Patent GB-555912-A (GB)
Title: Improvements in vessels adapted to withstand internal fluid pressure and in the manufacture of such vessels
IPC: B21D51/24
Filed: 1942-03-09
Abstract: 555,912. Storing gases under pressure. BABCOCK & WILCOX, Ltd. March 9, 1942, No. 3032. Convention date, May 17, 1941. [Class 8 (ii)] [Also in Group XXII] A vessel for containing fluids under pressure consists of an envelope formed of an inner cylindrical wall of thickness insufficient to withstand the hoop stress resulting from the pressure which a head butt welded to the end of the wall is designed to withstand, the envelope being formed of parts united by highclass fusion welds withstanding a stress which is a high percentage (e.g. 95 per cent.) of that to which the metal of the parts may be subjected, together with a number of relatively thin reinforcing layers surrounding the wall. A high-class fusion weld is defined as a weld that has been stress relieved, subjected to mechanical tests and proved by radiography. The wall may be formed by bending one or more plates 14, 16 with fusion welded, longitudinal parts 18 and the plates being fusion welded together at 20 and the end plates fusion welded at 22, 24 to leave spherical heads 10, 12 having ends of similar thickness. For vessels of large diameter each section 14, 16 may consist of a number of segments fusion welded together. After welding is effected the joints are X-rayed and any flaws are rectified and the envelope is then stress relieved in a furnace and allowed to cool. Round the wall is then wound a thin backup layer 35 with open joint 200 and then a number of layers 30, 32, 34, 36 are in turn applied and fusion welded at 70, 71, 72, 73. The points 70-73 are spaced from each other and from the point 18. Each layer may consist of a number of sections, the sections being separated by unwelded gaps 2. The welds in the reinforcing layers are not stress relieved as these parts withstand relatively smaller stresses than does the envelope. The welds may withstand up to 80 per cent. of the stress allowed for the metal of the layers. In order to weld the layers on to the envelope they are first clamped thereon by a cable 40, Figs. 12 and 13, wrapped in two loops therearound, the intermediate portion of the cable being taken round a yoke 45 connected to the piston 170 of an hydraulic cylinder 100 and the ends of which are secured to clevices 42 connected to bolts 56 screwed through a block 110 on the end of a frame. This frame comprises a body plate 102, web plates 104, an end plate 108 and block 110 welded together, the body having eye rings 112, 114 for supporting the apparatus and the webs having set screws 210 for positioning purposes. The frame also carries blocks grooved to receive adjustable side plates 122 to which are welded cross plates 154 provided with guide blocks 161, 163 and hook plates 252. The guide blocks serve as guides for members 166, 168 secured to the yoke 45. The piston is pushed forward by fluid admitted by the yoke 180 and is returned by fluid panel through hollow rods 232, 234 secured to the blocks 161, 163 and communicating with bores 220, 222 in the piston. After clamping each plate it is tack welded at 202, the clamp removed and the point then fusion welded. Wide layers may be successively clamped and tack welded first in the centre and then on each side. A nozzle portion 63, Fig. 5, may be fusion welded to a ring 64 fusion welded to the inside of the wall before stress relieving and the nozzle flange welded to the portion 63 after applying the welded reinforcing layers 30-35 and also a number of additional welded reinforcing layers 75-82 of successively decreasing width. The head may be provided with a manhole 83, Fig. 7, having reinforcing rings, 282, 84 welded thereto, the rings 282 forming a seat 86 for a cover 88 held in position by bolts 90, 92 and bar 84. In another form, Fig. 8, the head is formed of thickness gradually increasing towards the end of the external spherical surface showing a radius R<SP>1</SP> with centre on the line V-W and the spherical surface having a radius R<SP>2</SP> with centre in the line T-U. The reinforcing layers in this form centre beyond the weld between the head and walls of the envelope.