GB1231839A - - Google Patents

Abstract

1,231,839. Minimising fires in fuel tanks. NORMALAIR - GARRETT Ltd. 28 Nov., 1968, No. 56453/68. Heading A5A. [Also in Division G3] Fire prevention means supplying an inert gas to a storage enclosure dispensing combustible material, e.g. an aircraft fuel tank, comprises a liquid-to-gas converter system supplying gas to the enclosure by way of a flow regulating valve means which includes a variable volume chamber, variation of the volume effecting the regulation of gas flow to the enclosure, and at least one pressure relief valve in communication with said enclosure and said regulating valve means. Liquid N 2 gas converter 10 is connected via heat transfer coil 13 in fuel tank 14 and pipe 11 to flow-regulating valve 12. N 2 delivery pipe 15 leading from 12 to tank 14 is joined beyond non-return valve 17 by ground filling pipe 16. Relief pipe 18 communicates space 19 above the fuel with pressure relief valve 20 associated with aneroid or evacuated capsule 21 sensitive to ambient atmospheric pressure, and, via line 22, with servo valve chamber 23 of valve 12. Valve 12 comprises servo chamber 23 and main valve chamber 33/34 divided by wall 25 having a port with valve seat 26 obturated by lever valve 27 which is actuated by diaphragm 28 separating the servo portion into spring chamber 29 and servo valve chamber 23. Normally 27 is urged open by the pressure on 28 of spring 30 mounted on evacuated capsule 31; chamber 29 is in communication with ambient atmospheric pressure. Valve seat 35 on the end of pipe 11 cooperates with pad valve 36 attached to diaphragm 32 separating control pressure chamber 33 from delivery chamber 34 in the main valve portion. Small tube 37 with orifice 38 connects pipe 11 with chamber 33. In use N 2 is delivered via valve 35/36 to 34 and via tube 37 to 33, fully gasifying on passage through 13, and fills space 19, pipe 18, pipe 22 and chamber 23. This communication allows the pressure in 33 to be overcome by that exerted on valve pad 36, which then deflects diaphragm 32 to discharge N 2 via pipe 15 into the fuel to a predetermined pressure. Such pressure is sensed by diaphragm 28, which returns to a null position, closing 27 on seat 26. Thereon pressure in 33 and 34 equalises and 32 closes pad 36 on to seat 35. Reducing pressure over the fuel initiates further N 2 delivery in accordance with the fuel usage. To maintain the predetermined presure in 14, in the event of low ambient atmospheric pressure on 20, capsule 21 expands and seals 20. Similarly capsule 31 compensates pressure loss on diaphragm 28.