Abstract:
A method of hydrostatic testing a selected section of a pipeline having fluid flow therethrough, including the steps of introducing into the pipeline a pig train including a leading seal pig, a supply liquid slug, a first isolation tool, a test liquid slug and a second isolation tool; permitting the train to traverse the pipeline interior by the force of fluid flow until the lead isolation tool is forwardly of and the second isolation tool is rearwardly of the selected selection of the pipeline; securing the position of the pig train by applying exteriorly of the pipeline appropriate signals to actuate the isolation tools to each engage and seal the interior of the pipeline trapping the test liquid slug therebetween; and pumping liquid from the supply liquid slugs into the test liquid slug to a hydrostatic testing pressure. In addition to testing, the pipeline can be repaired by moving the pig train into position where a defective area can be isolated by additional isolation tools.

Description:
REFERENCE TO PENDING APPLICATIONS 
   This application is not based upon any pending domestic or international patent applications. 
   REFERENCE TO MICROFICHE APPENDIX 
   This application is not referenced in any microfiche appendix. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to methods for hydrostatic testing a section of a pipeline that employs a pig train including plugging tools, at least one sealing pig, slugs of fluid between the sealing pig and plugging tools and a pumping system for increasing the hydrostatic pressure interior of the pipeline between spaced apart plugging tools. 
   2. Description of the Prior Art 
   The invention herein discloses methods and systems for hydrostatic testing a pipeline. 
   In North America, Europe and other industrialized areas of the world, vast quantities of fluids, including liquids and gases, are transported through pipelines. These fluids include crude oil, lubricating oil, natural gas, gasoline and so forth. These pipelines are often of considerable length and extend over all types of geographic terrains. Many pipelines today are located underneath rivers and lakes and growing mileages of pipelines are located on the surface of the earth covered by seawater, that is, submerged or subsea pipelines. 
   In the event of damage, deterioration from age, or changing conditions including need for modification or structural changes to a pipeline, a serious problem rises as to the manner in which the flow of liquid, either fluid or gases, through the pipeline can be controlled during repair, maintenance and testing. Most pipelines in use today are continuously filled with liquids or gases. Since the volume contained in a relatively long length of pipeline is great, the value of the contained fluid is great. In addition, in most instances if it is necessary to repair, replace or test a pipeline it is not feasible to drain the pipeline due not only to the cost of the contents but many of the products carried by pipelines are deleterious to the environment. Many governmental restrictions around the world prohibit discharging pipeline contents into the environment for the purpose of facilitating repair, maintenance or testing. 
   One method used to test or repair a pipeline is to isolate and evacuate a section of the pipeline by using internally transportable plugging devices or pigs. In order to employ a plugging pig it is necessary to be able to stop the pig at a pre-selected location and by internal means, closing the plugging pig to seal the interior of the pipeline against further fluid flow. When repair, maintenance, testing or so forth is completed, it is then necessary to release the grip of the plugging pig to permit it to resume passage through the interior of the pipeline by the force of fluid flow. In this way, the plugging device in the form of a fluid transportable pig, can be removed from the pipeline after its use has been completed and the pig reused for further applications. 
   A commonly used method to stop flow in a pipeline temporarily is by the utilization of a product commercially available under the trademark STOPPLE® as manufactured and supplied by T.D. Williamson, Inc. of Tulsa, Oklahoma. A method of use of the STOPPLE® plugging system includes installing an access fitting followed by boring a large diameter hole at each of two extremities of the pipeline to be worked on or tested, inserting a plug in each large hole and pivoting the plug about a transverse axis to plug the pipe. After the repair work is done, the plugs are pivoted back and removed from the hole and large flanges are secured on the fittings. While this system functions successfully in areas where the pipe is readily accessible from the earth&#39;s surface, in many locations accessibility is a continuous problem and this is particularly a burdensome problem with pipelines running under lakes, rivers and especially pipelines running on the ocean floor. For this reason and in recent years plugging tools or plugging pigs have been developed. These devices are insertable in the pipeline for movement by fluid flow and can be actuated at a selected point to grip the interior wall while simultaneously sealing the interior wall of the pipeline against fluid flow. The invention herein includes methods, systems and devices for employing such plugging pigs in pipelines particularly for hydrostatic testing of pipelines. 
   For additional information relating to the background of the subject matter of this invention, reference may be had to the following United States patents and publications: 
   
     
       
             
             
             
           
         
             
                 
             
             
               Patent 
                 
                 
             
             
               Number 
               Inventor 
               Title 
             
             
                 
             
           
           
             
               RE33,160 
               Guthrie 
               Method and Apparatus For Inspecting Lateral 
             
             
                 
               et al. 
               Lines 
             
             
               3,746,026 
               Herring 
               Pipeline Plugging Pig 
             
             
               3,750,711 
               Conklin 
               Method and Apparatus For Testing For Leaks 
             
             
                 
               et al. 
               In Pipes 
             
             
               3,837,214 
               Guest 
               Self-Propelled Pipeline Plug 
             
             
               3,908,682 
               Thompson 
               Methods and Apparatuses For Remotely and 
             
             
                 
                 
               Releasably Sealing A Pipe Line 
             
             
               4,026,329 
               Thompson 
               Method and Apparatus For Remotely and 
             
             
                 
                 
               Releasably Sealing A Pipeline 
             
             
               4,314,577 
               Brister 
               Installation, Hydrostatic Testing, Repair and 
             
             
                 
                 
               Modification of Large Diameter Fluid Trans- 
             
             
                 
                 
               mission Lines 
             
             
               4,441,328 
               Brister 
               Method and Apparatus For Forming A 
             
             
                 
                 
               Temporary Plug In A Submarine Conduit 
             
             
               4,484,602 
               Guthrie 
               Packer For Sealing Lateral Lines 
             
             
               4,691,728 
               Mathison 
               Electronic Test and Seal Apparatus and 
             
             
                 
                 
               Method 
             
             
               4,854,384 
               Campbell 
               Pipeline Packer 
             
             
               4,991,651 
               Campbell 
               Pipeline Packer For Plugging A Pipeline At 
             
             
                 
                 
               A Desired Location 
             
             
               5,139,576 
               Davis 
               Method and A Horizontal Pipeline Pig 
             
             
                 
                 
               Launching Mechanism For Sequentially 
             
             
                 
                 
               Launching Pipeline Pigs 
             
             
               5,272,646 
               Farmer 
               Method For Locating Leaks In A Fluid 
             
             
                 
                 
               Pipeline and Apparatus Therefore 
             
             
               5,372,162 
               Frey 
               Repair Device For The In Situ Repair of 
             
             
                 
                 
               Pipes, And A Method of Repairing Pipes 
             
             
               5,433,236 
               Zollinger 
               Apparatus For Moving A Pipe Inspection 
             
             
                 
               et al. 
               Probe Through Piping 
             
             
               5,842,816 
               Cunningham 
               Pig Delivery and Transport System For 
             
             
                 
                 
               Subsea Wells 
             
             
               5,983,948 
               Yagi et al. 
               Method of Repairing An Existing Pipeline 
             
             
                 
                 
               Including A Main Pipe and A Branch Pipe 
             
             
               6,022,421 
               Bath et al. 
               Method For Remotely Launching Subsea Pigs 
             
             
                 
                 
               In Response To Wellhead Pressure Change 
             
             
               6,348,869 
               Ashworth 
               Pipe Leak Detection 
             
             
                 
             
           
        
       
     
   
   BRIEF SUMMARY OF THE INVENTION 
   The methods and systems of this invention for testing a length of a pipeline includes the use of at least two isolation tools introduced into the pipeline. The isolation tools having means for being propelled by fluid flow (liquid or gas) through the pipeline. Further, the isolation tools have means by which they may be set at selected locations and actuated for sealing the pipeline against fluid flow therethrough. Specifically the isolation tools each have facilities for receiving a signal applied from the exterior of the pipeline to initiate the steps required for gripping the interior of the pipeline to stop movement through the pipeline and for sealing the interior of the pipeline against fluid flow. 
   A sealing pig is introduced in the pipeline a pre-selected time or distance prior to the introduction of the first isolation tool. The sealing pig is typically a pig that does not include moving parts or communication systems but includes only cups or discs that extend from a central body to slidably engage the interior wall of the pipeline. The cups or discs of the sealing pig slide on the interior of the pipe wall as moved along by fluid flow. When the fluid flow stops, the sealing pig stops since it has no means of locomotion. Further, the sealing pig has no means whereby it can be commanded to stop nor can the speed of movement of the sealing pig be effected by externally applied signals since the sealing pig is solely controlled by the speed of movement of the fluid through the pipeline. 
   After a sealing pig is introduced into a pipeline, such as by the use of a pig launcher, the interior of the pipeline may be filled with a selected fluid that is different from the fluid normally flowing through the pipeline. For instance, after a sealing pig is introduced a quantity of fluid, such as water, can be introduced into the pipeline. This fluid that is introduced into the pipeline and that is different from the fluid or gas that is normally flowing through the pipeline is referred to as a “first testing liquid slug”. After the pre-selected quantity of the liquid slug is introduced into the pipeline, then the first isolation tool is immediately introduced. 
   After the first isolation tool is introduced, a time delay or liquid volume displacement occurs before a second isolation tool is introduced. The spacing between the first and second isolation tools is selected in accordance with the time delay or liquid volume displacement of launching the second isolation tool. That is, the speed of travel of the liquid in the pipeline multiplied by the time of delay between launching the first and second isolation tool, or a measured volume of liquid is pumped, thereby determines the spacing between the two isolation tools. This spacing can vary according to the intended purpose. When the purpose is to hydrostatically test a portion of the length of a pipeline, the spacing between the isolation tools equal to the length of the pipeline to be hydrostatically tested. This can vary from a few feet to several miles. 
   After the second isolation tool is introduced into the pipeline in a preferred practice of the invention a second or follow up slug of liquid is introduced into the pipeline in a quantity as required for the procedure to be employed. After the required follow up slug of liquid is introduced into the pipeline, a trailing seal pig is launched into the pipeline. 
   Thus the basic system of this invention is a pig train made up of a lead seal pig, a leading liquid slug, a lead or first isolation tool, a test liquid slug and a second isolation tool and a trailing seal pig, if needed. Thus, in addition to the pigs making up a basic train for use in practicing the invention, that is a seal pig and two isolation tools, the train includes a leading liquid slug between the leading seal pig and the leading plug pig and a test slug between the two isolation tools. 
   The system further includes a pump for pumping liquid from the leading liquid slug past the lead isolation tool and into the test slug. When the system is used for a pipeline located on the earth&#39;s surface, the pump can be located exteriorly of the pipeline. To provide access from the pump to the interior of the pipeline, small diameter branch fittings are secured to the pipeline, such as by welding, and then by using a hot tapping system the pipeline is penetrated. This can be accomplished while the pipeline is under pressure by employing hot tapping equipment illustrated and described in the following patents: 
   
     
       
             
             
             
           
         
             
                 
             
             
               Patent 
                 
                 
             
             
               Number 
               Inventor 
               Title 
             
             
                 
             
           
           
             
               4,579,484 
               Sullivan 
               Underwater Tapping Machine 
             
             
               4,880,028 
               Osburn et al. 
               Completion Machine 
             
             
               5,439,331 
               Andrew et al. 
               High Pressure Tapping Apparatus 
             
             
               6,012,878 
               Hicks 
               Pressure Balanced Subsea Tapping Machine 
             
             
               6,648,562 
               Calkins et al. 
               Apparatus For Tapping A Hole In A Pipeline 
             
             
                 
             
           
        
       
     
   
   Instrumentation is contained in a control module portion of at least one of the isolation tools for measuring and recording fluid pressure in the test section to provide the hydrostatic testing information obtained by the use of the system of the invention. Each isolation tool as employed in the invention will consist of at least three sections, including a gripper module, a packer module and an instrument module. The gripper and packer modules typically include hydraulic cylinders and therefore a source of hydraulic fluid pressure is employed in each isolation tool. 
   The invention herein uses a pig train formed of a combination of isolation tools (plugging pigs), batching pigs, and liquid batches, also referred to as “slugs”, which can be propelled along inside the pipeline. This test “train” can be set, a hydrostatic test performed and the train moved along to the next position, and the whole sequence repeated, without the need for welding on test heads, filling the pipeline with test medium, draining the pipeline of test medium and removing the test heads—as in a conventional hydro-testing approach. Therefore, the concept of this invention has the benefit of faster and/or lower cost pipeline hydrostatic testing. The invention herein makes it possible to hydrostatically test relatively short sections of a new pipeline just behind the pipe welding crew during the construction process—resulting in commissioning of new pipelines sooner than by conventional testing methods. 
   With an additional isolation tool in the pig train, an in-service pipeline can be hydrostatically tested and leaking or failed sections can be repaired while maintaining operating pressure in the pipeline, eliminating the need to completely remove the pipeline from service and without draining down or blowing down the pipeline to remove product therefrom. 
   The methods of this invention may be used for post-construction proof that a pipeline is capable of withstanding the intended design or operating pressure. Another purpose for this invention may be to qualify an in-service pipeline for an increase in operating pressure over what it has been operating at heretofore in the event the pipeline requires re-rating. The methods of this invention are useful for pipeline hydrostatic testing to meet governmental or industrial code requirements, as well as for insuring general safe operating practices. 
   A section of a pipeline may be hydrostatically tested and isolated for repair, using a “pig train” (a combination of isolation tools and batching pigs), in relatively short or long sections. The “isolation tools” referred to in this document may also be termed “plugging pigs” and are special purpose “smart” pipeline pigs that are designed to travel along in the pipe, propelled by the flow of product (by pumping or compression), stopped at selected locations and activated by a through-the-pipe-wall communication device to engage the inside diameter of the pipeline with grips and packers to hold back pressure in the pipeline. The isolation tools can then be commanded to release, following equalization of pressure, by external communication devices. “Seal pigs” as referred to herein may be termed “batching pigs” and are designed to provide a tight seal with the pipe wall while traveling along inside a pipeline as propelled by fluid flow and to contain a “batch” or “slug” of fluid that may be of a different type than that within the pipeline ahead or behind the pig train. 
   The basic configuration of the hydrostatic testing plugging pig train consists of a sealing pig in front, followed closely by a lead isolation tool with a short “make-up” batch or slug of test medium (water or other incompressible fluid) in between. The lead isolation tool is followed by any practical length of test medium and a second isolation tool oriented in the opposite direction in order to hold test pressure in the test section when both isolation tools are set and their packers energized. The length of this test section can be determined by taking into consideration testing time, hold time (for leak detection), elevation changes of the pipeline, which can result in variation of pressure along the test section, and other factors. 
   A problem exists with elevation changes in that when using water or other liquid as the test medium, pressure will vary significantly with elevation change (approximately 15 psi for every 33 feet of elevation due to the effect of gravity or “head”) along the length of the test medium slug. This may limit the length of the test section due to the possibility of over pressuring the pipeline by the packer module. 
   In the case of new construction where there is no need to isolate operating pressure during repairs of failed or leaking sections, the trailing isolation tool may be followed closely by another seal pig with a slug of make-up test medium in between. In the case of an operating pipeline, where a defective section of pipeline needs to be isolated from operating pressure during repair, a third isolation tool may follow the second isolation tool by some practical distance with a slug of test medium in between primarily to maintain a fixed distance behind the second isolation tool and to prevent a compressible gas “bubble” from seeping into the test section. 
   The main purpose of the make-up media is to provide make up volume during test pressurization and to prevent a compressible gas “bubble” from seeping into the test or isolation media. Another purpose of the trailing “make up” slug is to carry a fluid such as methanol or glycol to allow drying of an on-stream gas line while the pig train moves along. The hydrostatic test slug (water or mostly water) leaves a wet pipe wall which results in gradual loss of test medium volume as the train moves down the pipe. This make-up slug can serve the dual purpose of providing make-up medium and drying the line behind the test train. 
   As previously stated, pumping up the test section utilizes hot-tapping with two small pipe nipples welded to the pipe on either side of an isolation tool with a pumping manifold installed in between by way of temporary external piping. This manifold transfers test medium from a leading slug during pressure testing and returns it to the leading slug during depressurization. Test pressure pumping may also be accomplished by the use of on-board pumping capabilities with a passageway through an isolation tool to transfer liquid into the test section. 
   If a leak is discovered and located in an operating pipeline, the pig train of this invention can be advanced until the leak is straddled by an isolation section of the train. The isolation tools to either side of the leak can be set and the isolated section of pipe containing the leak can be depressurized and repaired without draining or venting product beyond the relatively short isolated section. After repairs, the isolation tools can be unset and the train moved along to the next test section. 
   Because of the chance of having a rupture during hydrostatic testing of an operating pipeline, an additional isolation tool may be included to block ambient pipeline pressure downstream of the pig train while a different isolation tool can be set to block ambient pipeline pressure upstream of the pig train. In this case, the additional isolation tool prevents the dislodging and movement of the other isolation tools toward the rupture, possibly saving damage and loss of much or all of the hydrostatic test media. This extra step may be necessary because isolation tools typically only hold pressure in one direction and may be dislodged if pressure is reversed. 
   In a deep subsea environment a huge hydrostatic head exists on the outside of the pipeline so hydrostatic testing of the pipeline takes on different problems. When the pipeline in question is a gas line, the internal pressure may be low compared to the external pressure. The methods of this invention are advantageous in finding and isolating leaks. If two isolation tools are moved into a pipeline with a fluid slug between them, they can be set and let the external (ambient) hydrostatic head of the water column provide the test pressure. If a pressure rise occurs between the isolation tools, then a leak is present. In this case, since the external pressure is greater than the internal pressure the leak can be located and isolated without moving the pig train. The pipeline could then be repaired or a repair clamp installed for repair at a later date. 
   In the case where the gas pressure in a subsea pipeline is higher than the ambient pressure, a plugging pig train with two outward looking isolation tools with a slug of water between can be launched into the pipeline and moved along by the internal hydrostatic pressure of a surface riser water column balancing pressure with the external ambient pressure, and with gas at a higher pressure than ambient sub-sea hydrostatic pressure on the other side of the pig train. In this case, the water column in the riser balances the ambient pressure while a hydrostatic pump at the surface is used to provide the testing pressure. The lead isolation tool is set, pressure is pumped up, the trailing isolation tool is set, pressure in the riser is released, resulting in test pressure remaining in the slug between the isolation tools. A sensed pressure drop would indicate a leak. Alternatively, an on-board pump can provide the additional test pressure between the isolation tools when set, eliminating pressure cycles in the riser. 
   A better understanding of the invention will be obtained from the following detailed description of the preferred embodiments and claims, taken in conjunction with the attached drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic cross-sectional view of a length of pipeline that is broken into three adjacent segments. This figure shows a pig train positioned within the pipeline, the pig train being made up of a leading isolation tool followed at a selectable distance by a second isolation tool. Preceding downstream within the pipeline of the lead isolation tool is a lead seal pig and trailing behind the second isolation tool is a trailing seal pig. Between the lead seal pig and the first isolation tool the pipeline is filled with a selected liquid and this quantity of liquid is identified as a leading liquid slug. Between the isolation tools the liquid within the pipeline is identified as a test slug. Following the second isolation tool and between it and the trailing seal pig is a quantity of liquid termed a “trailing liquid slug”. Apparatus is provided by which elevated fluid pressure may be applied to the test slug to thereby hydrostatically test the pipeline. 
       FIG. 2  is a schematic representation of a length of pipeline broken in segments and shows a first alternate embodiment of practicing the invention. In  FIG. 2  three isolation tools as well as leading and trailing seal pigs form four liquid slugs that are part of the total pipeline pig train. 
       FIG. 3  is a diagrammatic cross-sectional view of a length of pipeline as in  FIGS. 1 and 2  and showing a second alternate embodiment of the invention that employs four isolation tools, two seal pigs and five liquid slugs making up the pig train. 
       FIG. 4  is a cross-sectional view of the major portions of a packer module as used in an isolation tool. The invention herein is not concerned with the details of construction of the packer module or of any of the pigs used in the systems.  FIG. 4  is included only to indicate how a packer module portion of an isolation tool can function to seal the interior of the pipeline against fluid flow and to show piping that may be used to pass fluid to the test section in the case where an on-board pump is used.  FIG. 4  is a cross-sectional view of a packer module as taken along the lines  4 - 4  of  FIG. 1 . 
       FIG. 5  is a cross-sectional view of a gripper module such as taken along the line  5 - 5  of  FIG. 1  and also shows fluid transfer piping. 
       FIG. 6  is an enlarged cross-sectional view of the gripper module as taken along the line  6 - 6  of  FIG. 5 .  FIG. 5  shows the gripper module located within a pipeline that is not shown in  FIG. 6 . As with the packer module, the details of the gripper module are not part of the present invention and the gripper module illustrated in the details of  FIGS. 5 and 6  are intended only to be illustrative of the concept of an isolation tool that includes apparatus for locking itself in position within a pipeline and for closing the pipeline against flow therethrough, and for showing fluid transfer piping. 
       FIG. 7  is an elevational view of an isolation tool of the type that is illustrated in  FIGS. 1 through 3  but shown in greater detail and with the increased elements as may be required in practicing some aspects of the invention. Particularly,  FIG. 7  is illustrative of an isolation tool having multiple power modules formed in the train in combination with a packer module, a gripper module and a control module with fluid transfer piping. The embodiment of  FIG. 7  is particularly important in one method of practicing the invention wherein hydrostatic testing of a portion of the length of a pipeline can be accomplished without the necessity of attaching piping fittings to the exterior of the pipeline. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   It is to be understood that the invention that is now to be described is not limited in its application to the details of the construction and arrangement of the parts illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. The phraseology and terminology employed herein are for purposes of description and not limitation. 
   Elements illustrated in the drawings are identified by the following numbers: 
   
     
       
             
             
           
         
             
                 
             
           
           
             
               10A, B, C 
               Pipeline sections 
             
             
               12 
               Lead seal pig 
             
             
               14 
               Lead isolation tool 
             
             
               16 
               Second isolation tool 
             
             
               18 
               Trailing seal pig 
             
             
               20 
               Leading liquid slug 
             
             
               22 
               Test liquid slug (hydro-test section) 
             
             
               24 
               Trailing liquid slug 
             
             
               26A, B 
               Pipe nipples 
             
             
               28A, B 
               Piping 
             
             
               30 
               Pumping manifold 
             
             
               32 
               Packer module 
             
             
               34 
               Universal joint (ball joint) 
             
             
               36 
               Gripper module 
             
             
               38 
               Universal joint (ball joint) 
             
             
               40 
               Control module 
             
             
               42 
               Elastomeric discs 
             
             
               44 
               Central body 
             
             
               46 
               Radial rails 
             
             
               48 
               Rail edge 
             
             
               50 
               Grip saddle 
             
             
               52 
               Inclined edge 
             
             
               54 
               Grip shoes 
             
             
               56 
               Gripping surface 
             
             
               58 
               Pipeline interior wall 
             
             
               60 
               Actuator body 
             
             
               62 
               Piston 
             
             
               64 
               Wheels 
             
             
               66 
               Coiled spring 
             
             
               68 
               Tubular body 
             
             
               70 
               External cylindrical surface 
             
             
               72 
               Fixed forward flange 
             
             
               74 
               Internal cylindrical wall 
             
             
               76 
               Cylindrical surface 
             
             
               78 
               Double ended piston rod 
             
             
               80 
               Rearward flange 
             
             
               82 
               Ball joint 
             
             
               84 
               Back up flange 
             
             
               86 
               External cylindrical surface 
             
             
               88 
               First elastomeric packer 
             
             
               90 
               Second elastomeric packer 
             
             
               92 
               Internal cylindrical surface 
             
             
               94 
               Contacting surface 
             
             
               96 
               Sidewall surfaces 
             
             
               98 
               Backup ring 
             
             
               100 
               Internal opening 
             
             
               102 
               Opposed sidewalls 
             
             
               104 
               Outer circumferential surface 
             
             
               106 
               Piston 
             
             
               108 
               Cylinder head 
             
             
               110 
               Opening 
             
             
               112 
               Cylindrical area 
             
             
               116 
               Rearward wheels 
             
             
               118 
               Forward wheels 
             
             
               120 
               First power module 
             
             
               122 
               Second power module 
             
             
               124 
               Universal joint 
             
             
               126 
               Universal joint 
             
             
               128 
               Flexible conduit 
             
             
               130 
               Flexible conduit 
             
             
               132 
               Third isolation tool 
             
             
               134 
               Isolation liquid slug 
             
             
               136 
               Fourth isolation tool 
             
             
               138 
               Second isolation liquid slug 
             
             
               140 
               Instrumentation 
             
             
               142 
               Actuation hydraulic pump 
             
             
               144 
               On-board test pump 
             
             
               146 
               On-board battery 
             
             
               148 
               Fluid inlet 
             
             
               150 
               Fluid outlet 
             
             
                 
             
           
        
       
     
   
   This invention provides systems and methods to test a portion of the length of a pipeline. The test can be of various types but basically constitute hydrostatic testing, that is testing the reaction of the pipeline to fluid pressure in the pipeline. Such tests can be made for many reasons. As an example, a length of a pipeline can be tested to see if there are leaks in the pipeline within the test section. The pipeline sections can be tested to determine whether it is capable of withstanding increased fluid pressure. This need arises frequently when pipelines that have been constructed and operated for several years are considered for upgrade to increase the flow rate which mandates increasing the pressure of fluid moving through the pipeline. 
   The invention herein makes use of devices that are sometimes referred to as “plugging pigs” but which will be referred to herein as “isolation tools”. Pipeline pigs of this type typically are formed by a packer module in cooperation with a gripper module. These components can be manufactured separately and then joined to form an integral unit in which the components work in cooperation with each other. A “gripper module” means a section of the pipeline pig that can be actuated to grip against the interior wall of the pipeline and thereby lock the pig assembly into a temporarily fixed position in the pipeline. A packer module is an apparatus that can be expanded to close fluid flow through the pipeline. 
   The system for practicing the invention is in the form of a train of elements introduced by a launching device into the interior of the pipeline. In  FIG. 1 , a section of a pipeline is illustrated, broken into sections  10 A,  10 B and  10 C. The basic elements making up the pigging train illustrated in  FIG. 1  is a lead seal pig  12  contained with pipeline section  10 A; a lead isolation tool generally indicated by the numeral  14  contained in pipeline section  10 B; a second isolation tool generally indicated by the numeral  16  contained in pipeline section  10 C; and a trailing seal pig  18  that is also contained within pipeline section  10 C. 
   In addition to the physical apparatus making up the train of components as illustrated in  FIG. 1  for performing hydrostatic testing of the interior of the pipeline, a leading liquid slug  20  is introduced into the interior of the pipeline filling the space between lead seal pig  12  and lead isolation tool  14 . Between lead isolation tool  14  and second isolation tool  16 , there is a test slug  22 , that is, a column of water traveling in the pipeline between the first and second isolation tools. Between second isolation tool  16  and trailing seal pig  13  is a trailing liquid slug  24 . 
     FIG. 1  illustrates the placement of the train of isolation tools, seal pigs, and liquid slugs within pipeline  10  as used in the process of conducting a hydrostatic test of the pipeline through a length of the pipeline designated as D 2  that contains test liquid slug  20 . This length D 2  could be a little as a few feet, such as testing a weld joint or a single joint of pipe, or can be as much as several miles. To hydrostatically test the pipeline through the length of D 2  it is necessary to increase the hydrostatic pressure of the test liquid slug  22 . In order to do this, two small pipe nipples  26 A and  26 B are affixed to the exterior of the pipeline and the pipeline is hot tapped to provide access to the interior. Nipples  26 A and  26 B are welded to the pipeline to either side of lead isolation tool  14 . After the nipples are welded to the pipeline, by the use of hot tapping equipment, such as is available from T.D. Williamson, Inc. of Tulsa, Okla., holes are drilled through the pipe wall and into the interior of pipe  10 . Thereafter piping  28 A and  28 B can be affixed to the pipe nipples  26 A and  26 B to connect to a pumping manifold  30 . By means of a pump within manifold  30  test media liquid can be extracted from leading liquid slug  20  and pumped into test liquid slug  22  thereby raising the hydrostatic pressure in the test liquid slug. Within piping manifold  30  instrumentation is provided to measure and record the pressure applied to test liquid slug  22  which represents the hydrostatic pressure applied to section D 2  of the pipeline. The instrumentation within pumping manifold  30  can include facilities for measuring and recording the maximum pressure to which the pipe section D 2  is subjected. Further, after a predetermined pressure is applied to test liquid slug  22 , pressure can be maintained for a period of time and a record made as to whether the pressure decreases indicating whether there is a leak in the pipe section D 2 . 
   After completing the hydrostatic testing of pipe section D 2  by pumping fluid from leading liquid slug  20  into test liquid slug  22  and making a record of fluid pressure measurements, the pressure can be relieved by allowing fluid flow back into slug  20 . The pipe nipple  26 A and  26 B can then be closed and the pumping manifold and piping  28 A and  28 B can be removed. Thereafter, the entire train of equipment illustrated in  FIG. 1  can be moved along by releasing the gripper and packer modules making up each of the isolation tools  14  and  16 . 
     FIG. 7  illustrates one embodiment of an isolation tool. In the embodiment of  FIG. 7 , a packer module  32  is shown connected by universal joint  34  to a gripper module  36 . Gripper module  36  is, in turn, connected by a universal joint  38  to a control module  40 . 
   Each of the isolation tools  14  and  16  provides a system for closing fluid flow through the interior of a pipeline  10 . The isolation tools are transported through pipeline  10  by the force of fluid flow. Each isolation tool can be remotely controlled to grip the interior of the pipeline to stop travel through the pipeline and remotely controlled to form a seal that terminates fluid flow. This type of tool is known in the industry as an “isolation tool” since it can be used to isolate portions of a pipeline. 
   Isolation tools  14  and  16  each includes instrumentation that is utilized to react to a remote signal to cause the tool to set itself in a selected position within pipeline  10 . This instrumentation is well known in the pipeline industry and is not part of the invention herein. Stated another way, the invention herein is not concerned with the electronics by which isolation tools  14  and  16  are remotely controlled by means from exterior of the pipeline but is concerned with systems and methods of making use of such tools for hydrostatic testing pipelines. 
   In  FIG. 1 , isolation tools are indicated generally by the numerals  14  and  16 . An example of an isolation tool is illustrated in more detail in  FIG. 7 . As illustrated in this figure the isolation tool is in the form of a train of components flexibly coupled together and configured to travel within a pipeline as a unit and for isolating a portion of the pipeline by closing off fluid flow through it. The isolation tool as shown in  FIG. 7  includes, as major components thereof, a packer module  32 , a grip module  36  and a control module  40 . The rearward end of the packer module  32  is attached to the forward end of gripper module  36  by a ball joint  34 . The rearward end of grip module  36  is secured to the forward end of control module  40  by a ball joint  38 . Ball joints  34  and  38  are representative of mechanical means of flexibly connecting the basic elements of the isolation tool to each other so that the tool can move around bends in a pipeline without putting stress on the individual connected components. 
   Control module  40  includes a housing which is typically tubular as indicated with closed ends and in which the forward closed end includes a portion of ball joint  38 . Positioned on the exterior of the tubular housing are radially extending elastomeric discs  42  that have exterior diameters that are less than that of the pipeline (not shown in  FIG. 7 ) in which the isolation tool is employed. Discs  42  function essentially to support the control module centrally within the interior of a pipeline and to slidably seal against a pipeline interior wall. 
   Within control module  40  there is electronic instrumentation that functions in accordance with known techniques familiar to those in the pipeline pigging and isolation tool industry by which signals can be received from the exterior of a pipeline. Hydraulic control compartment controls the application of hydraulic fluid pressure to gripper module  36  and packer module  32 . 
   An example of a grip module as used in the isolation tool of this invention is illustrated in  FIGS. 5 and 6 .  FIG. 5  shows a pipeline  10  in which grip module  36  is positioned. Grip module  36  includes an elongated central body frame member  44  that is shown to be of hexagonal cross-section in  FIG. 6 . Radially extending from frame member  44  are six radially extending rails  46 . Each of rails  46  is in the form of a flat metal plate with a rail edge  48  that is inclined relative to the central body longitudinal axis. Slidably received on each rail edge  48  is a grip saddle  50 , each having an inclined edge  52  that slides on a rail edge  48 . Affixed to each of the grip saddle  50  is a grip shoe  54  that has a serrated surface as seen in  FIG. 5  to non-slidably engage pipeline interior wall  58 . The angular relationship between rail edge  48  and grip saddle inclined edge  52  is such that the grip shoe surface  56  engages the pipeline interior surface  58  in a parallel relationship. 
   Secured to a side wall of each of rails  46  is an actuator body  60 , seen in  FIG. 6 , each of which slidably supports a double ended piston  62 . An intermediate portion of each piston  62  is secured to a grip saddle  50  so that the displacement of each grip saddle and in turn each grip shoe  54  that slides on an edge  48  of each rail  46  is controlled by a piston  62 . Each of the actuator bodies  60  includes an actuating cylinder. When pressure is applied to the actuating cylinders, pistons  62  function to move the grip saddles  50  and thereby grip shoes  54  in the direction towards or away from pipeline interior wall  58 . 
   It is important that the grip shoes  54  are not in engagement with the interior surface of pipeline, such as surface  58  as seen in  FIG. 5 , as the isolation tool moves through the pipeline prior to reaching a point where closure of the pipeline is required. For this reason the grip module  36 , as seen in  FIG. 5 , includes wheels  64  that roll along the interior surface of the pipeline. 
   As seen in  FIG. 7 , grip module  36  is connected at its rearward end to ball joint  38  that is positioned between the grip module and control module  40 . As a part of each of ball joints  34  and  38  as seen in  FIG. 7  a coiled spring  66  is employed for the purposes of preventing relative rotation between the components making up the isolation tool train. 
   An embodiment of a packer module, indicated by the numeral  32  in  FIG. 7 , is illustrated in the cross-sectional view of  FIG. 4 . Packer module  32  includes a tubular body  68  having an external cylindrical surface  70  and, at one end thereof, a radially extending fixed forward flange  72 . The tubular body  68  includes a portion defining a cylinder wall  74  with an internal cylinder surface  76 . Centrally received within cylindrical surface  76  is a double ended piston rod  78 . Secured to a rearward end of piston rod  78  is a radially extending rearward flange  80 . Piston rod  78  has a threaded opening in the rearward end thereof that receives a threaded end of a ball joint  82 . Rearward flange  80  is captured between the rearward end of piston rod  78  and ball joint  82 . Secured to a forward surface of rearward flange  80  is a backup flange  84  that is slidably received on external cylindrical surface  86 . Backup flange  84  is opposed to fixed forward flange  72 . 
   Received on external cylindrical surface  86  is a first elastomeric packer  88  and an identical second elastomeric packer  90 . Each of the elastomeric packers  88  and  90  is, in radial cross-section, frusto-conical, that is, each has sloped wall surfaces. Each of the elastomeric packers have an internal cylindrical surface  92  that is slidably positioned on external cylindrical surface  86 . Each of the elastomeric packers has an outer pipe wall contacting surface  94  and opposed side wall surfaces  96 . 
   Slidably received on tubular body external cylindrical surface  70  is a backup ring  98  having opposed sidewalls  102  that taper towards an outer circumferential surface  104 . Side wall surfaces  102  of backup ring  98  mirror the side wall surfaces  96  of elastomeric packers  88  and  90 . 
   Extending radially from piston rod  78  is a piston  106  having an outer cylindrical surface that sealably engages internal cylindrical surface  76 . 
   Affixed at the rearward end of cylinder wall  74  is a cylinder head  108  having an opening  110  therein that slidably receives piston rod  78 . Thus there is created within internal cylindrical wall  74  a cylindrical area  112  that, when pressure is applied thereto tends to move piston rod  78  forwardly towards the right, and consequently rearward flange  80  and backup flange  84  towards the right, to compress elastomeric packers  88  and  90  against forward flange  72 . This action causes the outward displacement of the elastomeric packers so that the outer circumferential surfaces  94  thereof engage the interior wall of a pipeline to thereby close fluid flow through the pipeline. That is, when fluid pressure is applied to cylindrical area  112 , as dictated by control module  40 , elastomeric packers  88  and  90  are squeezed and radially outwardly expanded to close fluid flow through the pipeline. 
   To support the plugging module of  FIG. 4 , a number of rearward wheels  116  are employed. In the same way, forward wheels  118  support the forward end of the plugging module away from a pipeline internal wall as the isolation tool train moves through a pipeline. 
   The typical isolation tool as identified by tools  14  and  16  of  FIG. 1  include, as a part thereof, as have been described, a control module  40  that typically includes a power source in the form of a battery. Further, the control module typically includes a hydraulic pump powered by battery power that is used to actuate the packer module  32  and gripper module  34 .  FIG. 7  illustrates a modified isolation tool that has each of the components as have been discussed with respect to  FIG. 1  but, in addition, includes first and second auxiliary power modules  120  and  122 . First power module  120  is connected to the rearward end of control module  40  by a universal joint  124  and second power module  122  is connected to the rearward end of first power module  120  by a universal joint  126 . Power modules  120  and  122  are providing auxiliary and enhanced power, particularly battery power, for operating an on-board hydro-test pump or for the actuation of the other components making up an isolation tool.  FIG. 7  illustrates flexible conduits  128  and  130 . These flexible conduits interconnect the various elements of the isolation tool for purposes of supplying electrical energy and hydraulic fluid pressure from one component to another. For instance, one of the flexible conduits may be used to supply hydraulic pressure to actuate packer module  32  and gripper module  36 . The flexible conduits can also be employed for providing electrical power from one unit to another such as electrical power from power modules  120  and  122  to a pump contained in control module  40 . Further, one of the flexible conduits  128  and  130  of  FIG. 7  may be employed for the transmission of pipeline liquids, such as liquid from leading liquid slug  20  passed lead isolation tool  14  and into the test liquid slug  22  as shown in  FIG. 1 . That is, one of the conduits  128  and  130  may be employed as required for hydrostatic testing the section of the length of the pipeline indicated by designation D 2  on  FIG. 1 . 
     FIG. 1  of the drawings shows the use of two plugging pigs  14  and  16  to conduct a hydrostatic test of a length of pipe indicated by the designation D 2 .  FIG. 2  illustrates an alternate embodiment of the methods and systems of this invention that is particularly useful in the case of an operating pipeline where a defective section of the pipeline needs to be isolated from operating pressure during repair. In this case a third isolation tool  132  is employed. The third isolation tool  132  follows isolation tool  16  and is separated by a liquid slug  134 . The function of liquid slug  134  is to maintain a fixed distance behind second isolation tool  16  and to prevent a compressible gas bubble from seeping into the test liquid slug  22  that is contained between isolation tools  14  and  16 . Thus, liquid slug  134  makes up an isolation section between isolation tools  16  and  132 . In the arrangement of  FIG. 2  the lead seal pig  12 , lead liquid slug  20 , lead isolation tool  14 , first liquid slug  22 , second isolation tool  16 , trailing liquid slug  24 , and trailing seal pig  18  functions for essentially the same purposes as described with respect to  FIG. 1 . In summary, the difference between  FIGS. 1 and 2  is  FIG. 2  provides an additional isolation tool  132  to provide for an isolation liquid slug section  134 . 
   A main purpose of each of make-up medium slugs  20  and  24  is to provide make-up volumes to test liquid slug  22  during test preparation and to prevent a compressible gas bubble from seeping into either the test liquid slug  22  or the isolation liquid slug  134 . 
   Another purpose of the trailing liquid slug  24  can be to carry a liquid, such as methanol or glycol, to allow drying of new or on-stream gas line while the pig train moves along. The test liquid slug  22  when hydrostatic testing a pipeline is nearly always water or mostly water and leaves a wet pipe wall which results in gradual loss of test slug volume as the train moves along the length of the pipeline. This trailing liquid slug which may also be termed a “make up liquid slug”, then can serve the dual purpose of providing make-up liquid to isolation liquid slug  134  and drying the interior wall of the pipeline behind the test train. 
     FIG. 3  shows an additional alternate embodiment of the systems and methods of this invention for hydrostatically testing a pipeline.  FIG. 3  adds to  FIG. 2  the use of an additional isolation tool, that is, a fourth isolation tool  136  that provides for a second isolation liquid slug  138  between it and isolation tool  14 . Second isolation liquid slug  138  is supplementary to leading liquid slug  20  as described with reference to  FIGS. 1 and 2  but, in addition, the fourth isolation tool  136  helps isolate the basic test system from the downstream pressure of an operating pipeline, in the event of a rupture in the test section, in order to prevent isolation tool  14  from being pushed toward the rupture resulting in damage to the tool. 
   As previously stated, pressure within test liquid slug  22  is provided by a pumping manifold  30  and piping  28 A and  28 B connected to pipe nipples  26 A and  26 B which are hot tapped onto the exterior of the pipeline  10 . This system works satisfactorily when the pipeline  10  is on the earth&#39;s surface but represents a problem if the pipeline hydrostatic test section D 2  is on an ocean floor, that is, subsea or even if on the floor of a lake or river. For these applications test pumping pressure may be accomplished by on-board pumping capabilities provided by one or more of the isolation tools  14  and  16 . As illustrated in  FIG. 7 , within control module  40  is instrumentation  140  which includes systems for measuring and recording the hydrostatic pressure applied to the pipe section D 2 . Also included within control module  40  is an actuation hydraulic pump  142  to apply hydraulic fluid pressure to packer module  32  and gripper module  36  so these devices can be set and unset as dictated by signals conveyed from exterior of the pipeline. In addition, an isolation tool may contain, such as within control module  40 , an on-board test pump  144  powered by an on-board battery  146 . On-board test pump  144  is connected to draw liquid from leading slug  22  and pump this liquid past isolation tool  14  and into test liquid slug  22  to increase the hydrostatic pressure on the length of the pipeline D 2 . This is accomplished without the use of pumping manifold  30 , piping  28 A and  28 B and without the necessity of installing pipe nipples  26 A and  26 B. If the hydrostatic test section  22  is of relatively short length, such as if the length of this section was only sufficient to test a weld joint or a joint of pipe, then the power required to drive on-board test pump  144  could be supplied from on-board battery  146 . On the other hand, if the length of pipeline D 2  that is being hydrostatic tested is relatively long, substantial additional power or energy source is required and thus, as is illustrated in  FIG. 7 , the use of auxiliary power modules  120  and  122  would likely be required. The number of power modules obviously can vary according to the quantity of fluid required to hydrostatically test pipeline section D 2  according to the volume thereof which is directly related to the internal diameter of the pipe and the length of the pipe section D 2 . 
   Referring back to  FIG. 7 , if the hydrostatic fluid to be injected into test liquid slug  22  is to be moved by power supplied from within the pipeline, the test fluid can flow from a fluid inlet  148  on the rearward end of second power module  122 , through flexible conduit  130  to a fluid outlet  150  on packer module  32 . If auxiliary power modules  120  and  122  are not employed, fluid inlet  148  would typically be positioned on the rearward end of control module  40 . 
   The invention thus provides a unique system that is in the form of a pig train made up of pipeline pig components that are moved by the force of fluid flow through the interior of a pipeline, which components include at least two isolation tools, at least one seal pig and a power pumping system for moving fluid under pressure into the interior of the length of the pipeline between the two isolation tools to hydrostatically test the pipeline. The system is adaptable for use to hydrostatically test pipelines on the earth&#39;s surface or in subsea environments. 
   While the invention has been described with a certain degree of particularity, it is manifest that many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. It is understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.