ON INSTALLING A PIPE JOINT

The present invention relates to a pipe joint comprising a socket for receiving respective pipe ends, the socket being welded at its ends to the respective pipes.

Such welded pipe joints have been known in the art for a long time, and they are still in fairly wide use on account of their good strength properties and simple installation.

However, they have a serious drawback: it has not previously been possible to make them sufficient¬ ly clean interiorly. This is because there remains a small gap between the inner surface of the socket and the outer surface of the pipe, and pickling liquid (acid) is able to enter the gap, whereas neutraliza¬ tion liquid applied after the pickling liquid is not able to flush it off. The remaining acid damages the welds in particular. Moreover, there is an opening between the end surface of each particular pipe and an internal shoulder in the socket. This opening gathers impurities both in connection with flushing and regular operation. The impurities will loosen later on and cause serious disturbances. The object of the present invention is to provide a novel pipe joint of the type described in the beginning so as to overcome the above-mentioned problems.

The pipe joint of the invention is mainly char- acterized in that an at least substantially cylindri¬ cal metal seal ring in contact with conical inner surfaces of the pipe ends is arranged in axial con¬ tact with the ends of the respective pipes within the socket, the wall thickness of the cylindrical seal ring being so dimensioned that the ends of the ring

wall are bent into close elastic contact with the conical inner surfaces of the pipe ends under the influence of an axial pressure exerted by the pipe ends, whereby the wall of the cylindrical seal ring is provided with means extending between the pipe ends to facilitate the installation of the seal ring.

The seal ring prevents the internal pressure of the pipes and the fluid from entering the gap between the inner surface of the socket and the outer surface of the pipe ends. In this way the pressure acting radially outwards on the socket is considerably smaller than with prior art pipe joints of the same general type. On account of this, the wall thickness of the socket can be smaller than previously and the end welds of the socket need not be tight as they only have to be able to resist the axial forces tend¬ ing to drive the pipes apart from each other.

The smaller weld so obtained can in most cases be accomplished without oxidation which would require flushing with pickling liquid as in the case of pipe joints previously available.

On installing pipe joints, it is often necessary to press the pipe ends to be joined with great force against each other. Previously, this has been carried out with powerful means gripping the pipe from the outside. Such means are difficult to handle and take up plenty of space.

An object of the present invention is to provide a novel apparatus for pressing together pipe ends on installing a pipe joint. This novel apparatus is small in size and easy to handle.

The apparatus according to the invention comprises two support members displaceable towards each other under the influence of pressure, the support

members being intended to be positioned internally on both sides of the joint to be formed and comprising end parts enlarging in a direction away from said joint; a plurality of rolls with surface grooves or the like, the rolls being positioned around the support members, respectively; the surface of the enlarging end part of each support member, along which the rolls are caused to roll, being provided with surface grooves for co-operation with surface grooves provided on the rolls, respectively; and a spring means positioned between the rolls around one support member and the rolls around the other support member, the spring means being arranged to cause the rolls to roll along the surface of the enlarging end part of the respective support member into engagement with the inner surface of the respective pipe end when the support members are dis¬ placed towards each other under the influence of said pressure, and thereafter allow further displacement of the support members towards each other when the pressure is increased, thus bringing the pipe ends, through the engagement of the rolls, axially against each other with a predetermined force. The cooperation of the surface grooves of the enlarged, preferably conical end parts of the support members and the roll grooves, respectively, is essen¬ tial in order to obtain a sufficiently firm grip be¬ tween the rolls and the internal surface of the pipe ends to be joined. In pipe joints here contemplated, one should be able to apply an axial force in the range of 10 to 50 tons when urging the pipe ends to¬ gether. When completed, the pipe joint should prefer ably be able to withstand axial forces of up to 165 tons.

In the following, the invention will be described with reference to exemplifying embodiments shown in the attached drawing.

Figure 1 is a partial longitudinal section of a preferred embodiment of the apparatus of the inven¬ tion.

Figures 2, 3 and 4 illustrate the operation of the apparatus shown in Figure 1 when installing a welded pipe joint. Figure 5 shows the pipe joint with completed welds.

Figure 6 shows an alternative embodiment of the apparatus, intended for use in the installation of a flange to a pipe end. The apparatus shown in Figure 1 comprises a body 1 preferably circular in cross-section. One end portion 2 of the body 1 (to the right in the drawing) has a greater diameter than the middle portion of the body 1. A cylinder sleeve 3 is provided in close sliding contact around said end portion 2 and an adjacent part of the middle portion of the body 1, so that an annular chamber 4 is defined between the sleeve and the inner end surface of the end portion 2 of the body 1. The chamber 4 communicates by means of a conduit 5 with a pressure line 6.

An outer end part 7 of the cylinder sleeve 3 is arranged to enlarge, preferably conically, and the conical surface is provided with grooves 8 or the like for co-operation with similar surface grooves 9 provided on a plurality of wheels or rolls 10 posi¬ tioned around the cylinder sleeve 3 and inter¬ connected by means of spiral springs 11, for example.

An end piece 13 is attached, by means of a threaded joint, for example, to the other end portion 12 of the body 1 (to the left in the figure).

Similarly as the end part 7 of the cylinder sleeve 3, the end piece 13 enlarges conically towards its end and is provided with surface grooves 14 or the like for co-operation with similar surface grooves 15 pro- vided on a plurality of wheels or rolls 16 positioned around the end piece 13 and interconnected with spiral springs 17, for example.

A first spiral spring 18 is arranged between the inner end surfaces of the cylinder sleeve 3 and the opposite end piece 13, in close contact with said surfaces; and a second spiral spring 20, preferably stronger than the first spiral spring 18, is arranged around the cylindrical sleeve 13 and an axially in¬ wardly directed cylindrical support 19 in the end piece 13. A ring 21 and 22 with a smooth surface is arranged between the ends of the second spiral spring 20 and the wheels or rolls 10 and 16, respectively. The wheels or rolls 10 and 16 as well as the rings 21 and 22 are preferably of metal. The reference numeral 23 designates a hook to which a rope can be attached for drawing the apparatus through the pipe to the joint in question if the stiffness of the pressure line 6 is not sufficient to push in the apparatus.

In the following, the operation of the apparatus will be described with reference to Figures 2, 3 and 4.

Two pipes to be joined are designated with 24 and 25, and a sleeve to be welded across the joint by means of end welds is designated with 26. A seal ring 27 is provided between the ends of the pipes 24 and 25. The seal ring 27 comprises an inner, substantial¬ ly cylindrical part 28 and a guide part 29 extending between the end surfaces of the pipes. The guide part 29 is preferably provided with such side bends or the like as disclosed in US Patent 4,728,126. Preferably

the guide part 29 is cut at least at three points along its circumference and the edges at each cutting point are bent in opposite directions. In the posi¬ tion shown in Figures 3 and 4, there is a small gap between the guide part 29 and the adjoining pipe ends 24 and 25, in order to permit a thermal axial expansion of the pipe ends inwards when applying the weld 33 shown in Figure 5.

The pipe ends are provided with internal be- veilings 30 and 31 so as to bring the cylindrical part 28 of the ring 27 in close elastic contact with the pipe ends when the pipes are pressed axially to¬ gether, as is shown in Figures 3, 4 and 5. The angle of the bevellings is rather small in order to provide good sealing contact with the elastically bent cyl¬ indrical part 28.

In Figure 2, the apparatus according to the invention has been inserted into the joint to be formed and it is in inactivated state similarly as in Figure 1.

When pressure is applied to the chamber 4 through the conduit 5 from the line 6, the cylinder sleeve 3 is displaced to the left in the drawing so that it compresses the inner spring 18. The outer spring 20 causes, by means of the rings 21 and 22, the wheels 10 and 16 to roll upwards along the conical surfaces of the end pieces 7 and 13 into engagement with the inner surfaces of the pipes 24 and 25. After a firm engagement has been achieved between the wheels 10 and 16 and the inner surface of the pipes 24 and 25, respectively, the pressure in the chamber 4 is further increased so that the pipes are brought axially together into the position shown in Figure 3 while the outer spring 20 is in com-

pressed state. In Figure 3, the cylindrical part 28 of the seal ring 27 is in close elastic contact with the bevellings 30 and 31, and the end surfaces of the pipes 24 and 25 are positioned against the guide part 29 of the seal ring 27.

Thereafter the weld sleeve is positioned in place and it can be fixed temporarily by means of spot welds 32, Figure 4. The pressure is decreased in the chamber 4, whereby the cylinder sleeve 3 is dis- placed to the right in the drawing and the wheels 10 and 16 are disengaged from the pipes 24 and 25. The apparatus is withdrawn, and the sleeve 26 is fixed finally by means of end welds 33. In principle, the end welds can be made immediately while the apparatus of the invention still keeps the pipes together; there is, however, a risk that the heat damages the seals.

In the embodiment of Figure 6, the pipe 25 and the sleeve 26 are replaced with a flange 34, and the wheels 10 with a retainer ring 35. In principle, the situation in Figure 6 is the same as in Figure 3; the flange 34 is temporarily fixed to the pipe 24 by means of spot welds 32.

An axial press force as high as about 10 tons can be readily achieved by means of the apparatus of the invention. No stationary powerful means are needed. The apparatus can be used to advantage also in connection with thin-walled pipes, whereby deviations from circular shape frequently occurring in the production of such pipes will be automatically compensated for.

The socket, designated 26 in the drawing, of the pipe joint may, instead of being in one piece, be formed of two axial parts with flange-like portions abutting each other and provided with axial co-

inciding bores for bolts cooperating with nuts, as in flange connections in general. For small pipe dimen¬ sions with a comparatively low internal pressure, other lighter connection means for the flange-like parts can be used. The mutual abutment surfaces of the flange-like portions are preferably positioned aside of the metal seal ring 27 to provide guidance for the respective pipe end when assembling the pipe joint. An advantage of such an embodiment is that it can be opened without destroying the socket end welds 33.