Abstract:
A method of repairing leakage in pipelines comprising the steps of forming a first and second openings ( 14   a,    14   b ) in the pipeline ( 10 ) upstream and downstream, respectively, of the leakage location, inserting through the first opening ( 14   a ) a first body (C 1 ), filling the space arrear of the first body (C 1 ) with a first viscose sealing material (M 1 ), inserting through the first opening ( 14   a ) a second body (C 2 ) arrear of the first viscose sealing material (M 1 ) compressing the first sealing material by applying a pressure against the first and the second bodies (C 1,  C 2 ) in opposite directions, causing the first and second bodies (C 1,  C 2 ) and the compressed first sealing material (M 1 ) to move in unison in the direction of the second opening ( 14   b ), and retrieving the first and second bodies (C 1,  C 2 ). Preferably, the method is performed using three bodies (C 1,  C 2,  C 3 ) and two sealing materials (M 1,  M 2 )

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the repair or restoration of local cracks in pipes, in particular of large diameter water, fuel or gas underground pipelines. More specifically the invention concerns the repair of such pipes when the exact site to be repaired is either unknown or unreachable. 
       BACKGROUND OF THE INVENTION 
       [0002]    In order to conduct water, fuel or gas over large distances, pipelines that span immense lengths are installed. Occasionally, due to corrosion or other different wearing processes, small cracks might occur in the pipes, resulting in a leakage of the fluid that flows through the pipe. Since the pressure in such pipes may reach up to 100 at., the fluid is rapidly lost into the soil. 
         [0003]    A leakage is usually discovered by a sharp pressure-drop, or by the recognition of a stain over the leakage location, indicating that a large amount of the fluid has already been lost. Besides the environment-harming aspect, such leakages may cause the loss of thousands of dollars per hour. 
         [0004]    The repair of underground pipelines poses a series of complicated technological problems considering the relevant factors, mainly, difficult accessibility to the damaged part of the pipelines if welding or complete replacement thereof needs to be applied. This is particularly true when considering pipelines that are thousand of kilometers long or pipelines that lay underneath buildings and roads. 
         [0005]    Also due to the high pressure prevailing in the pipeline, the use of simple adhesives and other common sealing agents had to be ruled-out. 
         [0006]    The closest prior art known to applicants is Russian Patent No. 2063273 (Appln. No. 92007181/26 filed Nov. 23, 1992), describing a method of in-situ repair (namely from the inside of the pipe), by injecting specific chemical substances from both sides of the damaged location. 
         [0007]    It is the prime object of the present invention to provide a more efficient method of in-situ repair of pipelines. 
         [0008]    It is a further object of the invention that the actual repair process be completed instantly, reducing to a minimum the time period during which the flow through the pipeline must be discontinued. 
         [0009]    It is a still further object of the invention to offer one or more sealing agents formulations especially suitable for the purposes the invention herein disclosed. 
       SUMMARY OF THE INVENTION 
       [0010]    According to the invention there is provided a method of repairing leakage in pipelines comprising the steps of forming a first opening in the pipeline upstream of the leakage location, forming a second opening in the pipeline downstream of the leakage location, inserting through the first opening a first body, conforming the size of the pipeline, into the pipeline downstream of the first opening, filling the space arrear of the first body with a first viscose sealing material, inserting through the first opening a second body conforming the size of the pipeline into the pipeline arrear of the first viscose sealing material, compressing the first sealing material by applying a pressure against the first and the second bodies in opposite directions, causing the first body, the compressed first sealing material and the second body to move in unison in the direction of the second opening, and retrieving the first and second bodies from the pipeline through the second opening. 
         [0011]    The method preferably comprises the further steps of filling the space arrear of the second body with a second viscose sealing material, inserting through the first opening a third body, conforming the size of the pipeline, into the pipeline arrear of the second viscose sealing material, compressing the first and second sealing materials by applying a pressure against the first and the third bodies in opposite directions, causing the first body, the compressed first sealing material, the second body, the compressed second sealing material, and the third body to move in unison in the direction of the second opening, and retrieving the first, second and third bodies from the pipeline through the second opening. 
         [0012]    The said bodies are preferably spherical, made of a semi-rigid material such as Polyurethane. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    These and additional constructional features and advantages of the present invention will become more readily understood in the light of the ensuing description of preferred embodiments thereof, given by way of example only, with reference to the accompanying drawings, wherein— 
           [0014]      FIG. 1  is a schematic layout of a typical pipeline with a leaking portion and including a preparatory stage of the repair method according to a preferred embodiment of the present invention; 
           [0015]      FIGS. 2   a - 2   g  represent further steps of the method; and 
           [0016]      FIGS. 3   a  and  3   b  illustrate a way of nesting the respective sealing materials in their desired locations. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    In  FIG. 1  there is shown a length of pipeline  10  buried in ground G. Anywhere upstream of the pipeline  10  there is provided a shutting valve  12 . 
         [0018]    A leaking location L has been identified, typically due to a hole or a crack caused by excessive corrosion developed over many years of use. 
         [0019]    The first stage of the repairing method consists of shutting-off the flow in the pipe by the valve  12  and digging-away the ground over the pipe at two distanced locations A and B at both sides of the leaking location L. The distances A to L and B to L need not be equal, and in fact selected according to the accessibility conditions which may change from one site to another. 
         [0020]    At each location A and B, the pipe is torch-cut so as to form a first circular opening  14   a,  and a second circular opening  14   b,  respectively, both of a diameter equal to that of the pipe  10 . Up-rise pipe sections (“manholes”)  16   a  and  16   b  are welded or otherwise affixed to the pipe  10 , as shown. 
         [0021]    In the next stage ( FIG. 2   a ), a first spherical body C 1  is inserted through the manhole  16   a  down into the pipe  10 . Right thereafter a viscose sealing material M 1 , the chemical formula of which will be given below, is filled into the pipe, followed by a second spherical body, C 2  ( FIG. 2   b ). The bodies C 1  and C 2 , acting as pistons, are preferably made of a semi-rigid material such as Polyurethane so that they may easily pass through the pipe which may have bumps and protrusions along its inner surface. 
         [0022]    It should be emphasized at this stage that the sealing method as proposed according to the present invention can be applied by using the spherical bodies C 1  and C 2  and a viscose sealing material M 1  only, in the exact manner as will be described further below. However, it is highly preferable to use a combination of materials M 1  and M 2 , which needs the introduction of a third spherical body C 3 , as depicted in  FIG. 2   c . The advantages of this last-mentioned feature will be explained in detail below. 
         [0023]    Whether or not the option of  FIG. 2   c  is adopted, the material M 1  (as well as M 2 ) should be compressed during the repair process to allow its penetration into the crack/hole H. 
         [0024]    To this end, pressure should be applied from both sides of the array C 2 -M 1 -C 1  (or C 3 -M 2 -C 2 -M 1 -C 1 ). For this purpose, as seen in  FIG. 2   d , the manholes  16   a  and  16   b  are closed and a pressurized fluid or gas is pumped into the pipe  10  in order to press the bodies C 1 , C 2  and C 3  one against the other and hence compact the materials M 1  and M 2 . 
         [0025]    It is further requested that the pressure P 1  applied from  16   a  be somewhat greater then that P 2  applied from the opposite side, which pressure difference will cause the propagation of the array C 3 -M 2 -C 2 -M 1 -C 1  in unison, in the direction of the manhole  16   b.    
         [0026]    The amount of pressure P 2  that should be applied against the array is preferably given by the formula: 
         [0000]    
       
      
       P 
       2 
       ≧a−b/D  
      
     
         [0000]    wherein:
   P 2 —pressure (bar);   a—an empirical factor that varies between 2.5 and 3.5;   b—an empirical factor that varies between 0.035 and 0.045; and   D—diameter of the pipe (meters).   
 
         [0031]    During the travel of the array, as shown in  FIG. 2   d  and  FIG. 2   e , there will be formed on the inside surface of the pipe  10 , including the crack H, a first layer of the material M 1 , and over it a second layer of the material M 2 . A chemical interaction between these two layers will bring to the solidification of their combination and assure the complete, durable filling of the crack H (see below). 
         [0032]    In the further stage ( FIG. 2   f ) the bodies C 1  and C 2  (and C 3 —if applicable) are retrieved through the manhole  16   b.    
         [0033]    The pipe sections  16   a  and  16   b  are then removed and replaced by covers  18   a  and  18   b  of any conventional type ( FIG. 2   g ). 
         [0034]    According to a preferred embodiment of this invention ( FIG. 3   a ), in order to prevent their spreading away in different directions while passing from the manhole  16   a  into the pipe  10 , the materials M 1  and M 2  are supplied in bags K 1  and K 2 , respectively. 
         [0035]    The bags are preferably made of a readily tearable sheet material, such as cellophane or polyethylene, so that they become ruptured when pressure is applied to the array from both sides ( FIG. 3   b ). Upon the tearing of the bags, the materials will intensively contact and wet the inner surface of the pipe and penetrate the cracks once reaching them. 
         [0036]    Let us now turn to the specification of the materials recommended according to an additional aspect of the present invention. 
         [0037]    In an embodiment wherein only one sealing material M 1  is employed, the material should be selected from the group of conventional hardeners. 
         [0038]    In the preferred embodiment, according to which two materials M 1  and M 2  are used, the materials may consist of a mix of a compound A, a hardener B, a softener S, a filler mineral Z, an elastic filler E and a hard filler D, wherein:
   A is an organic polycondensate compound;   B is a hardener such as phenylenediamine or diamino-difenylsulfone;   S is a softener such as dibutyl phthalate or diphenyl phthalate;   Z is a filler mineral such as ash of granular size ranging between 2 to 15 microns;   E is an elastic filler such as the commercially known “Isoltherm™” (described in U.S. Pat. No. 6,057,378) of size ranging between 4 to 7 millimeters; and   D is a hard filler such as granules of nylon of size ranging between 1 to 4 millimeters.   
 
         [0045]    The proportional amount of each of the components regarding the respective materials is given below (in weight parts). 
       Material M 1   
       [0046]    100 units of component A, 0-10 units of component S, 110-130 units of component Z, and component B, the amount of which is given by the formula: 
         [0000]    
       
      
       B=A*λ−K 
       1  
      
     
       Wherein: 
       [0000]    
       
         K 1 —an empirical factor that varies between 0 and 25; and 
         A—an empirical factor that varies between 0.2-0.45. 
       
     
       Material M 2   
       [0049]    20-60 units of component A, 0-10 units of component S, 50-100 units of component Z and component B, the amount of which is given by the formula: 
         [0000]    
       
      
       B=A*λ+K 
       2  
      
     
       Wherein: 
       [0000]    
       
         K 2 —an empirical factor that varies between 0 and 30; and 
         A—an empirical factor that varies between 02-0.45. 
       
     
         [0052]    Additionally, material M 2  should contain 10-15 units of component E and 5-10 units of component D that are meant to penetrate the crack together with material M 2  and create a partial barrier between the filling materials and the fluid upon restarting of the flow in the pipe, so that the filling will not become washed away. 
         [0053]    The total amount of the sealing materials that should be injected between two adjacent spherical bodies is given by the formula: 
         [0000]      G≧ρD 
         [0000]    wherein:
   G—quantity (tons);   ρ—an empirical factor that varies between 1 and 1.2; and   D—internal diameter of the pipe (meters).   
 
         [0057]    The time that will take for the combination of the materials M 1  and M 2  to solidify is expected to follow the formula: 
         [0000]      T≧γLD 
       Wherein: 
       [0000]    
       
         T—time (hours); 
         γ—an empirical factor that varies between 2.5 and 3.5; 
         L—length of pipe (kilometers); and 
         D—internal diameter of the pipe (meters). 
       
     
         [0062]    After that period of time it will be safe to renew the flow through the pipe without the danger of washing away the seal layer. 
         [0063]    In order to achieve optimal results in regard to the solidification of the combination of these two materials, according to a preferable embodiment, the first material M 1  should contain a certain amount of material M 2 , and the material M 2  should contain a certain amount of material M 1 . This could be achieved either by simply mixing all the ingredients together or by using capsules that contain M 1  and M 2  and inserting them into the bags of M 2  or M 1 , respectively, so that when material M 1  is pushed into the crack, the capsules will break and release a preset quantity of the material M 2 . 
         [0064]    While the invention as herein described includes numerous specifics it should be readily apprehended by those skilled in the art to which the invention pertains that the scope thereof should not be limited by such specifics but rather in and by the appended claims.