The present invention relates to coupling the inner annular space and the outer annular space of a double-walled fuel pipe to a pump housing that carries fuel from an underground storage tank to a fuel dispenser.
In service station environments, fuel is delivered to fuel dispensers from underground storage tanks. The underground storage tanks are large containers located beneath the ground that contain fuel. A separate underground storage tank is provided for each fuel type, such as low octane gasoline, high octane gasoline, and diesel fuel. In order to deliver the fuel from the underground storage tanks to the fuel dispensers, a pump is provided that draws the fuel out of the underground storage tank and delivers the fuel through a main fuel piping conduit that runs beneath the ground in the service station. The pump may be a “submersible turbine pump.” An example of a submersible turbine pump can be found in U.S. Pat. No. 6,223,765 assigned to Marley Pump Company. Branch conduits from each fuel dispenser are coupled to the main fuel piping conduit so that fuel from the branch conduit can be delivered to the fuel dispenser.
Due to regulatory requirements governing service stations, the main conduit fuel piping is usually required to be double-walled piping. Double-walled piping contains an inner annular space that carries the fuel. An outer annular space surrounds the inner annular space so as to capture and contain any leaks that occur in the inner annular space. An example of double-walled fuel pipe can be found in U.S. Pat. No. 5,527,130, incorporated herein by reference in its entirety.
It is possible that the outer annular space of the double-walled fuel piping could fail thereby leaking fuel outside of the fuel piping if the inner annular space were to fail as well. Fuel sump sensors that detect leaks are located underneath the ground in the submersible turbine pump sump and the fuel dispenser sumps. These sensors detect any leaks that occur in the fuel piping at the location of the sensors. However, if a leak occurs in the double-walled fuel piping in between these sensors, it is possible that a leak in the double-walled fuel piping will go undetected since the leaked fuel will leak into the ground never reaching one of the fuel leak sensors. The submersible turbine pump will continue to operate as normal drawing fuel from the underground storage tank; however, the fuel may leak to the ground instead of being delivered to the fuel dispensers.
Therefore, there exists a need to be able to monitor the entire double-walled fuel piping system to determine if there is a leak in the double-walled fuel piping that could cause fuel to leak outside of the double-walled fuel piping.
The present invention relates to coupling the secondary containment system of a service station to a pump housing that is used to draw fuel from an underground storage tank to be delivered to fuel dispensers. The secondary containment system is usually provided in the form of a double-walled fuel pipe that carries fuel from the pump to the fuel dispensers. The double-walled fuel piping is comprised of an inner annular space that provides the delivery path for fuel, surrounded by an outer annular space. Double-walled fuel piping is typically required when fuel piping is exposed to the ground so that any leaks that occur in the inner annular space of the double-walled fuel piping are contained in the outer annular space of the double-walled fuel piping.
In one embodiment, the inner and outer annular spaces of the fuel piping are run back into the pump housing. In this manner, a pressure generating source in the pump housing can exert a pressure in the outer annular space of the fuel piping to pressurize the outer annular space to a negative pressure thereby preventing any fuel that leaks from the inner annular space to the outer annular space from leaking outside of the fuel piping.
The pressure generating device that generates a pressure in the outer annular space of the fuel piping may be generated by the same pump that draws fuel out of the underground storage tank, or a separate secondary pump. One type of pump that draws fuel out of the underground storage tank is referred to as a “submersible turbine pump.” In the case of a secondary pump, the same electronics in the submersible turbine pump housing that drives the submersible turbine pump may also drive the secondary pump.
In an alternative embodiment, a bypass tube couples the outer annular space of the double-walled fuel piping to the pump housing instead of the outer annular space being run directly into the housing.
The pressure generating device generates a pressure in the outer annular space, and a control system monitors the pressure in the outer annular space using a pressure sensor. The control system may be in the pump housing, a tank monitor, site controller, fuel dispenser, or other control system. Changes in pressure in the outer annular space may be indicative that a leak or breach has occurred in the outer annular space of the fuel piping such that a fuel leak would occur if the inner annular space of the fuel piping occurs. Repeating lowering pressure changes over the same amount of time are typically indicative of thermal effects rather than leaks in the outer annular space. Repeating pressure changes that are the same or greater over the same amount and/or large changes in pressure are typically indicative of a breach or leak in the outer annular space.
If a breach or leak is detected in the outer annular space, an alarm may be generated, and the pump that draws fuel out of the underground storage tank may be shut down in order to prevent and/or stop any fuel leaks from occurring underneath and the ground and/or in the service station environment.
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 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.
Fuel 22 that is dispensed by the fuel dispenser 10 is stored beneath the ground in an underground storage tank 20. There may be a plurality of underground storage tanks 20 in a service station environment if more than one type of fuel 22 is provided to be delivered by the fuel dispenser 10. For example, one underground storage tank 20 may contain a high octane of gasoline, another underground storage tank 20 may contain a low octane of gasoline, and yet another underground storage tank 20 may contain diesel. The fuel 22 in the underground storage tank 20 rests at the bottom of the underground storage tank 20. The empty space above the fuel 22 in the underground storage tank 20 is the ullage area 24. The ullage area 24 contains a vapor/air mixture. More information on underground storage tanks 20 in service station environments can be found in U.S. Pat. No. 6,116,815, incorporated herein by reference in its entirety.
A method is provided of delivering the fuel 22 from the underground storage tank 20 to the fuel dispenser 10. Typically, a submersible turbine pump 30 is provided, like that illustrated in
The submersible turbine pump 30 is comprised of submersible turbine pump electronics 34 (which can also be referred to simply as “electronics”) contained in a submersible turbine pump housing 36. The submersible turbine pump housing 36 is connected to a riser pipe 38 that is mounted using a mount 40 connected to the top of the underground storage tank 20. A pipe extends from the submersible turbine pump housing 36 down through the riser pipe 38 and into the underground storage tank 20 in the form of a boom 42. The boom 42 is coupled to a turbine housing 44 that contains a turbine or also called a “turbine pump” (not shown), both of which terms can be used interchangeably. The turbine is electrically coupled to the submersible turbine pump electronics 34 in the submersible turbine pump housing 36. The submersible turbine pump electronics 34 causes the turbine inside the turbine housing 44 to rotate to create a pressure inside the boom 42. This pressure causes fuel 22 to be drawn through the turbine housing 44 through a turbine housing inlet 46 through the boom 42 which extends inside the riser pipe 38 into the submersible turbine pump housing 36. A fluid connection is made between the boom 42 carrying the fuel 22 and an outlet orifice 37 on the side of the submersible turbine pump housing 36.
A main conduit fuel piping 48 is coupled to the submersible turbine pump housing 36 and/or outlet orifice 37 to receive the fuel 22 drawn from the underground storage tank 20. This fuel 22 is delivered via the main conduit fuel piping 48 to each of the fuel dispensers 10 in the service station environment. Typically, regulatory requirements require that any main conduit fuel piping 48 exposed to the ground be contained within a housing or other structure so that any leaked fuel 22 from the main conduit fuel piping conduit 48 is captured. Typically, this secondary containment is provided in the form of a double-walled main conduit fuel piping 48, as illustrated in
The main conduit fuel piping 48, in the form of a double-walled pipe, is run underneath the ground in a horizontal manner to each of the fuel dispensers 10. Each fuel dispenser 10 is placed on top of a fuel dispenser sump 16 that is located beneath the ground underneath the fuel dispenser 10. The fuel dispenser sump 16 captures any leaked fuel 22 that drains from the fuel dispenser 10 and its internal components so that such fuel 22 is not leaked to the ground. The main conduit fuel piping 48 is run into the fuel dispenser sump 16, and a branch conduit 50 is coupled to the main conduit fuel piping 48 to deliver fuel 22 into each individual fuel dispenser 10. The branch conduit 50 is typically run into a shear valve 52 located proximate to ground level so that any impact to the fuel dispenser 10 causes the shear valve 52 to engage, thereby shutting off the fuel dispenser 10 access to fuel 22 from the branch conduit 50. The main conduit fuel piping 48 exits the fuel dispenser sump 16 so that fuel 22 can be delivered to the next fuel dispenser 10, and so on until a final termination is made. A fuel dispenser sump sensor 18 is typically placed in the fuel dispenser sump 16 so that any leaked fuel from the fuel dispenser 10 or the main conduit fuel piping 48 and/or branch conduit 50 that is inside the fuel dispenser sump 16 can be detected and reported accordingly.
Pressure sensors may be placed in the outer annular space 56 in a variety of locations, including but not limited to inside the submersible turbine pump housing 36 (60A), in the outer annular space 56 inside the fuel dispenser sump 16 (60B), in the outer annular space 56 of the main conduit fuel piping 48 exposed to the ground (60C), and/or in the outer annular space 56 that extends to the sheer valve 52 (60D). In the embodiment illustrated in
In the case of the submersible turbine pump 30 providing the pressure generating source for the outer annular space 56, any method of accomplishing this function is contemplated by the present invention. One method may be to use a siphon system in the submersible turbine pump 30 to create a pressure in the outer annular space 56, such as the siphon system described in U.S. Pat. No. 6,223,765 (labeled as element 166 in
In the case of a second pump provided in a submersible turbine pump housing 36, the submersible turbine pump electronics 34 may also be used to provide power to the second pump. Also, the second pump may not be located in the submersible turbine pump housing 36, but only coupled to the submersible turbine pump housing 36 in order to generate a pressure in the outer annular space 56.
In
Next, readings from the pressure sensors 60A, 60B, 60C, 60D are monitored by the control system (block 106). If a pressure sensor 60A, 60B, 60C, 60D reading is not outside an allowable tolerance from the expected pressure in the outer annular space 56 (decision 108), the system continues to repeat monitoring the pressure sensors 60A, 60B, 60C, 60D readings (block 106). If a pressure sensor 60A, 60B, 60C, 60D reading is outside the allowable tolerance (decision 108), the pressure-generating source is caused to generate a negative pressure in the outer annular space 56 (block 110). This step will comprise turning on the pressure-generating device if it is currently turned off. If the pressure-generating device is turned on, then the pressure-generating device will be left on. Next, a timer is started in the control system (block 112) and the pressure sensor 60A, 60B, 60C, 60D readings are again monitored by the control system (block 114). At this point, the control system does not know if the change in pressure outside of the tolerance (decision 106) is from thermal effects or a leak in the outer annular space 56 or both.
If the pressure sensor 60A, 60B, 60C, 60D readings show the same change in pressure over a longer period of time than the timing of previous same change in pressure in the outer annular space 56 as prescribed by the control system (decision 116), this is indicative that the change in pressure in the outer annular space 56 is due to thermal effects. Thermal effects may cause a change in pressure in the outer annular space 56, but this change in pressure will be generated over longer periods of time until virtually nil if no other leaks are in the outer annular space 56. Any thermal effects that occurs is noted by the control system (block 118), and the process repeats, going back to block 106.
If the pressure sensor 60A, 60B, 60C, 60D readings are outside the allowable tolerance within the time limit prescribed by the control system indicating that the time for the change in the same amount of pressure is not decreasing (decision 116), the control system is programmed to indicate this situation as a leak in the outer annular space 56. The process continues onto
The control system next determines if the breach of the secondary containment 54 is a result of a catastrophic event (decision 124). If not, the process continues to repeat again by returning to block 102 in
Again in Region 2, the pressure in the outer annular space 56 rises to a point where it is outside an allowable tolerance, and the pressure-generating device is activated when the pressure in the outer annular space 56 falls back down to the steady state pressure in less amount of time than it took for the pressure to rise in the Region 1. This is indicative that the pressure in the outer annular space 56 was possibly caused by thermal effect and hence no alarm is generated since the pressure change is decreasing over time.
In Region 3, again the pressure in the outer annular space 56 rises above the allowable tolerance level, and the pressure-generating device is turned on to lower the pressure back down to the steady state pressure.
In Region 4, the pressure in the outer annular space 56 again rises, going outside the tolerance limit and beyond the previous pressure in Region 3. This is indicative of the fact that the pressure rise in the outer annular space 56 is not repeating from the previous pressure reading and therefore is not a result of thermal effects. An alarm would be generated in this instance indicating that a breach of the secondary containment system 54 has occurred. Also, if in Region 4, the change in pressure was the same amount as shown in Region 3, but the change in pressure in Region 4 occurred in the same or longer period of time as it occurred in Region 3, this would also be indicative of a leak in the outer annular space 56 and not due to thermal effects.
In Region 5, a catastrophic leak is shown wherein the pressure rises in the outer annular space 56 outside the tolerance and to a level wherein activating the pressure-generating device in the outer annular space 56 cannot cause the pressure in the outer annular space 56 to either fall at all or fall back to the steady state pressure. This is indicative of a catastrophic leak.
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.
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