Abstract:
Electrical conduits and conductors may be sealed using a chamber configured for attachment to a conduit through which at least one conductor runs such that the at least one conductor also runs through the chamber. A vent allows gas that enters the chamber from the conduit to exit the chamber. A sealing compound fills the chamber and surrounds the conductor and the vent.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of and claims priority to U.S. application Ser. No. 10/695,651, filed on Oct. 29, 2003 and titled “Seal for Cables and Conduits,” which is incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     This document relates to a seal for cables and conduits.  
       BACKGROUND  
       [0003]     A seal is typically used to prevent harmful fluids and vapors in a high-pressure process area from entering an electrical conduit that may leave the process area. If the seal fails, the harmful vapors may enter the electrical conduit and travel down the conduit to an unprotected location. The vapors may ignite in the unprotected location due to arcing or sparking.  
       SUMMARY  
       [0004]     In one general aspect, electrical conduits and conductors may be sealed using a chamber configured for attachment to a conduit through which at least one conductor runs such that the at least one conductor also runs through the chamber. A vent allows gas that enters the chamber from the conduit to exit the chamber. A sealing compound fills the chamber and surrounds the conductor and the vent.  
         [0005]     Implementations may include one or more of the following features. For example, a pressure relief tube may connect to the vent. The pressure relief tube may extend from the conduit to the vent such that the gas may pass from the conduit to the vent through the pressure relief tube.  
         [0006]     The conductor may be a stranded conductor. A connector may connect the stranded conductor to a solid conductor. A second connector may connect the solid conductor to a second stranded conductor.  
         [0007]     A plug, a pressure gauge that monitors vapor pressure within the vent, an explosion-proof drain, a breather, or a rupture disk may be attached to the vent.  
         [0008]     The chamber may include a base and a cover that is threaded to screw onto the base. The cover may include a port that permits access to the chamber. The sealing compound may be injected into the chamber through the port.  
         [0009]     The vent may include a tube that permits access to a portion of the chamber that is not filled with the sealing compound. The gas from the conduit may exit the chamber through the tube. The at least one conductor may run perpendicularly through the tube, or perpendicularly across an outer surface of the tube. The tube may include two interlocking halves between which the at least one conductor is placed.  
         [0010]     The sealing compound may form an explosion-proof seal in the chamber.  
         [0011]     In another general aspect, sealing electrical conduits and conductors includes attaching a chamber to a conduit to be sealed. At least one conductor runs through the conduit. A vent tube that opens to the outside of the chamber is mounted within the chamber. The at least one conductor is threaded though the chamber such that the at least one conductor contacts the vent tube. The chamber is covered with a cover, and a sealing compound is injected into the chamber.  
         [0012]     Implementations may include one or more of the following features. For example, threading the at least one conductor though the chamber such that the at least one conductor contacts the vent tube may include threading the at least one conductor through the chamber such that the at least one conductor runs perpendicularly through the vent tube, or such that the at least one conductor runs perpendicularly across an outer surface of the vent tube.  
         [0013]     One end of a pressure relief tube may be attached to the vent tube. An opposite end of the pressure relief tube may be placed within the conduit.  
         [0014]     A plug, a pressure gauge, an explosion proof drain, a breather, or a rupture disk may be attached over an end of the vent tube on the outside of the chamber.  
         [0015]     Mounting the vent tube in the chamber may include mounting a bottom half of the vent tube in the chamber. The at least one conductor may be passed across the bottom half of the vent tube, and a top half of the vent tube may be mounted in the chamber over the at least one conductor and the bottom half of the vent tube.  
         [0016]     Covering the chamber with the cover may include screwing the cover onto the chamber. Putting the sealing compound in the chamber may include injecting the sealing compound into the chamber through a nozzle in the cover. A plug may be placed over the nozzle, and the sealing compound may be allowed to expand and harden.  
         [0017]     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0018]      FIG. 1  is a schematic diagram of a first implementation of a seal.  
         [0019]      FIG. 2  is a perspective illustration of a base from the seal of  FIG. 1 .  
         [0020]      FIG. 3  is a cross section of the seal of  FIG. 1  taken along section  3 - 3  of  FIG. 1 .  
         [0021]      FIG. 4  is a perspective illustration of half of a vent tube from the seal of  FIG. 1 .  
         [0022]      FIG. 5  is a diagram of a pressure gauge attached to the seal of  FIG. 1   
         [0023]      FIG. 6  is a flow chart of a process for assembling the seal of  FIG. 1 .  
         [0024]      FIG. 7  is a perspective illustration of a base from a second implementation of a seal.  
         [0025]      FIG. 8  is a cross section of the base of  FIG. 7 .  
         [0026]      FIG. 9  is a perspective illustration of a vent tube from the base of  FIG. 7 .  
         [0027]      FIG. 10  is a flow chart of a process for assembling the second implementation of the seal of  FIG. 7 .  
         [0028]      FIG. 11  is an illustration of a system for sealing stranded conductors with solid conductors. 
     
    
       [0029]     Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0030]     A seal may be used to prevent migration of pressurized fluids and vapors down an electrical conduit. The conductors within the seal are separated by an expanding sealing compound that blocks movement of the vapors. The seal may also include a vent tube though which the vapors may exit the seal to a hazardous or classified location, or to a well vented area, such as the atmosphere. A pressure relief tube may guide the vapors from the electrical conduit to the vent tube. The seal also may include a pressure gauge or other mechanisms for containing, monitoring, or diverting the vapors within the seal.  
         [0031]     Referring to  FIG. 1 , a first implementation of a seal  100  includes a base  105  and a cover  110  that may screw onto the base  105 . The base  105  and the cover  110  may be made out of iron, aluminum, or any other suitable material. One or more conductors, such as the conductor  115 , run through the base  105  of the seal  100 . The conductor  115  enters and exits the base  105  through two conduit attachment points  120   a  and  120   b  that are located on opposite sides of the seal  100 . The conduit attachment points  120   a  and  120   b  are threaded such that an electrical conduit containing the conductor  115  may be screwed into the base  105 . The conduit attachment points  120   a  and  120   b  provide access to the center of the base  105  until a sealing compound is placed in the base  105 .  
         [0032]     The seal  100  may be used as a standalone, or primary, conduit seal, as a backup, or secondary, seal to a primary conduit seal, or as a drain seal. When the seal  100  is used as a secondary seal, conduits may be attached to each of the conduit attachment points  120   a  and  120   b.  When the seal  100  is used as a primary seal, a conduit may be attached to one of the conduit attachment points  120   a  and  120   b,  while the other of the conduit attachment points  120   a  and  120   b  is directly connected to a process area. For ease of discussion, the following description assumes that the seal  100  is being used as a secondary seal.  
         [0033]     Two venting points  125   a  and  125   b  provide access to the center of the base  105  even after the sealing compound has been placed in the base  105 . As illustrated below with reference to  FIG. 2 , a vent tube connecting the two venting points  125   a  and  125   b  is perpendicular to a line extending between the two conduit attachment points  120   a  and  120   b.  The venting points  125   a  and  125   b  may be blocked with plugs to prevent fluids and vapors from exiting the seal  100 . In addition, a pressure gauge may be attached to one of the venting points  125   a  and  125   b  to measure the pressure within the seal  100 . The pressure gauge also may be positioned entirely within the vent tube, and may be accessed through conductors that extend out of one of the conduit attachment points  120   a  and  120   b.  An explosion-proof drain, a breather, or a rupture disk also may be attached to the venting points  125   a  and  125   b.  Additional pipes or conduits that lead to the outside atmosphere also may be attached to the venting points  125   a  and  125   b.  The additional pipes or conduits may lead to additional seals that lead to the outside atmosphere such that multiple seals are connected in series.  
         [0034]     A nozzle  130  extends from the top of the cover  110  and permits access to the center of the base  105  through an access port  135 . The access port  135  and the nozzle  130  are used to inject the sealing compound into the base  105 . The access port  135  may be blocked with a plug to prevent access to the inside of the seal  100  once the sealing compound has been injected into the base  105 . Since the sealing compound expands upon being injected into the base  105 , the plug may also serve to prevent the sealing compound from exiting the base when the sealing compound expands. The seal  100  can be attached to a surface with fasteners, such as screws, that extend through a pair of attachment points  140   a  and  140   b.    
         [0035]     Referring to  FIG. 2 , one implementation of the base  105  of a seal  100  may accommodate one or more conductors, such as the conductors  115   a - 15   d,  for the purpose of sealing an electrical conduit containing those conductors from harmful vapors. The conductors  115   a - 115   d  enter and exit the base  105  through the conduit attachment points  120   a  and  120   b,  where the electrical conduits that contain the conductors  115   a - 115   d  are attached to the base  105 .  
         [0036]     The seal  100  prevents the migration of harmful vapors from a conduit attached to one of the conduit attachment points  120   a  and  120   b  to a conduit attached to the other of the conduit attachment points  120   a  and  120   b.  To this end, a sealing chamber  245  within the base  105  is filled with the sealing compound to prevent harmful vapors from entering the seal  100  at one of the conduit attachment points  120   a  and  120   b  and exiting at the other of the conduit attachment points  120   a  and  120   b.    
         [0037]     The venting points  125   a  and  125   b  do not provide access to the sealing chamber  245 . Instead, the venting points  125   a  and  125   b  attach to the opposite ends of a vent tube  250 . Any vapors or fluids that enter the seal  100  may enter the vent tube  250 . After entering the vent tube  250 , the vapors may exit the seal  100  through the venting points  125   a  and  125   b,  if the venting points  125   a  and  125   b  are not capped. If the venting points are capped, vapors entering the vent tube  250  may be detected using a pressure gauge positioned within or connected to the vent tube  250 .  
         [0038]     Referring to  FIG. 3 , a cross sectional view of the seal  100  taken along section  3 - 3  reveals the inner configuration of the seal  100 . The base  105  and the cover  110  are placed together to form the chamber  245  through which conductors  115   a  and  115   b  extend.  
         [0039]     The nozzle  130  on the cover  110  of the seal  100  is used to inject the sealing compound  355  into the base  105 . As shown, the sealing compound  355  has been allowed to expand and harden within the base  105  and the cover  110  of the secondary process seal  100 . In one implementation, the sealing compound  355  is a two-part mixture that starts to expand once the two parts are mixed. The sealing compound  355  expands to approximately four times its size immediately after being mixed. As expansion occurs, the sealing compound  355  moves between the conductors  115   a  and  115   b  to prevent the conductors  115   a  and  115   b  from touching each other or the sides of the base  105 . The cover  110  may be screwed onto the base  105  to hold the base  105  and the cover  110  together to confine the expanding sealing compound  355  within the sealing chamber  245 . At full expansion, the sealing compound  355  extends within the base  105  approximately to the hub stops  360   a  and  360   b  at the edge of the base  105 .  
         [0040]     In one implementation, the sealing compound  355  is provided in a self-contained mixing and applying cartridge. The two parts or materials of the sealing compound  355  are separated by a barrier, such as a foil barrier, partway between a top and bottom of the cartridge. A mixing rod is coupled to a plunger within the cartridge. After the barrier between the two materials is broken, the plunger is moved up and down within the cartridge with the mixing rod to combine the two materials. After the two materials have been mixed, a nozzle is attached to the cartridge, and the mixing rod is used to force the mixed sealing compound  355  out of the cartridge through the nozzle. The nozzle is placed in the access port  135  of the nozzle  130  of the cover  110  so that the sealing compound may be injected into the base  105 . A plug is quickly placed over the access port  135  of the nozzle  130  to prevent the sealing compound from expanding outside of the chamber  245 .  
         [0041]     In one implementation, the sealing compound  355  is Chem-Cast 637 sealing foam that includes Chem-Cast 637 isoocyanate and Chem-Cast 637 polyol. Isocyanate is a dark brown liquid that is insoluble in water with a boiling point of 392° F. (200° C.), a vapor density of 0.00016 (mm Hg), and a specific gravity of 1.2 g/mL. Polyol is a gray liquid, partially soluble in water with a specific gravity of 1.05 g/mL. When mixed together, the resultant material is gray in color and has a rise time of 1.5-2.5 minutes and a gel time of 4-5 minutes. When fully cured, the foam density is 15-20 lb/ft 3 . The compression strength is greater than 60 psi, the porosity is greater than 900% closed cell, and the water absorption is less than 1%.  
         [0042]     Chem-Cast 637 is a fire resistant two-part rigid polyurethane foam that expands to form a dense, high strength foam and has excellent adhesion to many surfaces without the use of primers. The sealing compound  355  should be held between 4° C. and 29° C. The sealing compound  355  may be used in various hazardous areas, including Class I, Division  1  &amp;  2 , Groups A., B, C, .D and Class I, Zones  0 ,  1 , &amp;  2 . Chem-Cast 637 is available from Chemque, Inc. of Indianapolis, Ind.  
         [0043]     In further implementations, the sealing compound  355  may be a single material that may start expanding at a controlled time, such as by exposure to air or other gases or by electrical stimulation, heat or any other controllable event.  
         [0044]     Since the sealing compound  355  does not enter the vent tube  250 , the vent tube  250  provides a port through which any vapors that pass through the conductors  115   a  and  115   b  may escape. The vent tube  250  includes a lower half  365  and an upper half  370 . The conductors  115   a  and  115   b  fit through openings defined between the lower half  365  and the upper half  370  of the vent tube  250 .  
         [0045]     During assembly and installation of the seal  100 , the lower half  365  is placed in the base  105  and the conductors  115   a  and  115   b  are placed across the lower half  365 . The upper half  370  then is placed over the lower half  365  and the conductors  115   a  and  115   b  to form the vent tube  250 . The cover  110  then is screwed onto the base  105  and the sealing compound  355  is injected to complete the seal  100 .  
         [0046]     Referring to  FIG. 4 , tube half  365 , which is identical to tube half  370 , includes a pair of teeth  475   a  and  475   b  near one end that mate with a pair of indentations  480   a  and  480   b  near the opposite end of the other tube half. A snap fit between the teeth  475   a  and  475   b  and the indentations  480   a  and  480   b  holds the two halves  365  and  370  together to form the cylindrical vent tube  250 .  
         [0047]     The tube half  365  also includes notches  485   a - 485   h  between the teeth and the indentations. More particularly, the notches  485   a - 485   d  are on one side of the tube half  365 , and the notches  485   e - 485   h  are on an opposite side of the tube half  365 . The notches  485   a - 485   h  form holes through which the conductors  115   a  and  115   b  pass when combined with notches from the tube half  370 . For example, one of the conductors may pass through a hole formed by the notches  485   a  and  485   e  and corresponding notches from the tube half  370 .  
         [0048]     Each half  365  of the vent tube  250  also includes tapered ends  490   a  and  490   b  that fit into the venting points  125   a  and  125   b.  The sealing compound may not form a tight seal against the conductors. Instead, there may be a small gap between the sealing compound and the conductor through which vapors can flow. As a result, the vapors may move from the electrical conduit and into the seal  100  along the path of the conductors  115   a  and  115   b.  As a result, the vapors may enter the vent tube  250  with the conductors through the holes formed by the notches  485   a - 485   h  from the lower half  365  and corresponding notches from the upper half  370  of the vent tube  250 . The vapors exit the vent tube  250  through the venting points  125   a  and  125   b  rather than the holes formed by the notches  485   a - 485   h  and the corresponding notches because there is less resistance to flow out of the venting points  125   a  and  125   b  than to flow through any gaps defined between the conductors and the notches  485   a - 485   h  or the sealing compound.  
         [0049]     Referring to  FIG. 5 , a seal  100  may have a plug  570  or a pressure gauge  575 , an explosion-proof drain, a breather, a rupture disk, or a tube leading to a well vented area installed in the venting points  125   a  and  125   b.  When simultaneously installed in both venting points  125   a  and  125   b,  the plug  570  and the pressure gauge  575  block any vapors that enter the vent tube  250 , which connects to the venting points  125   a  and  125   b,  from exiting the seal  100 . The pressure gauge  575  also measures the pressure inside the seal  250 . Alternatively or additionally, a pressure gauge could be installed entirely within the vent tube  250 , and the venting points  125   a  and  125   b  could both be blocked with plugs  570 . In this case, the pressure gauge  575  may be accessed through conductors that extend out of one of the conduit attachment points  120   a  and  120   b.    
         [0050]     Referring to  FIG. 6 , an assembly process  600  is used to assemble a seal, such as the seal  100  of  FIG. 1 . The assembly process  600  allows for a quick and simple installation of the seal for protection against leakage of harmful fluids and vapors into electrical conduits. To ensure a proper fit, a base of the seal is attached to an electrical conduit to be sealed ( 605 ). The conduit may be attached by the base by screwing the conduit into a threaded conduit attachment point of the base, such as one of the conduit attachment points  120   a  and  120   b  of  FIGS. 1-3 .  
         [0051]     A bottom half of a vent tube into the base of the seal ( 610 ). One or more conductors that run through the conduit are threaded through one of the conduit attachment points in the base and are brought into the center of the base ( 615 ). The conductors are fit into the notches in the bottom half of the vent tube and are taken out of the base through a second conduit attachment point in the base ( 620 ).  
         [0052]     The top half of the vent tube then is placed over the bottom half of the vent tube and the conductors ( 625 ). Notches in the top half of the vent tube line up with notches in the bottom half and fit over the conductors. The top half is snapped together with the bottom half to create the vent tube. Placing the two halves of the vent tube together holds the conductors in place within the base and provides a pathway for the vapors to leave the secondary process seal.  
         [0053]     A cover is placed over the base ( 630 ). The cover may be screwed onto the base to hold the base and the cover together. A pressure gauge is attached to the base ( 635 ). The pressure gauge attaches to one of the venting points on the outside of the base, or it may be placed within the vent tube. A plug may also be inserted into a venting point to prevent the vapors from exiting the base ( 640 ).  
         [0054]     A sealing compound is injected into the base through a hole in the cover ( 645 ). Immediately after the sealing compound is injected into the base, a plug is placed into the hole in the cover to contain the sealing compound as it expands to fill the inside of the base ( 650 ). When expanded and hardened, the sealing compound forms an explosion-proof seal that prevents the migration of vapors down the conduits to which the seal is attached.  
         [0055]     Referring to  FIGS. 7 and 8 , a second implementation of a seal  700  also includes a base  705  and a cover (not shown). The base  705  is similar to the base  105  of  FIG. 1 , and the cover is similar to the cover  110  of  FIG. 1 . Conductors  715   a - 715   d,  which are similar to the conductors  115   a - 15   d  of  FIGS. 1-3 , run through the base  705  of the seal  700 . The base  705  includes conduit attachment points  720   a  and  720   b,  venting points  725   a  and  725   b,  and attachment points  740   a  and  740   b,  all of which are similar to the corresponding components of the seal  100  of  FIG. 1 . The base  705  and the cover form a sealing chamber  745  that is similar to the sealing chamber  245  of  FIG. 2 . A sealing compound that is similar to the sealing compound  355  of  FIG. 3  is injected into the chamber  745  through a port in the cover. The base  705  also includes a vent tube  750  and a pressure relief tube  755  that enable harmful fluids or vapors that enter the seal  700  to be vented from the seal  700 . Plugs, pressure gauges, explosion proof-drains, breathers, rupture disks, or pipes that lead to the outside atmosphere may be attached to the venting points  725   a  and  725   b  to monitor, contain, or divert the harmful fluids or vapors.  
         [0056]     Referring also to  FIG. 9 , the vent tube  750  includes tapered ends  905   a  and  905   b,  a port  910 , and wire wells  915   a - 915   e.  The vent tube  750  may include a single component or multiple interlocking components. The vent tube  750  may be made of plastic or a flexible material, such as silicone rubber.  
         [0057]     The tapered ends  905   a  and  905   b  fit into the venting points  725   a  and  725   b,  thereby connecting the vent tube  750  to the venting points  725   a  and  725   b.  As a result, harmful vapors or fluids that enter the vent tube  750  may exit the seal  700  through the venting points  725   a  and  725   b.    
         [0058]     The harmful fluids or vapors enter the vent tube  750  through the port  910 , which leads to the interior of the vent tube  750 . The pressure relief tube  755  connects to the vent tube  750  through the port  910 . The pressure relief tube  755  extends out of the seal  700  and into an electrical conduit connected to the seal  700  at one of the conduit attachment points  720   a  and  720   b.  As a result, pressurized fluids within the conduit may enter the pressure relief tube  755 , and the fluids may flow through the pressure relief tube  755  to the vent tube  750  through the port  910 . The fluids exit the vent tube  750  through the venting points  725   a  and  725   b  rather than through the port  910  because there is less resistance to flow out of the venting points  725   a  and  725   b  than to flow through the port  910 . The pressure relief tube  755  may be made of plastic or a flexible material, such as silicone rubber. The port  910  may be tapered to create a tight fit between the vent tube  750  and the pressure relief tube  755 .  
         [0059]     The conductors  715   a - 715   d  run across the vent tube  750  and fit into the wire wells  915   a - 915   e.  The wire wells  915   a - 915   e  are indentations that are molded into an outer surface of the vent tube  750 . The wire wells  915   a - 915   e  extend perpendicularly across the vent tube  750  such that the conductors  715   a - 715   d  may be placed within the wire wells  915   a - 915   e.  The vent tube  750  may be oriented within the base  705  such that the wire wells  915   a - 915   e  are located near the cover of the seal  700 . The wire wells  915   a - 915   e  organize and provide spaces between the conductors  715   a - 715   d  within the seal  700 .  
         [0060]     Referring to  FIG. 10 , an assembly process  1000  is used to assemble a seal, such as the seal  700  of  FIG. 7 . The process  1000  is similar to the process  600  of  FIG. 6 . The process  1000  begins when a base of the seal assembly is attached to an electrical conduit to be sealed ( 1005 ). The conduit may be attached by the base by screwing the conduit into a threaded conduit attachment point of the base, such as one of the conduit attachment points  720   a  and  720   b  of  FIGS. 7 and 8 .  
         [0061]     A vent tube, such as the vent tube  750  of  FIGS. 7 and 9 , is inserted into the base of the seal, such as the base  705  of  FIG. 7  ( 1010 ). The vent tube may be inserted into the base such that tapered ends of the vent tube, such as the tapered ends  905   a  and  905   b  of  FIG. 9 , fit into venting points of the base, such as the venting points  725   a  and  725   b  of  FIG. 7 . Furthermore, the vent tube may be oriented such that wire wells of the base, such as the wire wells  915   a - 915   e,  are located near an opening of the base over which a cover may be placed.  
         [0062]     One or more conductors that run through the conduit are threaded through a conduit attachment point of the base, such as one of the conduit attachment points 720 a  and  720   b  of  FIG. 7 . As a result, the conductors are brought into the center of the base ( 1015 ). The conductors are brought across the top of the vent tube and are fit into the wire wells of the vent tube ( 1020 ). The conductors are threaded through a second conduit attachment point out of the base.  
         [0063]     A pressure relief tube, such as the pressure relief tube  755  of  FIG. 7  is inserted into the base ( 1025 ). The pressure relief tube may be inserted into the base through the same conduit attachment point through which the conductors were inserted into the base. Alternatively, the pressure relief tube may be inserted into the base through the opening over which the cover may be placed. Harmful fluids and vapors from the conduit to which the seal is to be attached may enter the pressure relief tube. To enable venting of the harmful fluids and vapors that may enter the pressure relief tube, one end of the pressure relief tube is inserted into a port of the vent tube ( 1030 ). As a result of the orientation of the vent tube, the port may point towards the conduit attachment point at which the conduit is attached to the seal. An opposite end of the pressure relief tube may be inserted into the conduit through the conduit attachment point.  
         [0064]     The cover is placed over the base ( 1035 ). The cover may be screwed onto the base to hold the base and the cover together. Plugs, pressure gauges, or other mechanisms for containing, monitoring, or diverting the harmful fluids may be attached to the venting points of the base. Alternatively or additionally, one or more pressure gauges may be placed entirely within the vent tube.  
         [0065]     A sealing compound is injected into the base through a hole in the cover ( 1040 ). Immediately after the sealing compound is injected into the base, a plug is placed into the hole in the cover to contain the sealing compound as it expands to fill the inside of the base ( 1045 ). When expanded and hardened, the sealing compound forms an explosion-proof seal that prevents the migration of vapors down the conduits to which the seal is attached.  
         [0066]     Referring to  FIG. 11 , an electrical system  1100  may include multiple seals  700   a  and  700   b.  The seals  700   a  and  700   b  are connected by a conduit  1105 . Stranded conductors  1110   a - 1110   d  run into the seal  700   a.  Solid conductors  1115   a - 1115   d  run between the seals  700   a  and  700   b.  Stranded conductors  1120   a - 1120   d  run out of the seal  700   b.  A connector  1125  connects the stranded conductors  1110   a - 1110   d  to the solid conductors  1115   a - 1115   d.  A connector  1130  connects the solid conductors  1115   a - 1115   d  to the stranded conductors  1120   a - 1120   d.  For ease of description, it is assumed that the electrical system  1100  is oriented such that electricity flows from the stranded conductors  1110   a - 1110   d  through the solid conductors  1115   a - 1115   d  to the stranded conductors  1120   a - 1120   d.    
         [0067]     The conduit  1105  is screwed into a conduit attachment point of each of the seals  700   a  and  700   b.  The solid conductors  1115   a - 1115   d  are threaded through the conduit  1105 . In some implementations, a sealing compound that is similar to the sealing compound injected into the chambers of the seals  100  of  FIG. 1  and  700  of  FIG. 7  is injected into the conduit  1105  after the solid conductors  1115   a - 1115   d  have been threaded through the conduit  1105 .  
         [0068]     Each of the stranded conductors  1110   a - 1110   d  and  1120   a - 1120   d  includes a bundle of individual conductors surrounded by insulation. Typically, the insulation is removed from the ends of the stranded conductors  1110   a - 1110   d  and  1120   a - 1120   d  to permit electrical connection to the stranded conductors  1110   a - 1110   d  and  1120   a - 1120   d.  As a result, harmful vapors may enter the stranded conductors  1110   a - 1110   d  and  1120   a - 1120   d  and may occupy the spaces between the individual conductors of the stranded conductors  1110   a - 1110   d  and  1120   a - 1120   d.  Such vapors may not be vented from the seals  700   a  and  700   b  because the vapors are prevented from entering pressure relief tubes of the seals  700   a - 700   b  by the insulation surrounding the stranded conductors  1110   a - 1110   d  and  1120   a - 1120   d.  As a result, the vapors may travel the entire length of the stranded conductors  1110   a - 1110   d  and  1120   a - 1120   d.    
         [0069]     By contrast, each of the solid conductors  1115   a - 1115   d  is a single conductor surrounded by insulation. As a result, the solid conductors  1115   a - 1115   d  do not include any interstitial space through which harmful vapors may flow.  
         [0070]     The connector  1125  connects the stranded conductors  1110   a - 1110   d  to the solid conductors  1115   a - 1115   d  within the seal  700   a  such that any vapors flowing through the stranded conductors  1110   a - 1110   d  do not exit the seal  700   a.  If the stranded conductors  1110   a - 1110   d  were allowed to run completely through the seal  700   a,  then vapors within the seal would be enabled to flow through the seal  700   a  towards the seal  700   b.  Connecting the stranded conductors  1110   a - 1110   d  and the solid conductors  1115   a - 1115   d  with the connector  1125  allows electricity to flow through the seal  700   a  on the conductors  1110   a - 1110   d  and  1115   a - 1115   d  while harmful vapors are prevented from exiting the seal.  
         [0071]     In one implementation, the connector  1125  connects the stranded conductors  1110   a - 1110   d , respectively, by sealing the ends of the stranded conductors  1110   a - 1110   d.  For example, the connector  1125  may represent soldered connections between the ends of the stranded conductors  1110   a - 1110   d  and the ends of the solid conductors  1115   a - 1115   d  within the seal. Soldering the ends of the stranded conductors  1110   a - 1110   d  also seals the ends of the stranded conductors  1110   a - 1110   d,  which prevents vapors that are flowing through the stranded conductors  1110   a - 1110   d  from exiting the stranded conductors  1110   a - 1110   d  within the seal  700   a.    
         [0072]     In another implementation, the connector  1125  may represent pigtail connections between the stranded conductors  1110   a - 1110   d  and the solid conductors  1115   a - 1115   d.  In such a connection, ends of a stranded conductor and a solid conductor are twisted together, and a cap is placed over the twisted portion of the conductors. The cap includes a heat shrink and solder. When the pigtail connection is heated, the heat shrink collapses, and the solder melts, thereby making a solid core to seal the conductors. In other implementations, the connector  1125  may represent a terminal block, twist-on or screw-on connectors, or other connectors.  
         [0073]     The connector  1130  connects the solid conductors  1115   a - 1115   d  to the stranded conductors  1120   a - 1120   d  within the seal  700   b.  As a result, stranded conductors both enter and exit the electrical system  1100 . The connector  1130  may connect the solid conductors  1115   a - 1115   d  to the stranded conductors  1120   a - 1120   d  in a manner similar to how the connector  1125  connects the stranded conductors  1110   a - 1110   d  to the solid conductors  1115   a - 1115   d.    
         [0074]     The seal  700   a  vents harmful vapors flowing down a conduit that includes the stranded conductors  1110   a - 1110   d  that are not flowing through the stranded conductors  1110   a - 1110   d.  Vapors flowing through the stranded conductors  1110   a - 1110   d  encounter the connector  1125 . As a result, the vapors are blocked from exiting the ends of the stranded conductors  1110   a - 1110   d  that are within the seal  700   a.  Therefore, vapors may be trapped within the stranded conductors  1110   a - 1110   d.  Vapors may continue to enter the stranded conductors  1110   a - 1110   d  at ends of the stranded conductors  1110   a - 1110   d  that are within the conduit, thereby increasing the vapor pressure within the stranded conductors  1110   a - 1110   d.  Once the vapor pressure reaches a threshold value, further vapors will not enter the stranded conductors  1110   a - 1110   d.  Instead, those vapors flow down the conduit and are vented through the vent tube and the pressure relief tube.  
         [0075]     Because harmful vapors from the solid conductors  1110   a - 1110   d  may not flow through the solid conductors  1115   a - 1115   d,  and because other harmful vapors flowing into the seal  700   a  are vented by the seal  700   a,  no harmful vapors flow into the seal  700   b.  As a result, the seal  700   b  need not include a vent tube and sealing compound to vent vapors within the seal  700   b.  In fact, the seal  700   b  may act simply as a housing for the connector  1130 . In some implementations the connector  1130  may be included in the seal  700   a,  thereby eliminating the need for the seal  700   b.  In other implementations, the electrical system may include other housings for the connector  1130  that are separate from the seal  700 .  
         [0076]     In some implementations, rather than connecting stranded conductors to solid conductors to prevent vapors from flowing through the conductors, the spaces through which the vapors may flow at the ends of the conductors may be filled. For example, the spaces at the ends of the stranded conductors may be filled with a plastic, metal, or semi-metallic compound. In such implementations, the conductors  1115   a - 1115   d  and  1120   a - 1120   d  and the connectors  1125  and  1130  are not required, and the stranded conductors  1110   a - 1110   d  may flow entirely through the electrical system  1100 .  
         [0077]     Electrical conduits are used throughout as an example of a tube through which conductors may pass into a seal. In other implementations, other pipes, tubes, or conduits may be used. For example, the conductors may run into the seal through a cable gland or through a sealing gland.  
         [0078]     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, the steps in the described process may be performed in a different order, or the seal may be modified to include only a single venting point. Accordingly, other implementations are within the scope of the following claims.