GB371021A - Improvements relating to the protection of stored combustibles against fire - Google Patents

Abstract

371,021. Oil tankers. WILLENBORG, W. J., 36, Clifton Terrace, Weehawken, New Jersey, U.S.A. Jan. 13, 1931, No. 1134. Convention date, Jan. 13, 1930. [Class 113 (ii).] In a protective system for combustibles in oil tankers wherein an atmosphere of inert gas is maintained in the space above the combustible, samples of the gas are continuously withdrawn from the space and tested by thermal conductivity methods for their degree of inertness. The testing apparatus is arranged automatically to control the admission of fresh inert gas to the space when a tested sample falls below a predetermined standard of inertness. The tanker is provided with groups of main tanks 16-19 separated by vertical shafts 13, 14, and with a generator 23 for inert gas. The generator shown comprises an internalcombustion engine 24, scrubbers 25 for the exhaust gases, and pressure storage reservoirs 26 connected by delivery pipes to reducing valves 27. Each tank is provided with a unidirectional " breather " valve 20, Fig. 7, controlled by the pressure in the tank acting through a diaphragm chamber 102. The escaping gases are delivered over the side of the ship by a pipe 21 provided at its end with a float valve 109. A flash arrestor 107 is arranged in the pipe 21. The lower ends 15 of the shafts 13, 14 are cut off by decks 32, 'and house the oil pumps. An inert atmosphere is maintained also in these pump rooms. The testing apparatus for the inert gases. are mounted on the decks 32. Each apparatus includes blowers 34... 38, Fig. 3, which respectively effect a circulation of the inert gases in the tanks 16 .. 19 and the pump room 15. Considering the blower 34, this withdraws gas from the tank 16 by a suction pipe 46, and returns it by a pipe 39 provided with a check valve 53. Between the blower and the check valve, a small pipe 54 branches off to a gas testing device 55. Beyond the check valve, a pipe 56 connects the pipe 39 with a header 58 connected by a pipe 29 to the reducing valve 27 of the inert gas generator 23. The pipe 56 includes a control valve 57 actuated by the testing device 55. The blowers 35 .. 38 are associated with similar testing &c. elements. The testing device, Fig. 6, includes a Wheatstone bridge 64, of which the arms 70, 71 are formed as thermal conductivity units. The unit 70 contains a gas of predetermined character for comparison, and the unit 71 is supplied by the pipe 54 with the gas to be tested. A galvanometer 72 connected across the bridge is empirically calibrated from 0 to 100, the point 50 representing the standard quality of inert gas to be maintained. A departure of 15 points on either side of the standard is reckoned to be permissible, the zero point corresponding to pure air and the 100 point to pure inert gas. When the permissible variation on either side is exceeded, a brush 77 on the pointer 76 of the galvanometer makes contact with the contact element 78 or 79. These elements are in circuit respectively with relays 83, 84 having a common armature 86 which acts as circuit closer for the solenoid circuit 94 of the valve 57. When the relay 83 is operative, the circuit 94 is broken and the valve 57 is open. This allows fresh inert gas to pass from the header 58 into the discharge pipe 39 of the blower 34, and so into the tank 16. When the inertness of the gas in the tank has risen to the limiting degree, the relay 84 is energized, the circuit 94 closed, and the valve 57 closed. An alarm 90 is included in the circuit of relay 83. The discharge pipes of the blowers may be connected to the header 58 by separate pipes provided with check valves, so that fresh inert gas is drawn into the tanks to replace losses by " breathing." In a modification, the inert gases are not circulated in the tanks, but are static. Small pumps are arranged continuously to supply samples of gas to the testing apparatus. When the solenoidal valves 57 are opened to supply additional inert gas to the tanks, the excess pressure is relieved by the " breather " valves 20. Specification 352,006, Group [XXIX], is referred to.