Abstract:
Method and apparatus for internally sealing live low pressure residential gas supply lines, including gas main tap and associated fittings, by applying sealant to the inside surface of the gas line. Sealing assemblies allow tapping and insertion of tools without gas escape to atmosphere, as well as application of sealant under gas pressure passed through a supply line which has the ability to rotate in order to feed itself through elbows and fittings to the point where sealing is required, as well as achieve uniform spray coverage of the target pipe&#39;s inner surface with sealant.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the field of pipeline repair, specifically low pressure gas line repair without service interruption. 
     2. Description of the Related Art 
     Previously, gas line repairs involved expensive and labor-intensive excavation of the gas line for replacement. Insitu gas line repair via insertion of a pipeline lining as described in British Gas plc U.S. Pat. No. 6,056,016 enables sealing via relining of a length of straight piping, but does not enable sealing or repairing of fittings creating bends in the flow path, such as the connections of the supply line to the gas main which could be, for example, a tap and elbow. The current invention solves this problem. 
     SUMMARY OF THE INVENTION 
     The invention apparatus and method are designed to allow a sealant spray coating to be applied to the inside surface of a gas main tap and/or elbow without requiring excavation of the surrounding area. Exposure of the operator to gas is minimal through the use of locking techniques so that the line, while not shut off, may have various tools inserted into it, including the spray head for applying a coating to the inside of the target area of the piping. Nitrogen is used to inflate a sealing bladder once the line has been tapped, allowing change-over from the residence supply gas and metering pipe assembly to a sealing assembly. A polyethylene hose is fed into the pipe. Within the polyethylene hose is a smaller nylon hose whose end is a steering spray head attached to a spring, the spring being rotatable via the nylon hose to allow feeding through any obstacles in the line all the way into the gas main. The steering spray head has nozzles in it through which, while it is rotating, the sealant may be applied, the rotation and spray pattern allowing complete coverage of the inside of the target pipe area. Nitrogen is also used to pressure pump the sealant down the line to the target area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic of a typical low pressure residential gas installation from the gas main to the residential gas meter. 
     FIG. 2 is a schematic diagram of an apparatus for sealably penetrating the live gas line. 
     FIG. 3 is a schematic of an apparatus for feeding the sealant supply line to the target area. 
     FIG. 4 is a schematic of an apparatus for applying the sealant through the piping to the target area. 
     FIG. 5 is a schematic of a stuffer gasket. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Large numbers of gas main and residential gas supply lines have been installed which now requires maintenance. Often, maintenance is accomplished by digging down to the buried gas lines and physically replacing them. Often, due to labor costs, natural features or construction subsequent to the original piping installation, digging is not economically feasible. Technology exists for lining straight lengths of residential gas supply lines with polyethylene, but it cannot be extended all the way through to the gas main, therefore leaks may exist at the gas main tapping fitting, and associated service connection fittings. 
     A typical low pressure residential gas installation is demonstrated by FIG.  1 . The gas main  1  may be a considerable distance from the residence, the gas line residential supply line  4  typically of steel or black malleable iron piping. At the gas main, the residential gas supply line  4  will mate to the gas main  1 , for example, through an elbow  3  and gas main tap  2 . To repair a leak or corrosion in the area of the gas main tap  2  and elbow  3  without disconnecting service to the gas main, as shown in FIG. 1, the user will find the residential gas meter attached to the leaking line in question, and attach the clamp-on tapping fitting  20  to the first fitting  7  in the residence, as shown in FIG.  2 . This will be found either below ground at the external gas meter, or if it is internal to the residence, in the basement at the first connection past the residence foundation  6  where the gas supply line  4  is coming through the basement wall. The clamp-on tapping fitting  20  comprises a metal encapsulating collar with a gasket which is held in place by chains wrapped around the target pipe. Coming off at an angle is a threaded piece to which a sealing assembly  32  is attached. An appropriately sized sealing assembly  32  and/or adapter coupling is used to mate to the desired component. The sealing assembly  32  consists of a ball valve  21 , an intermediate length of piping  19  with a bleed/sample port  22  mounted into it, and a stuffing box  24 . The stuffing box  24  allows the insertion of tooling while sealing around the tooling. Stuffing boxes with different internal sealing diameters are matched to the object being sealably passed through them. For ease of use, a quick release  23  may be used between the intermediate length of piping  19  and the stuffing box  24 . If the quick release  23  is not used, the intermediate length of the piping  19  is unscrewed from the ball valve  21  when tooling is inserted into the sealing assembly  32 . 
     Sealing assembly  32  is opened by unscrewing intermediate length of piping  19  from ball valve  21  to allow insertion of tapping drill bit  25 . Tapping drill bit  25  has solid drive  26  which is inserted through the stuffing box  24 . Then intermediate length of piping  19  is reattached, placing the tapping drill bit  25  in the sealing assembly  32  intermediate area. The drive end of solid tapping drive  26  is then attached to a pneumatic or electric drill  27 . With the tapping drill bit  25  sealed within the sealing assembly  32 , the ball valve  21  is opened, and the tapping drill bit  25  inserted up to the clamp-on tapping fitting  20  which guides the drill bit  25  into the target fitting  7 . Once the tapping drill bit  25  has penetrated into the first fitting  7  in the residence, the tapping drill bit  25  is retrieved into the intermediate section of the sealing assembly, and the ball valve  21  is closed. Once the ball valve  21  is closed, intermediate length of piping  19  is unscrewed, and the stuffing box  24  removed along with the tapping drill bit  25 . 
     An inflatable sealing bladder with attached polyline  29  and schrader valve  30  is connectable to nitrogen supply  31 . The schrader valve  30  is inserted into stuffing box  24 , and polyline  29  pulled through so that inflatable sealing bladder  28  is introduceable into the sealing assembly  32  intermediate area, and intermediate length of piping  19  reattached to the ball valve  21 . Then, ball valve  21  is opened, and the inflatable sealing bladder  28  fed into gas supply line  4  to a point beyond the residence foundation  6 . When activated by connection of the schrader valve  30  to nitrogen supply  31 , the nitrogen supply  31  feeds nitrogen through the polyline  29  to the inflatable sealing bladder  28 , inflating it, thereby sealing the gas supply line  4 . The seal may be verified by checking the bleed valve/sample port  22  for pressure. If no pressure is present, the inflatable sealing bladder  28  may reasonably be assumed to have made a good seal. With the inflatable sealing bladder  28  sealing the gas supply line  4 , the sealing assembly  32  may be removed, as well as the clamp-on tapping fitting  20  and the first fitting  7 , and attached gas meter  9  and shut-off valve  8 . Outlet valve  10  is also shown in this figure. The polyline  29  is sealed by a schrader valve  30  when it is disconnected from the nitrogen supply  31  to allow feeding through the sealing assembly  32 , clamp-on fitting  20 , and the first fitting  7  in the residence. 
     With the first fitting  7  in the residence and associated gas meter piping  8 ,  9  removed, an appropriately sized sealing assembly  32  is attached directly to the gas supply line  4  as it exits the residence foundation  6 . 
     The inflatable sealing assembly is attached again with the polyline  29  of the inflatable sealing bladder  28  fed through the stuffing box  24 , and the schrader valve  30  pressed to release the pressure in the inflatable sealing bladder  28 , deflating it, allowing it to be pulled back to the intermediate section between stop valve  21  and the stuffing box  24 . Then the ball valve  21  is closed, and the quick-release  23  opened to remove the inflatable sealing bladder and its stuffing box  24 . 
     As shown in FIG. 3, the feeding/sealing assembly consists of a steering spray head  40  which is attached to a pliable polyline  42  about which a spring  41 , also connected to the steering spray head, is coiled up to a barbed coupling  43  which attaches the pliable polyline  42  to the stiff polyline  44 , which is stiffer, allowing rotation of the drive head without shearing the polyline. In trials, “nylon 11” was used for the pliable polyline  42  and “nylon 6” was used for the stiff polyline  44 . The polyline is inside a ⅝ inch polyethylene sleeve  45 . The ⅝ inch size is selected to allow the passage of the assembly through a common residential gas supply line, including couplings  11 , street shut-off valve  5  and a “Renu”™ repaired piping system. The stiff polyline  44  and ⅝ inch polyethylene sleeve  45  are rotatably and sealably attached at a modified service head adapter  46 . The stiff polyline  44  is attached via adapter coupling  47  to a length of stainless steel tubing  48  which is connected to a pneumatic or electric drill  27 . Stuffing box  49  is attached to modified service head adapter  46 , sealing the outer diameter of stainless steel tubing  48 . Fed through a stuffing box  24 , the drive and nozzle heads and spring  41  and ⅝ inch polyethylene sleeve  45  are fed into the intermediate area between the stuffing box  24  and the ball valve  21 . Then the ball valve  21  is opened, and the sealing/feeding line is fed down the piping a predetermined length (pre-measured by pipe location equipment) until a resistance is felt, indicating that the gas main elbow  3  (or other fitting equipment) until a resistance is felt, indicating that the gas main elbow  3  (or other fitting associated with the gas main  1 ) has been reached. Once reached, the ⅝ inch polyethylene sleeve  45  is marked with tape, for example, and then is withdrawn approximately 6 inches. A reference mark is made on the polyethylene sleeve  45  to indicate the position of the sleeve within the service line under repair. Next, the drive is turned on, and the steering head  40 , while spinning, engages the edges and surfaces of the elbow, feeding around the corners, all the way to the gas main  1 . The steering spray head  40  may have a friction pattern  99  on its outer surface. The spring  41  guides the polyline as it spins, preventing kinking in the pipe and abrasion against the pipe surface which might cause debris to break off and foul the line. 
     Once the gas main  1  has been reached by the steering spray head  40 , the sealant assembly shown in FIG. 4 is attached. The stainless steel tubing  48  is attached via adapting compression fitting  50  to the rotating union  51 , which is driven by pneumatic/electric drill  27 . From the rotating union  51 , the polyline  55  connects to a pressure pot  52 . The pressure pot uses overpressure to force a sealant  53  up the polyline to the nozzle/drive head  40 . In this application, the pressure pot  52  is driven by a 50 psi nitrogen supply  31 , connected via polyline  56  to nitrogen supply  31 , allowing nitrogen  54  to fill the pressure pot  52 , thereby forcing sealant  53  down the polyline  55  to the rotating union  51 , through the rotating union  51  and up the stiff polyline  44  to the steering spray head  40 . With the sealant being applied by pressure, the steering spray head  40  is spun by the pneumatic/electric drill  27  via the rotating union  51 . As the sealant goes through the line and out the steering spray head  40 , a spray pattern is created covering the inside of the pipe. As the line is pulled backwards, the exact coverage area may be repeatedly coated with sealant. 
     The sealant may be “Locktite type 290”©, “Carboline® rust bond penetrating sealer”, “Vulkem 460-462”, “Diamant® plastic metal”, “Diamant® Dichtol”, “Diamant® Ultrametal”, or other polymer, resin, epoxy or urethane suitable for coating the inside of a pipe. “BYK 333”© may be used to improve substrate wetting ability. Spray coverage exists along the length of horizontal play allowed by the stainless steel tubing  48  between the rotating union  51  and the ⅝ inch polyethylene cover  45 . Repeated applications over longer distances may be achieved by partially withdrawing the polyethylene sleeve  45  and enclosed polyline and covering another area. A relatively small amount of sealant is used, perhaps one-third to one-half liter of sealant for a typical multiple coating repair to a gas main tap and elbow. When pumping is nearly complete, the sealant supply may be discontinued and the sealant remaining in the polyline chased down the polyline by the nitrogen  54 , thereby conserving the sealant  53 . Once sealing is complete, the sealing/feeding assembly is withdrawn to the sealing assembly intermediate area and the ball valve  21  is closed. Then the stuffing box  24  with driver assembly may be released by the quick-release fitting  23 . 
     To seal the repaired line during reinstallation of the residential gas meter and replacement first fitting  7 , a stuffer gasket  57 ,  58 , shown in FIG. 5, is inserted into the sealing assembly up through the stuffing box  24  to the ball valve  21 . Then the ball valve  21  is opened, and the stuffer gasket  57  is inserted into the gas supply line  4 , sealing it. A good seal may be verified again by checking the bleed valve/sample port  22 . If no pressure exists, a good seal may be reasonably assumed to have been achieved. With the stuffer gasket  57  in place, the sealing assembly  32  may be removed. A new first fitting  7  and new residence shut-off valve  8  is installed. A sealing assembly  32  is then attached to new residence shut-off valve  8 . The stuffer gasket  57 ,  58  is then retrieved through a new first fitting  7  in the residence and residence shut-off valve  8 . As the stuffer gasket  57  clears the residence shut-off valve  8 , it is closed and the repair completed.