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 . 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 ). fig4 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 fig4 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 .