GB862140A - Improvements in or relating to tubulous vapour generating and heating units - Google Patents

Abstract

862,140. Steam superheaters. BABCOCK & WILCOX Ltd. July 29, 1959 [July 29, 1958], No. 24432/58. Class 123(3) In a water-tube steam boiler having a furnace 1 from which gases flow through a lateral pass 2 containing a secondary superheater 95 into a downpass 4 containing reheater banks 100...102 and economizer banks 45...46, a radiantly heated primary superheater 89 is disposed in the top of the furnace adjacent the inlet to the lateral pass. The superheater 89 consists of a number of vertical platens of parallel connected, single-bend U-tubes, the platens being widely spaced across the width of the furnace. The limbs of different tubes of each platen are disposed in a row, the adjacent limbs of neighbouring tubes being rigidly connected together and arranged for flow of steam therethrough in the same direction. In the form shown in Fig. 3, each platen comprises two tube groups 114, 116 each consisting of a number of tubes arranged in pairs. The tubes of the first group 114 extend from an inlet box 88 to a transfer header 115 whilst those of the second group 116 connect the transfer header to an outlet box 90. The platen group 114 comprises pairs of tubes such as the tubes 117, 118 which respectively consist of downflow. limbs 123, 126, return bends 124, 127 of small radius and upflow limbs 125, 128, the return bends being respectively angled out to the right and the left so that whilst the limbs of adjoining tube pairs alternate they all lie in the same plane. The upflow limb 128 is joined to the neighbouring upflow limb 133 of the next tube pair by a welded-on plate 141. This arrangement is repeated throughout eadh platen group so that the tubes are held rigidly in position whilst thermal stresses are avoided since the tubes joined by the plates 141 carry steam at the same temperature. In a modification, Figs. 7-9 (not shown), the superheater has a number of serially connected passes, the end tubes of adjoining passes being connected by a sliding joint. In a further modification, Fig. 11, which shows a single pass superheater, the tube limbs of adjoining pairs do not overlap. Thus, a first tube 240 has downflow and upflow limbs 241, 244 connected by a small radius return bend 243 whilst the adjoining tube 246 has downflow and upflow limbs 247, 249 connected by an oppositely directed return bend 248, the upflow limbs 244, 249 being adjacent and connected by a welded-on plate 250.