Abstract:
There is described a method and an apparatus for testing or isolating a section of pipe, the apparatus comprising a cylindrical mandrel for insertion into a section of pipe, the mandrel including at least one portion of progressively increasing diameter, and at least one seal disposed around the mandrel and actuatable in response to applied fluid pressure to move along the increasing diameter portion of the mandrel, causing the seal member to radially expand into sealing contact with an inner surface of the pipe.

Description:
RELATED APPLICATIONS  
       [0001]    This application is a Divisional Application of U.S. patent application Ser. No. 09/631,645 filed Aug. 2, 2000, which in turn claims priority to Canadian Application No. 2,312,577 filed Jun. 27, 2000, each of which is hereby incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to a tool for testing or isolating a section of any tubing, pipe, flange, fitting, or combination of the same.  
         BACKGROUND TO THE INVENTION  
         [0003]    In industrial applications such as oil or gas refineries, offshore drilling and production platforms, pulp and paper plants, power utilities, pipelines, coiled tubing, oil and gas wells, marine facilities, or any other industry or plant involving piping, the integrity of welds and of flanges or fittings often needs to be tested. In the oil and gas industry, for example, tight environmental and operating regulations exist on emissions from a weld or joint. Further, with thousands of welds in each plant, it is in the industry&#39;s interest to minimize the amount of fluid lost in each weld. Testing tools are therefore required to test the integrity and permeability of each weld. Fittings must also be tested after welding to test and confirm structural strength.  
           [0004]    Furthermore, in these industries it is often necessary to isolate a section of pipe for various reasons. In maintenance applications, safety dictates that when work is being performed on a section of pipe connected to a system, the portion of the pipe being worked on should be isolated from the rest of the system in order to prevent accidental harm to an operator through fluid discharge in the pipe. Also, when TIG welding or welding stainless steel piping, the oxygen level around the weld should be minimized, necessitating a means of isolating the section around a weld in order to introduce a purge gas. Another application is a positive purge with an inert gas through the tool to a vent point.  
           [0005]    These problems are well known, and tools for solving these problems exist in the prior art. For example, U.S. Pat. No. 5,844,127 to Berube et al. teaches a tool to isolate a section of pipe or to test the internal integrity of the pipe. The tool uses two o-rings spaced at a certain distance apart and a method of introducing pressure between the o-rings.  
           [0006]    The problem with this design of tool is that o-rings do not provide a good seal. In order for the tool to be able to be inserted into a pipe, the tool&#39;s diameter must necessarily be less than the inner diameter of the pipe. The difference is made up by using flexible o-rings. The problem is that because the o-rings are flexible, high pressures will cause the o-rings to extrude into the gap between the tool and the pipe wall, diminishing the effectiveness of the seal. This will cause a slow drop in test pressures even though there may be no leak. The test pressure must then be topped up which will negate a true hydro test in accordance with ASME standards B31.1 and 31.3. After the test pressure is released, the extruded seals may remain wedged in the tool/pipeline gap necessitating that the operator disassemble the tool inside the pipeline for piece by piece removal.  
           [0007]    Canadian Patent No. 1,312,557 to Dufort teaches an alternate method whereby a membrane is forced into the pipe wall, creating a seal. However, this tool again has a gap between the tool and the pipe wall, and the membrane will again be distorted under high pressure, negating the effectiveness of the seal.  
           [0008]    Other sealing methods in the prior art including using “torquing” methods to set a seal or metal grip in place. This however results in the introduction of “hoop stress” to the inside or outside of the pipe, distorting the pipe and creating a future weak spot. The use of metal grips also creates problems because the inner surface of the pipe is damaged by the torqued connections, potentially creating future crevice corrosion problems. Also when metals are in contact the potential always exists for galvanic corrosion to occur. The longer the metals are in contact, the more severe this problem becomes.  
           [0009]    Besides sealing deficiencies, the prior art also fails to teach a tool that is able adaptable to the various configurations required in industry. Tools such as &#39;557 to Dufort are solely for testing weld integrity, and do not provide an isolation tool. Patent no. &#39;127 to Berube discusses both isolation and testing, but does not discuss an adaptation of the tool to aid in low oxygen welding. The lack of these capabilities means that other tools must be used, increasing the costs of maintaining and testing pipes.  
         SUMMARY  
         [0010]    The present invention overcomes the deficiencies of the prior art by creating a sealing means which cannot be extruded under operational pressures. It further provides a tool whose configuration can easily be modified in order to accommodate a number of scenarios, making the tool more versatile by allowing the tool to have multiple purposes.  
           [0011]    The present invention uses a novel sealing method in which a seal is compressed into a rigid cavity, preventing the creep problems associated with prior art tools. Because there is no creep, a better seal is formed, allowing tests to be conducted with higher precision results. The lack of creep also makes removing the tool much easier, since the tool will not become jammed within the pipe. This saves the operator time since the tool will not have to be disassembled in situ. The configuration of the seal further allows both low and high pressure sealing, enabling a better seal to be made in either situation. Also, the seal includes a number of ridges along its outer pipe-contacting surface, allowing the seal to accommodate imperfections on the inside wall of the pipe, such as pits or scratches, or to cut through any films or wax buildup on the inside wall of the pipe. All of these improvements create a better seal.  
           [0012]    The seal in the present invention is also non-damaging to the pipe. The tool therefore does not cause scratching, galvanic conductance, or torquing stresses. This is a significant improvement over the prior art since the tool does not weaken the integrity of the pipe being tested.  
           [0013]    The present invention uses the above novel seal in a number of ways, making the present invention versatile. The tool can be configured to test welds by introducing water at high pressure under the weld and monitoring whether the weld can withstand the pressure. The tool can also be used to test a flange by isolating the flange and again introducing water at high pressure, thus determining whether the flange is properly welded to the pipe.  
           [0014]    The tool can further be used to test for leaks in a weld by isolating the section under the weld and introducing helium. By creating a shroud around the outside of the weld and by using a helium testing tool an operator can determine whether or not any leaks exist within the weld.  
           [0015]    The tool can further be used as a welding aid. In welds involving certain types of metals it is important to minimize the oxygen level at the weld. The present tool can be used to isolate the down-pipe section of the pipe being welded to facilitate the introduction of inert gas that can be used to create the proper environment for this type of weld.  
           [0016]    The unique seal and the versatility of the various configurations of the present invention results in a significant improvement over the prior art.  
           [0017]    According to the present invention then, there is provided apparatus for testing or isolating a section of pipe, comprising a cylindrical mandrel for insertion into a section of pipe, said mandrel including at least one portion of progressively increasing diameter; at least one seal member disposed concentrically around said mandrel and actuatable in response to applied fluid pressure to move along said at least one portion, causing said seal member to radially expand into sealing contact with an inner surface of said pipe.  
           [0018]    According to another aspect of the present invention, there is also provided a resilient seal member for sealing against the inner surface of a tubular member to contain fluid pressure, said seal member comprising a first portion normally smaller in outer diameter than the inner diameter of said tubular member and being radially expandable into sealing contact with said inner wall, and a second portion normally biased into slidable contact with said inner surface.  
           [0019]    According to yet another aspect of the present invention, there is also provided a method of containing a resiliently expandable seal member to constrain its extrusion due to pressure, comprising the steps of providing a resilient seal member that expands radially when subjected to a seal setting force for sealing contact with an opposed surface; and contacting said sealing member during its radial expansion against an axially outwardly disposed member that provides a rigid containment surface constraining extrusion of said sealing member. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Preferred embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which:  
         [0021]    [0021]FIG. 1 is a cross sectional view of the prior art method of sealing demonstrating distortion in the o-ring;  
         [0022]    [0022]FIG. 2 is a cross sectional view of the sealing means used in the present invention in an engaged position;  
         [0023]    [0023]FIG. 3 is a cross sectional view of one type of fastening means for the flange testing tool of the present invention;  
         [0024]    [0024]FIG. 4 is a cross sectional view of a second type of fastening means for the flange testing tool of the present invention;  
         [0025]    [0025]FIG. 5 is a cross sectional view of an alternative sealing means for the present invention, particularity suitable for low pressure applications;  
         [0026]    [0026]FIG. 6 is a cross sectional view of the present invention in a weld test configuration with the seals in a retracted position;  
         [0027]    [0027]FIG. 7 is a cross sectional view of the present invention in a weld test configuration with the seals engaged;  
         [0028]    [0028]FIG. 8 is a cross sectional view of the present invention in a flange test configuration;  
         [0029]    [0029]FIG. 9 is a cross sectional view of the present invention in a leak test configuration; and  
         [0030]    [0030]FIG. 10 is a cross sectional view of the present invention in a configuration adapted to isolate a welding area. 
     
    
     DETAILED DESCRIPTION  
       [0031]    [0031]FIG. 1 illustrates a typical sealing configuration for prior art testing tools as outlined above in the background section. In this configuration, testing tool  100  is inserted into pipe  101 . In order to allow insertion of testing tool  100 , the diameter of o-ring supports  102  must necessarily be less than the inner diameter of pipe  101 . This creates a gap between the inner wall of pipe  101  and o-ring supports  102 .  
         [0032]    A seal is created between testing tool  100  and pipe  101  using an o-ring  103 . In order for a proper seal to be made, o-ring  103  must be comprised of an elastomer (e.g. neoprene, fluorocarbon, polyurethane, etc.). The problem with this is that the combination of a gap and a flexible material can result in o-ring  103  creeping into the gap when under severe pressure. In extreme cases, the o-ring can be completely extruded through the gap. While the flexibility of o-ring  103  can be altered to reduce this creep, a less flexible material will not create a proper seal when there are imperfections such as pits or scratches on the inside wall of pipe  101 . To create a proper seal, o-ring  103  cannot therefore be comprised of a rigid material, and creep becomes an inevitable problem.  
         [0033]    Creep in prior art applications reduces the effectiveness of the seal, creating a substandard testing tool. First, creep in the o-rings allows fluid in testing tool  100  to displace the distorted o-rings. Because of this displacement, the pressure of the test fluid will decrease. The issue is that these types of tools are used to test the integrity of welds, and a pressure decrease could be interpreted as a weld problem, even though no such problem exists. A true hydro test according to the ASME B31.1 10 and 31.3 code is thus never achieved.  
         [0034]    The creep into the gap between pipe  101  and o-ring supports  102  can result in tool  100  becoming jammed within pipe  101 . Thus even when the test pressure and torque loads are removed, tool  100  will still be lodged in place. In order to remove the tool, the time consuming process of disassembling tool  100  within pipe  101  must be undertaken.  
         [0035]    The present invention overcomes the problem of creep through the use of a seal configuration shown in isolation in FIG. 2 in a pressured-up pipe engaging position, and as part of the present tool shown in its entirety in FIG. 6 in a retracted position prior to the application of seal setting pressure. Due to the lack of gaps in this configuration, pressure on the seal will not cause distortion or creep, allowing a true seal to be formed, and permitted easy extraction of the tool when pressure is released.  
         [0036]    Reference will initially be made to FIG. 6 which shows a weld test configuration of the tool  400  in a pipe  101  in a retracted position before being pressured to set the seals and expose a weld  104  to a test pressure. Generally, tool  400  comprises a central, axially extending, cylindrical mandrel  300  which supports on its exterior surface the various spacers, seals and backup rings that will be described below and which are used to form a fluid tight seal between the mandrel and the inner pipeline wall on both sides of the weld.  
         [0037]    Mandrel  300  is comprised of a cylindrical portion  320  disposed towards the open end of pipe  101  when mandrel  300  is in use, and a conical section  330  which is disposed away or downstream from the open end of pipe  101 , and thus towards the isolated section of the pipe when the mandrel is in use. The conical portion of the mandrel terminates with a circumferentially extending shoulder  301 .  
         [0038]    As will be described in greater detail below, conical portion  330  of the mandrel provides a ramp up which seal  201  moves when exposed to pressurized fluid for sealing against the inner surface of pipe  101 . To provide a similar ramp at the mandrel&#39;s upstream end along cylindrical portion  320 , the mandrel is fitted with a tapered annular ring or sleeve  305  which corresponds in shape, size and slope to conical section  330 , and which similarly includes a shoulder portion  301 . A nut  308  is threadedly connected to the mandrel&#39;s upstream end to locate ring  305  and to prevent its axial separation from the mandrel. Fluid tight sealing between ring  305  and the mandrel is provided by one or more o-rings  307 .  
         [0039]    Sealing between the mandrel and the inner pipeline wall is provided as mentioned above by annular resiliently deformable seals  201 . Each seal consists of two sections seen most clearly in FIG. 2 and in the retracted position of the tool shown in FIG. 6. Section  206  is a high pressure section which, in the retracted position shown in FIG. 6, has an outer diameter (OD) smaller than the inner diameter (ID) of pipe  101  for clearance with the pipe as the tool is installed and with the weld when the tool is removed. Section  207  is a lour pressure section which is normally biassed into contact with the pipe&#39;s inner wall for a slidable interference fit thereagainst.  
         [0040]    Separation between seals  201  in the retracted position shown in FIG. 6 is maintained by a tubular spacer  202  disposed concentrically around the mandrel.  
         [0041]    To prevent extrusion of seals  201  under pressure, each end of the mandrel at the culmination of the tapered portion is provided with a combination solid annular ring  203  and a radially expandable conical backup ring  204  preferably made of a rigid substantially noncompressible material such as a hard plastic. A spiral split (not shown) in the ring allows it to expand. Other means of allowing the ring to expand are also contemplated. Rings  203  are each notched at  212  to engage shoulders  301  to prevent their outwards axial separation from the mandrel. Each ring  203  includes an inwardly facing sloped face  213  that slidingly enclages a correspondingly and oppositely sloped face  215  of ring  204 . As seals  201  move up the conical portions of the manifold as pressure is applied to the area between the seals, the flat sides  220  of the seals bear against the opposed flat sides of rings  204 . The spiral splits in rings  204  allow them to expand and to move up the sloped surfaces of solid rings  203  until the split rings seal the clearance gaps  225  between rings  203  and the inner pipeline wall. Thus, when the tool is fully pressurized, seals  201  are effectively constrained within a rigid cavity defined by the inner pipeline wall, ring combination  2031204  and mandrel  300 . This therefore eliminates any pressure induced flow or creep of the seals into any gaps which in turn facilitates a faster and easier removal of the tool following use due to the absence of any seal creep or extrusion-induced lockup. The sealing is self-actualizing and increases with increasing test pressures.  
         [0042]    The outer surfaces of the seals that engage the inner pipeline wall are advantageously ribbed or serrated as shown at  210 . This profile conforms to any small blemishes in the pipe&#39;s inner wall such as pits, seams or scratches, and the ribs will also penetrate any dirt, wax or other loose material coating the pipe. It will be additionally appreciated that the seal design presents a large surface area in contact with the pipeline wall for increased seal integrity. Moreover, the seals themselves are of relatively soft material that will not itself damage coatings applied to some pipe inner diameters.  
         [0043]    To pressurize the tool, pressurized fluid is pumped into the annular space between seals  201  via a conduit  303  formed through the mandrel as shown and which discharges through spacer  202  as shown most clearly in FIG. 6. The upstream end of the mandrel is fitted with an adapter  314  held in place by a secondary nut  311  that threads onto primary nut  308 . The adapter receives standard couplings  318  to connect conduit  303  to an hydraulic supply line  317  that delivers the pressurized fluid from an external pump. When the test is complete, the same lines are used to exhaust the pressurized fluid and release the tool.  
         [0044]    In operation, the tool with supply line  317  attached is inserted into pipe  101  to straddle weld  104 . The design of the present tool allows the minimum five centimeters of clearance between the seals on either side of the weld. Pressurized fluid is then introduced into the area between the seals. The fluid is initially contained by the interference fit between the low pressure sections  207  of the seals and the inner pipeline wall to prevent blowby. As the pressure builds, the low pressure sections flatten against the inner pipeline wall and high pressure sections  206  ramp up the tapered portions of the mandrel until complete sealing of portions  206  and  207  with the inner pipeline wall is obtained, as shown most clearly in FIG. 7. Contact between seals  201  and split rings  204  causes the latter to expand ahead of the seals to close the clearance gap between solid rings  203  and the pipe ID. Complete sealing is therefore achieved without any torquing of the tool and the volume of seals  201  ensures that the seals conform to any out of round pipe, as well as tolerating misalignment of the pipe bores at the welds.  
         [0045]    When the test is complete, and the test fluid is exhausted from the tool, the elastic nature of the seals allows them to contract which in turn allows the tool to be withdrawn or moved to the next test location. Even when retracted, the low pressure sections of the seals remain in frictional contact with the pipeline walls, to provide some vapour sealing even though internal pressure is absent.  
         [0046]    Mandrel  300  can be fabricated advantageously from aluminum or stainless steel. Rings  203  will generally be made of the same material. Split rings  204  are advantageously made from a rigid plastics material, and seals  201  are fabricated from any suitable elastomer, such as neoprene, fluorocarbon, polyurethane and so forth. The material used must be adequate to meet operational pressures including an adequate safety factor, and in specific applications, must also be heat and chemical resistant.  
         [0047]    Tool  400  is readily adaptable to various inner diameters of pipe  101 . By replacing only rings  203 / 204 , and seals  201 , the tool can be configured for various sized pipes. This presents an economical advantage since a new tool does not need to be used for each differently sized pipe.  
         [0048]    The tool of the present invention can be used in various configurations, as is illustrated in FIGS. 6, 7,  8 ,  9 , and  10 . These various configurations allow the present invention to be used as a weld testing tool, an isolation tool, a welding aid, or a flange testing tool, creating a further advantage of the present invention over the prior art.  
         [0049]    As previously described, FIGS. 6 and 7 show the present invention in weld test configuration. This configuration involves the creation of a seal on either side of a weld  104  and the introduction of a pre-determined pressure within pipe  101  under weld  104  to test the weld&#39;s integrity.  
         [0050]    The pressurized fluid, usually water, can be brought to a predetermined pressure, usually 1.5 times the weld operating pressure, at which point the pressure is monitored to ensure that there is no drop. The high pressure of the water ensures the integrity of weld  104  and fulfills ASME B31.1 and B31.3 requirements for weld tests. Further, the Welding Institute (ASME) requires that the test pressure be applied over a minimum area extending five centimeters from each side of the weld which encompasses the heat affected zone.  
         [0051]    The weld test configuration can alternatively be used when welding to isolate the down-pipe section of pipe  101  from the weld area. This ensures operator safety and is required by ASME regulations. The tool is simply inserted into pipe  101  beyond the area being welded. The operator then attaches a hydraulic pump to line  317 , together with any necessary valves, a vent pipe, and pressure monitors. The tool is charged using the hydraulic pump, and the section of the pipe being worked on is thus isolated.  
         [0052]    An alternative configuration for the present invention is illustrated in FIG. 8 for flange testing. The purpose of the flange test configuration is to test the integrity of weld  104  which connects flange  501  to the end of pipe  101 . Flange tests are well, known in the art.  
         [0053]    The flange test configuration is comprised of the same down-pipe elements used for the weld test configuration shown in FIG. 6. Spacer  202  is still disposed about mandrel  300 , but may be lengthened as shown to extend all the way to a flange  502  connected to the mandrel and to the welded flange.  
         [0054]    In this configuration annular ring  305 , upstream seal  201  and rings  203 / 204  have been replaced by flange  502 . Flange  502  is comprised of a centrally bored cylinder whose inner diameter is adapted to fit closely over the outer diameter of cylindrical portion  320  of mandrel  300 . Fluid sealing between flange  502  and mandrel  300  is provided by o-rings  503 .  
         [0055]    A gasket  504  is disposed between welded flange  501  and flange  502  to provide a seal between these two elements. Flange  501  and flange  502  are then connected using stud and nut combination  505 . Alternatively, flange  501  and flange  502  can be connected using a fast-bolt  506 , as illustrated in FIG. 3, or by a cam lock system  507  as illustrated in FIG. 4. Primary nut  308  is threaded onto the protruding end of the mandrel to further secure the flange and so that secondary nut  311  can be used for connection of adaptor  314 .  
         [0056]    The flange test configuration works in a similar manner to the weld test configuration. The tool is charged to a predetermined pressure using hydraulic supply line  317  which is connected through adaptor  314  to conduit  303 . Water flows between flange  502  and seal  201 , creating pressure and causing seal  201  to be engaged as described above. The pressure can then be monitored to check the integrity of weld  104 .  
         [0057]    A further alternative configuration of the present invention is illustrated in FIG. 9. FIG. 9 shows a leak test configuration used to test for leaks in weld  104 . Leak test configuration  700  is identical to the weld test configuration with the exception of the addition of helium testing unit  710 .  
         [0058]    Helium testing unit  710  is comprised of sniffer  711 , flexible shroud  712 , and hose clamps  713 . Flexible shroud  712  is placed on pipe  101  around weld  104  and affixed by means of hose clamps  713  on either side of weld  104 .  
         [0059]    The leak test configuration words similarly to the weld test configuration with the exception that helium is used rather then water. Due to the small size of helium atoms and the properties of helium gas, helium is a better molecule than water for testing for weld leaks. If there are any points along the weld which leak, helium will escape through that point into flexible shroud  712 . Sniffer  711  will then detect the presence of helium to confirm a leak.  
         [0060]    A further alternative configuration for the present invention is illustrated in FIG. 10 for use during welding. This configuration is used when welding a pipe which requires a purge gas to be introduced. The use of a purge gas is well known in the art and is generally used when oxygen levels around the weld are to be reduced, such as when welding stainless steel or when TIG welded pipe.  
         [0061]    The welding configuration uses the weld test configuration to isolate the down pipe portion of pipe  101 . In addition, a shield tube  601  is affixed to secondary nut  311 . Shield tube  601  is a hollow metal cylinder that has an inwardly disposed thread on one end for connection to an outwardly disposed thread on secondary nut  311 . Shield tube  601  is used to enclose hydraulic lines  317  to protect them from the heat of the weld.  
         [0062]    Shield tube  601  is further used to support disk collar  602 . Disk collar  602  is a centrally bored cylinder whose inner diameter is approximately the same as the outer diameter of shield tube  601 . Disk collar  602  is formed with a circumferentially extending groove  610  on its outer surface to receive an inner edge of disk seal  604 . Sealing between disk collar  602  and shield tube  601  is provided by an o-ring  603  which prevents gas from escaping between the two elements.  
         [0063]    Disk-seal snap fits into groove  610  of disk collar  602 . Disk-seal  604  is made of a flexible material and is used to create a low pressure seal at the end of flange  501 , or whatever is being welded to pipe  101 .  
         [0064]    A purge gas is provided into the area under weld  104  via a purge gas supply line  605  inserted through a hole in disk-seal  604  to allow the inert gas to flow around the weld.  
         [0065]    To assist in the welding, a welder&#39;s magnet  606  can be attached to pipe  101  to hold a ground clamp  607 . Another such clamp  607  can be connected to collar  602 . A wire  608  connects the two clamps to prevent an electrical buildup across the weld.  
         [0066]    Mandrel  300  can include a second conduit  302  which extends completely through the mandrel. In the configuration shown in FIG. 10, this conduit can be connected to a line  327  including a pressure gauge  609  and a valve  610  that can be used to monitor pressure on the system side of pipe  101  or to vent away off gases or fluids. Further, if a heat sink is required, water can be circulated through the area between seals  201  using conduit  303 .  
         [0067]    In some applications, there may be insufficient fluid pressure used to fully expand and set seals  201 . In such situations, a mechanical preloading force can be applied to the seals in the manner shown schematically in FIG. 5 using for example a torquable nut  501 , with fluid pressure acting directly against the seal in the area between the nut and pipe  101 . In this application, the seal consists only of section  206  without “lip”  207 .  
         [0068]    All of the above features provide an illustration of preferred embodiment of the invention, but are not intended to limit the scope of the invention, which is fully described in the claims below.