GB564931A - Improvements in or relating to pressure vessels - Google Patents

Abstract

564,931. Steam generators. BABCOCK & WILCOX, Ltd. April 15, 1943, No. 6045. Convention date, April 16, 1942. [Class 123 (ii)] [Also in Groups XXII and XXVIII] In attaching a tubular nipple round the opening in a pressure vessel, such as a drum or header of a steam generating unit, a nipple formed with an end terminating in an axial inner peripheral flange is positioned with the flange in the opening, the nipple is welded to the vessel by depositing metal round the outside of the nipple, and the nipple is then bound to eliminate the flange. When all the nipples have been welded, the header is stress relieved in the shop. To the ends of the nipples are welded in the field the steam generating wall tubes and riser tubes. Inspection openings have nipples similarly welded thereto to the ends of which cap closures are welded. An upper furnace side wall header 10 forged from a single billet and with a reduced neck 11 to which a cap 12 is welded has a series of openings 13 for the attachment of the tubes and a series of inspection openings 25. The nipples which may have a uniform inside diameter and a wall thickness gradually increasing towards the header end are externally bevelled at 19 at 45 degrees leaving at the outer end an unbevelled annular inner peripheral portion 21 and having on the inner end an axially projecting inner peripheral flange 22 which fits the header opening and acts as a welding ring or backing-up strip. The flange is pushed into the opening and the nipple fusion-welded in position by weld metal filling the space between the bevelled end and the circumferential surface of the header. The flanged end 22 is then eliminated by boring out to a diameter slightly greater than the outer diameter of the flange. The remaining unbevelled part of the end 21 is then bevelled at 10 degrees to meet the 45 degrees bevel. Stress relieving is then effected. The tubes 15 and semi-spherical end caps 30 are secured in the field to the nipples by bevelling their ends, placing a backing ring 23 in the 10 degrees recesses and then uniting by weld metal. If desired, the nipples may be made of uniform wall thickness from tubular stock or their ends may be formed with a flange 22b of reduced external-diameter so that only the inner end of the nipple need be bored out to receive the flange. The header may be received at 3 2 to provide pockets for additional weld metal. For inspection purposes the caps may be cut . away by acetylene blow-pipes and the plates subsequently reshaped and rebevelled until the nipple is too short, when it is replaced,