GB733647A - Improvements in or relating to pressure tight joints between tubular elements - Google Patents

Abstract

733,647. Tube joints. BABCOCK & WILCOX, Ltd. July 28, 1953 [July 30, 1952], No. 19246/52. Class 99 (1). [Also in Group XXII] In a joint between tubular elements 1, 2, e.g. the tubes of a superheater, of steels having different thermal coefficients of expansion, the element 1 is formed with an annular axially-extending pocket 22, e.g. between a tube 3 of ferritic steel and a collar 4, which houses a length of the element 2, e.g. of austenitic steel. The inner and outer circumferential surfaces are in intimate contact with the inner and outer walls of the pocket, and there are locking means which prevent relative longitudinal movement between the elements 1, 2. The internal surface of the element 2 may be formed with a number of evenly spaced, circumferential grooves 33 of rectangular cross-section, and equally spaced longitudinally extending grooves 35. The collar 4 may be provided with an internal, annular flange 11, the opening 12 of which fits the outside of the tube 3, having inner and outer curved shoulders 13, 14; the inner surface of the collar is formed with a number of longitudinally spaced, circumferential grooves 21. The elements are assembled as shown in Fig. 1 by inserting the element 2 in the pocket 22 such that the curved end 30 of that element fits the shoulder 13 of the collar 4, and the grooves 21, 33 are staggered by a half-pitch. An initial expanding operation of the tube 3 is carried out to nip the parts together in the correct relative positions. In the final expansion, the outer surface of the tube 3 is caused to flow into the grooves 33, 35 of the element 2 and the outer surface of the element 2 is caused to flow into the grooves 21 of the collar 4, thereby preventing relative rotational and longitudinal movements between the elements 1, 2. The collar 4 and tube 3 are united by the deposition of weld metal in the groove 17, and the element 2 and tube 3 are cut away at 28 and 7 to provide one side of a welding groove. In an alternative method of assembly of the joint, a steel support ring is disposed around the collar 4, the element 2, in this instance ungrooved, being pushed home in and fully expanded against the collar, after which the grooves 33, 35 are machined on the interior surface of the element. The tube 3 is threaded through the flange 11 of the collar 4 to form the pocket 22 and fully expanded into engagement with the element 2. Finally, the collar 4 and tube 3 are united by welding at the groove 17 and a final expanding operation is given to the whole assembly. Specification 686,656, [Group XXII], is referred to.