Abstract:
A submersible turbine pump (STP) comprising a manifold, a yoke assembly including a yoke sleeve integrally connected to the manifold, and a packer removably secured to the manifold is provided. The manifold includes an electrical cavity that receives electrical wiring from an external source. The yoke sleeve has a hollow interior and is integrally connected to manifold, and a first end of the yoke sleeve is within the electrical cavity. The packer includes a chamber having a yoke sleeve inlet port and an electrical conduit inlet port. The yoke sleeve inlet port receives a second end of the yoke sleeve extending from the manifold, and the electrical conduit inlet port receives an electrical conduit extending from a pump within an underground storage tank. The electrical wiring passes from the electrical cavity to the chamber through the yoke sleeve and then to the pump through the electrical conduit.

Description:
RELATED APPLICATIONS 
     This application claims priority to Provisional Patent Application Ser. No. 60/510,735 filed on Oct. 11, 2003, which is hereby incorporated by reference in its entirety. 
     This application is related to the following commonly owned U.S. patent applications, which are hereby incorporated by reference in their entireties:
         i) U.S. patent application Ser. No. 10/959,869, entitled “Spring Loaded Submersible Turbine Pump”, filed on Oct. 6, 2004,   ii) U.S. patent application Ser. No. 10/959,705, entitled “Integral Contractors Box For A Submersible Turbine Pump”, filed on Oct. 6, 2004,   iii) U.S. patent application Ser. No. 10/959,899, entitled “Check Valve for a Submersible Turbine Pump”, filed on Oct. 6, 2004, and   iv) U.S. patent application Ser. No. 10/959,415, entitled “Siphon System For A Submersible Turbine Pump That Pumps Fuel From An Underground Storage Tank”, filed on Oct. 6, 2004.       

    
    
     FIELD OF THE INVENTION 
     The present invention relates to a submersible turbine pump, and more particularly relates to a submersible turbine pump having an improved yoke assembly. 
     BACKGROUND OF THE INVENTION 
     In service station environments, fuel is delivered to fuel dispensers from underground storage tanks (UST), sometimes referred to as fuel storage tanks. USTs are large containers located beneath the ground that contain fuel. A separate UST 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 USTs to the fuel dispensers, a submersible turbine pump (STP) is provided that pumps fuel out of the UST and delivers the fuel to fuel dispensers through a main fuel piping conduit that runs beneath the ground in the service station. 
     A typical STP is illustrated in U.S. Pat. No. 6,223,765. As illustrated in FIG. 4 of U.S. Pat. No. 6,223,765, the STP includes a casing body 12 and a removable top 22 secured to the casing body 12. A contractors box 274, also called a junction box, is removably mounted within the casing body 12. The contractors box 274 has an externally threaded neck 286 that passes through an opening in the casing body. The contractors box 274 is attached to the casing body 12 by securing a nut 290 onto the externally threaded neck 286. An electrical conduit 294 is threading into the neck 286. The electrical conduit 294 contains wires 296 such as wires from an external power source. Within the contractors box 274, the electrical field wires extend upwardly through a tube 298 that extends into a yoke 300. The yoke 300 is secured to the casing body 12 partly above the contractors box 274 by a bolt 302 extending through the yoke 300 and threaded into a lug 304 extending from the contractors box 274. Part of the yoke 300 is secured on top of the contractors box 274, and another part of the yoke 300 is secured on top of a wing 306 of a power head 40 of the STP. The wires 296 extend from the contractors box 274, through the yoke 300, and into the power head 40. From the power head 40, the wires 296 extend into conduit 318 (FIG. 3) and eventually connected to an electric pump 36 (FIG. 3) within the UST 18 (FIG. 3). 
     To access the wiring 296, the removable top 22 and the yoke 300 must be removed from the casing body 12. The top 22 is removed by removing the bolts 34, and the packer is removed by removing the bolt 302 from the lug 304. Therefore, there remains a need for a STP having an improved packer and yoke that simplifies the process of gaining access to the electrical wiring within the STP. 
     SUMMARY OF THE INVENTION 
     The present invention provides a submersible turbine pump (STP) comprising a manifold, a yoke assembly including a yoke sleeve integrally connected to the manifold, and a packer removably secured to the manifold. In general, the manifold includes an electrical cavity that receives electrical wiring from an external source, such as a power source and controller. The yoke sleeve has a hollow interior and is integrally connected to manifold such that a first end of the yoke sleeve is inserted into the electrical cavity. The packer includes a wiring chamber having a yoke sleeve inlet port and an electrical conduit inlet port. The yoke sleeve inlet port receives a second end of the yoke sleeve extending from the manifold, and the electrical conduit inlet port receives an electrical conduit extending from a pump within an associated underground storage tank. The electrical wiring from the external source passes from the electrical cavity in the manifold to the wiring chamber in the packer through the yoke sleeve and from the wiring chamber to the pump through the electrical conduit. 
     When the packer is removed from the manifold, the yoke assembly operates to automatically sever the electrical wiring at a critical point. By automatically severing the electrical wiring when the packer is removed, the yoke assembly ensures that any gas vapors that may enter the electrical cavity upon removing the packer are not ignited by a spark from exposed wiring. 
     The electrical wiring is brought into the electrical cavity in the manifold through a field wiring conduit. The electrical chamber in the manifold may be sealed to form an explosion proof chamber. In one embodiment, a rubber bushing is placed within the field wiring conduit, and the electrical wiring passes through the bushing into the electrical cavity. Plates are located above and below the rubber bushing and operate to adjustably compress the rubber bushing to provide strain relief to the electrical field wiring. One or more screws pass through the plates such that when the screws are tightened, the plates compress the rubber bushing. When the screws are loosened, the compression of the rubber busing is relieved. 
     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 invention in association with the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIG. 1  is a schematic diagram of the submersible turbine pump (STP) according to the present invention; 
         FIG. 2  is a cross sectional diagram of the STP illustrated in  FIG. 1 ; 
         FIG. 3  is a schematic diagram of a yoke design integral to the manifold of the STP; 
         FIG. 4  is a schematic diagram of the STP illustrated in  FIG. 1  with field wiring access electrical contractors boxes open and illustrated; 
         FIG. 5  is a schematic diagram of the electrical cavities inside the STP that are accessible via the electrical contractors box; 
         FIG. 6  is a schematic diagram illustrating electrical wiring passing into the yoke design of  FIG. 3  from the turbine pump; 
         FIG. 7  is a schematic diagram illustrating the electrical wiring of  FIG. 6  passing from the yoke design of  FIG. 3  into the electrical cavities of  FIG. 5 ; 
         FIG. 8  is a schematic diagram of a check valve in the fuel piping inside the STP; 
         FIG. 9  is a more detailed schematic diagram of the check valve illustrated in  FIG. 6  and a c-spring extraction device; 
         FIG. 10  is a schematic diagram of a second embodiment of check valve of  FIGS. 8 and 9 ; 
         FIG. 11  is a schematic diagram of the check valve of  FIG. 10  illustrating the check valve in a locked-down state; 
         FIG. 12  is a schematic diagram of a nozzle in the STP that is used to generate an external vacuum source siphon; 
         FIG. 13  is a schematic diagram of the siphon cartridge designed to couple to a siphon connection. 
     
    
    
     DETAILED DESCRIPTION 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. 
       FIG. 1  illustrates a submersible turbine pump (STP)  10  that embodies various inventive aspects that are the subject of this provisional patent application. The STP  10  is comprised of a casing that contains a body  12  which is generally cylindrical. A riser pipe  14  is coupled to the manifold  19 . The riser pipe  14  is designed to be secured on the top of an underground storage tank (not shown), and contains fuel piping that carries fuel pumped by the STP  10  to be delivered to one or more fuel dispensers (not shown). The riser pipe  14  typically rests on the underground storage tank at the tank opening, and the weight of the casing body  12  and the components is borne by the underground storage tank. More information on the general operation of a STP  10  in a service station environment can be found in U.S. Pat. No. 6,223,765 B1, entitled “Casing construction for fuel dispensing system,” in  FIGS. 3 and 10  in particular. U.S. Pat. No. 6,223,765 B1 is incorporated hereby by reference in its entirety. 
     Before describing the particular inventive aspects of the STP  10  contained in this patent application in detail, a continued overview of the various components of the STP  10  is illustrated in  FIG. 1  follows. 
     The casing body  12  has a top  18 , also called a “packer,” that is normally closed. The casing body  12  is also comprised of a manifold  19 . The packer  18  fits on top of the manifold  19  to form a tight seal when the STP  10  is its normal configuration. The packer  18  can be removed if the STP  10  needs to be serviced. If the STP  10  needs to be serviced by gaining access to the internal hydraulics cavity  20  (illustrated in  FIG. 2 ) of the STP  10 , the packer  18  is removed from the manifold  19 . The packer  18  is secured to the casing  12  and manifold  19  [gs] by a plurality of fasteners, also called “nuts”  22  [gs for “nuts”] that fit into studs  23  (illustrated in  FIG. 2 ) which are tightened down to secure the packer  18  to the manifold  19 . Typically, the nuts  22  can be loosened by applying a socket or wrench to the nuts  22  and rotating the nuts  22  counterclockwise. 
     After the nuts  22  are loosened by rotating them counterclockwise, the packer  18  can be removed from the manifold  19  by applying a pulling force to a handle  24  that is secured to the packer  18 . The handle  24  has a curly shaped head  26  that is designed to allow a rope or chain to be placed inside an orifice  28  formed by the head  26  to apply such force. When the packer  18  is placed on body  12  on top of the manifold  19  and the nuts  22  are tightened, the casing  12  is fluid tight. The packer  18  is removable so that access can be obtained to the internal hydraulics cavity  20  of the STP  10 . 
     The manifold  19  contains an integral contractors box  29  that allow a service personnel to gain access to electrical cavity  30  (illustrated in  FIGS. 4 and 5 ) inside the STP  10  for performing field wiring in the STP  10  without breaching the hydraulic cavity  20  of the STP  10 . The integral contractor box  29  is comprised of one or more plugs  32  that each contain an integral hexagon fastener  34  on top. Each of the plugs  32  are threaded as male connections underneath (not shown) such that they fasten with female threaded ports  37  (illustrated in  FIG. 4  below) on the inside walls of the cavities  30 . An o-ring is provided between the plugs  32  and the cavities  30  so that a fluid tight seal is made between the plugs  32  and the cavities  30  when the plugs  32  are screwed tightly into the female threads of the cavities  30 . More detail about the integral contractor box  29  on the STP  10  is discussed below and illustrated in  FIGS. 4 and 5 , below. 
     The STP  10  also contains a check valve extraction housing  36  that allows extraction of a check valve  38  (illustrated in  FIGS. 8-11 , below) located in the manifold  19 . The check valve extraction housing  36  is comprised of a lock down screw  92  (see  FIG. 8 ) that is rotated clockwise to attach to the check valve  38  for extraction and depressurization of fuel inside the STP  10 . The check valve  38  generally prevents fuel pumped by the STP  10  from the underground storage tank (not shown) from flowing back to the underground storage tank  10  and generally allows fuel to only flow in one direction within the STP  10 . When the STP  10  is serviced, it is necessary to relieve the pressure differential between the inlet  86  and outlet side  88  (illustrated in  FIG. 8 , below) of the check valve  38  so that fuel inside the STP  10  is not pressurized when service personnel obtains access to the hydraulics cavity  90  by removing the check valve housing  36 . More detail about the check valve extraction is discussed in more detail below and is illustrated in  FIGS. 8-11 , below. 
     The manifold  19  contains two siphon connections  42  that provide a siphon system. The siphon connections  42  are designed to receive a siphon cartridge  44  to provide coupling to a vacuum created inside the STP  10  via a nozzle  102  (illustrated in  FIG. 12 ). In  FIG. 1 , only one siphon cartridge  44  is included. The other siphon connection  42  is unused and contains a dummy plug  46 . The siphon system allows the STP  10  to generate a vacuum internally from fuel flow through a venturi to pull a separate vacuum on other systems as will be later described in this patent application. 
       FIG. 2  illustrates a cross sectional view of the STP  10  illustrated in  FIG. 1  to illustrate die springs  52  that are included in the manifold  19  of the STP  10 . If the STP  10  is required to be serviced by service personnel, the service personnel may need to remove the packer  18  from the manifold  19  to access the hydraulic cavity  20  of the STP  10 . Three sets of o-rings  49  are included between the packer  18  and the manifold  19  to provide sealing for three different pressure zones within the hydraulic cavity  20 . Each of the three pressure zones are labeled as pressure zone  1  (P 1 ), pressure zone  2  (P 2 ), and pressure zone  3  (P 3 ) in  FIG. 2 . Pressure zone  3  is at the same pressure as inside the underground storage tank (not shown). Pressure zone  2  is where the pump is developing pressure inside the fuel supply piping that is coupled to fuel dispensers and receives the fuel from the STP  10 . Pressure zone  1  returns fuel from the nozzle  102  inside the STP  10  back to the underground storage tank. 
     After a while, the o-rings  49  swell when exposed to fuel inside the manifold  19  thereby increasing the friction between the packer  18  and the manifold  19  if separated. Before the present invention, this causes a great deal of force to have to be exerted on the handle  24  to remove the packer  18  from the manifold  19  to gain access to the hydraulic cavity  20 . 
     In the present invention, the manifold  19  includes two female pockets  50  that are located directly beneath the nuts  22  that secure the packer  18  to the manifold  19 . Die springs  52  are placed inside each of the two female pockets  50  while the packer  18  is removed during manufacturing or servicing of the STP  10 . Springs  52  are selected so that the springs  52  extend beyond the top of upper plane  54  of the manifold  19  when not under any compression. When the packer  18  is placed on top of the manifold  19 , and the nuts  22  are tightened to seal the packer  18  to the manifold  19 , the springs  52  are compressed inside the pockets  50  causing the springs  52  to store energy. When service personnel desires to remove the packer  18  from the manifold  19 , the service personnel applies a pulling force to the packer  18 , usually via the handle  24  after the nuts  22  are loosened. The die springs  52 , under compression, are exerting a force against the packer  18  so that less pulling force is required to be applied to the handle  24 . In essence, as the packer  18  is pulled upward, the energy stored in the springs  52  is also exerting force upward against the packer  18  thereby aiding in the removal of the packer  18  from the manifold  19 . 
     The inclusion of die springs  52  in the manifold  19  is an improvement over prior STP  10  designs that provide the ability to remove a packer  18  from the manifold  19 . Depending on the springs  52  selected and the amount of energy stored in the springs  52  when compressed, when the packer  18  is sealed onto the manifold  19 , the springs  52  may even contain enough stored energy to separate the packer  18  from the manifold  19  after the nuts  22  are loosened without any pulling force being applied on the handle  24 . Before inclusion of the die springs  52 , a larger amount of force had to be applied to the packer  18  to remove it from the manifold  19  especially since the o-ring seals  49  provide a pressurized seal between the packer  18  and the manifold  19  requiring high extraction/separation forces to remove the packer  18  from the manifold  19  for servicing. 
     Any type of spring may be used as the springs  52 . Further, even though the current design of the STP  10  includes two springs  52 , only one spring  52  and pocket  50  combination may be used, or more than two springs  52  and pocket  50  combinations may be used. It may be more advantageous to provide only one spring  52  for space conservation so long as a single spring  52  can store enough energy to aid in the extraction of the packer  18  from the manifold  19 . According to one embodiment of the present invention, the springs  52  are Raymond® die springs manufactured by Associated Spring. 
     Another aspect of the STP  10  that is a subject of this application is an improved yoke assembly  56  illustrated in  FIG. 3 . An example of a yoke assembly in the prior art is illustrated and described in detail in FIGS. 3 and 10 of U.S. Pat. No. 6,223,765 B1, previously reference above. 
     Turning to  FIG. 3 , electrical wires  58  include electrical lead wires. The yoke assembly  56  design according to the present invention includes a yoke sleeve  60  that is an integral part of the manifold  19  unlike prior art systems where the yoke is a separate device that is bolted onto the packer  18 . The yoke sleeve  60  is hollow and forms a conduit  62  for the electrical wires  58  that bring electricity from the STP  10  to the turbine pump inside the underground storage tank (not shown). The yoke sleeve  60  is held into place into the manifold  19  using a set screw  64  that is bored into the outer side of the manifold  19 . The set screw  64  may extend outside of the manifold  12  and is designed to fit into a groove  66  located in the outer wall  68  of the yoke assembly  56 . In another embodiment, the set screw  64  may be captive within the manifold  12  in which case the set screw  64  would not extend outside of the manifold  12 . This may be desirable to prevent the potential for service personnel inadvertently failing to reinstall the set screw  64  after removal. Removal of the set screw  64  allows the yoke sleeve  60  to be removed if servicing and/or replacement of the yoke sleeve  60  is required. However, during normal operation and servicing, the yoke sleeve  60  is not removed and it forms an integral part of the manifold  19  unlike prior art STP systems. 
     It is necessary for safety reasons to ensure that the electrical wires  58  that connect to the turbine pump (not shown) are disconnected from the electrical wires  58  that run inside the conduit  62  in the yoke sleeve  60  if the packer  18  is removed from the manifold  19 . When the packer  18  is removed, the electrical wires  58  are broken at the critical point  70 . In prior art systems, the yoke assembly was a separate device from the STP  10 , like in aforementioned U.S. Pat. No. 6,223,765 B1. The yoke was provided in an explosion proof housing in case a spark were to occur at the joint where an electrical connection is made between the yoke and packer. In this prior art system, service personnel had to first remove the yoke assembly separately before gaining access to the hydraulics cavity  20  to remove the pump via removal of the packer. Now with the present invention, service personnel only need to remove the packer  18  to automatically sever the electrical wires  58  when the packer  18  is removed from the manifold  19  since the yoke assembly  60  is integral with the manifold  19  and not the packer  18 . 
     The STP  10  also contains an integral contractors box  29  comprised of one or more electrical cavities  30 . In the example illustrated in  FIG. 4 , there is only one electrical cavity  30 . This electrical cavity  30  is provided to provide access to field wires that are brought into the cavity  30  from underneath the STP  10  through the field wiring conduit  74  (illustrated in  FIG. 5 ). The electrical cavity  30 , when sealed, serves as an explosion proof area where field wiring connections can be made for the STP  10  for a device that contains a Class 1, Division 1 area due to fuel handling. 
     When service personnel make wiring connections necessary to put the STP  10  into service in the field, the service personnel bring the wiring into the electrical cavities  30  via the field wiring conduit  74  in  FIG. 5 . The pump wires that are connected to the turbine pump (not shown) come over from the yoke assembly  60 . After the service personnel runs the field wiring into the field wiring conduit  74 , a seal is made by placing a piece of rigid conduit in the field wiring conduit  74  to seal off the electrical cavities  30  from its environment including the underground storage tank and any vapors that may be proximate to the field wiring conduit  74 . The field wiring is brought into the electrical cavity  30  by running the wiring through a rubber bushing  82  that is compressed between two steel plates  80  on the top and bottom of the rubber bushing  80 . The screws  84  are tightened and the bushing is compressed to provide strain relief to the wiring in case the wiring is pulled from the field wiring conduit  74 . 
     When service personnel later want to access the field wiring without breaking the seal formed at the field wiring conduit  74  underneath the manifold  19 , the service personnel can loosen the plugs  34  to gain access to the electrical cavity  30 . The plugs  34  seal the electrical cavity  30  off and o-rings  76  are provided between the plugs  34  and the threaded ports  37  to form a tight seal when the plugs  34  are tightened. 
     One reason that an electrical cavity  30  is provided that contains two plugs  34  for access in the STP  10  is that a capacitor  78  is included inside the electrical cavity  30  in this example. A capacitor  78  may be used to store energy to assist the motor (not shown) in the STP  10  when a fuel dispenser is activated to dispense fuel. Please note that the capacitor  78  is an optional component and is not required. 
       FIG. 6  illustrates the flow of the electrical wiring  58  from the turbine pump within the UST (not shown) into an internal hydraulics electrical cavity  89  within the packer  18 . As shown, the electrical wiring  58  passes through an electrical conduit within the column pipe  16  into the internal electrical cavity  89 . From the internal electrical cavity  89 , the electrical wiring  58  passes through the yoke sleeve  60  of the yoke assembly  56 . As illustrated in  FIG. 7 , from the yoke sleeve  60 , the electrical wiring  58  passes into the electrical cavity  30  within the manifold  19  where it may optionally be connected to the capacitor  78 . From the electrical cavity  30 , the electrical wiring passes through the field wiring conduit  74  and may be connected to an external source, such as an external power source. 
     As discussed above, the rubber bushing  82  within the field wiring conduit  74  is compressed between the two steel plates  80  on the top and bottom of the rubber bushing  80 . The screws  84  are tightened and the bushing  82  is compressed to provide strain relief to the electrical wiring  58 . It should also be noted that the steel plates  80  have multiple holes through which individual wires of the electrical wiring  58  pass. As illustrated, the two steel plates  80  include five holes. Since there are only three wires in the electrical wiring  58 , two of the holes are plugged by plugs  85 . 
       FIG. 8  illustrates another aspect of the present invention where a check valve  38  is provided in the hydraulics cavity  90  of the STP  10 . The check valve  38  is provided in a check valve housing  36 . As fuel is pumped from the turbine pump (not shown) through a column pipe  16  (not illustrated in  FIG. 8 ) and into the STP  10 , the fuel flow encounters the inlet side  86  of the check valve  38 . The check valve  38  is designed so that fuel can flow from the inlet side  86  to the outlet side  88  of the check valve  38 . The force exerted by the fuel flow pushes up on the check valve  38  on its inlet side  86  and allows fuel to flow around the outsides of the check valve  38  and through the hydraulic cavity  90  to the right of the check valve  38 . The check valve  38  is biased to a closed position by a spring  91  and prevents fuel from back flowing to the underground storage tank. 
     When the STP  10  is serviced, the STP  10  is shut off and the service personnel must remove the packer  18  to pull out the pump in the hydraulic cavity  20  for servicing. However, after the STP  10  is turned off, there is still residual pressure trapped in the pipeline when the check valve  38  is closed since fuel will no longer flow to keep the check valve  38  opened. There is a differential pressure between the outlet side  88  of the check valve  38 , which is hydraulic cavity  90 , and atmosphere. If the check valve housing  36  is removed by service personnel to gain access to the check valve  38 , the pressure build up on the outlet side  88  of the check valve  38  will equalize with atmosphere (or the pressure on the outside the STP  10 ) and fuel will possibly spill outside of the manifold  19  and STP  10  to the environment and possibly make contact with the service personnel. The present invention provides the ability to depressurize the outlet side  88  of the check valve  38  before the check valve  38  is serviced by actuation of a lock down screw  92 , which has not been done before the present invention. 
     Depressurization of the check valve  38  is accomplished by placing a tool inside receptacle  94  and rotating the receptacle  94  which lowers the lock down screw  92  on the check valve stem  98  illustrated in  FIG. 8 . Specifically, it is the c-spring retainer  96  as part of the lock down screw  92  that engages the check valve stem  98 . 
       FIG. 9  illustrates a more detailed view of the check valve  38  and how the present invention provides for depressurization of the check valve  38 . The c-spring retainer  96  contains a c-spring  100  that grabs onto the stem  98  of the check valve  38  and forms a secure fit to the stem  98 . After the lock down screw  92  is fully engaged, the screw  92  can be rotationally reversed to pull up on the stem  98  of the check valve  38 . This pulls up the check valve  38  and couples the inlet side  86  to the outlet side  88  of the check valve  38  together so that the pressure between the two sides equalizes and pressure on fuel contained on the outlet side  88  of the check valve  38  is relieved. 
     The lock down screw  92  also allows the check valve  38  to be locked into position when fuel supply piping is checked for leaks during installation and on service calls. When the check valve  38  is locked into a closed position, the STP  10  effectively cannot release pressure. This effectively isolates the STP  10  from the fuel supply piping that connects the STP  10  to the fuel dispensers for delivery of fuel. It may be desired for service personnel to pressurize and test the fuel supply piping to ensure that no leaks are present. With the present invention, service personnel can use the STP  10  to lock down the check valve  38  to isolate the STP  10  from the fuel supply piping. In this manner, if a leak is detected when pressurizing and testing the fuel supply piping for leaks, the STP  10  can be eliminated as the source of the leak since it is isolated from the fuel supply piping. 
       FIG. 10  illustrates a second embodiment of check valve  38  of  FIGS. 8 and 9 . In this embodiment, the check valve  38  includes one or more passages  99  through the check valve stem  98  that couple the outlet side  88  of the check valve  38  and thus the hydraulic cavity  90  ( FIG. 8 ) to an internal chamber  103  within the check valve stem  98 . When the turbine pump is off, pressure at the outlet side  88  may increase due to vapor expansion. When the pressure increases to a predetermined threshold, the pressure forces a check valve  101  within the check valve stem  98  open, or downward, such that a passage is created between the outlet side  88  and the inlet side  86  of the check valve  38  and excess pressure is relieved. Once the pressure drops below the predetermined threshold, the check valve  101  within the check valve stem  98  moves upward, thereby sealing the passage through the check valve stem  98  between the outlet side  88  and the inlet side  86  of the check valve  38 . 
       FIG. 11  illustrates the check valve  38  of  FIG. 10  in a locked-down state. As discussed above, the lock down screw  92  allows the check valve  38  to be locked into position when fuel supply piping is checked for leaks during installation and on service calls. In this embodiment, when the lock down screw  92  is rotated downward, the lock down screw  92  comes to rest against the check valve  38 , thereby locking the check valve  38  in a closed position. In doing so, the lock down screw  92  forces the check valve  38  into a closed position such that the inlet side  86  is sealed from the outlet side  88  by an o-ring  105 . When in this position, the lock down screw  92  also seals the passages  98  in the check valve  38  using o-ring  107  such that the passage between the outlet side  88  and the inlet side  86  of the check valve  38  discussed with respect to  FIG. 10  is also sealed. 
       FIGS. 12-13  illustrate another aspect of the present invention relating to a siphon system. In  FIG. 12 , siphon cartridge  44  is shown as being installed in the manifold  19 . The siphon cartridge  44  is comprised of a nozzle  102 . The nozzle  102  directs fuel from the STP  10  when the siphon cartridge  44  is installed through a venturi  103  (illustrated in  FIG. 13 ) and a vacuum is created as a result in a chamber  104  perpendicular to the axis of the nozzle  102 . This vacuum can be applied against other components and systems independent of the STP  10  for purposes that will be described herein. The siphon cartridge  44  contains a check valve  106  that maintains vacuum in whatever component is connected to the siphon connection  42  when the pump is de-energized. Thus, when the pump is de-energized, the pressure in the chamber  104  returns to the pressure that is resident in zone P 1 , and check valve  106  operates to maintain the vacuum in whatever component is connected to the siphon connection  42 . 
       FIG. 13  illustrates a more detailed view of siphon cartridge  44 . Once the siphon cartridge  44  is connected to the siphon connection  42 , the check valve  106  is forced to be opened and the chamber  104  is fluidly coupled to whatever component is connected to the siphon cartridge at connection point  108 . The siphon cartridge  44  is designed to be inserted into the manifold  19  of the STP  10  so that a service personnel can simply connect a siphon cartridge  44  to a siphon connection  42  to use the STP  10  to generated a vacuum inside the nozzle  102 . The STP  10  illustrated in the drawings contains two siphon connections  42 , but the STP  10  could only contain only one siphon connection  42  or could contain more than two siphon connections  42 , which is simply a design choice. If the siphon connection  42  is not to be used, a dummy plug  46  illustrated in  FIG. 1  can be used to seal up the siphon connection  42 . 
     The vacuum created by the siphon connection cartridge  44  may be used for a number of purposes. For instance, the vacuum may be used to siphon two underground storage tanks together, as is shown and described in U.S. Pat. No. 5,544,518 entitled “Apparatus and Method for Calibrating Manifolded Tanks,” incorporated herein by reference in its entirety. The vacuum may also be used to generate a vacuum in a defined space for leak detection purposes. For example, pending patent application Ser. No. 10/238,822 entitled “Secondary Containment System and Method;” Ser. No. 10/430,890 entitled “Secondary Containment Leak Prevention and Detection System and Method;” and Ser. No. 10/390,346 entitled “Fuel Storage Tank Leak Prevention and Detection,” all of which are incorporated herein by reference herein in their entireties, and disclose pressure monitoring and leak detection systems where a vacuum generated by the STP  10  is used to generate a vacuum in an interstitial space, including but not limited to a double-walled underground storage tank interstitial space, the interstitial space of double-walled fuel piping. 
     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.