MXPA96001940A - Vapor recovery system with integrated monitoring unit - Google Patents

Abstract

A vapor recovery system (20) with integrated monitoring unit (28). The system includes one or more tanks (22, 24, 26) into which captured vapor is returned. A pressure sensor (52) is mounted into each tank not in fluid communication with the other tanks. The signals produced by the pressure sensors are forwarded to a control module (54). In the event the measured pressure drops below a selected level the control module actuates an alarm (56). The control module also disables the dispenser (31, 32) generating the liquid that is being vaporized.

Description

VAPOR RECOVERY SYSTEM WITH INTEGRATED SUPERVISION UNIT FIELD OF THE INVENTION The present invention relates generally to steam recovery systems, and more particularly, to a steam recovery system with an integrated monitoring unit for monitoring the operating status of the steam recovery system.

BACKGROUND OF THE INVENTION Steam recovery systems are used in many commercial and industrial environments to move gaseous fluids from a first source location to a second destination location. Steam recovery systems are often found at gas stations. At a gas station, a vapor recovery system is used to recover vaporized petroleum products that are discharged as an inevitable result of filling a vehicle's fuel tank. Figure 1 schematically shows a vapor recovery system 10 for preventing the loss of flammable volatile vapor while delivering the fuel (gasoline, kerosene, or alcohol) F to the filling gate FP of a PV energized vehicle. The system 10 includes a metering device D for pumping fuel from an ST storage tank (typically an underground storage tank) through a metered introduction assembly (not shown) to a dual fuel / steam hose 12. A trigger is connected manual T to the end of the hose 12 to control the discharge of the fuel F through a nozzle N that can be inserted in the fuel gate of the FP vehicle. Associated with the nozzle N, and insertable with it in the fuel gate FP, there is a vapor collection, schematically identified as VPU. The steam flow VPU is connected via a steam return duct 13 which extends through the center of the hose 12. The steam return duct 13 is connected to a steam recovery pump 11. The pump vapor recovery 11 can be located as shown near the top of the doser D, or it can be located near the ground level adjacent to the ST storage tank. The steam recovery pump 11 removes a vacuum V in the vapor collection VPU, to remove the steam from the nozzle in the steam collection gate VPU, and return it to the storage tank ST through the return duct 14. With In order to facilitate the return of the steam to the ST storage tank, the storage tank is sealed in relation to the environment. In this way, the system 10 supplies fuel from the ST storage tank while simultaneously recovering the vapors generated during the fuel filling, so that the recovered vapors can be returned to the ST storage tank or another storage container. In this way, the vapor recovery system 10 prevents the release of volatile vapors into the atmosphere. The recovery of these vapors also allows them to return to the ST storage tank, in such a way that they can be used as fuel. Accordingly, the vapor recovery system minimizes contamination and prevents the unnecessary loss of vaporized fuel. A drawback of many vapor recovery systems is that it has been difficult to provide monitoring units that evaluate whether the steam recovery equipment is functioning properly or not. This supervision is sometimes used to provide an indication to the people servicing the vapor recovery system that the system is malfunctioning and requires maintenance. In geographic regions that suffer from poor air quality, environmental regulators may even require the installation of comprehensive monitoring units with vapor recovery systems installed in facilities that would otherwise emit vapors that cause pollution. In some locations, the regulatory authorities have proposed to connect the monitoring unit of the steam recovery system to the steam generating equipment. In these locations, if the monitoring unit indicates that the steam recovery system is malfunctioning, then the monitoring unit will deactivate the steam generating equipment. Despite the obvious advisability of providing a steam recovery system with a monitoring unit, to date it has been difficult to provide this unit that is both economical to install and simple to maintain. For example, it has been proposed to install flow meters in the vapor recovery lines 13 to monitor the flow of fluid therethrough. In the event that the flow meter indicates that fluid flow has ceased, the downstream signal processing equipment will interpret the change in the flow rate status as an indication of a malfunction of the vapor recovery system. This type of unit requires that flow meters be installed at or near the inlet port of each steam recovery pump 11. One drawback of this configuration is that it provides individual flow meters for each steam recovery pump 11. in a gas station with multiple pumps, it can be very expensive. Yet another drawback of this type of configuration is that given the compact space in which most of the steam recovery pumps 11 are housed, it may be difficult, if not impossible, to find the space needed to install the flow meters. . Moreover, flow meters tend to have numerous work components. Over time, the components of 1 or more flow meters may fail, which in turn could cause the monitoring unit itself to malfunction. Still another type of monitoring unit that has been proposed for a vapor recovery system, includes a series of gas monitoring sensors. These sensors would be connected to the signal processing equipment configured to assert alarm signals in the event that the detected gas indicates that the vapor recovery system was malfunctioning, and that an excess of volatile vapors is being released into the air . One drawback of these units is that it would be difficult to design their signal processing systems in such a way that they would only assert malfunction alarm signals when the vapor recovery systems with which they are actually associated are malfunctioning. There are still other problems associated with monitoring units designed to be used in conjunction with vapor recovery systems used for the recovery of explosive or flammable vapors. The supervisory units built to work with these systems should be designed in such a way that their operation does not increase the risk that vapors that are recovering may ignite inadvertently.

SUMMARY OF THE INVENTION The present invention relates to a steam recovery system with an integral monitoring unit, wherein the monitoring unit is economical to manufacture, easy to install, and requires relatively little maintenance or ability to operate.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is pointed out with particularity in the claims. The above and other advantages of the invention can be better understood with reference to the following description, taken in conjunction with the accompanying drawings, in which: Figure 1 is a schematic illustration of gasoline dispensers to which a system can be installed of vapor recovery of the present invention. Figure 2 is a schematic illustration of gasoline storage tanks, where the monitoring unit of the vapor recovery system of this invention is installed. Figure 3 is a heliographic illustrating the manner in which the schematic diagrams of Figures 3A and 3B are assembled together to form a schematic diagram of the components of a particular monitoring assembly.

DETAILED DESCRIPTION Figure 2 illustrates a series of underground gas storage tanks 22, 24, and 26, to which a vapor recovery system 20 is connected with an integral monitoring unit 28 in accordance with the present invention. Underground storage tanks 22, 24, and 26 are of the type found in commercial gas stations. Each tank 22, 24, and 26 is used to store a different grade or type of gasoline. For example, tank 22 can be used to store leaded gasoline, tank 24 can be used to store low octane unleaded gasoline, and tank 26 can be used to store high octane unleaded gasoline. A vent stack 27 is connected to each tank 22, 24, and 26, and extends above ground level. Connected to the top of each vent stack, there is a bidirectional pressure release valve 30. In the event that the pressure in the associated tank 22, 24, or 26 falls below a selected level, or rises above At a selected level, the associated pressure release valve opens to allow the tank pressure to at least partially equal the external pressure. In some gas metering systems, the pressure release valve is set to open when the tank pressure drops below -8"H20, or exceeds 3" H20. Two of the above metering devices 31 and 32 are provided for pumping gasoline from tanks 22, 24, and 26. Meter 31 only connects to tank 22 to serve as the sole metering device for leaded gasoline. A single supply line 34 is connected between the tank 22 and the dispenser 31 to supply gas to the doser. The doser 32 is connected to the tanks 24 and 26 to serve as the doser for unleaded gasoline. A supply line 36 is connected between the tank 24 and the doser 32 to provide the low octane unleaded gasoline to the dispenser. A supply line 38 is connected between the tank 26 and the doser 32 to provide the dispenser with high octane unleaded gasoline. Associated with each doser 31 and 32, there is a series of supply pumps that direct the gasoline from the associated tanks 22, 24, or 26, through the dispenser, and outwardly through the hose H. Typically, a submersible pump is located 33 (one shown) in the tank, for pumping gasoline through the associated supply line 34, 36, or 38. A suction pump 35 (shown one), located in the dispenser 31 or 32, forces the gasoline through the hose. The dosers configured to dose multiple grades of gasoline can have multiple suction pumps 35. Integral with each doser 31 and 32, there is a steam recovery unit 40 identical in its basic structure and function to the steam recovery system of the prior art 10 described with respect to Figure 1. The steam captured by the steam recovery assembly 40 integral with the dispenser 31, the tank 22 is returned through the return line 42. The steam captured by the integral steam recovery assembly with the doser 32, is returned to the tank 24 through a manifold 44. The manifold 44 is also connected with tank 26, to ensure that tanks 24 and 26 have approximately the same pressure. In order to facilitate the return of steam to tanks 22, 24, and 26, it should be understood that the tanks are sealed, and that as fuel F is removed from the tanks, the pressure in the space above the fuel , referred to as shrinkage, initially falls. The monitoring unit 28 of the present invention includes two sensors 52, each of which monitors the operation of a separate steam recovery unit 40.

The sensors 52 are connected with a single control module 54, which monitors the status of the sensors. An alarm 56 is connected to the control module 54. In the event that one of the sensors 52 indicates that the associated vapor recovery unit 40 is malfunctioning, the control module 54 triggers the alarm 56. In some versions of the invention, the control module 54 is also connected to the gas metering units 31 and 32. In these versions of the invention, when a failure of the steam recovery unit 40 is detected, the control module 54 deactivates one or both metering units. 31 and 32, to prevent the release of vapors that cause pollution into the environment. More particularly, the control module 54 is connected to the submersible pumps 33 and / or to the suction pumps 35. When the failure of the steam recovery unit 40 is detected, the control module 54 deactivates the pumps submersibles 33 and / or the suction pumps associated with the failed vapor recovery unit. Sensors 52 are intrinsically safe, explosion-proof differential pressure switches. A differential pressure switch that is believed to be suitable for the present invention is the 1950 Series Differential Pressure Switch manufactured by D yer Instruments Inc. of Michigan City, Indiana. Each sensor 52 is mounted in the waste space, to which the steam is returned from a separate steam recovery assembly 40. A suitable depletion location for mounting a sensor 52 is in the stack 27 upstream from the position of the pressure release valve 30. Still another suitable depletion location for securing a sensor 52 is in the riser tube for the dry brake that is typically provided for each tank 22, 24, and 26 (the elevator tube). In addition, it will be understood that a first of the sensors is mounted in the ventilating stack 27 associated with the tank 22, with the tank disconnected from the second and third tanks 24, and 26, respectively. The second sensor 52 is mounted in the vent stack 27 associated with any tank 24 or 26. Only one sensor 52 is required to monitor the operation of the vapor recovery unit 40 associated with the tanks 24 and 26, because the Multiple 44 maintains these tanks at an identical pressure. In some preferred versions of the invention, the sensors 52 are normally closed differential pressure switches. These switches are set to open when the pressure in the spaces where the sensors 52 are located falls below a selected level. For example, in some preferred embodiments of the invention, the switches forming the sensors 52 open when a vacuum pressure is detected between -3"and -7.5" of H20. In still more preferred embodiments of the present invention, a switch forming a sensor 52 is opened when the vacuum pressure drops below -6"of H20.The control module 54 and the operation of the monitoring unit 28 are described with reference to the schematic drawings of Figures 3A and 3B.The control module 54 includes a power supply circuit 62 for supplying the required supply voltages needed to energize the other elements of the control module.There are two sensor channels 64A and 64B , each of which is designed to monitor the signal from a separate sensor 52. There is also a test circuit 66, which performs a self-test on the monitoring unit 28, when initially operated, and which is further configured to allowing personnel to test the operation of the unit 28 to taste The power supply circuit 62 includes a terminal pin 70 for connecting the control module 54 to an external power supply terminal, for example, a 120 VAC plug. A pair of conductors 72 and 74 are connected to the opposite contacts of the terminal pin (the contacts are not identified). A switch 75 connected to one of the conductors is used, here the conductor 74, to control the activation of the monitoring unit 28. In some versions of the invention, the switch 75 may be integral with a circuit breaker. A metal oxide veristor 76 is connected through the conductors 72 and 74. A fast-acting fuse 78 is connected in series to the conductor 72 between the terminal pin 70 and the veristor 76. In the event that a abnormal voltage pin to terminal pin 70, or the terminal pin is inadvertently connected to a power supply that provides a power signal greater than 120 VAC, the veristor 76 operates as a suppressor to prevent the signal from being applied to the components down line. In the event that any voltage surge is greater than a momentary spike, the fuse 78 will blow to prevent damage to any of the downstream components. The conductors 72 and 74 are connected to the opposite ends of the primary coil of a stepped transformer 80. The secondary coil of the transformer 80 is linked through a bridge rectifier 82. A capacitor 84 is connected between the output terminal of the rectifier of bridge 82 and earth, to soften the rectified direct current voltage. A current-limiting resistor 86 is also connected to the output terminal of the bridge rectifier through a slow-blow fuse 88. The resistor 86 is connected to ground through a polarized LED 89 to positive. In the described version of the invention, the transformer 80, the bridge rectifier 82, the capacitor 84, and the resistor 86 are selected in such a way that a supply voltage of +12 VDC is available in the output terminal of the rectifier. bridge. This +12 VDC signal is then used by the other components of the control module 54, the connections not being illustrated. Fuse 88 is a slow cast fuse. In some preferred embodiments of the invention, the fuse 88 has a maximum current rating of 375 mA. The power supply circuit 62 also includes a DC direct current voltage regulator 90, to which the +12 VDC power signal is applied. The voltage regulator 90 produces a constant, intrinsically safe +5 VDC signal, which is supplied to the other components of the control module 54. An integrated circuit available for use as the voltage regulator 90, is the 7805 manufactured by National Semiconductor . A capacitor 92 is connected between the output of the voltage regulator 90, and the ground, to minimize any ripple in the output signal from the voltage regulator. A suppressor diode 94 is connected in parallel through the capacitor 92. The suppressor diode 94 is reverse biased, to link the output signal from the voltage regulator 90 to ground, as long as the signal exceeds a potential of approximately 6 volts. Accordingly, the fuse 88 and the diode 94 cooperate to prevent the power supply circuit from generating power supply signals that may damage the components or present a risk of explosion in certain environments where the supervisory assembly is employed. Each sensor channel 64A and 64B monitors the vacuum measured by a sensor separate from the sensors 52. Accordingly, only one of the channels, channel 64A, will be described in detail. As seen in Figure 3A, the sensor 52 is represented as a normally closed switch. A 5 VDC signal is applied to one end of the sensor 52 from the power supply 62 through a normally closed switch 96 that is part of the test circuit 66. A current limiting resistor 97 is connected in series between the switch 96 and the sensor 52. The opposite end of the sensor 52 is applied to the first sensor channel 64A and more particularly to the reversing input of a comparator of the first cover 98. A resistor pulling to negative 102 is connected between the input of the sensor. inversion of comparator 98 and the earth, to ensure that a signal voltage is presented to the comparator 98. In the described version of the invention, the comparator 98 has an open collector output transistor. A reference voltage is applied to the non-inverting input of the comparator 98. In the illustrated version of the invention, the 5 VDC signal is applied to the non-inverting input of the comparator 98 through a resistor 104. Two diodes connected in series 106 are connected between the non-inverting input of the comparator 98 and the ground, to cause a reference voltage of approximately 1.2 VDC to be presented to the comparator. The output of comparator 98 is applied to a capacitor 108 that is linked to the ground. The 5 VDC signal is also applied to the capacitor 108 through a two-part resistor network. The first part of the resistor network consists of a variable resistor 110 and the resistor 112 which is connected in series with resistor 110. The resistor 110 is an adjustable resistor in order to facilitate the charging time of the capacitor 108. The second part of the resistor network consists of a resistor 114. The resistor 114 and a normally closed relay 116 connected in series, are connected in parallel through the resistors 110 and 112. The resistor 114 has a resistance that is substantially less than the resistance of the resistor 112. In some preferred embodiments of the invention, the resistor 114 has a resistance that is only 1/400 or less of the resistance of the resistor 110. As will be described later herein, the relay 116 is normally maintained in the state of open, energized switch. Accordingly, the resistor 114 is normally disconnected from the resistor network. The signal present at the output of the comparator 98 is applied to the reversing input of a comparator of the second stage 118, through a resistor 120. A voltage divider, consisting of resistors connected in series 122 and 124, is used to supply a reference voltage to the non-reversing input of the comparator 118. The input to the voltage divider is the 5 VDC signal. The signal from the junction of the resistors 122 and 124 is applied to the non-inverting input of the comparator 118 through a resistor 126. A positive feedback resistor 128 is connected between the output of the comparator 118 and the input that does not It is investment. A resistor 129 is linked between the non-inverting input of the comparator 118 and the ground. The 5 VDC signal is applied to the output terminal of the comparator 118 through a resistor 127. The comparator 118 and the associated components thus function as a Schmitt trigger which ensures that once the output signal from the comparator 98 rises above the reference signal, the output will drop rapidly from comparator 118. The output signal from comparator 118 is applied to bipolar transistors 130, 132, and 134. More specifically, the signal from output from the comparator 118 is applied to the base of the transistor 130 through a resistor 136, to the base of the transistor 132 through a resistor 138, and to the base of the transistor 134 through a resistor 140.

The emitters of transistors 130 and 132 are all connected to ground. As will be described later herein, the emitter of the transistor 134 is connected in series with the collector of a second transistor 134 that is part of the second sensor channel 64B. The 5 VDC signal is applied to the collector of the transistor 130 through a resistor 142. An LED 150a is connected in parallel with the collector of the transistor 144 and the ground. +12 VDC is applied to the collectors of the transistors 132 and 134. More particularly, +12 VDC is applied to the collector of the transistor 132 through the control inputs of a normally open relay 152, to function as the gate signal of On / off controlling the state of the relay 152. +12 VDC is applied to the collector of the transistor 134 through the control inputs of a normally closed relay 154, to serve as the on / off gate signal controlling the state of the relay 154. The second sensor channel 64b contains the same components as the first sensor channel described above. It will be noted that the transistor 130 of the second sensor channel 64b is connected to an LED 150b. The +12 VDC signal is applied to the collector of the transistor 132 of the second sensor channel 64b through the control terminals of a normally open relay 156. The collector of the transistor 134 of the second sensor channel 64a is linked to the emitter of the first channel 64b sensor In the illustrated version of the invention, the alarm 56 is represented as a piezoelectric member that is driven by the line voltage of 120 VAC. In this version of the invention, the conductors 157 and 158 connect the alarm 56 to the conductors 72 and 74, respectively. The conductor 157 is connected to the conductor 72 before the location where the fuse 78 is connected to the conductor 72. The flow of current to the alarm is controlled by the contact elements of the relay 154, which is connected in series with the separate sections of the conductor 157. The test circuit 66, as described above, includes two normally closed switches 96, each of which controls the application of the 5 VDC signal to a separate sensor of the sensors 52. The circuit of test 66 includes a resistor 160 and a capacitor 162 connected in series, to which the +12 VDC signal is applied. The signal present at the junction of the resistor 160 and the capacitor 162 is applied to the base of a bipolar transistor 164 through an inverted polarized zener diode 166. The emitter of the transistor 164 is connected to ground. The +12 VDC signal is applied to the collector of transistor 164 through the control terminals of relay 116.

The test circuit 66 further includes a switch 168 that extends between the junction of the resistor 160 and the capacitor 162 and the ground. Switch 168 is normally open. Switches 96 and switch 168 are operated together. The single-button manual test drive (not shown) will open the switches 96 and close the switch 168. The monitoring unit 28 of the vapor recovery system 20 of the present invention operates by monitoring the pressure in the tanks. petrol 22, 24, and 26, towards which the recovered steam is returned. When the steam recovery units 40 are operating normally, they pump the vapor charged air to the tanks 22 or 24 and 26, from which the gasoline is being dosed simultaneously. The discharge of air to the waste of the tanks in this way will maintain the pressure at the depletion at approximately atmospheric levels, from approximately -1 to 1"of H20.When the steam recovery units 40 are functioning properly, the differential switches of pressure acting as the sensors 52 are in the closed state.Accordingly, the 5 VDC signal is applied through each sensor 52 to the comparator of the first stage 98 of the associated sensor channel 64a or 64b. in the inverting input of each comparator 98 is greater than the signal present in the non-inverting input, the comparator will produce a relatively low output signal.This low output signal of the comparator 98 is applied to the investment input of the comparator of the second stage 118. Accordingly, when the steam recovery units 40 are functioning properly, the signal present at the inputs of i The comparison of the comparator 118 will be less than the reference signal present in the non-investment inputs. Each comparator 118 will in this way produce a relatively high signal that drives the associated transistors 130, 132, and 134. The drive of the transistors 130 forms short circuits that prevent the application of energizing voltages to the LEDs 150a and 150b. The actuation of transistors 132 allows current to flow through the control terminals of relay 152 and relay 156. Accordingly, relays 152 and 156 are maintained in their closed states to allow control / drive currents to flow to through the relay contact elements, to be applied to the associated components of the doser 31 or 32. The actuation of the transistors 134 causes the control signal to flow through the terminals of the relay 154. The application of this control current opens the contact element of the relay 154. The opening of the relay 154 prevents the flow of current through the lead 157, required to drive the alarm 56. Accordingly, when the sensors 52 indicate that the steam recovery units are functioning properly , the control module 54 allows the dosers 31 and 32 to be energized, and prevents the activation of the alarm 56. In the event that one of the the steam recovery units 40 malfunction, the pressure in the associated tank 22 or in tanks 24 and 26, will begin to drop as gasoline is dosed from the tanks. Once the tank pressure falls below the level at which the sensor 52 is set, the switch forming the sensor will open. The opening of this switch will cause the signal applied to the inverting input of the comparator of the associated first stage 98, to fall to zero. The reversal of the relative signal levels at the inputs to the comparator 98 will cause the output transistor of the comparator 98 to turn off. This will allow the capacitor 108 to be charged through the resistors 110 and 112. The time period it will take Charging the capacitor 108 is a function of the resistance of the variable resistor 110. In some preferred embodiments of the invention, the resistor 110 is selected such that the charging time for the capacitor 108 can be set from a period of 1 to 60 minutes Once the voltage across the capacitor 108 reaches a selected level, the reference voltage applied to the non-inverting input of the comparator 118 will be exceeded. Accordingly, the output of the comparator 118 will rapidly decrease to cause the deactivation of the transistors 130, 132, and 134. Disabling transistor 130 causes an energizing voltage to be applied to associated LED 150a or 150b, to drive the LED. The actuation of the LED 150a or 150b thus provides a visual indication of which of the two steam recovery units 40 malfunctioned. The deactivation of transistor 132 in this way stops the flow of current through the control terminals of associated relay 152 or 156. Accordingly, contact elements of relay 152 or 156 return to their normal open state. The opening of these contact elements interrupts the application of a driving signal to the associated dispenser 31 or 32, to deactivate the dispenser, and more particularly, the submersible pumps 33 and / or the suction pumps 35 associated with the recovery unit. of steam 40 that is malfunctioning. Disabling any of the transistors 134 interrupts the flow of current through the control terminals of the relay 154. The contact elements of the relay 154 in this manner return to their normal closed state. Closing the relay contact elements 154 in this manner allows an energizing current to be applied to the alarm 56, to cause the alarm to be triggered. Therefore, when any of the steam recovery units 40 malfunctions, the control module 54 of the monitoring unit 28 deactivates the associated doser 31 or 32, provides an indication of the specific steam recovery unit that malfunctioned. , and generates an audio alarm to provide notification of malfunction. The test circuit 66 initially tests the monitoring unit 28 on the initial drive, and is further used to test the unit 28 after the drive. At the moment when the monitoring unit 28 is activated, the moment switch 75 is closed, there is a zero voltage present at the junction of the resistor 160 and the capacitor 162. Accordingly, the transistor 162 is turned off. transistor 162, there is no current flow through the control terminals of the relay 116. Accordingly, when the monitoring unit 28 is operated for the first time, the contact elements of the relay 116 are in their normal closed state. When the relay 116 is not actuated, the primary current flow to the capacitors 108 in this manner is through the low resistance resistors 114. Accordingly, in the event that a low or zero voltage is present at the input of inversion of any comparator of the first stage 98, the associated capacitor 108 will be quickly charged. Rapid charging of the capacitor 108 will result in deactivation of the transistors 130, 132, and 134. Therefore, if there is an open connection in the signal from any sensor 52 to the control module 54, the control module, on the drive, will assert an alarm signal that serves as an indication of the fault. If the sensors 52 are functioning properly, the control module 54, on the drive, will not assert an alarm signal. Instead, the capacitor 162 will charge slowly. Once the signal through the capacitor 162 exceeds the cutoff voltage for the diode 166, the diode will allow an activation voltage to be applied therethrough, to the base of the transistor 164. The activation of the transistor 164 causes it to flow current through the control terminals of the relay 116. The actuation of the relay 116 opens the contacts of the relay, to disconnect the resistors 114 from the resistor networks associated with the capacitors 108. Accordingly, after the relay 116 is operated, the capacitors 108 will charge relatively slowly, according to the establishments of the resistors 110. The operating status of the monitoring unit is tested by operating the test button. The depression of the test button opens the switches 96 and closes the switch 168. The closing of the switch 168 results in the discharge of the capacitor 162 and the deactivation of the transistor 164. The deactivation of the transistor 162 and the associated relay 116, results in the reconnection of the resistors 114 to the networks associated with the capacitors 108. The opening of the switches 96 results in the interruption of the application of the 5 VDC signal to the sensors 52. Since the low resistance resistors 114 become to connect to the capacitors 108, then the sensor channels 64a and 64b, in turn, must quickly reset the relays 152, 154, 156, to deactivate the dosers and the drive of the alarm 56, and both LEDs 150a and 150b. In this manner, the vapor recovery system 20 includes an integral monitoring unit 28 that continuously monitors whether the actual steam recovery unit 40 of the vapor recovery system 20 is functioning properly or not. The actual supervision is carried out by means of a sensor 52 that is easily mounted in the waste space of the tanks in which the recovered vapors are stored. This eliminates the need to have to make space for a sensor in the space associated with the vapor recovery unit itself. Moreover, in a situation where a single steam recovery unit 40 is employed to capture the vapor and return it to multiple tanks that are put together with a manifold, only one sensor 52 needs to be provided in order to monitor the operating state of the steam recovery unit. Still another feature of the present invention is that it is only necessary to supply the sensor 52 with an intrinsically safe, relatively low voltage, and low current energizing signal. More particularly, in the preferred version of the invention, the signal applied to the sensors is 5 volts, and has a current of 12 mA or less. This signal is well below the energy levels that could cause the ignition of many flammable vapors. Accordingly, the monitoring unit 28 of the present invention is well suited for use with vapor recovery systems employed to capture flammable vapors, such as petroleum products. Moreover, the monitoring unit 28 of the present invention is provided with multiple channels 64a and 64b. Therefore, the monitoring unit can be used to monitor the operating status of multiple steam recovery units 40. Alternatively, it is possible to reconfigure the monitoring unit, such that each tank 22, 24, or 26 towards which the captured vapor is returned, have two or more sensors 52. In some versions of this embodiment of the invention, the multiple sensors may be provided as a failure redundancy characteristic. In other versions of the invention, the sensors 52 can be set to change the signal state in response to the detection of different levels of differential pressure. In these versions of the invention, the first sensor 52 could then be used, for example, to cause the generation of an alarm signal from a possible steam recovery unit 40 that is malfunctioning.; the second sensor would then be used to generate an alarm indicating a critical failure of the steam recovery unit. Still another feature of the present invention is that it only consists of three subsets: the sensors 52; the control module 54; and alarm 56. Each of these units is relatively inexpensive to manufacture and easy to install. Collectively, this makes the monitoring unit 28 as a whole, easy to install. Accordingly, there are very few cost burdens associated with the installation of this monitoring unit 28, even when the unit is retrofitted in a previously existing vapor recovery system 20. Further, the monitoring unit 28 of the present invention has Very few moving parts, none of which is normally exposed. Consequently, the system requires little maintenance. No special abilities are required to operate the monitoring unit 28. The monitoring unit 28 of the present invention is further configured in such a way that the alarm 56 receives its energizing signal from a source that is independent of the source of energizing signals. for the sensors 52 and the components forming the sensor channels 64a, 64b. In the event that the power supply 62 fails, the relay 154 will automatically return to its closed state, to cause the activation of the alarm 56. When this occurs, the on / off LED 89 associated with the power supply will be in the state off. Therefore, collectively, alarm 56 and LED 89 will present an indication that the monitoring unit 28 itself is malfunctioning. This feature of the invention further contributes to the ease of operation of the monitoring unit 28 of the present invention by individuals with minimal training. It should be recognized that the above description of the vapor recovery system 20 with the integrated monitoring unit 28 of the present invention is for purposes of illustration only. It will be possible to see, however, from the description of this invention, which can be practiced using alternative components different from those that have been specifically described. For example, in the described version of the invention, the control module 54 is constructed from a series of analog circuit components. It should be understood that in other versions of the invention, the control module could be formed of digital components and / or a combination of analog and digital circuit components. In a similar manner, in the described version of the invention, the sensor 52 is a switch that asserts a two-state signal. This should also be understood as merely illustrative of a version of the invention. In other versions of the invention, the sensor, for example, could generate an analog or digital signal that varies with the detected pressure. In these versions of the invention, the control module could be configured to generate a warning signal if the pressure falls below a certain level, and then an alarm signal if the sensor signal falls below a second level. It should also be recognized that in some versions of the invention, the energizing signal applied to the sensors may be different from what has been described. In some versions of the invention, an energizing signal having a potential as high as 24 volts may be applied to the sensor 52. However, in the most preferred versions of the invention, the energizing signal must have a voltage of 8. volts or less, and a maximum current of 12 mA.

Furthermore, although the system is described for use in a gas station, it must be recognized that it can be installed in other locations where the environmental or economic reasons dictate the installation of a vapor recovery system with an integrated monitoring unit. In these environments, the tank to which the captured vapor is returned may not be the tank from which the liquid or other material that served as the source of the vapor was removed. Therefore, in these versions of the invention, it may be necessary to configure the monitoring unit 28 in such a way that the sensor 52 generates signals representative of the pressure in real time within the vapor return tank. Similarly, the control module 54 would be configured to compare the measured tank pressure with a projected tank pressure, based on factors such as the volume of vapor that should have been returned to the tank. If the signal from the sensor determines that the signal from the sensor 52 indicates that the actual pressure in the tank is below the projected pressure, the control module 54 will then assert the appropriate warning or alarm signal. Moreover, it should also be understood that the sensors 52 do not always need to be mounted in a shrink space already associated with vapor recovery tanks 22, 24, or 26. In some versions of the invention, the sensors can be placed in communication of fluid with the shrinkage space through tubing specifically provided for that purpose. In these versions of the invention, as well as in other versions of the invention, fire arrestors can be connected in the pipeline to further eliminate the risk that a malfunction associated with the sensor causes the ignition of any flammable vapor. Accordingly, it is an object of the appended claims to cover all modifications and variations that fall within the true spirit and scope of the present invention.

Claims (22)

1. A vapor recovery system for capturing steam, including this system: a vapor recovery unit having a conduit that is in fluid communication with a steam trap, a pump connected to the conduit to draw steam through the conduit , and a return line connected to the pump to receive the steam removed through this pump; a sealed return tank connected to the return line of the steam recovery unit to receive the steam removed by the pump from the steam recovery unit; and a monitoring unit, including this monitoring unit: a pressure sensor arranged in the return tank to monitor the pressure in the return tank, and configured to generate a sensor signal representative of the pressure; a control module connected to the pressure sensor for receiving the signal from the sensor, this control module being configured to compare the signal of the sensor with a reference signal, and based on that comparison, to selectively assert an alarm signal; and an alarm connected to the control module to receive the alarm signal, this alarm being configured to generate a detectable alarm when the alarm signal is ascertained.

2. The vapor recovery system of claim 1, wherein: the control module is configured to assert the alarm signal if the sensor signal maintains a selected signal level relative to the reference signal for a period of specified delay; and the control module is further configured to allow the delay period to be selectively adjusted.

3. The vapor recovery system of claim 2, wherein the sensor signal is a two-state signal.

The vapor recovery system of claim 2, wherein the control module includes: a comparator of the first stage for comparing the signal of the sensor with the first reference signal; an adjustable time charging circuit for receiving an output signal from the first stage comparator, and a second stage comparator for comparing an output signal from the charging circuit with a second reference signal, wherein, Based on this comparison, the comparator of the second stage asserts the alarm signal.

The steam recovery system of claim 4, wherein: the sensor of the monitoring unit is configured to receive an energization signal; the control module of the monitoring unit has a power supply, this power supply having a connection member configured to be connected to an external power source to receive an external power signal, and a power converting circuit connected to receive the external power signal from the connecting member, and configured to produce the energizing signal for this sensor therefrom, and the power converting circuit has a safety switch that deactivates the power converter circuit when the power converter circuit malfunctions, and an indicator that is operated by the power converter circuit when the power converter is in an active state; and the alarm of the monitoring unit is connected to the power supply connection member of the control module for receiving an energizing signal therefrom, and this alarm includes a relay that controls the actuation of the alarm in response to the alarm. alarm signal, where the relay of this alarm triggers the alarm signal from the control module, and is also configured to trigger the alarm when the power converter circuit of the power supply of the control module is deactivated by the power switch. safety of the power converter circuit.

6. The vapor recovery system of claim 1, wherein the sensor signal is a two-state signal.

7. A monitoring unit for use with a vapor recovery system, using the steam recovery system to capture vapors, the vapor recovery system having a return tank where the captured vapors are stored, including the monitoring unit: a pressure sensor disposed in the return tank of the vapor system. vapor recovery to monitor the pressure in the return tank, and configured to generate a sensor signal representative of the pressure; a control module connected to the pressure sensor for receiving the signal from the sensor, the control module being configured to compare the signal of the sensor with a reference signal, and based on this comparison, to selectively assert an alarm signal; and an alarm connected to the control module to receive the alarm signal, this alarm being configured to generate a detectable alarm when the alarm signal is asserted.

The monitoring unit of claim 7, wherein: the control module is configured to assert the alarm signal if the sensor signal maintains a selected signal level relative to the reference signal for a specified delay period; and the control module is further configured to allow the delay period to be selectively adjusted.

The monitoring unit of claim 8, wherein the pressure sensor is a differential pressure sensor configured to produce a two-state sensor signal, wherein the state of the sensor signal is a function of the pressure in the return tank of the vapor recovery system.

10. The monitoring unit of the claim 9, wherein the control module includes: a comparator of the first stage for comparing the sensor signal with the first reference signal; an adjustable time charging circuit for receiving an output signal from the comparator of the first stage; and a comparator of the second stage for comparing an output signal from the charging circuit with a second reference signal, wherein, based on this comparison, the comparator of the second stage asserts the alarm signal.

11. The monitoring unit of the claim 7, wherein: the sensor is configured to receive an energization signal; the control module has a power supply, this power supply having a connection member configured to be connected to an external power source to receive an external power signal, and a power converting circuit connected to receive the external power signal from the connecting member, and configured to produce the energizing signal for the sensor therefrom, and the power converter circuit has a safety switch that turns off the power converter circuit when the power converter circuit malfunctions, and a indicator that is operated by the power converter circuit when the power converter is in an active state; and the alarm is connected to the power supply connection member of the control module to receive an energizing signal therefrom, and the alarm includes a relay that controls the actuation of the alarm in response to the alarm signal, in where the alarm relay triggers the alarm signal from the control module, and is also configured to trigger the alarm when the power converter circuit of the power supply of the control module is deactivated by the safety switch of the power converter circuit. Energy.

The monitoring unit of claim 11, wherein the safety switch of the power converter circuit of the control module is configured to selectively deactivate the power converter circuit when the power converter circuit produces a signal having a current that exceeds a previously defined evaluation.

13. A dosing system for flammable volatile liquids, including this system: a first storage tank to contain a liquid to be dosed; a first dispenser connected to the first storage tank for controlling the dosing of the liquid, this dispenser having a dosing conduit with a nozzle through which the liquid is dosed; a first steam recovery unit including: a return duct located adjacent the metering duct of the first metering device, this return duct having a vapor collecting gate located adjacent the nozzle of the metering duct; a pump connected to the return duct to draw steam through the steam trap and the return duct; a return line connected between the pump and the first storage tank, this return line serving as a conduit through which the steam removed by the pump is returned to the first storage tank; and a monitoring unit, including this monitoring unit: a pressure sensor disposed in the first storage tank for monitoring the pressure in the first storage tank, and configured to generate a first sensor signal representative of the vapor pressure; a control module connected to the pressure sensor for receiving the first signal from the sensor, this control module being configured to compare the first signal of the sensor with a first reference signal, and based on this comparison, to selectively assert an alarm signal; and an alarm connected to the control module to receive the alarm signal, this alarm being configured to generate a detectable alarm when the alarm signal is asserted.

The dosing system of claim 13, wherein: the control module of the monitoring unit is configured to assert the alarm signal if the first sensor signal maintains a selected signal level in relation to the first reference signal during a specified delay period; and the control module is further configured to allow the delay period to be selectively adjusted.

The dosing system of claim 13, which further includes an integral power supply with the control module of the monitoring unit for supplying an energizing signal to the first sensor of the monitoring unit, and wherein the signal of energization applied to the first sensor has a voltage less than 24 volts and a current less than or equal to 2 mA.

The dispensing system of claim 13, wherein the control module of the monitoring unit includes: a comparator of the first step for comparing the first signal of the sensor with the first reference signal; an adjustable time charging circuit for receiving an output signal from the comparator of the first stage; and a comparator of the second stage for comparing an output signal from the charging circuit with a second reference signal, wherein, based on this comparison, the comparator of the second stage asserts the alarm signal.

The dosing system of claim 13, which further includes a second storage tank for storing liquid, and wherein the return line of the steam return unit is a manifold to return the vapor to both the first storage tank as to the second storage tank, and wherein the first sensor is configured to monitor the pressure of both the first storage tank and the second storage tank.

The dosing system of claim 13, wherein the control module is connected to the first dispenser to control the actuation of the first dispenser, and the control module is configured to prevent the actuation of the first dispenser based on the comparison of the first signal from the sensor with the first reference signal.

The dispensing system of claim 18, wherein the first dispenser has at least one supply pump associated therewith for pumping liquid from the first storage tank, and the control module is configured to prevent actuation when less a supply pump associated with the first dispenser, with the I object to prevent the actuation of the first dispenser.

20. The dosing system of claim 19, wherein at least one supply pump is a submersible pump located in the first storage tank.

The dosing system of claim 13, which further includes: a second storage tank for liquid; a second dispenser connected to the second storage tank for controlling the dosing of the liquid from the second storage tank; and a second steam recovery unit for removing the steam discharged by the second dispenser, the second vapor recovery unit having a return line connected to the second storage tank through which the removed steam is returned to the second tank. of storage, and wherein: the monitoring unit further includes a second pressure sensor disposed in the second storage tank for monitoring the pressure of the second storage tank, the second pressure sensor being configured to produce a second sensor signal representative of the pressure in the second storage tank, and the control module of the monitoring unit is connected to the second pressure sensor to receive the second signal from the sensor, and is further configured to compare the second sensor signal with a second signal reference, and based on this comparison, to selectively assert the alarm signal ma.

22. The dosing system of claim 13, wherein the control module is connected to the first feeder and the second feeder to control the actuation of the feeders, and the control module is configured to prevent the actuation of the first feeder based on this comparison of the first signal of the sensor with the first reference signal, and to prevent the actuation of the second doser based on this comparison of the second signal of the sensor with the second reference signal.