Patent Number: 051204886
Section: summary

FIELD OF THE INVENTION The present invention relates to a sealing sleeve of memory metal, especially suited to repair such leaks in pipes or the like which are difficult to reach, where the sealing sleeve must also be able to endure great temperature differences without being influenced such that the sealing effect is discontinued. The sealing sleeve is particularly suited for use in a nuclear reactor environment. BACKGROUND OF THE INVENTION In a nuclear reactor there are numerous pipes, pipe sockets and the like, in which cracks, especially in the vicinity of welds, may arise and where, during repair work, one end of the pipe may be released so as to form an open end for the fitting of a sealing sleeve. A plurality of various types of sealing sleeves are known--also such of memory metal (see, e.g., U.S. Pat. Nos. 4,773,680 and 4,149,911). Characteristic of these sleeves is that they are not suited for sealing of pipe joints, for example control rod drive (CRD) stub tubes in a nuclear reactor, in which the pipes on either side of the joint are eccentrically arranged. Nor are they adapted to withstand the dimensional changes, caused by the temperature, which occur in a nuclear reactor in which the temperature varies from about +40.degree. C. to about +280.degree. C. SUMMARY OF THE INVENTION The present invention relates to a sealing sleeve for, for example, a pipe socket of such a design that the above-mentioned drawbacks are eliminated. The sealing sleeve according to the invention is characterized in that it comprises a bellows-like mid-portion with annular ends, at least these ends or part of these ends being made of a memory metal with a suitable transition temperature and being given an internal diameter suitable for achieving sealing around the relevant pipe section on each side or the leak. That part of the ends which consists of memory metal is intended to thereafter, at a temperature below the transition temperature, be deformed into a diameter which permits the sleeve to be freely fitted-onto the pipe. In fitted position, the sleeve is intended to be subjected to heating to a temperature above the transition temperature in order to achieve the desired sealing when the memory metal in the sleeve strives to recover its original shape. According to one embodiment, the entire sleeve, including the bellows, is made of memory metal, the annular ends around the inner side being provided with an elevation or a number or grooves for obtaining more reliable sealing. In order to improve the sealing further around, for example, pipe sockets, the elevation or the grooves are replaced by sealing rings of stainless steel, the outer limiting surface of which is spherical and has an external diameter which fits inside the sleeve in its deformed state below the transition temperature. The rings have an inner diameter which permits them to be fitted freely onto the pipe socket. The outer spherical limiting surface of the rings facilitates the adoption by the device of any eccentricity between the pipe sections over which the sealing sleeve is fitted by permitting the sleeve-to slide over the spherical contact surfaces on the outside of the sealing rings. The sleeve finally reaches an oblique position which coincides with the connecting line between the spherical centers of the sealing rings. The aim is to produce a sealing sleeve of memory metal which may be stocked in its deformed state and which withstands all eccentricities up to a certain maximum value without any further enlarging deformation of the diameter of the sleeve being necessary.