GB658433A - Improvements in or relating to water tube boilers of re-entrant type - Google Patents

Abstract

658,433. Forced-flow boilers. CLARKSON, A. April 26, 1949, No. 11082. Convention date, April 29, 1948. [Classes 64(i), 64(iii), and 123(ii)] A steam or like boiler comprises an outer shell 13, Fig. 1, which locates at least two concentric banks 10, 11 of steam-generating tubes defining a central combustion chamber 18 and a convection passage 12 leading from the latter to a combustion gas outlet 23. The shell 13 is closed at one end by a fixed head 14 and at the other end by a removable closure plate 15 having an associated mixing and ignition chamber 38 fitted with a liquid or gaseous fuel nozzle 35 and air supply pipe 39. The tube bank 10 comprises two sections 16, 17 of tubing which are coiled helically so that the convolutions of each tube alternate with and abut those of the other, the inlet ends of said tubing being connected to the tube bank 11 by couplings 32 and the outlet ends being bent into volute spirals 19, 20 and connected to an outlet header 24. The tube bank 11 similarly comprises two sections 28, 29 of tubing to which water is supplied through a feed pipe 31. Heat-absorbing surfaces in the form of spiral helices 40 are secured to one or other of the tube banks, e.g. the outer side of the bank 10, preferably by spot welding; additional helices 40a may also be secured to the inner side of the bank 10 in the gas outlet passage surrounding the inner end of the mixing chamber 38. Instead of helices 40 a series of separate elements in the form of open loops 42, Fig. 4, may be welded to the tubes.