Abstract:
An apparatus for connecting two flanged pipes comprises at least one piston arrangement having a pair of opposed pistons slidable within a hydraulic cylinder. Each pair of pistons has a rod extending therefrom and is adapted to receive a threaded fastener at its end remote from the piston. Each rod extends through an aperture at the respective cylinder end and is adapted to pass through a respective aperture in the flange of a flanged pipe. Each piston has an associated biasing means in the form of a spring or similar which urges the piston away from its respective cylinder end. Pressurization of the hydraulic fluid in the cylinder causes the piston to move towards its respective cylinder end against the urging action of the biasing means, to allow the hand tightening of the threaded fastener. When the pressure is removed the action of the spring biases the flanges of the flanged pipes together to energize the ring seal between each flange and the apparatus.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to an apparatus for connecting flanged pipes, particularly large diameter flanged pipes which in use are subject to high pressure such as risers in oil-field applications. 
   It is a well-known requirement that shorter sections of pipe such as riser sections must be joined together to form longer pipes or risers. Such pipe sections are provided in standard lengths and delivered to the location in which the pipe is to be installed. Each section has a circular flange at each end, each flange being provided with a number of apertures and a circumferential groove in the mating surface of the flange, in which may be placed a ring seal. Two pipe sections are brought together such that the mating surfaces are aligned with a ring seal between them. Threaded fasteners or bolts are placed in the apertures and nuts are tightened onto the bolts. The nuts are tightened to a predetermined torque in order to energise the ring seal. 
   The known method of joining flanged riser sections suffers from the disadvantage that it is slow and difficult to carry out under adverse conditions. The method requires considerable strength, skill and reliability of operators, together with the use of heavy tools in confined spaces or areas of difficult access. Furthermore, the securing force is dependent on the extent of wear and the general condition of the threaded fasteners. 
   JP 0800-11063 discloses an auxiliary device for tightening the nuts and bolts that fasten the flanges of pipe sections. A piston portion of the device is attached to each of the bolts and hydraulic pressure is applied to the piston head which draws each bolt towards the device allowing the associated nut to be manually tightened. However, time and effort is required to attach each piston portion of the device to, and remove the portion from, each individual bolt for tightening the associated nut. 
   According to a first aspect of the invention, there is provided an apparatus for connecting two flanged pipes comprising at least one piston arrangement having a pair of opposed pistons slidable within a hydraulic cylinder,
         each of said pair of pistons having a rod extending therefrom and adapted to receive a fastener at its end remote from the piston,   each of said rods extending through an aperture at the respective cylinder end and being adapted to pass through a respective aperture in the flange of a flanged pipe,   each of said pistons having an associated biasing means which urges the piston away from its respective cylinder end,   wherein pressurisation of hydraulic fluid in the cylinder causes the piston to move towards its respective cylinder end against the urging action of the biasing means.       

   In use the apparatus may be placed between two flanged pipes such that the two opposing rods of the piston arrangement extend through the respective apertures in the flanges of the two flanged pipes. Nuts are secured to threaded ends of the rods, so that the apparatus is securely held between the two flanged pipes. When the hydraulic fluid is pressurised the pistons are forced against the biasing action so that the rods and nuts move outwards. The nuts may then be further tightened onto the threaded ends of the rods. When the pressure in the hydraulic fluid is removed the biasing means urges the pistons towards each other, so energising the connection between each flanged pipe and the apparatus. 
   Preferably the fastener is a threaded fastener. Preferably, the apparatus comprises a cylindrical body. Preferably, the cylindrical body has an axial through bore. This bore is preferably the same size as the internal bore of the two pipe sections to be joined. When the apparatus is used to join two pipe sections, the axial through bore is aligned with the internal bore of each of the pipe sections. 
   Preferably, the apparatus comprises a plurality of said piston arrangements spaced at intervals about and externally of the through bore. Preferably, there are four or more piston arrangements spaced equidistantly on a circumference. Preferably, the piston arrangements are arranged such that the pistons move parallel to the axis of the through bore. A standard flange has 12 apertures, so the apparatus for joining pipes having such flanges would have 12 piston arrangements arranged at the same relative positions as the 12 apertures. 
   Preferably, each of the biasing means comprises a spring. The spring may be arranged around the rod and may act between the piston and the respective end wall of the cylinder. Typically the spring comprises a number of conical washers, although a helical spring of appropriate stiffness may be used. 
   Preferably, hydraulic fluid is provided between the pistons in the cylinder. Preferably, the apparatus comprises one or more hydraulic fluid passages communicating with the one or more hydraulic cylinders at a connection point in each of the cylinders arranged between the two pistons. 
   Preferably the apparatus comprises first and second bearing faces at opposite ends adapted to bear in use against the end faces of the pipes to be joined. Preferably each of the bearing faces is provided with a circumferential groove adapted to house a ring seal. 
   According to a second aspect of the invention, there is provided a pipe connection comprising a first pipe having a first flange at the end thereof, a second pipe having a second flange at the end thereof, and an apparatus according to the first aspect of the present invention. 
   Preferably, the two opposing rods of the piston arrangement extend through respective apertures in the flanges of the two pipes. 
   Preferably, the pipe connection further comprises a threaded fastener secured to the end of each of the rods. Preferably, the end of each rod is provided with an external thread and the threaded fastener is a nut. 
   Preferably, the number of piston arrangements is equal to the number of apertures in each flange. 
   According to a third aspect of the invention, there is provided a method for connecting first and second flanged pipes, the method comprising the steps of:
         (a) providing an apparatus comprising at least one piston arrangement having first and second opposed pistons slidable within a hydraulic cylinder, each of said first and second pistons having a rod extending therefrom and having associated biasing means adapted to bias the piston away from the end of the cylinder;   (b) placing the apparatus between the opposing flanges of the flanged pipes such that the rod of the first piston projects through an aperture in the flange of the first pipe and the rod of the second piston projects through an aperture in the flange of the second pipe;   (c) securing a fastener to each of the rods and tightening the fastener against the respective flange;   (d) pressurising the cylinder between the pistons to cause the pistons and rods to move away from each other and to cause the fasteners to move away from the respective flanges;   (e) tightening further each fastener against the respective flange; and   (f) reducing the pressure in the cylinder to cause the pistons and rods to move towards each other under the action of the biasing means and to cause the fasteners to apply a greater clamping force to the respective flanges.       

   Preferably the or each fastener is a threaded fastener. 
   Steps (d) to (f) may be repeated as required, particularly in the case when a seal ring is provided between the apparatus and each of the flanges, and the seal ring deforms plastically under the action of the increased clamping force. 
   The method may further include the step of measurement of the clamping force. The force may be measured using at least one tension indicator connected to the or each fastener. Alternatively, the force may be measured using at least one load washer. 
   Preferably the apparatus is an apparatus according to the first aspect of the invention. 
   According to a fourth aspect of the invention, there is provided an apparatus for connecting a first pipe having a flange and a second pipe comprising at least one piston arrangement having a piston slidable within a hydraulic cylinder,
         the piston having a rod extending therefrom and adapted to receive a fastener at its end remote from the piston,   said rod extending through an aperture at the respective cylinder end and being adapted to pass through a respective aperture in the flange of the first flanged pipe,   said piston having an associated biasing means which urges the piston away from its respective cylinder end,   wherein pressurisation of hydraulic fluid in the cylinder causes the piston to move towards its respective cylinder end against the urging action of the biasing means.       

   Preferably the apparatus further comprises a flange remote from said rod for abutting a flange provided on the second flanged pipe. Preferably the flange of the apparatus has at least one aperture for receiving one or more fasteners. Alternatively the apparatus further comprises a weld neck remote from said rod for welding of the apparatus to the second flanged pipe. Alternatively the apparatus forms an integral part of the inlet of an item of equipment. 
   According to a fifth aspect of the invention, there is provided a method for connecting a first pipe having a flange and a second pipe, the method comprising the steps of:
         (a) providing an apparatus comprising at least one piston arrangement having a piston slidable within a hydraulic cylinder, said piston having a rod extending therefrom and having associated biasing means adapted to bias the piston away from the end of the cylinder;   (b) placing the apparatus between the pipes such that the rod of the piston projects through an aperture in the flange of the first pipe;   (c) securing a fastener to the or each rod and tightening the fastener against the flange of the first pipe;   (d) pressurising the cylinder between the or each piston to cause the or each piston and rod to move away from each other and to cause the or each fastener to move away from the flange of the first pipe;   (e) tightening further the or each fastener against the flange of the first pipe; and   (f) reducing the pressure in the cylinder to cause the or each piston and rod to move towards each other under the action of the biasing means and to cause the or each fastener to apply a greater clamping force to the flange of the first pipe.       

   Preferably the apparatus further comprises a flange remote from said rod and having at least one aperture, the second pipe is provided with a flange having at least one aperture, and the method further comprises the step of locating a bolt through the or each aperture of the flange of the apparatus and the or each aperture of the flange of the second pipe, securing a fastener to the or each bolt and tightening the or each fastener. 
   Alternatively the apparatus further comprises a weld neck remote from said rod, and the method further comprises the step of welding the apparatus to the second pipe. 
   Example embodiments of the invention will now be described by way example only, with reference to the accompanying Figures, in which:— 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of a connecting apparatus according to the first aspect of the present invention; 
       FIG. 2  is an enlarged sectional view of a piston of the connecting apparatus of  FIG. 1 ; 
       FIG. 3  is a plan view on the apparatus of  FIG. 1  with the flange of the pipe and the ring seal omitted for clarity; and 
       FIG. 4  is a sectional view of a connecting apparatus according to the fourth aspect of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A connecting apparatus generally described at  1  comprises a cylindrical body  2  having an axial through bore  3 . The apparatus is shown in the unenergised state between the first flange  20  of a first pipe  10  and the second flange  22  of a second pipe  12 . Between each of the end faces  4 ,  5  of the cylindrical body  2  and the respective end faces  24 ,  26  of the flanges  20 ,  22  there is provided a ring seal  30  which, in its unenergized state, stands proud of the circular grooves  6 ,  28  in the end faces  4 ,  5 ,  24 ,  26  of the cylindrical body  2  and flanges  20 ,  22 , thereby creating a gap between the adjacent faces  4 ,  5 ,  24 ,  26  of the cylindrical body  2  and flanges  20 ,  22 . 
   In order to prevent the existence of this gap, and to provide an effective seal between the flanges  20 ,  22  and the cylindrical body  2 , it is necessary to forcibly push the flanges  20 ,  22  against the cylindrical body  2 . This is achieved by the piston arrangements generally indicated at  50 . The effect of compressing the flanges  20 ,  22  against the cylindrical body  2  is to energise or compress the seal  30 . This compression is desirable to increase the effectiveness and efficiency of the seal  30 . 
   Each piston arrangement  50  includes a cylinder  52  adapted to house an opposed pair of slidable pistons  54 ,  56 , a plug  58  closing each end of the cylinder  52  and clamping springs  60 . The pistons are provided with piston rings  72  which seal between the pistons  54 ,  56  and the cylinder  52 . The springs  60  serve to bias the pistons away from the plugs  58  at the ends of the cylinder  52 . Each piston  54 ,  56  is provided with an integral rod  64 ,  66  which extends through an aperture in the plug  58  sealed with an O-seal  62 . The springs  60  are provided around the rods  64 ,  66  and act between the plugs  58  and the piston bodies  54 ,  56 . The rod  64 ,  66  is provided with an externally threaded portion  68  at its free end, adapted to receive an internally threaded nut  70 . 
   The rod  64 ,  66  passes through an aperture  32 ,  34  provided in the respective flange  20 ,  22 . A washer  74  is provided between the nut  70  and the flange  20 ,  22 . One or more dowels (not shown) engage both the piston  54 ,  56  and the cylinder  52  in each arrangement for the purpose of preventing rotation of the piston  54 ,  56  when the nut  70  is tightened. 
   In the embodiment shown, there are provided  12  piston arrangements  50  arranged equidistantly on a circumference whose radius corresponds to the radius of the circumference in which the apertures  32 ,  34  in the flanges are arranged. The piston arrangements are permanently secured to the cylindrical body  2 , although the nuts  70  are detachable, thereby allowing removal of the flanges  20 ,  22  from the connecting apparatus  1 . 
   A hydraulic hose connection  80  is provided at the edge of the cylindrical body  2 . A network of hydraulic fluid passages  82  links the connection  80  to the central portion of each of the cylinders  52  of the piston arrangements  50 . These passages  82  are formed by drilling and then plugging the ends  84 , so that the passages  82  do not communicate with the exterior except through the hose connection  80 . 
   The connecting apparatus  1  can be used to connect any flanged pipes, but it is particularly appropriate for use with 7 1/16″ snubbing riser sections, when a number of flanged connections (typically 10 to 15) need to be made up in as short a time as possible in order for the snubbing or oil drilling rig to be able to start its drilling operation. During assembly the individual lengths of riser must be connected at a location above the rig floor which is difficult to access. 
   In use, a connecting apparatus  1  is provided which has an internal bore  3  equal in size to the bore of the pipe sections  10 ,  12  to be joined. The upper and lower faces  4 ,  5  of the apparatus have gasket or ring seal arrangements which match those on the flanges  20 ,  22  of the pipe sections  10 ,  12  to be joined. The apparatus  1  has a number of threaded connecting rods  64 ,  66  protruding from each face  4 ,  5  and these are engaged with corresponding apertures  32 ,  34  in the flanges  20 ,  22 . The threaded connecting rods  64 ,  66  are equal in number, length and diameter to the threaded connectors used to join conventionally the pipe sections  10 ,  12 . 
   Once the apparatus  1  is in place between the opposing flanges  20 ,  22  of the flanged pipes such that the rods  64  on the upper side project through the apertures  32  in the flange  20  of the upper pipe  10  and the rods  66  on the lower side project through the apertures  34  in the flange  22  of the lower pipe  12 , a threaded fastener or nut  70  is secured to each of the rods  64 ,  66  and the fastener  70  is tightened against the respective flange  20 ,  22 . It is only necessary to tighten the nuts  70  by hand or to a low torque at this stage, sufficient to cause the nuts  70  to bed down. 
   The following sequence of events is then followed:
     1. The cylinders  52  are hydraulically pressurised between the pistons  54 ,  56  to cause the pistons  54 ,  56  and rods  64 ,  66  to move away from each other thereby compressing the springs  60  and causing the threaded fasteners  70  to move away from the respective flanges  20 ,  22 ;   2. Each fastener  70  is tightened further against the respective flange  20 ,  22  (again low torque or hand tightening is appropriate);   3. The pressure in the cylinders  52  is reduced to cause the pistons  54 ,  56  and rods  64 ,  66  to move towards each other under the action of the springs  60  which serve as biasing means and to cause the threaded fasteners to apply a greater clamping force to the respective flanges.   

   Steps 1 to 3 above may be repeated as required, until the required clamping force is achieved, so that the tension in the rods  64 ,  66  is equal to the tension exerted on the equivalent studs of a standard threaded stud connection by tightening them to their recommended torque. Therefore, should the connecting apparatus  1  fail for any reason, the fasteners  70  can be removed using conventional tools. 
   When a seal ring  30  is provided between the apparatus  1  and each of the flanges  20 ,  22 , repetition of steps  1  to  3  may be necessary, since the seal ring  30  deforms plastically under the action of the increased clamping force, to form a seal against the inclined sides of the seal groove  6 . 
   Measurement of the clamping force can be performed, in order to verify the clamping force provided by each piston arrangement  50 . To measure the force, a number of tension indicators (not shown) can be connected to the fastener  70  in a manner known in the art. Alternatively, the force may be measured using one or more conventional load washers (not shown). 
     FIG. 4  shows a second embodiment of the present invention. The apparatus is identical to that of the first embodiment above the line A—A shown in the figure, and identical elements will not be described. 
   In this embodiment, the connecting apparatus  1  comprises only one piston  54  within each piston arrangement  50 . The cylinder  52  is blanked off at the head end  55 . Thus, when the cylinders are pressurised via the hydraulic connection  80 , the hydraulic pressure will act only on one piston head  54  for each piston arrangement  50 . 
   Connection to a first pipe, using the piston arrangements  50 , is the same as described above. The apparatus also comprises a conventional flange  57  with apertures  59  for connecting the apparatus  1  to the flange  22  of the second pipe  12 . The two flanges  22 ,  57  may be joined together using any conventional means such as nuts  70  and bolts  65 . 
   While the embodiment of  FIG. 4  includes a conventional flange  57  and nuts  70  and bolts  65 , the connecting apparatus  1  may be connected to the second pipe  12  in other ways known in the art. For instance, the apparatus may be provided with a weld neck (not shown), allowing welding of the apparatus  1  to the second pipe  12 . Typically, the second pipe would not require a flange  22  and the weld neck would be sized to fit around the outer diameter of the pipe  12 . The apparatus  1  could then be seam welded to the pipe  12 . In another alternative, a manufacturer may provide the apparatus  1  comprising a single piston  54  for each piston arrangement  50  at the inlet of an item of equipment. 
   The embodiment of the invention comprising a single piston  54  for each piston arrangement  50  can allow the apparatus  1  to be permanently attached to a pipe or item of equipment. 
   Referring now to either embodiment of the invention, it should be noted that the piston arrangement  50  of the apparatus and method described herein allows the nuts  70  to be tightened by hand and does not require a large torque. It will be appreciated that this is a considerable advantage over the requirement of using heavy tools which has been the practice in the past. Such tools include conventional wrenches and torquing devices, flogging wrenches and sledge hammers. 
   The invention permits greater repeatability and reliability of connections, since the hydraulic pressure to which the pistons  54 ,  56  are subjected may be monitored. Typically a pressure of between 10,000 and 20,000 psi may be achieved. Furthermore, the need for intensive manual or skilled labour by operators is also mitigated. Similarly, there is a reduced danger of injury to operators or bystanders during such operational and maintenance functions. 
   A further advantage of the invention is that the clamping pressure may be predetermined by the springs and it is possible to achieve uniform pressure around the periphery of the liner, which enables perfect liner alignment. 
   Other advantages of the invention will become apparent to operators and associated personnel involved in the implementation and operation of the invention, including the fact that reduced time is required to affect the connection of the pipes. 
   Further modifications and improvements may be incorporated without departing from the scope of the invention.