GB1249733A - Improvements in or relating to vapour generators - Google Patents

Abstract

1,249,733. Once-through steam generators; expansion joints for furnace walls. BABCOCK & WILCOX CO. 31 Jan., 1969 [1 Feb., 1968], No. 5324/69. Headings F4A and F4B. In a vapour generator including a gas pass having two walls meeting at a corner, wrapper means mounted on the outside of the walls define a gas-tight space, the boundaries of the wrapper means including upper and lower portions extending laterally from the walls and each having an expansion joint provided by an arcuate slot extending around the corner and closed by a flexible cover. A forced-flow oncethrough steam generator comprises four upright tube walls 14, 16, 18, 20, Fig. 2. A windbox (46), Fig. 1 (not shown), enclosing cyclone furnaces (44) disposed on opposite walls 18, 20, enclosures (68, 70) through which recycled flue gas is passed into upper and lower portions of the furnace chamber, and a jacket (78) enclosing fluid mixing headers (76) are all of the form typified by the enclosure 90 shown in Fig. 2. The enclosure 90 comprises a wrapper 92 having top and bottom plates 94, 96 connected by an annular side-plate 95. Each plate 94, 96 has a flange 104, Figs. 3 and 4, welded at 98 to a tiebar 105 mounted on each wall 14, 16, 18, 20. To allow for the fact that thermal expansion of the furnace chamber is greatest at each corner 19, the flanges 104 are spaced from the walls near each corner 19. A flange 106 at each corner 19 is also spaced from the corner. An extensionplate 108, Figs. 3 and 5, bent around the corner 19, is used to connect the flange 106 and the adjacent parts of the flanges 104 to the walls. Thermal expansion is also allowed for by providing each plate 94, 96 with an arcuate slot 124 at each corner 19, the slot being covered by an expansible and contractible arcuate plate 126 of pleated or corrugated cross-section, which is welded along its longer side to the plate. Each end of the arcuate plate 126 is covered by a plate 130 welded thereto and to the plate 94 or 96. The enclosure 90 is braced by truss assemblies 134, 136, Fig. 2, each truss assembly being made up of four interconnected trusses 140, Fig. 8. Each truss 140 comprises an inner chord 142 and an outer chord 144, the chords 144 of the upper and lower trusses being interconnected by vertical posts 152. Each inner chord 142 is rigidly connected at mid-length to the associated wall 14, 16, 18 or 20 and connected near its ends by tie clips 158 to a bar 154 which is welded to the wall. The tie clips 158 permit relative thermal expansion between the wall and the inner chord. Cross-members 146 interconnect the inner chords 142 and outer chords 144. Each truss 140 is connected to the neighbouring truss by link assemblies 160A, 160B. Alternatively, as shown in Fig. 9, adjoining bars 154 are interconnected by plates 180.