Patent Application
20070267088
The present invention relates to automatically adjusting an ORVR-compatible Stage II vapor recovery system to maintain the A/L ratio within desired tolerances or limits to meet regulatory and/or other requirements.
Gasoline dispensing facilities (i.e. gasoline stations) often suffer from a loss of fuel to the atmosphere due to inadequate vapor collection during fuel dispensing activities, excess liquid fuel evaporation in the containment tank system, and inadequate reclamation of the vapors during tanker truck deliveries. Lost vapor is an air pollution problem which is monitored and regulated by both the federal government and state governments. Attempts to minimize losses to the atmosphere have been effected by various vapor recovery methods. Such methods include: “Stage-I vapor recovery” where vapors are returned from the underground fuel storage tank to the delivery truck; “Stage-II vapor recovery” where vapors are returned from the refueled vehicle tank to the underground storage tank; vapor processing where the fuel/air vapor mix from the underground storage tank is received and the vapor is liquefied and returned as liquid fuel to the underground storage tank; burning excess vapor off and venting the less polluting combustion products to the atmosphere; and other fuel/air mix separation methods.
A “balance” Stage-II Vapor Recovery System (VRS) may make use of a dispensing nozzle bellows seal to the vehicle tank filler pipe opening. This seal provides an enclosed space between the vehicle tank and the VRS. During fuel dispensing, the liquid fuel entering the vehicle tank creates a positive pressure which pushes out the ullage space vapors through the bellows sealed area into the nozzle vapor return port, through the dispensing nozzle and hose paths, and on into the VRS.
It has been found that even with these measures, substantial amounts of hydrocarbon vapors are lost to the atmosphere, often due to poor equipment reliability and inadequate maintenance. This is especially true with Stage-II systems. One way to reduce this problem is to provide a vapor recovery system monitoring data acquisition and analysis system to provide notification when the system is not working as required. Such monitoring systems may be especially applicable to Stage-II systems.
When working properly, Stage-II vapor recovery results in equal exchanges of air or vapor (A) and liquid (L) between the main fuel storage tank and the consumer's gas tank. Ideally, Stage-II vapor recovery produces an A/L ratio very close to 1.0. In other words, returned vapor replaces an equal amount of liquid in the main fuel storage tank during refueling transactions. When the A/L ratio is close to 1.0, refueling vapors are collected, the ingress of fresh air into the storage tank is minimized, and the accumulation of an excess of positive or negative pressure in the main fuel storage tank is prevented. This minimizes losses at the dispensing nozzle and evaporation and leakage of excess vapors from the storage tank. Measurement of the A/L ratio thus provides an indication of proper Stage-II vapor collection operation. A low A/L ratio means that vapor is not moving properly through the dispensing nozzle, hose, or other part of the system back to the storage tank, possibly due to an obstruction or defective component.
Recently, the California Air Resources Board (CARB) has been producing new requirements for Enhanced Vapor Recovery (EVR) equipment. These include stringent vapor recovery system monitoring and In-Station Diagnostics (ISD) requirements to continuously determine whether or not the systems are working properly. CARB has proposed that when the A/L ratio drops below a prescribed limit for a single or some sequence of fueling transactions, an alarm be issued and the underground storage tank pump be disabled to allow repair to prevent further significant vapor losses. Many systems employ air flow sensors (AFS), also known as “vapor flow meters” to monitor the amount of recovered vapor to determine if the vapor recovery system is working correctly.
Even with use of AFS, CARB only requires monitoring and alarm generation if the A/L ratio is outside the prescribed limits. Automatic correction of the vapor recovery system is not required. However, if AFSs are used, the vapor recovery system can determine the difference between the desired A/L ratio versus actual performance. In this manner, in addition to monitoring, the vapor recovery system can automatically adjust itself in a closed loop, feedback manner to correct itself. A service call to adjust the vapor recovery system manually can be avoided thereby resulting in lower costs and convenience. A shut down of fuel dispensers may also be avoided. However, this vapor recovery system performance may be detrimentally effected by the introduction of vehicles with Onboard Refueling Vapor Recovery (ORVR) devices that recover refueling vapors onboard the vehicle. CARB also requires that Stage II vapor recovery systems be compatible for both ORVR and non-ORVR fueling transactions.
Vapors produced as a result of dispensing fuel into an ORVR equipped vehicle are collected onboard, and accordingly, are not available to flow through a vapor return passage to an AFS for measurement. Some vapor recovery systems are designed to block the vapor return path when an ORVR-equipped vehicle is being refueled. One such device is disclosed in U.S. Pat. No. 6,810,922, incorporated herein by reference in its entirety. This prevents the ingestion of air into the fuel storage tank, which in turn causes decreased pressure levels within the tank and a lesser possibility for fugitive emissions through the tank vent. With such systems, refueling an ORVR-equipped vehicle results in a positive liquid fuel flow reading, but no return vapor flow reading (i.e. an A/L ratio calculated using the AFS will be equal to 0 or close thereto). Because ORVR fueling transactions cause the AFS measurement to suggest a blockage requiring an A/L adjustment, an ORVR-compatible closed loop, self-adjusting vapor recovery system that employs the AFS will not operate properly.
Thus, there exists a need to provide a self-adjusting ORVR-compatible vapor recovery system that does not improperly adjust the vapor recovery rate during or due to ORVR fueling transactions. The present invention provides a solution to this problem.
The present invention is a system and method for automatically adjusting an ORVR-compatible Stage II vapor recovery system to maintain the air-to-liquid (A/L) ratio within desired tolerances or limits to meet regulatory and/or other requirements. An air flow sensor (AFS) or vapor flow meter measures the amount of recovered vapor for a dispensing point to calculate the recovery efficiency of the system in the form of the A/L ratio. Volume or flow rate measurements can be used. ORVR fueling transactions are either minimized or excluded from the A/L ratio calculation, so that the A/L ratio is not artificially lowered due to a blocked or altered recovery present during an ORVR fueling transaction. The A/L ratio is then compared to a desired or nominal A/L ratio. Adjustments are made to dispensing points that share a common recovery system vapor pump if the A/L ratio differs from the desired ratio. The adjustments are made to attempt to keep all dispensing points sharing a common vapor pump in desired A/L operating ranges, and if not possible, an alarm or error can be generated and/or reported.
The system can distinguish between ORVR and non-ORVR fueling events in different manners. If the ORVR valve 228 contains a sensing device that is coupled to the control system 270, the system can distinguish between ORVR and non-ORVR-equipped vehicles on a transaction-by-transaction basis. The system may also distinguish between ORVR and non-ORVR-equipped vehicles using a series of statistical algorithms to distinguish between ORVR and non-ORVR equipped vehicles using a set of collected A/L ratio data from all monitored dispensers at a station.
A calculation of the vapor recovery system adjustment for each grade of fuel at a dispensing point is calculated based on the non-ORVR fueling transactions. Multiple grades of fuel in the exemplary embodiment are coupled to a common vapor recovery system; thus, an adjustment to the recovery system affects the A/L ratio of each grade of fuel. The average of all the desired vapor pump adjustments for all grades of fuel of the dispensing point is calculated. The maximum positive and negative adjustment that can be made to a dispensing point and the recovery remain within prescribed safety ranges for all grades of fuel is determined. The final calculated adjustment is based the minimum of the maximum vapor pump adjustments calculated for all grades. This is so that the overall adjustment is made to be within maximum adjustment ranges of all grades of fuel for the dispensing point. The final adjustment is used to calculate the corrected vapor collection value, which in turn allows determination of a corrected A/L ratio for each grade of fuel. The system then adjusts the vapor pump 222 if variable speed, or proportional valves if constant speed, so that the corrected A/L ratio is achieved.
If any of the A/L ratios for the dispensing point are outside of prescribed safety range even with the adjustment being made, an alarm and/or report can be generated. The dispensing point could be shut down, or the error reported to the remote system, so that corrective measures can be taken to investigate.
Those skilled in the art will appreciate the scope of the present invention and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures.
The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the invention, and together with the description serve to explain the principles of the invention.
The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:
The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention and illustrate the best mode of practicing the invention. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the invention and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.
The present invention is a system and method for automatically adjusting an ORVR-compatible Stage II vapor recovery system to maintain the air-to-liquid (A/L) ratio within desired tolerances or limits to meet regulatory and/or other requirements. An air flow sensor (AFS) or vapor flow meter measures the amount of recovered vapor for a dispensing point to calculate the recovery efficiency of the system in the form of the A/L ratio. Volume or flow rate measurements can be used. ORVR fueling transactions are either minimized or excluded from the A/L ratio calculation, so that the A/L ratio is not artificially lowered due to a blocked or altered recovery present during an ORVR fueling transaction. The A/L ratio is then compared to a desired or nominal A/L ratio. Adjustments are made to dispensing points that share a common recovery system vapor pump if the A/L ratio differs from the desired ratio. The adjustments are made to attempt to keep all dispensing points sharing a common vapor pump in desired A/L operating ranges, and if not possible, an alarm or error can be generated and/or reported.
Vapor Recovery System
A first embodiment of the invention is described in connection with
As illustrated in
The dispenser controller 120 may be the Gilbarco G-Site® or Passport® point-of-sale system. The monitor 140 may be the Veeder-Root Company TLS-350® tank monitor. Both the dispenser controller 120 and the monitor 140 may be further communicatively coupled to an off-site or remote system 134 for communicating information and receiving instructions remotely. Both systems may communicate with the remote system 134 over telephone lines 136 or other network lines 136, including the Internet.
The fuel dispenser units 200 may be provided in the form of conventional “gas pumps.” Each fuel dispenser unit 200 may include one or more fuel dispensing points typically defined by nozzles 210. The fuel dispenser units 200 may include one coaxial vapor/liquid splitter 260, one vapor return passage 220, and one fuel supply passage 230 per nozzle 210. The vapor return passages 220 may be joined together before connecting with a common vapor return pipe 410. The fuel dispenser units 200 may also include one liquid fuel dispensing meter 240 per nozzle 210. The liquid fuel dispensing meters 240 may provide dispensed liquid fuel quantity information to the dispenser controller 120 via a liquid fuel dispensing meter interface 270, or control system, and interface wiring 130.
The main fuel storage system 300 may include one or more main fuel storage tanks 310. It is appreciated that the storage tanks 310 may typically be provided underground, however, underground placement of the tank is not required for application of the invention. It is also appreciated that the storage tank 310 may represent a grouping of multiple storage tanks tied together into a storage tank network. Each storage tank 310, or a grouping of storage tanks, may be connected to the atmosphere by a vent pipe 320. The vent pipe 320 may terminate in a pressure relief valve 330. A vapor processor 340 may be connected to the vent pipe 320 intermediate of the storage tank 310 and the pressure relief valve 330. A pressure sensor 350 may also be operatively connected to the vent pipe 320. Alternately, it may be connected directly to the storage tank 310 or the vapor return pipe 410 below or near to the dispenser 200, since the pressure is normally substantially the same at all these points in the vapor containment system. The storage tank 310 may also include an Automatic Tank Gauging System (ATGS) 360 used to provide information regarding the fuel level in the storage tank. The vapor processor 340, the pressure sensor 350, and the automatic tank gauging system 360 may be electrically connected to the monitor 140 by third, fourth, and fifth wiring busses 342,352, and 362, respectively. The storage tank 310 may also include a fill pipe and fill tube 370 to provide a means to fill the tank with fuel and a submersible pump 380 to supply the dispensers 200withfuel from the storage tank 310.
The means for connecting the dispenser units and the main fuel storage system 300 may include one or more vapor return pipelines 410 and one or more fuel supply pipelines 420. The vapor return pipelines 410 and the fuel supply pipelines 420 are connected to the vapor return passages 220 and fuel supply passages 230, respectively, associated with multiple fuel dispensing points 210. As such, a “vapor return pipeline” designates any return pipeline that carries the return vapor of two or more vapor return passages 220. In the illustrated embodiment in
An AFS's 500 is deployed in a common branch of the vapor return passages 220 to measure various groupings of dispensing point 210 vapor flows, down to a minimum of only two dispensing point vapor flows. The latter example may be realized by installing one AFS 500 in each dispenser housing 200, which typically contains two dispensing point's 210 (one dispensing point per dispenser side) or up to six dispensing points (hoses 212) in MultiProduct Dispensers (MPD's) (3 per side). The vapor flows piped through the vapor return passage 220 may be tied together to feed the single AFS 500 in the dispenser housing.
As stated above, the monitor 140 may connect to the dispenser controller 120, directly to the current loop interface wiring 130 or directly to the liquid fuel dispensing meter 240 to access the liquid fuel flow volume readings. The monitor 140 may also be connected to each AFS 500 at the facility 10 so as to be supplied with vapor flow amount (i.e. vapor volume) information. The liquid fuel flow volume readings are individualized fuel volume amounts associated with each dispensing point 210. Employing AFS's 500 allows determination of the actual A/L ratio of the vapor recovery system of the dispenser 200 in operation. If an AFS 500 is used to determine vapor flow volumes recovered for more than one dispensing point 210, as is illustrated in
Once the vapor flow information is determined for each dispensing point 210, the A/L ratios for each dispensing point 210 may be determined and a pass/fail determination may be made for each dispensing point based on the magnitude of the ratio. It is known that the ratio may vary from 0 (bad) to around 1.0 (good), to a little greater than 1.0 (which, depending upon the facility 10 design, can be either good or bad), to much greater than 1 (typically bad). This ratio information may be provided to the facility operator via an audio signal and/or a visual signal through the monitor 140. The ratio information may also result in the automatic shut down of a dispensing point 210, or a recommendation for dispensing point shut down.
In order to determine the acceptability of the performance of vapor recovery in the facility 10, the ratio of vapor flow to dispensed liquid fuel (A/L ratio) is determined for the fuel dispensing points 210 included in the facility. This A/L ratio may be used to determine if the fuel dispensing point 210 in question is in fact recovering an equal volume of vapor for each unit volume of liquid fuel dispensed by the dispensing point 210. Without use of AFSs 500, only initial calibration values could be used to control the vapor pump 222. Using AFSs 500 to calculate an actual A/L ratio allows the vapor recovery system to adjust the settings for the vapor pump 222 in a closed loop, feedback manner if the actual A/L ratio is different than desired. The adjustment can be made to attempt to bring the actual A/L ratio in line with desired tolerances or limits.
In the embodiment of the invention shown in
When an ORVR-equipped vehicle is being fueled, a negative pressure is created in the vapor return path 220. The ORVR blocking valve 228 is designed to block the vapor return path 220 in response to this negative pressure so that suction of the vapor pump 222 does not cause air to be ingested. When a non ORVR-equipped vehicle is being fueled, the valve 228 will not close, thereby allowing the vapor pump 222 suction to be applied to the vapor return path 220 to recovery vapors expelled. The valve 228 may include a sensor device (not shown) that is communicatively coupled to the dispenser control system 270 with status information via communication line 242. The status will either be closed or opened, thereby indicating either an ORVR-equipped vehicle or non ORVR-equipped vehicle, respectively. As discussed later, the vapor recovery system must distinguish between ORVR and non ORVR-equipped vehicles to adjust the vapor recovery system to the desired A/L ratio.
Adjustment of Vapor Recovery System
Turning to
The system can distinguish between ORVR and non-ORVR fueling events in different manners. If the ORVR blocking valve 228 contains a sensing device that is coupled to the control system 270, the system can distinguish between ORVR and non-ORVR-equipped vehicles on a transaction-by-transaction basis. Thus, the A/L ratio and adjustment, if necessary, can be calculated for non-ORVR-equipped vehicles on a per transaction basis or for an aggregate of non-ORVR fueling transactions. The system may also identify to exclude ORVR fueling transactions for the A/L ratio calculations using the techniques described in U.S. Pat. Nos. 5,728,275; 5,992,395; 6,026,868; 6,065,507; 6,460,579; 6,499,516; 6,810,922; 6,923,221; 6,941,978, all of which are incorporated by reference herein in their entireties.
The system may also distinguish between ORVR and non ORVR-equipped vehicles using a series of statistical algorithms to distinguish between ORVR and non-ORVR equipped vehicles using a set of collected A/L ratio data from all monitored dispensers at the fuel dispensing facility 10. Activity on one dispensing point 210 is compared to others at the fuel dispensing facility 10 using the technique described U.S. Pat. No. 6,622,757, incorporated herein by reference in its entirety. Thus in summary, the A/L ratio data may be for a single dispensing transaction, or data collected for a number of transactions over a given time period, including a day, days, and/or weeks. Further, the data collected may be for a rolling period.
After the A/L ratio selected data set is collected, whether it be for single or multiple transactions, the control system next calculates an A/L calibration adjustment value for a given fuel dispensing point 210 based on the A/L selected data set (step 1004). In the example of
The adjustment value may be calculated in any number of methods. For example, the adjustment value may be calculated like that described in the system of
Lastly, the vapor recovery rate is adjusted based on the calculated “A/L calibration adjustment value (step 1006). The process then repeats (step 1002) to continue to collect A/L ratio data and adjust the vapor recovery system accordingly to attempt to match the actual performance of the system to the desired performance, measured in terms of A/L ratios.
Next, the A/L selected data set data is filtered to reduce error, since some A/L ratio data may include error for any number of reasons (step 2004). For example, thermal effects may cause the AFS 500 to measure the vapor recovered as less or more than actual. Vapor compression may occur if the temperature of the vehicle tank is lower than the temperature at the AFS 500. Conversely, a lower temperature in the vehicle tank will cause vapor expansion. In an exemplary embodiment, the selected data set excludes the lower 40% and upper 10% of A/L ratio data. It is more probable that erroneous A/L ratio data will occur at the lower end of the data set than the upper end.
Next, a calculation of the vapor recovery system adjustment for each grade of fuel is calculated according to the following formulas for a vapor recovery system employing a variable speed vapor pump 222, like that illustrated in
A description of some of the calculations listed above are provided below:
maxA-L=the maximum A/L ratio for the vapor recovery system to be within the desired operating range
minA-L=the minimum A/L ratio for the vapor recovery system to be within the desired operating range
saftyMargin=the safety margin or tolerance used to determine the maximum positive and negative adjustment that can be made to the vapor recovery system without the system going outside a permitted safety range.
gradeFlowRate=a measured value provided by the common dispenser controller electronics, flow rate monitoring technology or an assumed 7.5 gallons per minute (GPM)
pumpSpeed=current pump speed in GPM
nominalA-L=middle of certified A/L range
collectionVariance=nominalA-L*totalLiquidDispensed−totalVaporCollected pumpingTime=totalLiquidDispensed/gradeFlowRate
desiredVaporPumpAdjustment=collection Variance/pumpingTime
The calculations described for the examples above are discussed in detail below according to steps 2006-2024 in
The nominal A-L ratio (nominalA-L) is the middle of the desired or required range of the A/L ratio performance, which is between 1.0 and 1.2 according to the example above. In the example, the A/L ratio is 1.1, meaning that 10% more vapor is to be recovered than fuel dispensed. The A/L ratio 1.1 may be set higher than 1.0 if there are losses at the nozzle of the dispensing point 210 to vehicle fuel tank interface. Some losses do occur in a non-sealed vapor recovery assist type system.
The total liquid dispensed (totalLiquidDispensed) is the total amount of fuel grade dispensed over the period of time being analyzed. This measurement is performed by the fuel meters 240, as previously discussed for
The total vapor collected (totalVaporCollected) is the total amount of vapor that was recovered for the given grade of fuel over the period of time being analyzed. This measurement is performed by the AFS 500 as previously discussed. In “Grade A” in the example above, the total vapor collected is equal to 400 gallons. Notice that the vapor collected is 100 gallons less than the fuel dispensed, thereby indicating an underachieving performing vapor recovery system.
A variance in the actual vapor collected compared to the vapor that should be recovered to achieve the nominal A-L ratio (nominalA-L), called “collectionVariance,” is now calculated according to step 2006 in
The flow rate of the grade of fuel being analyzed (gradeFlowRate) is listed as 7.5 gallons per minute (GPM). This setting can be determined in a number of methods. The rate can be fixed according to historical data, or can be calculated based on the flow rate of the dispensing points 210 providing the given grade of fuel being analyzed. The flow rate can be calculated as the total liquid dispensed divided by time (totalLiquidDispensed/pumpingTime). A more accurate technique is disclosed in U.S. Pat. No. 6,975,964, assigned to the same assignee as the present application, and incorporated herein by reference in its entirety. This technique uses the same variables as the flow rate divided by time method, but also includes techniques to reduce or eliminate the “dead time” during a dispensing transaction for a more pumping time (pumpingTime), and thus results in a more accurate flow rate calculation.
As shown in step 2008 in
Next, a maximum positive vapor pump adjustment (maxPosVaporPumpAdj) and maximum negative vapor pump adjustment (maxNegVaporPumpAdj) are calculated (step 2010 in
The maximum positive vapor pump adjustment (maxPosVaporPumpAdj) is calculated as follows:
The maxPosVaporPumpAdj determines what adjustment to the vapor pump 222 can be made such that the total VaporCollected does not exceed the totalLiquidDispensed within a safety range for a given maxA-L. For the “Grade A” example, the maxPosVaporPumpAdj is equal to 3.19 gal./min., meaning that a maximum vapor pump 222 adjustment to increase the recovery of vapor at a rate of 3.19 gal./min. can be made without putting the system outside the operating safety range. If the maxPosVaporPumpAdj is greater than zero, this means that the vapor pump 222 is not already beyond its maximum adjustment and can be adjusted further. If the maxPosVaporPumpAdj is less than or equal to zero, this means that the vapor pump 222 is already beyond the maximum adjustment and no further adjustment can be made to increase the recovery of vapor without exceeding safety limits.
Similarly, the maximum negative vapor pump adjustment (maxNegVaporPumpAdj) is the maximum adjustment that can be made to the vapor pump 222 negatively (i.e. reduce the vapor recovery rate) and the system be within operating safety range for a given minA-L. The maximum negative vapor pump adjustment (maxNegVaporPumpAdj) is calculated as follows:
For the “Grade A” example, the maxNegVaporPumpAdj is equal to 2.34 gal./min. If the maxNegVaporPumpAdj is greater than zero, the vapor pump 222 is already beyond its maximum negative adjustment and cannot be adjusted further. Since the maxNegVaporPumpAdj is 2.34 gal./min., no negative adjustment to the vapor pump 222 is possible without the system exceeding the bounds of the prescribed safety range.
Next, the average of all the desired vapor pump adjustments for all grades of fuel is calculated (step 2012). An average adjustment is made to the vapor pump 222 as a result of the process, because the vapor pump 222 and the AFS 500 for each side of the fuel dispenser unit 210 services all grades. The average of the desired vapor pump 222 adjustment (avgDesiredVaporPumpAdjustment)=0.93 gal/min. for the examples listed above (2.8−0.2+0.1 gal/min./3 grades). This value is the average desired vapor pump 222 adjustment that in theory is made to bring the average A/L ratio for all grades of fuel back within the desired tolerance for a gross correction.
Note that the average adjustment is a positive value, meaning a vapor pump 222 adjustment should be made to increase the rate of vapor recovery and bring the gross A/L ratios to the desired value. However, if the average of the desired vapor pump adjustment (avgDesiredVaporPumpAdjustment) is greater than any one grade's maximum positive vapor pump adjustment (maxPosVaporPumpAdj), the average correction (avgDesiredVaporPumpAdjustment) cannot be made. Since “Grade B” can only be adjusted 0.10 gal./min. as its maximum positive vapor pump adjustment (maxPosVaporPumpAdj), a final calculated adjustment (finalAdjustment) can only be 0.10 gal./min. (step 2014). In other words, the final adjustment (finalAdjustment) can only be the minimum of the maximum positive vapor pump adjustments (maxPosVaporPumpAdj) for all grades. Otherwise, the adjustment will adjust the vapor pump 222 in a manner that will take Grades B and C outside safety tolerance ranges for the example provided above.
Likewise, if the average of the desired vapor pump adjustment (avgDesiredVaporPumpAdjustment) was a negative value, this would mean that the vapor pump 222 should be adjusted negative instead of positively. The final adjustment (finalAdjustment) would be the maximum of the maximum negative vapor pump adjustments (maxNegVaporPumpAdjustment) for the grades of fuel. In this manner, the negative adjustment to the vapor pump 222 would be made in a manner that no grade of fuel is adjusted outside its calculated safety tolerance range. In the example above, the average of the desired vapor pump adjustment (avgDesiredVaporPumpAdjustment) is greater than zero, so a positive vapor pump 222 adjustment is made.
At this point, it has been determined that the final adjustment (finalAdjustment)=0.1 gal./min. to the vapor pump 222 as the maximum adjustment that can be made to the vapor pump 222 to improve the A/L ratio of the grades of fuel while not also adjusting any one grade of fuel outside a safety tolerance range. The final adjustment (finalAdjustment) is next used to calculate the corrected vapor collection value (correctedVaporCollection), which is a calculation of the amount of vapors that will be collected for each grade of fuel as a result of the calculated final adjustment (finalAdjustment) for the vapor pump 222 (step 2016).
For “Grade A” in the example above, the corrected vapor collection value (correctedVaporCollection) is the final adjustment (finalAdjustment) of 0.1 gal./min. times the pumping time (pumpingTime) of 53 min., plus the total vapor collected (totalvaporCollected) of 400 gal. This value is equal to 405 gallons, meaning that the vapor pump 222 should be corrected so that 405 gallons of vapor should have been collected instead of 400 gallons. Because the corrected vapor collection value (correctedVaporCollection) is calculated based on the final adjustment (finalAdjustment), the corrected vapor collection (correctedVaporCollection) can be achieved for the selected grade of fuel and still keep all grades of fuel within safety tolerance range.
Lastly, the corrected A/L ratio (correctedA-L) is calculated by dividing the corrected vapor collection (correctedVaporCollection) of 405 gallons by the total liquid dispensed (totalLiquidDispensed) to equal 0.81 (step 2018). The system then adjusts the vapor pump 222 so that the corrected A/L ratio (correctedA-L) is achieved.
Note that all of the grade's corrected A/L ratios (correctedA-L) are within the tolerance of the minimum A/L ratio (minA-L) of 1.0 and the maximum A/L ratio (maxA-L) of 1.2, except Grade A. Since the best correction that can be performed on Grade A is 0.81 corrected A/L ratio (correctedA-L), without taking the other grades outside the tolerances of adjustment, an alarm and/or report can be generated and/or communicated to the control system (steps 2020, 2022). The alarm and/or report indicates that even with the maximum corrected made to the dispensing point 210. Grade A's A/L ratio is still outside of the allowable tolerance range. From there, the dispensing point 210 could be shut down, or the error reported to the remote system 134, so that corrective measures can be taken to investigate, and the process ends (step 2024) or repeats (step 2002).
As alternatives, the control system 270 that controls the vapor pump 222 can store different pump settings for each grade of fuel on a given dispenser 200 side. This allows avoidance of making compromised adjustments to keep all grades within their certified A/L range without one dispenser side affecting the other. Further, a time weighted average of previous adjustments could also be used to make that actual vapor pump adjustment, since A/L ratios tend to drift slowly over time, abrupt large changes are indicative of a problem and adjustments should not be attempted under this situations.
Alternative Vapor Recovery System Embodiments
The vapor adjustment is made by changing the opening of the orifice in the valve 243 rather than variably controlling the speed of the vapor pump 222. However, all of the concepts described above regarding determination of A/L ratios for non-ORVR transactions, and calculating a vapor adjustment are equally applicable. Note that although the vapor pump 222 adjustment example previously discussed above is described with respect to a variable speed vapor pump 222 to control vapor recovery rate, the present invention may also be used to determine the adjustment of a proportional valve system employing a constant speed motor(s) to control the vapor recovery rate in a similar manner.
Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present invention. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.
The present application is related to U.S. patent application Ser. No. 11/210,715, filed on Aug. 24, 2005; which is a continuation patent application of U.S. patent application Ser. No. 10/935,024, now U.S. Pat. No. 6,964,283, filed on Sep. 7, 2004; which is a continuation patent application of U.S. patent application Ser. No. 10/180,047, now U.S. Pat. No. 6,802,344, filed on Jun. 27, 2002; which is a divisional patent application of U.S. Pat. No. 6,622,757, filed on Nov. 30, 2000, entitled “Fueling System Vapor Recovery And Containment Performance Monitor And Method Of Operation Thereof;” all of which are entitled to the benefit of the earlier filing date and priority of U.S. Provisional Patent Application Ser. No. 60/168,029, filed on Nov. 30, 1999, entitled “Fueling System Vapor Recovery Performance Monitor,” U.S. Provisional Patent Application Ser. No. 60/202,054, filed on May 5, 2000, entitled “Fueling System Vapor Recovery Performance Monitor,” and U.S. Provisional Patent Application Ser. No. 60/202,659, filed on May 8, 2000, entitled “Method of Determining Failure of Fuel Vapor Recovery System.” All of the aforementioned patents, regular patent applications, and provisional patent applications are hereby incorporated by reference herein in their entireties.
