Patent GB-800803-A (GB)
Title: Automatic tank switching system
IPC: F15B11/20
Filed: 1956-07-03
Abstract: 800,803. Filling and emptying tanks. U.S INDUSTRIES, Inc. July 3, 1956 [July 26, 1955], No. 20598/56. Class 21. [Also in Group XXIX] In a system for filling or emptying a series of tanks in which a corresponding series of valves is controlled by a series of switching means connected in series by a common energy conductor, the switching means are operable to a flow position wherein energy to succeeding switch means is interrupted and to a switched position wherein the means closes its respective valve and passes energy to a succeeding switch means and in which the switched position is attained in response to the level in the appropriate tank. A plurality of oil wells 20,21,22 are piped through three-way valves 31 to a production manifold 23, a dirty oil test manifold 24 and a clean oil test manifold 25. From these manifolds the oil is conducted to respective production separator 32, dirty oil test separator 33 and clean oil test separator 34, from which it flows through a tank header 38 and valves 45, 46, 47 to a plurality of tanks 39, 40, 41. The valves 39, 40, 41 are of the normally closed type opened by pneumatic pressure on a diaphragm. The opening pressure is applied to the diaphragms from a source S and common conduit 48, 49, 50 through pilot valves 51, 52, 53. Pressure air is also supplied to the pilot valves from a conduit 88 through fluid level sensing valves 85, 86, 87 and pipes 82, 83, 84. The pilot valves are also interconnected by pipes 89 and 90. The pilot valves 51, 52, 53 are similar and have a body 57, Fig. 2, with a central bore 61, to which lead passages 58, 59, 60 connected respectively with pipes 48, 54, 49 and which bore contains a slide valve 66 having a reduced diameter 65 between two 0-ring seals 63, 64. At each end of the bore 61 is an enlarged bore 70, 71 containing pistons 68, 69 respectively actable on by air pressure from pipes 82, 83, 84 from level valves 85, 86, 87 respectively and pipes 89 and 49. The piston 68 is normally urged to the left by a spring 75, but when the piston is moved to the right by pressure from valve 85 a spring-loaded detent 76 engages a groove 79 in the piston to retain the piston in the rightward position, until the detent is released by manual means. With the first tank of the series 39, empty and the detent 76 on the pilot valve 51 released, pressure from the source S will pass through pipe 48, bore 61 to pipe 54 to actuate the diaphragm of valve 45 to allow oil from header 38 to fill the tank 39. Pressure from S cannot reach the other pilot valves as pipe 49 is cut off by seal 64. On the tank 39 becoming full, the level controlled valve 85 opens to admit pressure to the piston 68 through pipe 82 and fitting 74, this moves the valve 66 to bleed air from the diaphragm through pipe 54 and hole 67 and at the same time pass air from pipe 48 to pipe 49 leading to the second pilot valve 52. The detent 76 holds the piston 68 and thus prevents the passing of air to open the valve 45 until the detent has been manually released. The second tank 40 fills on air being passed to pilot valve 52, until the valve is tripped by the level valve 86. The third tank 41 is then switched to fill in a similar manner until the pilot valve 53 is moved through level valve 87. When the pilot valve 53 moves to the left to shut valve 47, pressure from pipe 50 is fed to pipe 89 connected at 81 to the space to the right of the piston 69 of the pilot valves 51, 52. If either, or both of tanks 39, 40 have been since emptied and the appropriate manual detent released, the respective pistons 69 will move valves 66 to the left and the first tank in the series empty will commence to fill. Thus the tanks will always fill in sequence from left to right, starting each time at the first empty tank from the left. If all tanks are full, or none of the detents have been released, pressure from pipe 89 moves a timed delay valve 114 to supply pressure to pipe 115 to close diaphragm controlled valves 111, feeding the three separators, through shut-in pilot valves 112, Fig. 9. Movement of a slide valve 121 in valve 112 under pressure from pipe 115 vents the passage 117a through a bleed hole 123 to cause valve 111 to close and simultaneously closes the inlet 113 of pressing air from source S through valve 144. Valve 144, Fig. 10, contains two telescoped pistons 168, 169 urged apart by a spring 171, the internal passages in these pistons 158, 159 being so arranged in conjunction with the bands on the pistons that pressure from either pipe 113 or pipe 146, from pilot valve 112 of separator 33, or pressure from both, will cause shut-off of pressure from source S to pipe 147 to a sequence controller 140 to close the valves 31 through air pressure supplied through pipes 141, 143, 144. Similar pressure rise in the valve 144 is also generated by a closure of liquid level valves 110 of the three separators should one or more of them become full. The sequence controller 140 may also be timed to open the appropriate valve 31 to allow a timed flow to the test separator to allow a timed metered flow to be obtained for test purposes. In a modification, an interlock between the tank emptying valves and the fill valves 45, 46, 47 is obtained by the addition of a spring loaded piston to the detent 76, the detent being held engaged by air pressure from source S supplied through a valve mechanically operated by opening movement of the emptying valve of the respective tank. A further embodiment, Fig. 13, shows three pilot valves 51, 52, 53 controlling three fill valves 45, 46, 47 for three tanks 39, 40, 41 respectively and three additional pilot valves 213, 214, 215 controlling three run valves 210, 211, 212 for emptying the tanks. The valves 213, 214, 215 operate in a similar manner to that described for valves 51, 52, 53 but are controlled by the empty level in their respective tank. Additionally the signal which causes the fill valve to a tank to be closed also causes the run valve to open and interlocks are provided to prevent simultaneous opening of both valves for the same tank. A block valve 200 is installed in conduit 90 to prevent back flow therethrough, such that when all available tanks are full and conduit 54 is open to the atmosphere through the vent in pilot valve 51, pressure applied through conduit 89 cannot bleed to atmosphere through pilot valve 52 and conduit 90. The Specification states that the system could be operated electrically instead of pneumatically as described.