Abstract:
In a pipeline system having a plurality of pipe segments joining a fluid supply tank to a fluid dispenser, the invention includes a pipe coupling assembly for use on at least one terminal end of a fluid transfer pipe, where the transfer pipe has an inner tubular member for transferring fluid and an outer tubular member and an interstitial space there between. The coupling assembly comprises a transition coupling for attachment to the pipe segment to provide a first path for the fluid in the inner tubular member and a second path for the interstitial space. The coupling assembly further comprises a transition tube assembly for attachment to the transition coupling to provide separate paths for the transfer fluid and the interstitial space, where the interstitial space provides a means for performing leak detection or fitting integrity tests during application of either a vacuum condition or pressurized gas input via such selective access.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to transition coupling and fitting assemblies for connecting segment of pipes into systems. More particularly, the invention relates to a new system using an assembly for coupling coaxial pipes, such as flexible coaxial pipes, of the type used in environmentally conscious petroleum transfer systems.  
       BACKGROUND OF THE INVENTION  
       [0002]     Because vehicle fueling facilities, like retail service stations, are becoming more environmentally conscious, a shift has occurred from the use of rigid underground piping to flexible piping. A primary reason for this shift from rigid to flexible piping is that flexible piping has fewer pipe connections than rigid systems since the flexible system can accommodate virtually any orientation or alignment of the pumps and tanks. With fewer pipe connections, the piping system is considered more environmentally safe. Movement of the underground storage tank due to the shifting underground tanks is also more easily accommodated by flexible piping.  
         [0003]     Flexible underground piping systems have also gained popularity because these systems are more easily installed than rigid piping systems. Rigid systems require on-site measurements and cutting of each piece, along with the intensive labor involved in making two pipe connections every time the piping undergoes a change in direction. Flexible underground piping systems thus can be installed at a lower total cost than conventional rigid piping systems.  
         [0004]     As part of the development of underground piping systems, it has been necessary to provide a means of secondary containment for both the primary piping and for the associated fittings in order to provide a margin of safety in case of leaks or damage to the system. The secondary containment pipe protects the primary supply pipe from the ambient environment and from inadvertent damage, and further, provides for a method of containing the fluid from the primary pipe in the event of a rupture or leak of the primary pipe.  
         [0005]     Several types of double wall flexible piping systems are known. These include systems which have a small flexible pipe housed in a larger flexible containment pipe. One such system is described in U.S. Pat. No. 4,971,477 (the &#39;477 patent), wherein access chambers are separated by a secondary containment pipe which is sized to accept a primary pipe within the secondary containment pipe. This system, however, has a number of drawbacks, including the fact that the primary and secondary pipes are installed separately and that fittings are required for each of the two types of pipes. Moreover, because each of the pipes connects with an access chamber, a rapid and simple method of monitoring the condition of the primary piping may not be possible. Although the sumps in the &#39;477 patent are capable of being monitored visually by an attendant, but the demand of other tasks to be performed by the attendant eventually leads to fewer and fewer inspections. Most important is that leaks may occur randomly, not only just prior to a visual inspection, and especially when inspections grow less frequent over time.  
         [0006]     As taught in the &#39;477 patent, the flexible piping and the secondary containment piping require a sump or access chamber each time that sections of the flexible pipe are joined together. Most other systems also require a sump at each location where sections of flexible pipe are joined together.  
         [0007]     Other systems which have met with success using coaxial pipes and a secondary containment pipe are shown in U.S. Pat. Nos. 5,263,794 (the &#39;794 patent), and 5,297,896 (the &#39;896 patent) the entire disclosures of which are incorporated herein by reference. The advantages of flexible pipe systems are disclosed by these patents. Nevertheless, it is necessary to make individual connections each time sections of pipes are joined together.  
         [0008]     The &#39;794 and the &#39;896 patents disclose various definitions that have become standard in the industry, for example, “tanks”, “pumps”, “dispensers” and the like. Also disclosed therein are descriptions of double wall piping systems that provide secondary containment. In a system that employs secondary containment, a primary pipe carries the petroleum product or other hazardous material from the underground tank to the aboveground dispenser. The primary pipe, also known as the supply pipe, is located inside a larger, outer secondary containment pipe, known also as the containment pipe. Access sumps and other containment components are located around the tank pump, underneath the dispenser and at various junctions of piping.  
         [0009]     Recently, an effective system has become available and has met with substantial success in the industry. This pipe system&#39;s supply pipe is a flexible double wall pipe comprising an inner pipe and an outer pipe in radial communication with the outside surface of the inner pipe. Most preferred are pipes of this configuration that have internally facing longitudinal ribs on the inner surface of the outer pipe, or externally facing longitudinal ribs on the outer surface of the inner pipe. In either such design, a plurality of circumferentially spaced ribs extend radially from one pipe member to the other pipe member such that the ribs have a surface that confronts and snugly engages the other pipe to define an interstitial space between the two pipes.  
         [0010]     The flexible double wall pipe described immediately above is disclosed in my U.S. patent 5,527,130 entitled Environmentally Safe Underground Piping System, the entire disclosure of which is incorporated herein by reference. The co-axial pipes disclosed in the &#39;130 patent are normally suited for use with hazardous material transfer pipe systems of the type described herein. The inner most layer is formed from a material such as nylon, PVDF, polyethylene or the like, which is highly resistant to the hazardous transfer fluid. The outer jacket of the double wall pipe which is exposed to the ambient underground environment is formed from a material such as nylon, PVDF, polyethylene or the like, which is highly resistant to the ambient underground environment and which does not degrade over time. Between the outer wall of the primary pipe and the inner wall of the containment pipe is an intermediate layer, either in the form of ribs projecting from one surface to the other, or in a standoff layer formed from a cylindrical portion having circumferentially spaced ribs that define the interstitial space between the two pipes. As noted in the &#39;130 patent, other layers can be present in the design, such as intermediate layers formed from lower cost materials which do not directly contact either the hazardous material being transported or the ambient underground environment.  
         [0011]     The environment for both surfaces of the pipe is an important design aspect, which needs to be considered. Product components which make up primary or secondary containment systems for hazardous liquids, and in underground applications particularly, must be designed, manufactured and individually tested to insure that they will not fail due to material deterioration.  
         [0012]     The material employed are preferably resistant to hydrolysis, as it is expected that water and high moisture conditions will exist in underground burial applications both for contained and non-contained underground piping applications. Resistance to hydrolysis is important since some elastomers suffer an irreversible breakdown when exposed for lengthy periods to hot water, moisture vapor or tropical climates.  
         [0013]     In addition to the tanks, pumps, pipes and dispensers used in underground piping systems, sumps are used as part of the secondary containment system. One sump surrounds the pump on the tank and another sump is generally positioned below each dispensing system. Sumps typically have a base portion, a riser and a lid and are provided with means for permitting piping to enter and exit the sump. One type of sump called a tank sump is located on top underground storage tank and under a surface access manhole. Contained within the tank sump is a dispensing pump whereby the fuel is directed upwardly from the tank to the dispensing pump and outwardly through the opposite side of the tank sump to the next part of the system. Each time the pipe sections are connected to one another, these pipe connections are typically contained within another sump that, of course, requires a pipe penetration seal to seal the pipe entry or exit through the sump.  
         [0014]     As can readily be appreciated, every pipe must eventually end. It then becomes necessary to connect that end of the pipe to either a pump, to a fitting joining two or more other pipes or directly to a shear valve. Typically the inner, primary supply pipe is directly connected to fittings and the like, and another primary supply pipe is connected to the other end or ends of the fittings. Merely connecting the inner supply pipes, as in the past, has been no different than connecting a single pipe system. In the evolution of piping systems as discussed above, the relationship of the outer, secondary containment pipe to the system has become more complex.  
         [0015]     Initially, non-flexible pipes functioning as a secondary containment pipe were attached to the sump or other chambers by enlarging the hole in the sump to permit entry or exit of the outer pipe from the sump, and later by various fastening and sealing methods and devices. Initially, the interstitial space between the inner and outer pipes served as a conduit for fluid leakage to flow downhill into the next sump in the piping system. Leaks could come from fuel from the inner pipe, or from the outer pipe as ambient environmental liquids, such as water, penetrate the outer pipe.  
         [0016]     Leak detection initially consisted of opening the sump chamber and inspecting the bottom of the sump for fluid accumulation. Of course, whatever can be visually inspected can be monitored automatically. Systems were proposed for monitoring the liquid levels in the bottom of sumps. However, every sump had to have a monitoring device since each sump, by design, represented a low point where fluid could collect. The difficulty in such two pipe systems can easily be seen by viewing  FIG. 2  of &#39;477 patent where the outer pipe has a very limited, minor function of simply isolating the primary supply pipe from the ambient environment. Also shown in that Figure is the way that the interstitial space between the primary pipe and containment pipe merely opened into the larger sumps without any recognition that there may be other purposes for the interstitial space. As is shown in  FIG. 3  of the &#39;477 patent, the secondary containment pipe merely serves as a housing or conduit for sections of the primary supply pipe which may be inserted or removed as desired.  
         [0017]     In my U.S. Pat. 5,398,976, I disclosed a connecting boot that substantially improves utilization of the interstitial space. The connecting boot, commonly known as a “test boot”, comprises a device which fits onto one terminal end of a supply pipe, allowing the inner primary supply pipe to extend out from the connecting boot while the outer secondary containment pipe terminates inside the connecting boot. The exit end of the test boot where the primary supply pipe exits is clamped to, or otherwise sealingly engages, the outer surface of the primary pipe. The entrance end of the test boot that fits over the exterior of the secondary containment pipe is also clamped to, or is sealingly engaged with, the outer pipe surface. In between these two sealed ends of the test boot is a chamber, which communicates with the interstitial spaces of the two pipes and also communicates with a radially extending port. An elbow fitting and tube is usually provided which can be connected to the radially extending port and elbow fitting on the adjacent pipe, to which the primary pipe has been attached in a conventional manner.  
         [0018]     Thus, for the first time, it was possible to connect not only the interstitial spaces of two adjacent pipes but also the interstitial spaces of an entire system, which are connected to a single monitoring device. Such a monitoring device could be a system whereby the entire interstitial space of all of the piping is filled with a liquid to a level, which registers in a predetermined range of the monitoring device to indicate a securely contained system. When the level of the fluid in the interstitial space either drops below a certain amount or rises above a certain amount, indicating a change in the system, an alarm will sound.  
         [0019]     The test boot provided a substantial advance in the hazardous fluid piping system industry, primarily by permitting interconnection of all of the system wide interstitial spaces. The test boot, however, is not as structurally solid as an access sump, for example, and thus needs to be enclosed in a sump for protection.  
         [0020]     There are several additional considerations that need to be addressed in designing the connections between sections of pipes, particularly between sections of flexible coaxial pipes. First, it is desirable to avoid plastic adhesion or plastic thermally bonded connections, since temperature conditions, chemical exposure, vibrations over time can cause piping joints to fail. A much better seal is achieved when metal and plastic are joined together by mechanical means. However, in such cases it is necessary to protect the metal from the environment by a coating or isolation to avoid a corrosive and unsafe condition. Coatings on metal parts, however, often peel off or become damaged during handling of the metal parts. Also, if the coatings are too thick, the necessary metal to plastic contact to establish an effective seal is not achieved.  
         [0021]     As will be apparent from reviewing the above patents, there is an interstitial space between the inner primary supply pipe and the outer secondary containment pipe. This interstitial space has been used to transfer leaked fluid into the containment sump or access chamber. Typically, in early systems, the access chambers were inspected on a regular basis to see if quantities of fluid had collected. This, of course, does not provide a rapid response to a major leak of fluid such as fuel from the primary supply pipe.  
         [0022]     As shown in the &#39;794 and the &#39;876 patents, the entire system is connected such that the primary pipe functions as a closed system, transporting fuel from the supply tank to the various dispensers. However, the interstitial space between the primary supply pipe and the secondary containment pipe is a conduit allowing leaked fluid to flow to an access chamber for observation. Although it is possible to monitor the conditions of one or all of the access chambers, for example by visual inspection, no simple method of monitoring the entire system is possible.  
         [0023]     It is desirable to provide an underground piping system which employs coaxial pipe, such as those pipes described above, which include a inner primary supply pipe and a outer secondary containment pipe, in which the interstitial space between the two pipes can be connected to the interstitial spaces in other segments of piping to form a continuous closed system of interstitial space.  
         [0024]     It is also desirable to provide a coupling assembly for use with coaxial pipes that permits coupling of the interstitial space between the coaxial pipes with corresponding interstitial spaces in other segments of pipe.  
         [0025]     Such a system should also provide an effective monitoring system utilizing the interconnected interstitial space of the coupling assembly, particularly with the use of a constant vacuum or pressure applied to the interstitial space or monitoring the liquid level of a liquid filled interstice.  
       SUMMARY OF THE INVENTION  
       [0026]     The invention is a pipe system for distributing fluids from a storage tank to one or more dispensers comprising an originating adaptor fitting located at the tank and shear valves located at each of the one or more dispensers, a pipe segment extending between the adaptor fitting and one of the shear valves, the pipe segment having an interstitial space between an inner and an outer pipe. The invention further comprises a transition coupling connecting the adaptor fitting to the pipe segment, the transition coupling comprising a ferrule, an insert, a means for securing the coupling to the adaptor fitting, the transition coupling further comprising sealing means for preventing fluid leakage from the coupling connection to the fitting, the coupling further comprising sealing means for preventing fluid leakage from the interstitial space between the inner and outer pipes, and further comprising an interstitial access port for connecting a tube that provides access to the interstitial space between the inner and outer pipes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     These and other aspects of the present invention of the various details of the operation and construction thereof are hereinafter more fully set forth with reference to the accompanying drawings, wherein:  
         [0028]      FIG. 1  is a schematic illustration of one embodiment underground piping system.  
         [0029]      FIG. 2  is a schematic illustration of a second embodiment of underground piping system.  
         [0030]      FIG. 3  is a side, elevational view of a originating adapter fitting connected with a transition pipe coupling.  
         [0031]      FIG. 4  is a side, elevational view of a junction tee fitting connected with two transition pipe couplings.  
         [0032]      FIG. 5  is a side, elevational view of a terminating elbow fitting connected with a transition pipe coupling.  
         [0033]      FIG. 6  is a side, elevational view of a junction Y shear valve connected with two transition pipe couplings.  
         [0034]      FIG. 7  is a side, elevational view of a terminating shear valve connected with two transition pipe couplings.  
         [0035]      FIG. 8  is an end sectional view of double wall coaxial pipe section.  
         [0036]      FIG. 9  is an end sectional view of double wall coaxial pipe section fitted with a transition pipe coupling.  
         [0037]      FIG. 10  is a side sectional view of various components that make up o-ring seal transition coupling.  
         [0038]      FIG. 11  is a side, elevational view of various components that make up an o-ring seal transition coupling.  
         [0039]      FIG. 12  is a side, sectional view of various components that make up o-ring seal transition coupling.  
         [0040]      FIG. 13  is a side, elevational view of various components that make up butt seal transition coupling.  
         [0041]      FIG. 14  is a side, sectional view of various components that make up butt seal transition coupling.  
         [0042]      FIG. 15  is a side, elevational view of various components that make up transition coupling with a butt compression seal connection.  
         [0043]     FIG:  16  is a side, sectional view of various components that make up butt seal transition coupling. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0044]     Referring now to the drawings and particularly to  FIG. 1  and  2  thereof, there is shown schematically an underground piping system for conveying petroleum products from an underground storage tank to a plurality of aboveground dispensers. The piping system incorporates a novel coupling means in accordance with the present invention. The pipe transition coupling of the present invention is particularly adapted for interconnecting the interstitial regions in the piping to provide a closed, continuous monitoring system for detecting leaks that provides advantages over prior art piping systems used for this purpose.  
         [0045]     As best illustrated in  FIG. 1 , the basic elements of a underground fuel storage and delivery system include an underground storage tank  1  for containing a large quantity of a petroleum product. The storage tank  1  is equipped with tank sump  3  for secondary containment of the dispensing pump  2  that is connected to the top of the storage tank  1  and located under a manhole cover  6  to provide surface  32  access to the tank sump  3 . A plumbing assembly  4 , is connected on one end to the dispensing pump  2  and on the other end is fitted with an originating adapter fitting  70  for connection of a transition coupling  40  fitted to the end of a pipe segment  10 . The pipe segment  10  exits the sidewall  4  of the tank sump  3  through a sump penetration seal  25  that prevents liquids from entering or exiting the tank sump  3  though the penetration. Also illustrated in  FIG. 2  is a sealed attachment of a chase pipe  9  that is used for the future removal and replacement of a damaged pipe section  10  without the need for excavation.  
         [0046]     Also shown in both  FIGS. 1 and 2  is a monitoring system  7  that is connected to the transition coupling  40  by the test tube  49  to monitor the integrity of the interstitial space of the pipe system. The monitoring system  7  provides early warning of leaks in the underground piping system and thereby to minimize chances of contaminating the underground environment. The monitoring system  7  monitors a change in positive pressure or negative pressure or liquid level within the interstitial space of a double-walled pipe depending upon the type of monitoring system installed. Where there is no monitoring system  7  installed, the test tube  49  would typically be left open at its end for any piping leaks to flow in the tank sump for detection either visual inspection or a sump leak detection monitor.  
         [0047]     Referring to  FIG. 1 , a double wall pipe segment exits the tank sump  3  and then enters the sidewall  21  of a junction dispenser sump  20   a , mounted under an above ground dispenser  30 . Contained within the deep junction dispenser sump  20   a  is a riser pipe assembly that typically includes a rigid or flexible riser pipe  73 , a standard shear valve  74  and a junction tee fitting  71 . The standard shear valve  74  makes connection with the above ground dispenser  30 . Pipe segment  10   a  enters the sidewall  21  of the deep junction dispenser sump  20   a  and makes connection with the junction tee fitting  71  by means of the transition coupling  40  fitted to its end. Another pipe segment  10   b , which is connected to the other side of the junction tee fitting  71 , exits the sidewall  21  of the deep junction sump  20   a . The pipe entry and exit penetrations in the sidewall  21  are sealed by the pipe penetration seals  22 .  
         [0048]     The next piping segment  10   b  exits the first junction dispenser sump  20   a  and then enters the sidewall  21  of the terminating dispenser sump  20   b  where the piping system terminates. Contained within a deep terminating dispenser sump  20   b  mounted under an above ground dispenser  30 , is a riser pipe assembly that typically includes a rigid or flexible riser pipe  73 , a standard shear valve  74  and a terminating elbow fitting  72 . The standard shear valve  74  makes connection with the above ground dispenser  30 . A pipe segment  10   c  enters the sidewall  21  of the deep terminating dispenser sump  20   b  and makes connection with the terminating elbow fitting  72  by means of the transition coupling  40  fitted to its end. The pipe entry penetrations in the sidewall  21  are sealed by the pipe penetration seal  22 .  
         [0049]      FIG. 2  has the same basic elements as  FIG. 1  with exceptions that the deep dispenser sumps have been substituted with shallow dispenser sumps. Contained within a shallow junction dispenser sump  120   a  mounted under an above ground dispenser  30 , is junction Y shear valve  75  that makes connection with the above ground dispenser  30 . A pipe segment  10   a  enters the angled sidewall  21  of the shallow junction dispenser sump  20   a  and makes connection with the junction Y shear valve  75  by means of the transition coupling  40  fitted to its end. Another pipe segment  10   b , which is connected to the other side of the junction Y, shear valve  75 , exits the angled sidewall  21  of the shallow junction sump  120   a . The pipe entry and exit penetrations in the sidewall  21  are sealed by the pipe penetration seals  22 .  
         [0050]     The next piping segment  10   b  exits the first shallow junction dispenser sump  120   a  and then enters the angled sidewall  21  of the shallow terminating dispenser sump  120   b  where the piping system  9  terminates. Contained within a shallow terminating dispenser sump  120   b  mounted under an above ground dispenser  30 , is terminating elbow shear valve  76  that makes connection with the above ground dispenser  30 . A pipe segment  10   b  enters the angled sidewall  21  of the shallow terminating dispenser sump  120   b  and makes connection with the terminating elbow shear valve  75  by means of the transition coupling  40  fitted to its end.  
         [0051]      FIG. 3  is close up view of the plumbing connection between the originating adapter fitting  70  connected to a transition coupling  40  fitted on the end of a pipe section.  10 . Also shown are the tube fittings  50  fitted on each end of the test tube  49  which is connected to the interstitial port  47  of the transition fitting  40  by means of the tube fitting  50 .  
         [0052]      FIG. 4  is close up view of the plumbing connection between the junction tee fitting  71  connected to two pipe sections  10  each fitted with a transition fitting  40 . Also shown are the tube fittings  50  fitted on each end of a connector tube  48  which is connected to the interstitial port  47  of each transition fitting  40  by means of the tube fitting  50  to continue the interstitial space from one pipe section  10  to the other.  
         [0053]      FIG. 5  is close up view of the plumbing connection between the terminating elbow fitting  72  connected to a transition coupling  40  fitted on the end of a pipe section  10 . Also shown are the tube fittings  50  fitted on each end of the test tube  49  which is connected to the interstitial port  47  of the transition fitting  40  by means of the tube fitting  50 .  
         [0054]      FIG. 6  is close up view of the plumbing connection between the junction shear valves  75  connected to two pipe sections  10  each fitted with a transition fitting  40 . Also shown are the tube fittings  50  fitted on each end of a connector tube  48  which is connected to the interstitial port  47  of each transition fitting  40  by means of the tube fitting  50  to continue the interstitial space from one pipe section  10  to the other.  
         [0055]      FIG. 7  is close up view of the plumbing connection between the terminating elbow shear valves  76  connected to a transition coupling  40  fitted on the end of a pipe section  10 . Also shown are the tube fittings  50  fitted on each end of the test tube  49  which is connected to the interstitial port  47  of the transition fitting  40  by means of the tube fitting  50 .  
         [0056]      FIG. 8  shows an end section view of the pipe segments  10  which are preferably co-axial pipes of the type shown and described in my U.S. Pat. 5,527,130 entitled Environmentally Safe Underground Piping System, and commercially available from Environ Products, Inc., Smithfield, NC (USA) under the trademark GEOFLEX. Pipe segments  10  comprise an inner primary pipe  12  made of a non-degradable or inert material, such as nylon, PVDF and polyethylene, with respect to the petroleum products being handled in the piping system and an outer containment pipe  14  made of a non-degradable or inert material, such as nylon, PVDF and polyethylene when exposed to the ambient environment and thus is suitable for direct burial applications.  
         [0057]     The co-axial pipe also has a series of circumferentially spaced longitudinally extending standoff ribs  15  defining a series of longitudinal interstitial spaces  13  or passageways extending from end to end in the pipe segments  10 .  
         [0058]     The coupling assemblies, called “transition couplings” of the present invention have a double wall design and provide for transition of interstitial spaces in ways that have previously not been possible. Sealing the inner primary pipe is accomplished by a mechanically locked barb seals and radial o-ring seals or flat butt type compression seals. The coupling portion of the present invention effectively seals the inner pipe and the outer pipe simultaneously.  
         [0059]     The transition coupling assembly includes a ferrule preferable made of metal, attached to the outer wall of the pipe segment at the coupling end. The ferrule has an annular ring extending from the coupling end of the pipe segment in the axial direction of flow having a series of internal barbs for a sealed and secure engagement of the outer wall of the outer pipe of the pipe segment. The ferrule also has a small threaded interstitial access port for attachment of various tube assemblies that will redirect the path of the interstitial space.  
         [0060]     A second component of the transition coupling assembly is an insert, preferably made of metal, which is attached to the inner wall of the pipe segment at its coupling end. The insert, which is expanded into the inner pipe wall, includes an inner annular ring extending from the coupling end of the pipe segment in the direction of fluid flow. An exterior portion of the insert has a series of external barbs for a sealed and secure engagement of the inner wall of the inner pipe of the pipe segment.  
         [0061]     In a different type of transition coupling assembly design, the ferrule and insert would be of a one piece construction instead of the two piece construction as described above.  
         [0062]     A third component of the transition coupling assembly is an internally threaded swivel nut that is loosely attached to the insert or ferrule/insert in such a manner that it can freely rotate. A preferred means of attaching the swivel nut is to internally expand a portion of the insert to lock on the swivel nut.  
         [0063]     A fourth component of the transition coupling assembly is an externally threaded port of a single wall pipe fitting or shear valve, which can be attached to the swivel nut. The externally threaded connection port of the fitting or shear valve allows the swivel nut to draw the coupling insert to or into the port opening for making a sealed connection.  
         [0064]     There are two types of sealed connections that are described can be made between the coupling insert and connection ports of the fittings or shear valves. The first is a radially sealed o-ring connection. In this application there are two elastomeric o-rings mounted externally to the sealing surface of the coupling insert. Tightening of the swivel nut draws the male insert into the connection port of the fitting or shear valve where the o-rings seal the outer wall of the insert to the sealing surface of the inner wall of the connection port.  
         [0065]     The second application is a butt compression seal application. In this application there is a flat ring seal, typically made of a fluoroelastomeric material. Tightening of the swivel nut draws the end face of the connection port towards the flat ring seal in such a manner that it is compressed between the radial end of the insert and the radial end of the connection port making an effective seal.  
         [0066]     The transition coupling further includes an o-ring seal that seals the inside of the ferrule to the outside of the insert. The purpose of this o-ring seal is to create a closed interstice that prevents leaks in the joint located at the end of the ferrule adjacent to the swivel nut. By sealing this joint between the ferrule and insert the interstice can be directed to an interstitial access port extending through the wall of the ferrule.  
         [0067]     Having an interstitial access port that is internally threaded provides for the connection of tube assemblies that be used for connection of the interstice of one pipe section to another or may be used for periodic testing of one or more pipe sections.  
         [0068]     The integrity of the system is tested by applying pressure or vacuum to the interconnected interstitial spaces of the pipe segments, which have been formed into a closed system. If the pressure or vacuum does not hold over a reasonable period of time, the system likely has one or more fluid leaks. The fittings and other components can then be inspected to locate leaks. Moreover, after the entire system has been operating, the interstitial space may again be subjected to pressure or vacuum to test for leaks. If, for example, a vacuum is lost sooner than a predetermined period of time or takes more than a predetermined time to achieve a given vacuum, this will indicate that a leak is present. Also, a liquid detector in the vacuum system would alert the user to a leak.  
         [0069]     It is also possible in accordance with the invention to continuously monitor the interstitial space. One such method is to fill interstitial space of the closed system with a test fluid. This test fluid is then monitored, either visually or automatically, so that a sudden or gradual change in the amount of test fluid in the interstitial space indicates that the system has failed and that a leak exists. For example, if the inner tubular member were damaged, substantial increase in fluid in the interstitial space would occur, causing the fluid level in the monitoring device to rise. Similarly, if the outer tubular member were damaged, the test fluid would leak into the ambient environment and the fluid level in the monitoring device would drop indicating a break in the system. In all cases, controls are provided to override any pumps in operation at the time to shut down the system.  
         [0070]     Another method would be to apply a constant positive or negative pressure (vacuum) to the closed interstice of a piping system having one or more piping segments. The pressure would be continuously monitored by an electronic monitoring device that will alarm if there is any significant change in pressure.  
         [0071]      FIG. 9  shows a sectional end view of a coaxial pipe segment  10 , fitted with a transition coupling  40  taken along line A-A in  FIG. 10 . Pipe segment  10  comprises an inner primary pipe  12  and an outer containment pipe  14 . The coaxial pipe also has a series of circumferentially spaced longitudinally extending standoff ribs  15  defining a series of longitudinal interstitial spaces  13  or passageways extending from end to end in the pipe segments  10 . The end of the pipe segment  10  is fitted with a transition coupling  40  which is partially shown in this illustration to comprise an outer metal ferrule  43 . The ferrule has a series of internal annular barbs  62  that engage and secure the outside of the outer pipe  14 . A metal insert  44  having external annular barbs  62  engages and secures the inside of the inner pipe  12  when internally expanded with a internal expansion coupling machine. The internal expansion of the metal insert  44  compresses and secures both the inner pipe  12  and the outer pipe  14  in such a manner that it would take a significant force (approx. 3,000 lbs.) to pull the penetration coupling off of the end of the pipe segment  10 . The compression caused by the internal expansion is not sufficient to close off the interstitial space  14  created by the standoff ribs  15  on the inside of the outer pipe  14 . The threaded interstitial port  47  of the transition coupling  40  is shown to be situated forward of the end of the pipe segment  10  in such a manner that it is in fluid communication with the interstitial space  13  of the pipe segment  10 . The interstitial port  47  can be either plugged or connected to a tube fitting  50  of a connector tube  48  or test tube  49 .  
         [0072]      FIG. 10  is a cross-sectional view of end of a double wall pipe segment  10  fitted with o-ring seal type transition coupling  40 . The double wall pipe segment  10  has an outer pipe  14  having standoff ribs  15  ( FIG. 9 ) formed on its inside wall to create an interstitial space  13  between the inner  12  and outer pipe  14 . The end of the pipe segment  10  is compressed between the inside of a metal ferrule  43  and the outside surface of the metal insert  44 . The inside surface of the metal ferrule  43  has a series of barbs  62  that engage and secure the outside of the outer pipe  14 . The outside surface of the metal insert  44  has a series of barbs  62  that engage and secure the inside of the inner pipe  12 .  
         [0073]     The front inside end metal ferrule  43  has an o-ring seal  53  that seals the joint between the inside of the ferrule  43  and the outside wall of the insert  44 . The sealing of this joint allows a closed interstice to be directed through threaded interstitial port  47  located near the front-end wall of the ferrule  43 .  
         [0074]     A locating rib  63  separates the end of the front end of the ferrule  43  and the swivel nut  46  that is entrapped inside of the locking groove  54  so that it will not come off. The swivel nut  46  has internal female connection threads  61  to mechanical engage the connection port  60  of a fitting or shear valve.  
         [0075]     A threaded swivel nut  46  is loosely secured to the insert  44  by means of an internal expansion process that locks it into the locking groove  54 . The swivel nut  46  is used to mechanically draw the insert sealing surface  58  that is fitted with two o-ring seals  52  into the connection port  60  of the fitting or shear valve. Within the connection port  60  the two o-ring seals  52  fitted on insert sealing surface  58 , engage the port sealing surface  59  to form a liquid tight seal.  
         [0076]      FIG. 11  illustrates components of an o-ring seal transition coupling that makes a sealed connection to the inside of connection port  57  of a fitting or shear valve. Shown are the end of the pipe segment  10 , the metal ferrule  43  and its interstitial port  47 . The metal insert  44  is shown to have external barbs  62  on its back end and two o-ring seals  52  installed on the insert sealing surface  58  on the front end. A swivel nut  46  is loosely secured to the insert  44  by means of an internal expansion process that locks it into the locking groove  54 . The swivel nut  46  has internal connection threads (not shown) that engage the external connection threads  61  located on the end section of the connection port  60 . The swivel nut  46  is used to mechanically draw the insert sealing surface  58  that is fitted with the two o-ring seals  52  into the connection port  60  of the fitting or shear valve. Within the connection port  60  the o-ring seals  58  fitted on insert sealing surface  58 , engage the inside wall ( 59  in  FIG. 10 ) of the connection port  60  to form a liquid tight seal. Also illustrated is a connector tube  48  or test tube  49 , fitted with a tube fitting  50 .  
         [0077]      FIG. 12  is a cross-sectional view of the coupling assembly illustrated in  FIG. 11  and described in detail under  FIG. 10  descriptions.  
         [0078]      FIG. 13  illustrates components of a butt seal transition coupling that makes a sealed connection to the face of connection port  60  of a fitting or shear valve. Shown are the end of the pipe segment  10 , the metal ferrule  43  and its interstitial port  47 . The metal insert  44  is shown to have external barbs  62  on its back end and a butt type insert sealing surface  58  on the front end. A swivel nut  46  is loosely secured to the insert  44  by means of an internal expansion process that locks it into the locking groove  54 . The swivel nut  46  has internal connection threads  61  (not shown) that engage the external connection threads  61  located on the end section of the connection port  60 . The swivel nut  46  is used to mechanically draw the insert sealing surface  58 , which is fitted with a butt seal  52  to the port sealing surface  59  located on the end of the connection port  60  of the fitting or shear valve. By tightening the swivel nut  46  the butt seal  52  is compressed between the insert sealing surface  58  and the port sealing surface  59  to form a liquid tight seal. Also illustrated is a connector tube  48  or test tube  49 , fitted with a tube fitting  50 .  
         [0079]      FIG. 14  is a cross-sectional view of end of a double wall pipe segment  10  fitted with butt seal type transition coupling. The double wall pipe segment  10  has an outer pipe  14  having standoff ribs formed on its inside wall to create an interstitial space  13  between the inner pipe  12  and under pipe  14 . The end of the pipe segment  10  is compressed between the inside of a metal ferrule  43  and the outside of the backend of the metal insert  44 . The inside surface of the metal ferrule  43  has a series of barbs  62  that engage and secure the outside of the outer pipe  14 . The outside of the metal insert  44  has a series of barbs  62  that engage and secure the inside of the inner pipe  12 .  
         [0080]     The front inside end of the metal ferrule  43  has an o-ring seal  53  that seals the joint between the inside of the ferrule  43  and the outside wall of the insert  44 . The sealing of this joint allows a closed interstice to be directed through threaded interstitial port  47  located near the front end-wall of the ferrule  43 .  
         [0081]     A locating rib  63  separates the end of the front end of the ferrule  43  and the swivel nut  46  that is entrapped inside of the locking groove  54  so that it will not come off. The swivel nut  46  has internal female connection threads  61   a  to mechanical engage the connection port  60  of a fitting or shear valve.  
         [0082]     A threaded swivel nut  46  is loosely secured to the insert  44  by means of an internal expansion process that locks it into the locking groove  54 . The swivel nut  46  has internal connection threads  61   a  that engage the external connection threads  61   b  located on the end section of the connection port  60 . The swivel nut  46  is used to mechanically draw the insert sealing surface  58 , which is fitted with a butt seal  52  to the port sealing surface  59  located on the end of the connection port  60  of the fitting or shear valve. By tightening the swivel nut  46  the butt seal  52  is compressed between the insert sealing surface  58  and the port sealing surface  59  to form a liquid tight seal.  
         [0083]      FIG. 15  illustrates components of a butt seal transition coupling that makes a sealed connection to the face of connection port  57  of a fitting or shear valve. This particular type transition coupling is like that described under  FIG. 13  with the exception that this coupling has ferrule and insert that is of a one-piece construction. Illustrated are the end of the pipe segment  10 , the one-piece ferrule/insert  45  and its interstitial port  47 . The one-piece ferrule/insert  45  is shown to be a butt type insert sealing surface  58  on the front end. A swivel nut  46  is loosely secured to the insert  44  by means of an internal expansion process that locks it into the locking groove  54 . The swivel nut  46  has internal connection threads (not shown) that engage the external connection threads  61  located on the end section of the connection port  60 . The swivel nut  46  is used to mechanically draw the insert sealing surface  58 , which is fitted with a butt seal  52  to the port sealing surface  59  located on the end of the connection port  60  of the fitting or shear valve. By tightening the swivel nut  46  the butt seal  52  is compressed between the insert sealing surface  58  and the port sealing surface  59  to form a liquid tight seal. Also illustrated is a connector tube  48  or test tube  49 , fitted with a tube fitting  50 .  
         [0084]      FIG. 16  is a cross-sectional view of end of a double wall pipe segment  10  fitted with butt seal type transition coupling like that described under  FIG. 13  with the exception that this coupling has ferrule and insert  45  that is of a one-piece construction. Illustrated are the double wall pipe segment  10  that has an outer pipe  14  having standoff ribs formed on its inside wall to create an interstitial space  13  between the inner pipe  12 . The end of the pipe segment  10  is compressed within the interior walls of the one piece ferrule/insert that has a series of barbs  62  on each interior wall to engage and secure the end of the pipe section  10  when compressed. A ferrule/insert  45  of one-piece construction has no backend joint thus no o-ring seal is necessary to cause the closed interstice to be directed through threaded interstitial port  47  located near the front end-wall of the ferrule  43 .  
         [0085]     The locating rib  63  separates the end of the front end of the ferrule  45  and the swivel nut  46  that is entrapped inside of the locking groove  54  so that it will not come off. The swivel nut  46  has internal female connection threads  61  to mechanical engage the connection port  60  of a fitting or shear valve.  
         [0086]     The threaded swivel nut  46  is loosely secured to the insert  44  by means of an internal expansion process that locks it into the locking groove  54 . The swivel nut  46  is used to mechanically draw the insert sealing surface  58 , which is fitted with a butt seal  52  to the port sealing surface  59  located on the end of the connection port  60  of the fitting or shear valve. By tightening the swivel nut  46  the butt seal  52  is compressed between the insert sealing surface  58  and the port sealing surface  59  to form a liquid tight seal.  
         [0087]     One advantage of the present invention is that that the transition coupling permits the interstitial space of the entire piping system to be interconnected into one closed system. Thus, the interconnected interstitial space can be subjected to pressurized air, preferably, pressurized nitrogen, to test the entire system at one time. Moreover, liquid or gas interstitial monitoring is readily obtained using the present invention. A beneficial advantage of the present invention is that couplings, fittings and connectors are non-elastomeric and not degradable so the interstice may be pressurized to a much higher level if required.  
         [0088]     The transition coupling will not degrade after long-term exposure to fuel, water, microbes, ozone or UV. Installation of this transition coupling is much faster and more efficient than systems that incorporate rubber test boots. Additionally, the transition coupling assembly, system and method are capable of withstanding stress from movement of the system as tanks are filled and emptied and as water tables affect the components of the system.  
         [0089]     Even though particular embodiments of the present invention have been illustrated and described herein, the description and drawings are not intended to limit the invention and changes and modifications may be made therein within the scope of the following claims.