Patent GB-419116-A (GB)
Title: Improvements in and relating to fire-protecting apparatus for storage tanks
IPC: A62C4/00
Filed: 1933-10-09
Abstract: 419,116. Preventing fires. WOIDICH, F. S., 287, West 11th Street, Tulsa, Oklahoma, U.S.A. Oct. 9, 1933, No. 27785. [Class 47 (ii).] Relates to protective devices for storage tanks of the kind comprising a " breather " vent in combination with a flame arrester and a snuffing device for extinguishing any flame which may persist in the arrester, and consists in adapting the pressurevent valve, which normally allows the escape of gases from the tank, to act as the snuffer valve, and in arranging the arrester, which is common to both the pressure vent valve and the suction valve, between the said valves and the atmosphere. The breather pipe 2 of the tank 3 connects with a chamber 6 within which is the vent casing 7 which connects with the arrester 4 by a pipe 5 and is formed with mercury-sealed valve seats 13, 25<1> for the outlet and inlet valves 9, 10. The latter are carried by telescoping guide tubes 25, 26 and are formed with curved vanes, whereby they are rotated by the escaping or entering gases, so that wear of the valves and valve seats is equalised. A shaft 32 extending into the casing 7 from outside the chamber 6 carries at its inner end a fork 33 the arms of which carry rollers 34 spaced above the valve 9. On the outer end of shaft 32 is fixed a lever 35 counterweighted at 36 and movable between stops 43. The lever 35 is connected to a manual cable 37 and to a link 39 fixed to a bellows member within a fluid-tight chamber 41. The lever 35 is turned in a clockwise direction, by movement either of the cable 37 or the link 39, to cause the rollers 34 to press the valve 9 to its seat. The flame arrester 4 is supported on the tank 3 by cushioning members 45, and comprises telescoped tubes 50, 51 mounted respectively in headers 47, 48, Fig. 6. Above the header 47 is a chamber 54<1> open to the atmosphere through an annular port 56 with a wire screen 57. The tubes 50, 51, Fig. 8, are spaced by ribs 52, and a spiral member 53 defines spiral passages 54, 55 through the tube 50. Below the header 48 is a chamber 58 for receiving dirt, water, and condensed oil vapour from the gases passing through the tubes 50, 51. The chamber has a pivoted cover 62 held closed by a rod 63 which embodies a fusible link 65 and is connected at its upper end to a quick-release latch 68 supported by a spring 71. By release of the latch 68, the cover 62 is opened to allow dirt to be removed. Water and oil are removed by a pipe 74 connected to a separator 75 wherein the oil separates from the water and returns to the tank by a pipe 82, whilst the water flows to waste by a pipe 80. The pipe 74 within the separator 75 includes a spiral member 79, and discharges into an annular passage 77 closed by a gravity valve 79<1>. The pipes 50, 51 are cooled by an oil-covered water bath 83, in which a constant level is maintained by an overflow device 84 connected to the separator 75. The device 84 provides a means for filling the water bath and/or the separator. Tubular pressure bulbs 89, 90 arranged in the flame arrester as shown, are connected by a pipe 92 to the chamber 41, the closed system so formed being charged with a thermally-expansive liquid. In use, expansion in the tank causes the valve 9 to lift, the gases then passing to atmosphere by the pipe 5, pipes 51, passages 54, 55 in pipes 50, and chamber 54<1>. The cooling of the gases by the bath 83 causes condensation of water and oil vapours, the condensates being discharged as described. Decrease of pressure in the tank causes air to be drawn in through chamber 54<1>, passages 54, 55, pipes 51, and valve 10. If a flash-back occurs owing to ignition outside the chamber 54<1>, and the explosive mixture present in the arrester is lean, propagation of the flame is arrested in the passages 54, 55. If the gaseous mixture is rich, flame propagation will further be arrested in the passages between the tubes 50, 51 which are cooled by the bath 83. The development of steam in the latter will act both to dilute the mixture and to extinguish the flame. If the gases continue to burn inside the arrester, the bulbs 89 and/or 90 become heated. This acts to collapse the bellows within chamber 41, so that the link 39 rotates shaft 32 to close the valve 9, thus cutting off the further supply of combustible gases. In addition, fusion of the link 65 allows the cover 62 to fall open, so that a rush of cool air scavenges the arrester. Opening of the cover provides a visible signal of fire conditions in the arrester, so that an operator can close the snuffer valve 9 manually by the cable 37, if necessary. After the flame is extinguished, contraction in the bulbs 9, 10 restores the valve 9 to normal activity. If the flash-back is accompanied by a high pressure wave, the spring 71 allows the cover 62 to open to relieve the pressure. In a modified form of arrester, Fig. 10 not shown, the tubes 50, 51 are inverted relatively to the construction shown in Fig. 6, and the chamber 54<1> and water bath are dispensed with, the cover 62 being arranged at the top of the arrester and being opened by a counterweight when the latch 68 is operated or the link 65 fails. The tubes 50, 51 are connected to the upper header by corrugated collars, to assist the conduction of heat from the tubes. In a modified form of arrester tube, Fig. 13, the tubes 50<b>, 51<b> are spaced by a spiral rib 98, so that a spiral passage for the gases is provided between the tubes.