  610  is to be a locking fixture attached to probe  100  at a predetermined location. 
         FIG. 9  is also a cross-sectional representation of an alternate mode of representing the dual trigger water float  700 . Trigger weight  708  is located internally to the float. The secondary trigger weight  709  is externally located above the float. The two weights are supported by a fixture  707  located in close proximity to the probe&#39;s end  100 . 
         FIG. 10  is a flowchart  200  illustrating the operation of the water floatation system. The tank monitoring console will use the data obtained from the probe and uses the criteria described in this flowchart to evaluate water level. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     This invention is intended to be used in conjunction with a Magnetostrictive probe. Existing probes used in the industry make use of a water interface float to help determine the presence of water and ascertain the level of that layer in the tank. However, with the advent of oxygenated gasoline, most particularly ethanol blended fuels; the industry is facing the problem of not having the probe report the proper level of water in the tank. This is due in part to the affinity of the alcohol with water molecules. When water enters the tank, it forms a bond with ethanol and strips the fuel from its alcohol content leaving behind a depleted gasoline in the tank. That stripped ethanol and the water form an aqueous water layer residing at the bottom of the tank. That water layer could range in density from 780 kg/m3 up to 900 kg/m3. With this wide range of densities, the floats currently used in the industry become very unreliable at detecting the presence of aqueous water layer in a tank. 
     The preferred embodiment of this invention shows a cutaway representation of this design concept as seen in  FIG. 5A-5C  where the float group  300  is seen retrofitted into a probe group  100 . Internal to the float is trigger weight  308  immediately located on its resting location on top of probe boot  106 . 
     Probe boot  106  is set in such a way that with no water in the tank, it extends at a predetermined distance higher than the float&#39;s trigger point  305 . That distance is there to allow the float to have a range of motion in normal operation. It also allows the float to not be restricted in its upward motion when buoyed by a low density water-ethanol layer. 
     Residing on top of the boot is weight  308  that stays at that fixed location in normal operation when no water is detected. However, when the water level rises, the float travels up to that distance and this weight gets coupled into the float and adds to its mass. 
     In its current representation, the float is composed of frame  302  that forms the body of the whole assembly. This body is what keeps together the various float parts. Within the assembly, a cavity is also included where ballasts  303  are inserted to allow calibration of the mass of the whole float assembly. At the very top is inserted a position magnet  301 . 
     In this preferred embodiment, the float will rise as the level of water represented by demarcation line  10  increases in the tank. Once the level reaches the threshold where the trigger point  305  makes contact with weight  301 , a small lag is introduced in the free operation of the float and adds to the initial water offset of the float. As the lag is imposed to the float, that level will rise until the buoyant force imposed by the liquid overcomes the added mass of the float. 
     The intent of having trigger point  305  in close proximity to weight  308 , allows for the float&#39;s lowest tip to remain near the bottom of the tank in the event the fuel density increases causing the float to rise suddenly. By this approach, the system will be able to detect the rise of water without compromising its detection capability. 
     High density fuel may be due to a sudden drop in temperature where it would cause the density of the fuel to reach a level matching that of the float. To accommodate for detecting temperature drop, the probe is equipped with an array of temperature detection sensors capable of indicating the fuel temperature inside of the tank. Provision is made in the software algorithm to evaluate the data according to the steps highlighted in flowchart  200  which will be explained later. 
     Other phenomenon may contribute to the rise in fuel density as well. In some instances where the fuel is being tampered with, addition is made to the tank where a fuel of lower grade, such as Kerosene, may be added to the tank. This is done with the intent to replace the volume of the fuel removed, whereas, this addition causes an increase in fuel density and contributes to the sudden rise of water float  300 .  FIG. 5B  illustrates the float in this position. Note that in normal operation the float does reach that threshold as well. In such a case, the level seen is a true representation of what the float indicates. 
     Density increase alone would not suffice to cause float  300  to rise past trigger weight  308 . If this occurs as illustrated in  FIG. 5C , it shows that level  10  of water is truly rising inside the tank. However, when the fill port is near the location where the probe and floats are located, the pressure resulting from the flow of the fuel being delivered may cause an upward force to lift the float and keep it at a position exceeding the trigger point level for the duration of the delivery. Caution should be made in determining that the rise in the float&#39;s position is truly a result of high level water before posting an alarm. Reference should be made to flowchart  200  for the logic in this determination. 
     In an alternate embodiment, the float system  400  comprises of two trigger points  405  and  406 . The operation is identical to the case where only one trigger point is used, with the exception that the lags are smaller and contribute to a smoother operation of the float. 
     This  400  embodiment is more suitable to work in a larger diameter float since this extra volume offers the privilege of having the float construction shorter and can allow a longer cavity inside the frame to accommodate two trigger weights. Assuming the trigger distance X where trigger point  405  reaches weight  408  as being somewhere between 0.5″ to 0.75″, the distance it will take for weight  408  to travel up the shaft to reach weight  409  would be in the order of 1.5″ to 2″ ( FIG. 6D ), which would be large enough to place the system at a dangerous level where remedial actions should have been taken. Therefore, in this embodiment, the float is never expected to reach this point of contact if proper care is taken to maintain the fueling environment. 
       FIG. 6E  shows the float  400  in a very high region of the probe where the fueling environment would have to discard the entire tank&#39;s content in order to remedy the situation. At that level, the risk is present that the dispensed fuel may be an aqueous water-ethanol liquid. 
     The alternate construction presented in  FIGS. 7A and 7B  is for float  500  where the trigger weights are supported by a telescopic carrier  503 . The operation of this float is identical to construction  400  presented earlier. The difference is that the weights are suspended on float  500  and are lifted by a primary trigger point  505  and a secondary trigger point that is formed by the contact of the two tubes, or point  506 . 
     Float  600  illustrated in  FIG. 8  is identical in operation with float  400  and  500 . In this configuration, the weights are situated above the float where, as its rises, the float would be coupled with them based on the conditions highlighted in flowchart  200 . In this arrangement, a locking fixture  610  is positioned along probe tube  100  where the assembly containing weights  608  and  609  resides. 
     Membrane  607  of float  600  may be made of any flexible material capable of surviving the fuel environment where the float is intended to be used. The material must remain flexible even when temperature goes below 15° C. 
     Float  700  operates in an identical fashion as all the other “Two Trigger Point” assemblies mentioned thus far. In this configuration, it is shown with trigger weight  708  inside of float  700  and trigger weight  709  located above the float. The whole weight system is held in place by a fixture  707  assembled in close proximity with probe tube  100  with sufficient spacing to allow float  700  and trigger weights  708  and  709  to move freely about up and down the shaft. Contact between float  700  and trigger weight  708  is made by means of a protruded lip  705  from the float assembly intended to lift the weight when contact is established. 
     In the free operation of the floats, as the level of water increases, different regions of severity are established to allow setting alarms of different degree of severity. The graphical representation of this is seen in  FIGS. 2 and 4 . 
     Region 1 where the height ranges from 0 to 1″ allows for determining early presence of water. It also serves as the buffer zone where if fuel density rises and causes the float to lift, the prevention apparatus will still keep the float sitting low in the tank where detecting true rise in water would not be compromised. 
     Region 2 which ranges from 1″ to 2″ will provide sufficient protection to allow the station attendant to provide early remedial steps to rescue the content of the tank. 
     Region 3 which ranges from 2″ to 5″ will alarm a severe case of water level. At this point it is an indication that it is very late in taking the decision to correct the fuel. 
     Region 4 is where the level is in excess of 5″, which is a true indication that fuel of a poor quality or that water may be dispensed to customer&#39;s vehicles. At this stage, the tank must be emptied and the contents replaced. 
     Since there are many factors that could cause the interface float to rise above a safe zone inside the tank, caution should be taken to use the criteria described in flowchart  200  before posting an alarm. 
     Flowchart  200  shows the decision criteria to evaluate water level as heights are measured by probe  100 . At the console level, power is provided to probe  100  and a predetermined sequence of measurement takes place inside the probe to permit reading the various parameters. Fuel, Water, Temperature are cycled as programmed into the firmware embedded in the probe. Once state  201  is initiated, a water level measurement  202  is performed. 
     Due to the fact that many factors could affect a given reading, an evaluation process is introduced to help interpret a reading. At state  203  a decision is made based on whether the water height  10  has risen past the zero point or the state where the float is resting at the bottom of the tank. If the condition is false or returns a NO, the system moves on to state  206  where that data is recorded as well as the time measurement was taken to allow a rate evaluation of water reading. Then, the system waits until the next cycle when a water measurement may be performed again and repeat the process. 
     If state  203  returns a YES, then a further evaluation takes place to ascertain whether water is really present in the tank. State  204  verifies if the water is above the first trigger point. If No, it is considered safe since that region is allowed to be only 1″ or less. From there rate monitor  206  tag that reading and the cycle repeats. 
     If state  204  returns a YES, then further evaluations are made by state  205  where the temperature of the fuel is considered. If the temperature was not below 15° C. then state  207  uses the information kept at state  206  where the rate was monitored to determine whether this change happened suddenly. If it was not a sudden step change, then it is clear that water is present and an alarm is posted based on height level. 
     If state  205  or state  207  return a YES, then a level evaluation is made by state  208  to determine if level has increased past the trigger point. If NO, than it is safe to conclude that the fuel in the tank is of high density. If the temperature was not below the threshold of 15° C. at state  205 , then care is to be taken in ascertaining the cause of the high fuel density. 
     If state  208  returns a YES, then a further check should be made to verify that this rise is not due to an external influence such as a fuel delivery. So if state  210  is YES than a fuel delivery is in progress and therefore the decision to post an alarm should be held until the delivery has ended. 
     If state  210  reveals that the fuel level was not rising, than it is safe to conclude that water is in the tank. Alarm should be posted according to level in the tank. 
     The various constructions detailed in this invention constitutes embodiments of the construction of the “Fuel Storage Tank Water Detector With Triggered Density” concept. It remains that anyone skilled in the art will realize that other aspects of this invention not mentioned constitute other embodiments related to the spirit of the technique utilized and remain within the scope of this invention.