GB1584451A

GB1584451A - Repair of tube to tube-plate joints

Info

Publication number: GB1584451A
Application number: GB4902776A
Authority: GB
Original assignee: International Research and Development Co Ltd
Current assignee: International Research and Development Co Ltd
Priority date: 1978-02-23
Filing date: 1978-02-23
Publication date: 1981-02-11

Description

(54) REPAIR OF TUBE TO TUBE-PLATE JOINTS (71) We, INTERNATIONAL RESEARCH & DEVELOPMENT COMPANY LIMITED, a British Company of Fossway, Newcastleupon-Tyne NE6 2YD, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following state ment : - The present invention relates to the repair of a joint between a tube and a tube plate, for instance where failure of a conventional fusion weld has occurred in a tube to tubeplate installation, for example in a heatexchanger.

In constructions such as a heat-exchanger where a multiplicity of pipes have been welded to a tube plate by conventional fusion welding, leaks in individual joints may occur during operation, due, for example, to faulty welding, thermal cycling or corrosion. There is, therefore a problem of effecting a repair, usually on the site of the installation where access to the leaking joint may make repair by conventional fusion welding unsatisfactory or difficult and, in some cases, impossible.

In installations where the tubes have been welded to the inside face of the tube plate, explosive plugging of the tube-plate holes may readily be employed to seal off the leaks.

This course of action does, however, reduce the efficiency of the heat exchanger. When the tubes pass through the full thickness of the tube-plate and are welded to the outside of the tubeplate, it is not possible to plug so readily. The present invention enables leakage to be stopped up whilst allowing the individual tube to remain in service.

In accordance with the invention there is provided a method of repairing a joint between a tube and the wall of a passage in a tubeplate through which the tube partly extends comprising inserting a sleeve through the tubeplate and into the tube and explosively expanding the sleeve to form annular joints with the tubeplate and the tube.

Preferably the end of the tube wall in the passage is tapered from the inside surface in order to merge smoothly with the wall of the passage in the tube-plate. In a preferred application of the method to the repair of tube to tube-plate joints after failure of a conventional weld, the outer end of the tube is machined away, together with part of the surrounding tube-plate to leave a generally frusto-conical profile converging to the bore of the tube. The inserted sleeve has a smaller degree of convergence to leave a tapering gap around its outer end, while its inner end has a conical taper to form a tapering gap with the tube wall. The former tapering gap assists in the formation of a good joint upon detonation of an explosive charge contained in the sleeve, whilst the latter tapering gap ensures reasonable undisturbed fluid flow in the final joint.

This preferred embodiment of the invention will now be described in more detail with the aid of an example illustrated in the accompanying drawing, the single Figure of which is a cross-section of an assembly prepared for the repair of a tube to tube-plate joint.

The drawing shows a tube-plate 10 which conventionally has a large number d parallel bores in each of which the end of tube 11 is fitted and secured by welding. In the event of failure of the weld there may be dangerous leakage, for example, of high temperature gases from a heat exchanger, and it has been common practice to explosively expand the tube or to drill out the end of the tube to enable the tubeplate hole to be plugged thus putting the tube out of operation. To effect a repair it is now proposed that the outer end of the tube, where the original weld was formed, is first secured, if required, by mechanical or explosive expansion and then machined out to leave a conical convergent profile 12 at the outer end of the passage through the tube plate and a conical taper 13 at the outer end of the remaining part of the tube.

There is then inserted a sleeve 14 contain ing an explosive charge 15 and a detonator 16. The sleeve has a short cylindrical section 17 which fits within the tube 11 and has at "i"ts inner e d a tapered wall 19 leaving a tap ering gap 20 between the inner surface of the tube 1',l a,nd the outer surface of the wall 19.

The outer end of the sleeve 14 is flared, but with a lesser angle of divergence than the profile 12 in order to leave a a tapering gap 21.

The gap 21 increases in width towards the ends of the sleeve 14. Upon detonation of the explosive charge within the sleeve 14 the sleeve is expanded outwards to form an an- nular joint with the tube 11 and tube-plate 10 in the region of the tapering gap 21.

According to the type of explosive used and the materials and dimensions involved, the' force of the explosive expansion may 'be sufficient to form a welded joint or merely a fight ni-echanical joint ,a,'s as appropriate. The :dispos1t5,on, of the charge and 'det6natdr within the sleeve may be varied to obtain the required joints. The tapering gaps are desir able ,but @ not essential. Ideally the' sleeve would form a continuous joint with the whole of the tapred end of the tube and with the taper on the'tube plate over twice the wall of the tube.

"Th e' invention is not restricted to the spe- cific embodiment described, for example, welding of the tapered gap 20 can be effected by virtue of suitable positioning of the explosive charge 15. it may also be possible to effect a weld between the sleeve and the tu"beplate- using the construction described ,in our Pending British Patent Application No. 37642/74 (Serial No. 1,521,526), the explosive charge may also be held within a container separate from the sleeve, which container acts as a transmitting medium.

Claims

WHAT WE CLAIM IS: -

1. A method of repairing a joint between a tube 'a'nd the wall of a passage in a tube plate through which the tube partly extends comprising inserting a sleeve through the tubeplate and into the tube and explosively expanding the sleeve to form annular joints with the tubeplate and the tube.

2. A method as claimed in claim 1 in which the tube has a wall thickness which decreases from the inside towards the end of the tube in the passage in order to merge with the wall of the passage in the tube plate.

3. A method as claimed in claim 2 in which the wall of the passage in the tube, plate ---and the inner surface of the tube have been machined away to a frusto-conical profile converging towards the bore of the tube.

4. A method as claimed in claim 3 in which the sleeve is formed with a frusto conical outer surface with a -seni--cone angle less than that of the said frusto-conical pro file.

5. A method as claimed in any of claims 1 to 4 which the end of the sleeve that is positioned within the tube has a tapered outer surface to form a gap with the inner surface of the tube which increase towards the end of the sleeve.

6. A method of reparing a joint between a tube and a tube plate substantially as de scribed with reference to the drawing ac- companying the Provisional Specification.