A WELDED PIPE JOINT

Abstract: A welded pipe joint comprising a sleeve (3) welded (5, 6) at each end thereof to the respective pipe (1, 2). The wall of the sleeve (3) at each pipe provided with a boring in which a nipple (11, 12) for oil is arranged. In connection with each nipple, a peripheral groove (15, 16) is arranged to extend around the respective pipe (1, 2). Oil introduced through the nipples (11, 12) prevents pickling acid from entering clearances (9, 10) between the pipes (1, 2) and the sleeve (3), and impurities from gathering in gaps (7, 8) between the end faces of the pipes and a central shoulder (4) formed internally in the sleeve.

Description: A welded pipe joint The present invention relates to a welded pipe joint comprising a sleeve for receiving the end portion of at least one pipe to be joined, said sleeve being, at the respective end thereof, welded to the respective pipe. Welded joints of this type have been known for a long time, and are still used widely due to their good strength and simple installation. These pipe joints, however, have a serious draw¬ back; attempts to make the joints sufficiently clean in¬ ternally have previously been unsuccessful. This is be¬ cause there is a narrow clearance between the inside of the sleeve and the outside of the pipes and pickling liquid (acid) enters this clearance whereas the neutral¬ izing liquid applied thereafter is not able to flush it off. The remaining acid affects adversely the weld joints in particular. In addition, there is a gap be- tween the end face of the pipe and a respective shoulder formed internally in the sleeve, and this gap gathers impurities both during flushing and regular operation, which impurities eventually come loose and cause serious disturbances. The object of the present invention is to provide a new welded pipe joint of the type described in the be¬ ginning and by means of which the above problems can be solved. The pipe joint according to the invention is mainly characterized in that in the wall of the sleeve, at the pipe received therein, there is formed a through- going boring for introducing a lubricant, and that a pe¬ ripheral groove is formed in connection with said boring for distributing the lubricant. The boring is preferably positioned in the vici- nity of the sleeve end and it is threaded, as well as a nipple for the lubricant. The groove may be formed either on the inside of the sleeve or on the outside of the pipe. The latter alternative facilitates correct po- sitioning of the pipe end. The lubricant, usually oil, forced in prior to the pickling prevents the corrosive pickling acid from entering in between the pipe and the sleeve. Oil im¬ pacted during the flushing and regular operation pre- vents impurities from gathering in the gaps at the end faces of the pipes. In the following the invention will be described with reference to the attached drawing. Figure 1 is a partial longitudinal section of a first embodiment of a pipe joint according to the inven¬ tion. Figure 2 is a cross-sectional view along the line II-II shown in Figure 1. Figure 3 is a partial longitudinal section of a second embodiment of a pipe joint according to the in¬ vention. Figure 4 is an enlarged longitudinal section of the area A in figure 3. Figures 5 and 6 illustrate a preferred method of cutting a pipe, figure 6 being a cross-sectional view along the line VI-VI in figure 5, for the embodiment of figure 3. In figures 1 and 2, the reference numerals 1 and 2 designate two pipes to be joined. 3 designates a sleeve with a central annular shoulder 4 formed inter¬ nally therein; 5 and 6 designate weld joints at both ends of the sleeve 3. In a welded pipe joint of this type, there are annular gaps 7 and 8 between the end faces of the pipes 1 and 2 and the shoulder 4, and nar- row clearances 9 and 10 between the pipes and the sleeve. The annular gaps 7 and 8 are required in order to permit linear expansion of the pipes 1 and 2 within the sleeve during the welding operation. When internal cleanness is required, the gaps 7 and 8 as well as the clearances 9 and 10 have caused an insolvable problem. The internal cleaning is carried out by means of a pickling liquid, i.e. acid, whereafter flushing is effected with a neutralizing liquid. The neutralizing liquid is not able to remove the pickling liquid from the clearances 9 and 10 which results in that the weld joints 5 and 6 in particular are gradually corroded internally. In addition the gaps 7 and 8 gather impurities which come loose during the regular operation in more or less large lumps which cause serious disturb- ances. The present invention solves the problem by means of lubricant nipples 11, 12 provided in borings formed in the wall of the sleeve 3. Peripheral grooves 15 and 16 are arranged in connection with the borings for the even distribution of a lubricant, usually oil, injected through the nipples 11 and 12 around the pipes 1 and 2. Conduits in the nipples 11 and 12 are designated with 13 and 14. In the embodiment of figures 1 and 2, the grooves 15 and 16 are formed on the inside of the sleeve 3. In figure 2, the broken line 17 designates the bottom of the annular groove 15. Prior to and possibly also during the pickling oil is introduced through the nipples 11 and 12, so that it fills the clearances 9 and 10 and passes out through the gaps 7 and 8, thus preventing the pickling liquid from entering the gaps 9 and 10. During the flushing and regular operation, the oil prevents impurities from gathering in the gaps 7 and 8. When the nipples are po¬ sitioned relatively close to the weld joints 5 and 6, it can be ensured that the pickling liquid cannot reach these. The nipples 11 and 12 are preferably screwed into each boring in the shell of the sleeve 3. The embodiment of figure 3 differs from the one of ' figures 1 and 2 in that the peripheral grooves in connection with the boring through the wall of the sleeve 3 are formed on the outside of the pipe ends re¬ ceived in the sleeve. The groove of the pipe 2 is de¬ signated 20. These grooves in the pipe surface facilitate cor- rect positioning of the pipes 1 and 2 in relation to each other and in relation to the sleeve e.g. by means of screws 22 and 23 having a pointed end. The conven¬ tional internal shoulder 4 of the sleeve 3, earlier needed to ensure correct positioning, can be omitted and the two gaps 7 and 8 on either side of the shoulder 4 are reduced to one. After positioning the pipes and welding them to the sleeve the screws 22 and 23 are replaced by lubri¬ cant nipples, as shown in figures 1 and 2, for the time of the internal cleaning process. Thereafter the screws 22 and 23 may be locked in the respective borings. One way of doing this is illustrated in figure 4. The screw 23 has a hexagon socket 24 and a cone point 25. An expansion ball 28, preferably of metal, is forced into the socket 24 by means of a tool 26 with a magnetic head 27. During the welding process, a protective gas can be introduced through the boring of the sleeve 3 in order to reduce the formation of slag and oxides on the internal surfaces later to be cleaned. The protective gas can be fed in through nipples like 11 and 12, or by providing the screws 22 and 23 will feed bores, or by using separate means to be fitted into the borings through the wall of the sleeve 3. The invention can, of course, be applied to vari- ous branched joints as well as to the straight joints shown in the drawing, or to a joint with only one pipe end, if one end of the sleeve 3 is joined to a fixed connection, e.g. a pump. Figures 5 and 6 schematically illustrate one way of providing the outer pipe surface with a groove at a predetermined distance from the pipe end. Refernce nume¬ ral 30 designates a cutting wheel, numerals 31, 32 and 33 designate supporting wheels each provided with a pe- ripheral edge 34, 35 and 36, respectively. A fourth sup¬ porting wheel is behind the wheel 32 in figure 5. The cutting wheel and the supporting wheels are interconnected and rotate together around a pipe to be cut. While the cutting wheel cuts through the pipe the peripheral edges of the supporting wheels form grooves 20 and 21, each at a predeterminal distance from the pipe end.

Claims: Claims 1. A welded pipe joint comprising a sleeve for receiving the end portion of at least one pipe to be joined, said sleeve being, at the respective end there¬ of, welded to the respective pipe, c h a r a c t e r ¬ i z e d in that in the wall of the sleeve (3), at the pipe (1, 2) received therein, there is formed a through- going boring for introducing a lubricant, and that a pe- ripheral groove (15, 16; 20, 21) is formed in connection with said boring for distributing the lubricant. 2. A welded pipe joint according to claim 1, c h a r a c t e r i z e d in that the boring in the wall of the sleeve (3) is positioned in the vicinity of the sleeve end. 3. A welded pipe joint according to claim 1, c h a r a c t e r i z e d in that the boring is threaded. 4. A welded joint according to claim 1, c h a r - a c t e r i z e d in that the peripheral groove (15, 16) is formed on the inside of the sleeve (3). 5. A welded joint according to claim 1, c h a r ¬ a c t e r i z e d in that the peripheral groove (20, 21) is formed on the .outside of the pipe (1, 2).

Inventors: SUNDHOLM GOERAN, SUNDHOLM, GOERAN
Applicants: SUNDHOLM GOERAN, SUNDHOLM, GOERAN
Application year: 1988
Main classification: F16L13
IPC codes: B08B17, C23G1, F16L13