Abstract:
Disclosed is a liquid detection cable that is capable of quickly detecting the presence of liquid and resetting, so that the liquid detection cable can be reused after removal from the presence of a liquid. The liquid detection cable uses a reactive layer that has not been doped with a conductive material, rather, a conductive layer is used adjacent the reactive layer, which allows the reactive layer to react quickly and reset after removal from the presence of the liquid. A braided binder is also provided between sensor wires and the conductive layer to provide a layer of insulation, so that the liquid detection cable does not provide false alarms when an external force is applied to the cable.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is based upon and claims the benefit of U.S. Provisional Patent Application No. 61/405,539, entitled “CHEMICAL LEAK DETECTION CABLE”, filed Oct. 21, 2010, by Donald M. Raymond. The entire content of the above-mentioned application is hereby specifically incorporated herein by reference for all it discloses and teaches. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Liquid detection cables are employed to detect the presence of various liquid chemicals, such as liquid petrochemicals, including gasoline, oil, solvents, etc. Liquid detection cables are typically connected to detector electronics, which are, in turn, connected to an alarm that signals the presence of a liquid to be detected. Liquid petrochemical detection cables can be used in tank farms, petrochemical plants, refineries, airports and other locations where a petrochemical leak may occur. For example, petrochemical detection cables may be used in double wall containers for fuel transfer, such as jet fuel distribution. Petrochemical detection cables may also be placed around diesel generators to detect leaks from diesel storage tanks or leaks from the generator. Petrochemical detection cables may also be buried around underground tanks that store petrochemical fuels to detect if the underground tank is leaking and causing an environmental hazard. 
       SUMMARY OF THE INVENTION 
       [0003]    An embodiment of the present invention may therefore comprise a method of forming a liquid detection cable comprising: providing at least two sensor wires; placing insulating spacers between the sensor wires; surrounding the spacers with a binder layer that provides openings; surrounding the binder layer with a conductive layer that protrudes through the interstitial openings upon application of a force on the conductive layer; surrounding the conductive layer with a reactive layer that expands when contacted by a liquid; surrounding the reactive layer with a constricting layer that is capable of substantially constricting outward expansion of the reactive layer which causes the reactive layer to expand inwardly and force the conductive layer to contact the at least two sensor wires to provide a conductive path between the at least two sensor wires indicating the presence of a liquid chemical. 
         [0004]    An embodiment of the present invention may further comprise a method of forming a liquid detection cable comprising: providing a first sensor wire and a second sensor wire; surrounding the first sensor wire with a binder layer that provides openings; surrounding the binder layer with a conductive layer that protrudes through the openings upon application of a force to the conductive layer; surrounding the conductive layer with a reactive layer that expands when contacted by a liquid; disposing the second sensor wire between the conductive layer and the reactive layer so that the second sensor wire is in electrical contact with the conductive layer; surrounding the reactive layer with a constricting layer that substantially constricts outward expansion of the reactive layer, causing the reactive layer to expand inwardly and force the conductive layer to be in electrical contact with the second sensor wire and force the conductive layer to protrude through the openings in the binder layer and contact the first sensor wire so that an electrical connection is made by the conductive layer between the first sensor wire and the second sensor wire. 
         [0005]    An embodiment of the present invention may further comprise a liquid detection cable comprising: at least two sensor wires; spacers disposed between the sensor wires; a nonconductive binder layer that is disposed around the spacers and the at least two sensor wires, the non-conductive binder layer having openings; a conductive layer disposed around the nonconductive binder layer that protrudes through the openings upon application of a force on the conductive layer that is greater than a predetermined force; a reactive layer that is disposed around the conductive layer that expands when contacted by a liquid; a constricting layer surrounding the reactive layer that substantially constricts outward expansion of the reactive layer which causes the reactive layer to expand inwardly and generate a force on the conductive layer that is greater than the predetermined force so that the conductive layer contacts the at least two sensor wires to provide a conductive path between the at least two sensor wires indicating that the liquid is in the presence of the liquid detection cable. 
         [0006]    An embodiment of the present invention may further comprise a liquid detection cable comprising: a first sensor wire; a second sensor wire; a non-conductive binder layer that is disposed around the first sensor wire, the non-conductive binder layer having openings; a conductive layer disposed around the non-conductive binder layer that protrudes through the openings upon application of a force on the conductive layer that is greater than a predetermined force; a reactive layer that is disposed around the conductive layer that expands when contacted by a liquid; a second sensor wire disposed between the conductive layer and the reactive layer so that the second sensor wire is in electrical contact with the conductive layer; a constricting layer surrounding the reactive layer that substantially constricts outward expansion of the reactive layer, causing the reactive layer to expand inwardly and force the conductive layer to be in electrical contact with the sensor wire and force the conductive layer to protrude through the openings in the binder layer and contact the first sensor wire so that an electrical connection is made by the conductive layer between the first sensor wire and the second sensor wire. 
         [0007]    An embodiment of the present invention may further comprise a method of making a liquid detection cable comprising: providing at least two sensor wires; placing the sensor wires in grooves in a carrier so that gaps are created between an outside surface of the carrier and the sensor wires; surrounding the carrier and the sensor wires with a conductive layer that protrudes into the gaps upon application of a force on the conductive layer; surrounding the conductive layer with a reactive layer that expands when contacted by a liquid; surrounding the reactive layer with a constricting layer that is capable of substantially constricting outward expansion of the reactive layer which causes the reactive layer to expand inwardly and force the conductive layer into the gaps to contact the at least two sensor wires to provide a conductive path between the at least two sensor wires indicating the presence of a liquid. 
         [0008]    An embodiment of the present invention may further comprise a liquid detection cable for detecting the presence of a liquid comprising: at least two sensor wires; a carrier having grooves formed in an outer surface of the carrier and the sensor wires disposed in the grooves so that gaps are present between the sensor wires and an outer surface of the carrier; a conductive layer disposed around the carrier and the sensor wires that protrudes into the gaps upon application of a force on the conductive layer; a reactive layer that is disposed around the conductive layer that expands when contacted by the liquid; a constricting layer surrounding the reactive layer that substantially constricts outward expansion of the reactive layer causing the reactive layer to expand inwardly and generate a force on the conductive layer so that the conductive layer protrudes into the gaps and contacts the at least two sensor wires to provide a conductive path between the at least two sensor wires indicating the presence of the liquid. 
         [0009]    An embodiment of the present invention may further comprise a method of making a liquid detection cable comprising: placing a first sensor wire in a groove in a carrier so that a gap is created between an outside surface of the carrier and the first sensor wire; surrounding the carrier and the first sensor wire with a conductive layer that protrudes into the gap upon application of a force on the conductive layer; surrounding the conductive layer with a reactive layer that expands when contacted by a liquid; placing a second sensor wire between the conductive layer and the reactive layer so that the second sensor wire is in electrical contact with the conductive layer; surrounding the reactive layer with a constricting layer that substantially constricts outward expansion of the reactive layer which causes the reactive layer to expand inwardly and force the conductive layer into the gap so that the conductive layer contacts the first sensor wire and makes an electrical connection between the first sensor wire and the second sensor wire. 
         [0010]    An embodiment of the present invention may further comprise a liquid detection cable for detecting the presence of a liquid comprising: a carrier having a groove formed in an outer surface; a first sensor wire disposed in the groove so that a gap is present between the first sensor wire and an outer surface of the carrier; a conductive layer disposed around the carrier and the first sensor wire that protrudes into the gap upon application of a force on the conductive layer; a reactive layer that is disposed around the conductive layer that expands when contacted by the liquid; a second sensor wire disposed between the conductive layer and the reactive layer so that the second sensor wire is in electrical contact with the conductive layer; a constricting layer surrounding the reactive layer that substantially constricts outward expansion of the reactive layer causing the reactive layer to expand inwardly and generate a force on the conductive layer so that the conductive layer protrudes into the gap and contacts the first sensor wire to provide a conduction path between the first sensor wire and the second sensor wire through the conductive layer indicating the presence of the liquid. 
         [0011]    An embodiment of the present invention may further comprise a liquid detection cable comprising: sensor wire means for carrying a sensor signal; carrier means having a groove formed in an outer surface for carrying the sensor wire means so that a gap is created between the sensor wire means and the outer surface of the carrier means; conductive layer means disposed around the carrier means for creating an electrical path between the conductive layer and the sensor wire means when the conductive layer means protrudes into the groove upon application of a force on the conductive layer means; reactive layer means for absorbing and swelling in the presence of the liquid; constricting layer means disposed around the reactive layer means for constricting outward expansion of the reactive layer means and causing the reactive layer means to expand inwardly and generate the force on the conductive layer means so that the conductive layer means fills the gap and creates an electrical path between the sensor wire means. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A  is a schematic perspective, cutaway view of one embodiment of a liquid detection cable. 
           [0013]      FIG. 1B  is a schematic end view of the embodiment of the liquid detection cable illustrated in  FIG. 1A . 
           [0014]      FIG. 2A  is a schematic, perspective, cutaway view of another embodiment of a liquid detection cable. 
           [0015]      FIG. 2B  is an end view of the embodiment of  FIG. 2A . 
           [0016]      FIG. 3  is a schematic illustration of one application of a liquid detection cable. 
           [0017]      FIG. 4A  is a schematic isometric view of another embodiment of a liquid detection cable. 
           [0018]      FIG. 4B  is a cross-sectional view of the embodiment of  FIG. 4A . 
           [0019]      FIG. 5A  is schematic, perspective, cutaway view of another embodiment of a liquid detection cable. 
           [0020]      FIG. 5B  is a cross-section view of the embodiment of  FIG. 5A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]      FIGS. 1A and 1B  schematically illustrate one embodiment of a liquid detection cable  100 .  FIG. 1A  is a schematic, isometric, cutaway view of the embodiment of the liquid detection cable  100 . As illustrated in  FIG. 1A , the liquid detection cable  100  is implemented to detect various liquids. In fact, the liquid detection cable  100  can detect the presence of any liquid by selecting a reactive layer  104  that expands in the presence of a liquid. The same is also true for the reactive layers  156 ,  414  and  456 , illustrated in  FIGS. 2A and 4A , respectively. For example, materials that can be used for reactive layers  104 ,  156  and  456  can detect the presence of liquid petrochemicals, liquid oleo chemicals and liquid organic chemicals, as explained in more detail below. Other implementations of the cable  100  and cable  400  can be employed to detect other liquids. Liquid detection cable  100  has an inner braided layer  102  that is surrounded by an outer braided layer  101 . As used herein, the term “layer” may comprise a sheath, a covering, a wrap, a coating, a braid, wound tape, or other structures, and does not necessarily have to fully surround or enclose another layer. In that regard, the term “surround” and “surrounding” does not mean that a layer is fully enclosed or encapsulated, but may be only partially covered. The inner braided layer  102  is made of nylon, plastic or other materials that are resistant to the liquid chemical being detected. For example, inner braided layer  102  may be constructed to be resistant to solvents and other hydrocarbon-based liquid chemicals. The inner braided layer  102  forms a sheath of braided strands of a resistant material that is substantially unaffected by most petrochemicals, organic chemicals and solvents. The strands have a diameter on the order of 10 mils and have a denier of approximately 150 (S glass fibrons). The strands fit tightly around the reactive layer  104 . The inner braided layer  102  is capable of substantially maintaining its diameter in the presence of expansive forces of the reactive layer  104 . The strands of the inner braided layer  102  are tightly woven and are made of a material that does not substantially expand or stretch in response to pressures generated by reactive layer  104 . In that regard, the inner braided layer  102  is capable of substantially maintaining a predetermined diameter when subjected to such pressures in the presence of liquids, including petrochemicals, solvents and other liquid organic chemicals, depending upon the reactive layer  104  utilized in the liquid detection cable  100 . As such, the inner braided layer  102 , as well as inner braided layer  154  ( FIG. 2A ), high tensile strength inner layer  416  ( FIG. 4A ) and high tensile strength inner layer  454  ( FIG. 5A ) are considered to be constricting layers that constrict expansion of reactive layers in an outward direction. Outer braided layer  101  has a larger weave than the inner braided layer  102  and is constructed of larger diameter strands that are less likely to fray, which protects inner braided layer  102 . The outer braided layer  101  is constructed to allow the liquid detection cable  100  to be pulled and dragged over rough surfaces with little or no damage to the inner braided layer  102 . 
         [0022]    As also illustrated in  FIG. 1A , the inner braided layer  102  surrounds reactive layer  104 . Reactive layer  104  is made from a material that is hydrophobic, but can be selected to absorb petrochemicals, solvents and many hydrocarbon liquid chemicals, liquid oleo-chemicals, such as plant based oils, and/or liquid organic chemicals, which cause the reactive layer  104  to expand and swell. For example, a reactive layer  104  can be selected that expands and swells in the presence of most petrochemicals, as well as solvents, such as toluene, dichloromethane, tricholorethylene, trichlorethane, methylethylketone, acetone, N-methylpyrrolidone and isopropyl alcohol. Other liquid hydrocarbons and other chemicals may also be absorbed by the reactive layer  104  and cause the reactive layer  104  to expand. The material of the reactive layer  104  can be a plastic material that is an electrically insulating material. Various plastic materials can be used, including olefin polymers, thermoplastic elastomers (TPE) and thermoplastic rubber (TPR), including nitrils and SEBS materials. For example, a non-conductive, thermoplastic elastomer alloy of styrenic and olefinic elastomer, olefinic resins, inorganic filler and process oils can be used as the reactive layer  104 . In addition, the reactive layer  104  may use organics, aromatics and aliphatic materials. 
         [0023]    Other chemical detection cables, such as the chemical detection cable disclosed in U.S. Pat. No. 4,926,165, which is specifically incorporated herein by reference for all that is discloses and teaches, utilizes a reactive layer that is doped with a conductive material to render the reactive layer conductive. These conductive dopants, such as carbon, do not expand in the presence of chemicals. As a result, the amount and speed at which the reactive layer expands is reduced exponentially, as the amount of the conductive dopant is added to the reactive layer. In that regard, a significant amount of dopant is required to render the reactive layer conductive. For example, amounts of up to fifty percent or more of carbon may be added to the reactive layer in existing chemical detection cables, such as disclosed in U.S. Pat. No. 4,926,165, to obtain sufficient conductivity of the reactive layer. 
         [0024]    The reactive layer  104 , illustrated in  FIG. 1A , expands significantly faster and to a greater extent than existing reactive layers that are doped with conductive materials, such as disclosed in U.S. Pat. No. 4,926,165. In addition, the reactive layer  104  is constructed to have greater wall thickness than existing reactive layers, which also creates faster and greater expansion of the reactive layer  104 . Testing of the reactive layer  104 , which does not include any conductive dopants, has provided the unexpected result of expansion rates that are approximately 10 times faster than the expansion rates of reactive layers doped with conductive materials, such as disclosed in U.S. Pat. No. 4,926,165. 
         [0025]    As also illustrated in  FIG. 1 , the reactive layer  104  surrounds a conductive layer  106 . The conductive layer  106  may be made from conductive polyvinylchloride (PVC), a conductive polyolefin, a conductive fluoropolymer, or other conductive plastic or plastic-like material. For example, polytetrafluoroethylene (Teflon®) can be used as conductive layer  106 . In addition, other conductive materials can be utilized, such as polyesters, ionemers, polymers/plastics, copolymers and homopolymers (plastics). Conductive layer  106  can also be made from a malleable metal that can be deformed and pressed inwardly by the reactive layer  104 , as the reactive layer  104  expands. Adherence between the reactive layer  104  and the conductive layer  106  is desirable for the construction and operation of the detection cable  100 . 
         [0026]    As also illustrated in  FIG. 1A , the conductive layer  106  surrounds an insulating braided binder  108 . The insulating braided binder  108  is made from a braided material that is braided to allow sufficient interstitial spaces between the braided material and the conductive layer  106  to allow the conductive layer  106  to move through the interstitial openings when pressure is applied to the conductive layer  106  by reactive layer  104 , while simultaneously providing an insulating layer when lesser pressures are applied to the conductive layer  106 , such as a person stepping on the cable  100 . In one embodiment, the braided binder is constructed of glass braid or any number of materials, such as polyester, nylon, plastic, glass or fabric (natural or synthetic), having a strand groupings diameter of approximately &gt;2 mils and preferably about 5 mils, and is braided so that only forty percent of the surface of the conductive layer  106  is covered by the braid. As such, sixty percent of the inside surface of the conductive layer  106  is exposed. The binder functions as a thatched separator to keep the conductor  128  and conductive layer  130 , as well as the conductor  138  and conductive layer  136 , from touching the conductive layer  106  when the liquid detection cable  100  is bent or flexed, or weight is applied, such as by a human step, on the liquid detection cable  100 . When a chemical is detected, the conductive layer  106  contracts and squeezes through the thatching or braiding of the insulating binder  108  to cause electrical conduction between the conductive layer  130  and conductive layer  136  and the conductive layer  106 . In accordance with this embodiment, the insulating braided binder  108  has a thickness of approximately 10 mm. Of course, other thicknesses and other percentages of coverage can be used, depending upon the type of material used for the insulating braided binder  108  and the conductive layer  106 . In addition, the insulating braided binder  108  may comprise a layer of insulating material that has openings, or interstitial openings, that allow conductive layer  106  to move through these interstitial openings. As such, either braided materials, or a layer with openings, can be used as a binder layer  108 ,  162  ( FIG. 2A ). 
         [0027]    As also illustrated in  FIG. 1A , the insulating braided binder  108  surrounds spacers  114 ,  118 , sensor wires  110 ,  112  and continuity wires  116 ,  120 . The spacers  114 ,  118  are made from a non-conducting material. Sensor wires  110 ,  112  have a smaller diameter than the spacers  114 ,  118  and, as such, are recessed from the insulating braided binder  108  and the conductive layer  106 . Similarly, the continuity wires  116 ,  120  have an outer insulating layer and are approximately the same diameter as the spacers  114 ,  118 . Continuity wires  116 ,  120  provide a return path for the sensor wires  110 ,  112  at the end of the cable. Spacers  114 ,  118  can be made simply of an insulating material, or they can constitute an insulated wire, such as continuity wires  116 ,  120 , which can provide other information, such as communications data, or a redundant return path for the continuity wires  116 ,  120 . While spacers  114 ,  118  and continuity wires  116 ,  120  all have an insulating outer surface, the sensor wires  110 ,  112  have an outer layer that is conductive and capable of carrying current, as explained in more detail below. The spacers  114 ,  118 , continuity wires  116 ,  120 , and sensor wires  110 ,  112  are all spirally wrapped around a center wire  122 . Center wire  122  has an outer insulator  126  and a center wire conductor  124 . The center wire  122  provides stability to the overall structure. The center wire conductor  124  can also be used for various purposes, including carrying power, data or other information. Of course, other structures can be used to provide stability to the liquid detection cable  100 . 
         [0028]    As also shown in  FIG. 1A , the sensor wires  110 ,  112  are disposed between the spacers  114 ,  118 , so that when sensor wires  110 ,  112  are twisted in a spiral, the spacers  114 ,  118  prevent the sensor wires  110 ,  112  from touching. As indicated above, the insulating braided binder  108  provides an insulating layer between the conductive layer  106  and the sensor wires  110 ,  112 . If the liquid detection cable  100  is stepped on, the insulating braided binder  108  prevents the conductive layer  106  from contacting the sensor wires  110 ,  112 . In that regard, the force of an individual stepping on the liquid detection cable  100  is spread by the insulating braided binder  108  across the surface of the conductive layer  106 , so that the conductive layer  106  does not protrude through the insulating braided binder  108  and contact the sensor wires  110 ,  112 . The higher, more concentrated forces created by the expansion of the reactive layer  104  on the conductive layer  106 , cause the conductive layer  106  to penetrate through the openings in the insulating braided binder  108  and create a conductive path between sensor wire  110  and sensor wire  112 . 
         [0029]      FIG. 1B  is an end view of the liquid detection cable  100 . As shown in  FIG. 1B , the outer braided layer  101  covers the inner braided layer  102 . Again, the outer braided layer  101  has coarser fibers that protect the finer inner braided layer  102 . The inner braided layer  102  has smaller diameter fibers that are capable of maintaining the size of the inner braided layer  102 , which fits snugly around the reactive layer  104 . As illustrated in  FIG. 1B , the conductive layer  106  surrounds the insulating braided binder  108 . The insulating braided binder  108  holds the sensor wires  110 ,  112 , continuity wires  116 ,  120  and spacers  114 ,  118 , that are twisted around the center wire  122 , in close conformity to the center wire  122 . In other words, the insulating braided binder  108  assists in providing a sound structure of twisted cables, wires and spacers around the center wire  122  and assists in preventing the sensor wires  110 ,  112 , spacers  114 ,  118  and continuity wires  116 ,  120  from becoming unraveled. 
         [0030]    As also illustrated in  FIG. 1B , sensor wire  110  has a conductive layer  136  and a conductor  138  disposed within the conductive layer  136 . The conductive layer  136  may be made from a polymer or other plastic material that is doped with a conductive material, such as carbon. The conductive layer  136  is in electrical contact with the conductor  138 . Similarly, sensor wire  112  has a conductive layer  130  that surrounds a conductor  128 . Conductive layer  130  may also be made from a polymer or plastic that is doped with a conductive material, such as carbon or other conductive material so that the conductive layer  130  is conductive and in electrical contact with conductor  128 . Continuity wire  116  has an insulating layer  146  that surrounds a conductor  144 . Similarly, continuity wire  120  has an insulating layer  132  that is surrounded by a conductor  134 . The conductive layers  130 ,  136  protect the conductors  128 ,  138  from chemicals that may attack or cause corrosion to the conductors  128 ,  138 . Conductive layers  130 ,  136  provide a conductive medium while still protecting conductors  128 ,  138  from damage that may be caused by liquid petrochemicals and other corrosive materials that may penetrate the liquid detection cable  100 . Insulating layers  132 ,  146  protect conductors  134 ,  144 , respectively, from damage that may be caused by exposure of the liquid detection cable  100  to certain types of chemicals. Similarly, insulator  142  protects conductor  140  of center wire  122 . 
         [0031]    In operation, the liquid detection cable  100 , disclosed in  FIGS. 1A and 1B , is disposed in a location in which liquid detection cable  100  is contacted by a liquid. The liquid flows through the outer braided layer  101  and through inner braided layer  102  onto the reactive layer  104 . The reactive layer  104  absorbs the liquid, expands and swells in the presence in the liquid. As the reactive layer  104  expands and swells, it generates a force on both the inner braided layer  102  and the conductive layer  106 . The inner braided layer  102 , as set forth above, is made from a material that does not substantially expand and, as such, maintains a substantially consistent diameter. The force of the expanded reactive layer  104  is directed inwardly toward the conductive layer  106 . The conductive layer  106  is driven inwardly by the force generated by the reactive layer  104  toward the center of the liquid detection cable  100 . The force of the reactive layer  104  causes the insulating braided binder  108  to move inwardly toward sensor wires  110 ,  112 . The force further causes the conductive layer  106  to protrude through the openings in the insulating braided binder  108  and make electrical contact with the conductive layer and sensor wires  110 ,  112 . An electrical connection is then formed between sensor wire  110  and sensor wire  112  at the location of the exposure of the liquid detection cable  100  to the liquid. The detector electronics  310 , illustrated in  FIG. 3 , then detects the existence and location of the liquid on the liquid detection cable  100 , such as the location of a leak using time domain reflectometry. 
         [0032]      FIG. 2A  is a schematic, perspective, cutaway view of an embodiment of a liquid detection cable  150 . As illustrated in  FIG. 2A , the liquid detection cable  150  is implemented to detect various liquids, such as the liquids disclosed with respect to the description of  FIG. 1A . Liquid detection cable  150  has an inner braided layer  154  that is surrounded by an outer braided layer  152 . These layers can be made of the same materials, and in the same manner, as inner braided layer  102  and outer braided layer  101 , illustrated in  FIG. 1A . As such, these layers may be resistant to various liquids, in the same manner as disclosed above with respect to  FIGS. 1A and 1B . In addition, these layers can be made from strands that are the same size as the strands described with respect to  FIGS. 1A and 1B . The inner braided layer  154  is capable of substantially maintaining its diameter in the presence of expansive forces created by reactive layer  156 . The strands of the inner braided layer  154  are tightly woven and made of a material that does not substantially expand or stretch in response to pressures generated by reactive layer  156 . Outer braided layer  152  has a larger weave than the inner braided layer  154  and is constructed of larger diameter strands that are less likely to fray, so as to protect the inner braided layer  154 . The outer braided layer  152  is constructed to allow the liquid detection cable  150  to be pulled and dragged over rough surfaces with little or no damage to the inner braided layer  154 . 
         [0033]    The reactive layer  156 , illustrated in  FIG. 2A , is hydrophobic, but absorbs various other liquids, such as petrochemicals, oleo chemicals, such as plant based oils, and liquid organic chemicals. The same materials can be used for the reactive layer  156  that are disclosed with respect to the reactive layer  104  of  FIGS. 1A and 1B . 
         [0034]    The reactive layer  156 , that is disclosed in  FIG. 2A , does not contain conductive dopants and, as such, expands exponentially faster than reactive layers that are used in other liquid detection cables that contain conductive dopants. 
         [0035]    As also illustrated in  FIG. 2A , the reactive layer  156  surrounds a conductive layer  160 . The conductive layer  160  may be made from conductive polyvinylchloride (PVC), a conductive polyolefin, a conductive fluoropolymer, or other conductive plastic or plastic-like material. The conductive layer  160  can be constructed of materials that are the same as that disclosed for conductive layer  106 , as disclosed with respect to  FIG. 1A . As also illustrated in  FIG. 2A , sensor conductor  158  is disposed between the reactive layer  156  and the conductive layer  160 . The reactive layer  156  holds the sensor conductive  158  tightly against the conductive layer  160  to ensure conduction between the sensor conductor  158  and the conductive layer  160 . In this manner, a conductive path is created between the conductive layer  160  and the sensor conductor  158  throughout the length of the conductive layer  160 . Sensor conductor  158  has less resistance than the conductive layer  160  and is capable of carrying a sensor signal throughout the length of the liquid detection cable  150 . 
         [0036]    As also illustrated in  FIG. 2A , the conductive layer  160  surrounds an insulating braided binder  162 . The insulating braided binder  162  is made from a braided material that is braided to allow sufficient interstitial spaces between the braided material and the conductive layer  160  to allow the conductive layer  160  to move through the interstitial openings when pressure is applied to the conductive layer  160  by the reactive layer  156 , while simultaneously providing an insulating layer when lesser pressures are applied to the conductive layer  160 , such as a person stepping on the liquid detection cable  150 . The insulating braided binder  162  can be made from the same materials as the insulated braided binder  108  that is described with respect to  FIG. 1A . The interaction of the conductive layer  160  and the insulating braided binder  162  is the same as that described with respect to conductive layer  106  and insulated braided binder  108 , as disclosed with respect to  FIG. 1A . 
         [0037]    As also illustrated in  FIG. 2A , the insulating braided binder  162  surrounds spacers  168 ,  170  that are made from a non-conducting material. A single sensor wire  166  has a smaller diameter than the spacers  168 ,  170  and, as such, is recessed from the insulating braided binder  162  and the conductive layer  160 . Similarly, the continuity wires  164 ,  165  have an outer insulating layer and are approximately the same diameter of spacers  168 ,  170 . Continuity wires  164 ,  165  provide a return path for the sensor wire  166  and sensor conductor  158  at the end of the liquid detection cable  150 . Spacers  168 ,  170  can be made from an insulating material, or they can constitute an insulated wire, such as continuity wires  164 ,  165 . While spacers  168 ,  170  and continuity wires  164 ,  165  all have an insulating outer surface, the sensor wire  166  has an outer layer that is conductive and capable of carrying current, as explained in more detail below. The spacers  168 ,  170 , continuity wires  164 ,  165 , and sensor wire  166 , are all spirally wrapped around a center wire  171 . Center wire  171  has an outer insulator  174  and a center wire conductor  172 . Center wire  171  provides stability for the overall structure of the liquid detection cable  150 . The center wire conductor  172  can also be used for various purposes, including carrying power, data or other information. Of course, other structures can be used to provide stability to the liquid detection cable  150 . 
         [0038]    As also shown in  FIG. 2A , the sensor wire  166  is disposed between spacers  168 ,  170  and continuity wire  165 , so that when the sensor wire  166  is twisted in a spiral, the spacers  168 ,  170 , as well as continuity wire  165 , isolate the sensor wire  166 . As indicated above, the insulating braided binder  162  provides an insulating layer between the conductive layer  160  and the sensor wire  166 . If the liquid detection cable  150  is stepped on, the insulating braided binder  162  prevents the conductive layer  160  from contacting the sensor wire  166 . In that regard, the force of an individual stepping on the liquid detection cable  150  is spread by the insulating braided binder  162  across the surface of the conductive layer  160 , so that the conductive layer  160  does not protrude through the insulating braided binder  162  and contact the sensor wire  166 . A higher, more concentrated force, created by the expansion of the reactive layer  156  on the conductive layer  160 , causes the conductive layer  160  to penetrate through the interstitial openings in the insulating braided binder  162  and create a conductive path between the sensor wire  166  and the sensor conductor  158 , which is in electrical contact with the conductive layer  160 . 
         [0039]      FIG. 2B  is an end view of the embodiment of the liquid detection cable illustrated in  FIG. 2A . As shown in  FIG. 2B , the outer braided layer  152  covers the inner braided layer  154 . Again, the outer braided layer  152  has coarser fibers that protect the finer inner braided layer  154 . The inner braided layer  154  has smaller diameter fibers that are capable of maintaining the size of the inner braided layer  154 , which fits snuggly around the reactive layer  156 . As illustrated in  FIG. 2B , the conductive layer  160  surrounds the insulating braided binder  162 . The insulating braided binder  162  holds the sensor wire  166 , continuity wires  164 ,  165  and spacers  168 ,  170 , that are twisted around the center wire  171 , and assists in preventing the sensor wire  166 , spacers  168 ,  170 , and continuity wires  164 ,  165 , from becoming unraveled. As also illustrated in  FIG. 2B , sensor wire  166  comprises a bare conductor. Sensor wire  166  has a smaller diameter than the spacers  168 ,  170  and continuity wires  164 ,  165 , so that a gap  192  is created between the insulating braided binder  162  and the sensor wire  166 . Sensor conductor  158  is shown to be in contact with conductive layer  160  and reactive layer  156 . As disclosed above, the reactive layer  156  forces the sensor conductor  158  to be in electrical contact with the conductive layer  160 . 
         [0040]    As also illustrated in  FIG. 2B , continuity wire  164  has an insulating layer  188  that surrounds a conductor  190 . Similarly, continuity wire  165  has an insulating layer  182  that surrounds a conductor  180 . The insulating layers  188 ,  182  provide protection to the conductors  190 ,  180 , respectively. Center wire  171  has an insulator  186  that protects conductor  184 . Reactive layer  156  also provides protection for sensor wire  166 , sensor conductor  158  and center wire  171 . 
         [0041]    In operation, the liquid detection cable  150 , disclosed in  FIGS. 2A and 2B , is disposed in a location in which the liquid detection cable  150  is contacted by a liquid to be detected. The liquid flows through the outer braided layer  152  and through the inner braided layer  154  onto the reactive layer  156 . The reactive layer  156  absorbs the liquid, expands and swells in the presence of the liquid. As the reactive layer  156  expands and swells, it generates a force on both the inner braided layer  154  and the conductive layer  160 . The inner braided layer  154 , as set forth above, is made from a material that does not substantially expand and, as such, maintains a substantially consistent diameter. The force of the expanded reactive layer  156  is directed inwardly toward the conductive layer  160 . The conductive layer  160  is driven inwardly by the force generated by the reactive layer  156  toward the center of the liquid detection cable  150 . The force of the reactive layer  156  causes the insulating braided binder  162  to move inwardly toward sensor wire  166  and eliminate gap  192 . The force further causes the conductive layer  160  to protrude through the interstitial openings in the insulating braided binder  162  and make electrical contact with the sensor wire  166 . An electrical connection is then formed between the sensor conductor  158 , which is in electrical contact with the conductive layer  160 , and sensor wire  166  at the location of the exposure of the liquid detection cable  150  to the liquid being detected. Detector electronics  310 , illustrated in  FIG. 3 , then detects the existence and location of the liquid on the liquid detection cable  150 , such as the location of a leak using time domain reflectometry. 
         [0042]      FIG. 3  is a schematic illustration of an embodiment of an application for detecting the presence of petrochemical liquids leaking from an underground tank at a gas station  300 . As shown in  FIG. 3 , an underground tank  304  is connected to pump  302  at the gas station  300 . The underground tank  304  is surrounded by a petrochemical detection cable  306  on both side portions of the underground tank  304 , and bottom portions underneath the underground tank  304 . The petrochemical detection cable  306  is connected by connectors  308  to detector electronics  310  disposed in the gas station store  312 . Whenever gasoline, diesel fuel or other petrochemicals are detected from the underground tank  304 , the detector electronics  310  detects the presence of the petrochemical, and may sound an alarm, indicating the detection of leakage of petrochemicals from the underground tank  304 . 
         [0043]    In this manner, the structural integrity of the underground tank  304  can be monitored so that environmental hazards do not occur as a result of leakage of gasoline, diesel, or other petrochemicals, or organic chemicals from the underground tank  304 , over an extended period of time. It should be noted that there are various applications for liquid detection cables and  FIG. 3  discloses only a single application. In addition, the liquid detection cable  100  can be utilized not only for detecting leaks, but for detecting the presence of liquids and the location of those liquids along the length of the liquid detection cable  100 , for various other purposes. 
         [0044]      FIG. 4A  is a schematic isometric view of another embodiment of a liquid detection cable  400 . As shown in  FIG. 4A , the liquid detection cable  400  includes a high tensile strength braided outer layer  418 . The high tensile strength braided outer layer  418  is made from a very high tensile strength Teflon material, or similar material, that can have a tensile strength on the order of 9,000 pounds. The high tensile strength braided outer layer  418  is braided in a manner so that large openings, on the order of 2 mm, are formed between the braid of the high tensile strength strands. In this manner, liquids can easily move through the high tensile strength braided outer layer  418 . The high tensile strength braided outer layer  418  is braided in a manner that provides as much as 200 pounds of pull strength to the chemical detection cable  400 . As such, large forces can be applied to the high tensile strength braided outer layer  418  to pull the liquid detection cable  400  through openings and tight areas during installation. The strands of the high tensile strength braided outer layer  418  can be made from Teflon or other material that not only has a high tensile strength, but also provides a slippery surface that allows the chemical detection cable  400  to be more easily pulled through tight areas without damaging the chemical detection cable  400 . For example, the high tensile strength braided outer layer  418  may be constructed from Teflon coated yarn available from W. F. Lake Corp., 65 Park Road, P.O. Box 4214, Glens Falls, N.Y., 12804. The same materials can be used for high tensile strength braided outer layer  418  as outer braided layer  101 , illustrated in  FIG. 1A . 
         [0045]    As also illustrated in  FIG. 4A , the high tensile strength braided outer layer  418  surrounds and protects a high tensile strength inner layer  416 . The high tensile strength braided outer layer  418  is constructed of larger diameter strands that are less likely to fray than the smaller diameter strands of the high tensile strength inner layer  416 . In this manner, the high tensile strength braided outer layer  418  is better able to protect the high tensile strength inner layer  416 . The high tensile strength inner layer  416  is a thicker layer of material that uses finer strands in a tight weave pattern than the high tensile strength braided outer layer  418 , but may also be made from a Teflon material, or similar material, that is formed in a braid or mesh. The braid or mesh allows chemicals to move through the high tensile strength inner layer  416  to the reactive layer  414 . The high tensile strength inner layer  416  can also be made from a material such as Teflon, or similar material, which may have a tensile strength on the order of several thousand pounds. For example, ETFE (Tefzel) filaments can be used, which are available from Pelican Wire Company, Inc., 3650 Shaw Boulevard, Naples, Fla., 34117-8408. Also, the high tensile strength inner layer  416  can be constructed in the same manner and use the same materials as the inner braided layer  102 , illustrated in  FIG. 1A . The high tensile strength inner layer  416  is braided in a manner that the inner layer maintains the outer diameter of the reactive layer  414  as it swells in the presence of chemicals. A tighter weave can be used with the smaller diameter high tensile strength strands of the high tensile strength inner layer  416 , which provides a greater ability to constrict expansion. The mesh or weave of high tensile strength inner layer  416  has a tensile strength and a mesh or weave pattern so that forces created by the reactive layer  414 , when the reactive layer  414  swells in the presence of liquids, do not allow the reactive layer  414  to expand outwardly. In this manner, the high tensile strength inner layer  416  is capable of substantially maintaining its diameter in the presence of the expansive forces of the reactive layer  414 . The strands of the high tensile strength inner layer  416  are tightly woven and made of a material that does not substantially expand or stretch in response to the pressures generated by the reactive layer  414 . As such, the high tensile strength inner layer  416  does not expand, and holds the outer diameter of the reactive layer  414  at a diameter that substantially coincides with the inner diameter of the high tensile strength inner layer  416 , which constrains the reactive layer and causes the reactive layer  414  to expand inwardly. Accordingly, the high tensile strength inner layer  416  functions as a constricting layer. Both the high tensile strength braided outer layer  418  and the high tensile strength inner layer  416  can be made from materials that are not braided, such as a layer that has openings formed in the layer. Of course, the same is true for outer braided layer  101  and inner braided layer  102 , illustrated in  FIG. 1A , outer braided layer  152  and inner braided layer  154  of  FIG. 2A , and high tensile strength braided outer layer  452  and high tensile strength inner layer  454 , illustrated in  FIG. 5A . 
         [0046]    The reactive layer  414 , illustrated in  FIG. 4A , is made from a material that swells in the presence of a chemical. Reactive layer  414  is made from a material that is hydrophobic, but can be selected to absorb petrochemicals, solvents, and many hydrocarbon liquid chemicals, liquid oleo chemicals, such as plant based oils, and/or liquid organic chemicals. In one embodiment, petro-reactive compounds can include a nitril blend that is available from S&amp;E Specialty Polymers, 140 Leominster-Shirley Road, Lunenburg, Mass., 01462. Other materials can be used for the reactive layer  414  to detect the presence of other liquid chemicals, as set forth below. The hydrophobic nature of the reactive layer  414  prevents the reactive layer  414  from absorbing water, so that the liquid detection cable  400  does not activate in the presence of water. The reactive layer  414  can be made from the same materials as the reactive layer  104  described with respect to  FIG. 1A . 
         [0047]    The conductive layer  412 , illustrated in  FIG. 4A , can be made from a plastic material that is combined with a conductive material, such as carbon or other small particle conductive material. For example, conductive PVC may be used, having both standard and soft durometer, such as that sold by Teknor Apex Company, 505 Central Avenue, Pawtucket, R.I., 02861. In addition, conductive layer  412  can be made in the same way and from the same materials as reactive layers  104 ,  156 ,  456  to detect the same chemicals as liquid detection cables  100 ,  150 ,  450 . 
         [0048]    Carrier  410  of the chemical detection cable  400 , illustrated in  FIG. 4 , is made from a thermoplastic elastomer, or other plastic, which is non-conductive and flexible. Carrier  410  has two grooves, formed in a spiral shape around the outer surface of the carrier  410  in which the sensor wires  402 ,  404  are disposed. The grooves can be formed during extrusion of carrier  410 , or after extrusion. The grooves are sufficiently deep that the sensor wires  402 ,  404  are displaced below the surface of the carrier  410  by a predetermined amount. As such, gaps  420 ,  422  ( FIG. 4B ) exist between the surface of the sensor wires  402 ,  404 , and the outer surface of the carrier  410 . In the process of manufacturing, the sensor wires  402 ,  404  are pulled and twisted into the grooves  440 ,  442  in the carrier  410 . The grooves  440 ,  442  are sufficiently small and the thermoplastic elastomer of the carrier  410  is sufficiently flexible to hold the sensor wires  402 ,  404  in place in the carrier  410 . Since the sensor wires  402 ,  404  are pulled into the grooves  440 ,  442 , the tension on the sensor wires  402 ,  404 , as well as the forces from the conductive carrier  410 , cause the sensor wires  402 ,  404  to be disposed in and remain situated at the innermost portion of grooves  440 ,  442  to create and maintain gaps  420 ,  422  ( FIG. 5 ). Continuity wires  406 ,  408  are disposed in the carrier  410  during the extrusion process of the carrier  410 . Cross die extrusion processes may be used to create the carrier  410  and extrude the carrier  410  with the continuity wires  406 ,  408 . 
         [0049]      FIG. 4B  is a cross-sectional view of the embodiment of the liquid detection cable  400 , illustrated in  FIG. 4A . As shown in  FIG. 4B , the high tensile strength braided outer layer  418  surrounds the high tensile strength inner layer  416 . A reactive layer  414  is surrounded by the high tensile strength inner layer  416 . The inner diameter of the high tensile strength inner layer  416  holds the outer diameter of the reactive layer  414  so that the reactive layer  414  cannot expand outwardly and, as such, is considered to be a constricting layer. The reactive layer  414  surrounds a conductive layer  412 . As indicated above, the conductive layer  412  is made from a conductive malleable material. Conductive layer  412  can be constructed from the same materials and in the same manner as conductive layer  106 . The conductive layer  412  surrounds the carrier  410 . The carrier  410  is extruded with continuity wires  406 ,  408 , so that the continuity wires  406 ,  408  are disposed within the carrier  410 . The continuity wires  406 ,  408  include a conductor  424 ,  428 , respectively, which is surrounded by insulators  426 ,  430 , respectively. The insulators  426 ,  430  are made from a material that is different from the material of the carrier  410 . The material of the insulators  426 ,  430  is a material that has low adhesion with the material of the carrier  410 . In that manner, it is easier to strip the carrier  410  from the insulators  430 ,  426  of the continuity wires  408 ,  406 , respectively. Sensor wires  402 ,  404  include conductors  432 ,  438 . Conductors  432 ,  438  are surrounded by a non-permeable conductive layer  434 ,  436 . The non-permeable conductive layer is impervious to petrochemicals and other potentially corrosive and damaging liquids, which protects the conductors  432 ,  438 . The non-permeable conductive layers  434 ,  436  are capable of transmitting an electrical current to the conductors  432 ,  438 . The non-permeable conductive layers  434 ,  436  may be a conductive polyolefin or a conductive polyethylene. The conductive polyolefin or conductive polyethylene are available from Breen Color Concentrates, 11 Kari Drive, Lambertville, N.J., 08530. 
         [0050]    As illustrated in  FIG. 4B , gaps  420 ,  422  that are adjacent to sensor wires  402 ,  404  prevent conduction between the conductive layer  412  and each of the sensor wires  402 ,  404 . However, when a liquid seeps through the high tensile strength braided outer layer  418  and the high tensile strength inner layer  416  to the reactive layer  414 , the reactive layer  414  swells. The high tensile strength braided outer layer  418  and high tensile strength inner layer  416  do not allow outward expansion of the reactive layer  414 . Hence, the reactive layer  414  expands inwardly, as shown in  FIG. 4B . The forces created by the inward expansion of the reactive layer  414  are transmitted to the conductive layer  412 . The conductive layer  412  may be constructed from a somewhat malleable, soft durometer material, which allows the conductive layer  412  to expand into gaps  420 ,  422 , so that the conductive layer  412  contacts the non-permeable conductive layer  434  of sensor wire  402  and the non-permeable conductive layer  436  of sensor wire  404 . Both standard and soft durometer conductive PVC is available from Teknor Apex Company, 505 Central Avenue, Pawtucket, R.I., 02861. In addition, the conductive layer  412  can be made from the same materials and in the same manner as conductive layer  106 , as disclosed above. In this manner, a conductive path is created between sensor wire  402  and sensor wire  404  at a location where the chemical is present and permeates the liquid detection cable  400 . Continuity wires  406 ,  408  provide continuity information, while sensor wires  402 ,  404  can be used to detect the location of the leak using time domain reflectometry techniques. 
         [0051]    The structure illustrated in  FIGS. 4A and 4B  can also be used to detect other types of liquids. The same structure can be used, as illustrated in  FIGS. 4A and 4B , with the reactive layer  414  replaced with a sheath of materials that are reactive to and swell in response to a particular liquid being detected by detection cable  400 . For example, a nitril blend chemical-reactive compound available from S&amp;E Specialty Polymers, 140 Leominster-Shirley Road, Lunenburg, Mass., 01462, which is reactive to many hydrocarbon-based fuels, such as gasoline, diesel, jet fuel and highly volatile petrochemicals can be replaced with an SEBS (Styrene-Ethylene/Butylene-Styrene) material that swells in the presence of hydrocarbon oils, vegetable oils and other types of oils. Similarly, the reactive layer  414  can be replaced with materials that react to and swell in the presence of volatile organic materials, alcohol, ketones, and other similar liquids. Such materials may be a polypropylene-based material, a polyolefin, or polyethylene material. Hence, the structure of the liquid detection cable  400 , illustrated in  FIGS. 4A and 4B , can be used to detect the presence of other liquids and gases, other than petrochemicals, by simply replacing the reactive layer  414  with a material that swells in the presence of the liquid or gas to be detected. In this manner, the overall structure of the detection cable  400  can be used in various implementations to detect various liquids or gases. 
         [0052]    The size of the gaps  420 ,  422 , illustrated in  FIG. 4B , can be controlled with a high degree of precision based upon the manufacturing tolerances used during the construction process of the detection cable  400 . Gaps  420 ,  422  are made sufficiently large to allow for a tight bend radius of the liquid detection cable  400 . For example, bend radii of one inch have been used without creating a false detection. The size of the gaps  420 ,  422  also affects the sense time for sensing the presence of a liquid. For example, large gaps may increase the time for the reactive layer  414  of the embodiment of the liquid detection cable  400  to swell sufficiently to cause the conductive layer  412  to contact the non-permeable conductive layers  434 ,  436 . In that regard, the size of the gaps  420 ,  422  is carefully selected to create a reliable product that reacts in a quick time period to the detection of liquids. Gaps in the range of about 10 mils to about 50 miles, but preferably in the range of about 15 miles to about 25 miles, provide such results. 
         [0053]      FIG. 5A  is a schematic, perspective, cutaway view of an embodiment of a liquid detection cable  450 . As illustrated in  FIG. 5A , the liquid detection cable  450  is implemented to detect various types of liquids, such as disclosed with respect to the various embodiments disclosed herein. Liquid detection cable  450  has a high tensile strength inner layer  454  that is surrounded by a high tensile strength braided outer layer  452 . Both the high tensile strength braided outer layer  452  and the high tensile strength inner layer  454  can be made from the same materials and sizes of materials that are disclosed with respect to the various embodiments disclosed herein. High tensile strength inner layer  454  is capable of substantially maintaining its diameter in the presence of expansive forces created by the reactive layer  456  and, as such, is considered to be a constricting layer. The strands of the high tensile strength inner layer  454  are tightly woven and made of a material that does not substantially expand or stretch in response to pressures generated by reactive layer  456 . High tensile strength braided outer layer  452  has a larger weave than the high tensile strength inner layer  454  and is constructed of larger diameter strands that are less likely to fray, which protects the high tensile strength inner layer  454 . The high tensile strength braided outer layer  452  is constructed to allow the liquid detection cable  450  to be pulled and dragged over rough surfaces with little or no damage to the high tensile strength inner layer  454 . 
         [0054]    As also illustrated in  FIG. 5A , the high tensile strength inner layer  454  surrounds reactive layer  456 . Reactive layer  456  is made from a material that is hydrophobic, but can be selected to absorb petrochemicals, solvents and many hydrocarbon liquid chemicals, liquid oleo chemicals, such as plant based oils, and/or liquid organic chemicals, which cause the reactive layer  456  to expand and swell. For example, a material for the reactive layer  456  can be selected that expands and swells in the presence of most petrochemicals, as well as solvents, such as toluene, dichloromethane, trichloroethylene, trichloroethane, methyl ethyl ketone, acetone, N-methylpyrrolidone, and isopropyl alcohol. Other liquid hydrocarbons and other chemicals can also be absorbed by reactive layer  456  and cause reactive layer  456  to expand. The material of the reactive layer  456  can be a plastic material that is also an electrically insulating material. Various plastic materials can be used, including olefin polymers, thermoplastic elastomers (TPE), and thermoplastic rubber (TPR), including nitrils and SEBS materials. For example, a non-conductive, thermoplastic elastomer alloy of styrene and olefinic elastomer, olefinic resins, inorganic filler, and a process oil, can be used as the reactive layer  456 . In addition, the reactive layer may use organics, aromatics and aliphatic materials. Since the reactive layer  456  does not include conductive dopants, reactive layer  456  has much greater expansion rates than reactive layers that include conductive dopants. Reactive layer  456  can utilize any of the materials disclosed with respect to the other embodiments disclosed herein. 
         [0055]    As further illustrated in  FIG. 5A , reactive layer  456  surrounds a conductive layer  458 . Conductive layer  458  may be made from conductive polyvinylchloride (PVC), a conductive polyolefin, a conductive fluoropolymer, or other conductive plastic or plastic-like material. For example, polytetrafluoroethylene (Teflon®) can be used as a conductive layer  458 . In addition, other conductive materials can be used, such as disclosed with respect to the other embodiments disclosed herein. 
         [0056]    As also illustrated in  FIG. 5A , the conductive layer  458  surrounds a carrier  460 . Carrier  460  is made from a thermoplastic elastomer, or other plastic, which is non-conductive and flexible. Carrier  460  has a single groove, formed in a spiral shape around the outer surface of the carrier  460 , in which the sensor wire  462  is disposed. The groove is formed during extrusion of the carrier  460 , or can be formed in a subsequent process. The groove in carrier  460  is sufficiently deep that the sensor wire  462  is displaced below the surface of the carrier  460  by a predetermined amount. As such, gap  420  ( FIG. 5B ) exists between the surface of the sensor wire  462  and the outer surface of carrier  460 . In the process of manufacturing, the sensor wire  462  is pulled and twisted into the groove  470  formed in the carrier  460 . The groove  470  is sufficiently small and the thermoplastic elastomer of the carrier  460  is sufficiently flexible to hold the sensor wire  462  in place in the carrier  460 . Since the sensor wire  462  is pulled into the groove  470 , the tension on the sensor wire  462 , as well as the forces from the conductive carrier  460 , cause the sensor wire  462  to be disposed in, and remain situated at, the innermost portion of the groove  470 , to create and maintain gap  420 . Continuity wires  466 ,  468  are disposed in the carrier  460  during the extrusion process of the carrier  460 . Cross die extrusion processes may be used to create the carrier  460  and extrude the carrier  460  with the continuity wires  466 ,  468 . 
         [0057]    A second sensor wire  464  is also illustrated in  FIG. 5A . Sensor wire  464  is disposed between the reactive layer  456  and the conductive layer  458 . The reactive layer  456  exerts a force on sensor wire  464 , so that sensor wire  464 , which is a bare conductor, is in electrical contact with the conductive layer  458 , along the length of the liquid detection cable  450 . In this manner, sensor wire  464  can provide a low resistance conductive path, which is in electrical contact with the conductive layer  458  along the length of the liquid detection cable  450 . 
         [0058]      FIG. 5B  is a cross-sectional view of the embodiment of the liquid detection cable  450  illustrated in  FIG. 5A . As shown in  FIG. 5A , the high tensile strength braided outer layer  452  surrounds the high tensile strength inner layer  454 . A reactive layer  456  is surrounded by the high tensile strength inner layer  454 . The inner diameter of the high tensile strength inner layer  454  holds the outer diameter of the reactive layer  456  so that the reactive layer  456  cannot expand outwardly. The reactive layer  456  surrounds a conductive layer  458 . As indicated above, the conductive layer  458  is made from a conductive malleable material. Conductive layer  458  can be constructed from the same materials, and in the same manner, as disclosed with respect to the other embodiments set forth herein. Conductive layer  458  surrounds carrier  460 . Carrier  460  is extruded with continuity wires  466 ,  468 , so that continuity wires  466 ,  468  are disposed within the carrier  460 . Sensor wire  462  includes a conductor  474 , which is surrounded by a non-permeable conductive layer  472 . The non-permeable, conductive layer  472  is impervious to corrosive and damaging liquids and protects the conductor  474 . The non-permeable conductive layer  472  is capable of transmitting an electrical signal to the conductor  474 . The non-permeable conductive layer  472  may be conductive polyolefin or a conductive polyethylene. The conductive polyolefin or conductive polyethylene are available from Breen Color Concentrates, 11 Kari Drive, Lambertville, N.J., 08530. Continuity wires  466 ,  468  include conductors  480 ,  476 , respectively, that are covered with insulators  482 ,  478 , respectively. The insulators  482 ,  478  are made from a material that is different from the material of the carrier  460 . The material of the insulators  482 ,  478  is a material that has low adhesion with the material of the carrier  460 . In that manner, it is easier to strip the carrier  460  from the insulators  482 ,  478  of the continuity wires  466 ,  468 , respectively. 
         [0059]    As illustrated in  FIG. 5B , gap  420  provides a separation between the non-permeable, conductive layer  472  of the sensor wire  462  and the conductive layer  458 . However, when a liquid seeps through the high tensile strength braided outer layer  452  and the high tensile strength inner layer  454  to the reactive layer  456 , the reactive layer  456  swells. The high tensile strength braided outer layer  452  and the high tensile strength inner layer  454  do not allow outward expansion of the reactive layer  456 . Hence, the reactive layer  456  expands inwardly. The forces created by an inward expansion of the reactive layer  456  are transmitted to the conductive layer  458 . Conductive layer  458  may be constructed from any of the malleable materials disclosed herein, which allows the conductive layer  458  to expand into gap  420 , so that the conductive layer  458  contacts the non-permeable conductive layer  472  of sensor wire  462 . In this manner, a conductive path is created between the sensor wire  462  and the conductive layer  458 . Sensor wire  464  is a bare conductor that is in contact with conductive layer  458 . Hence, an electrical connection is made between the sensor wire  464  and sensor wire  462  at the location where the liquid has seeped through the outer layers of the liquid detection cable  450 . Using time domain reflectometry electronics, the location of the leak can be determined along the length of the liquid detection cable  450 . 
         [0060]    The size of the gap  420 , illustrated in  FIG. 5B , can be controlled with a high degree of precision based upon the manufacturing tolerances used during the construction process of the liquid detection cable  450 . Gap  420  is made sufficiently large to allow for a tight bend radius of the liquid detection cable  450 . For example, bend radii of one inch have been used without creating a false detection. The size of the gap  420  also affects the sense time for sensing the presence of the liquid. For example, large gaps may increase the time for the reactive layer  456  to swell sufficiently to cause the conductive layer  458  to contact the non-permeable, conductive layer  472 . In that regard, the size of the gap  420  is carefully selected to create a reliable product that reacts in a quick time period to the detection of liquids. Gaps in the range of about 10 mils to about 50 mils, but preferably in the range of about 15 mils to about 25 mils, provide such results. 
         [0061]    The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiment was chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.