Patent GB-880694-A (GB)
Title: A device for checking the level of liquids in containers, tanks or boilers
IPC: G01F23/14
Filed: 1958-07-30
Abstract: 880,694. Indicating liquid levels. LISAC, L. July 30, 1958, No. 24563/58. Class 123(1). A device for checking the level of liquids in containers which can be used for atmospheric and higher pressures, comprises a sounder which has two concentric tubes 71, 73, the outer one 73 of which communicates, through a passage 79 in a head, with an upper chamber 78 which is larger than a lower chamber 72 in communication with the inner tube 71. Diaphragms 42, 46 clamped to a cylindrical head portion 40 by lids 43, 47 respectively, enclose a central chamber accommodating a piston 48 balanced by a spring 49. The piston carries a transverse, centrally arranged, arm 50 with double contacts 52, 53 at one end which co-operate with contacts 60, 61 leading to elective alarm and pumping devices. All of the contacts are accommodated in a lateral bore arranged in the cylindrical body 40 and closed by a plug 69. The other end of the arm 50 is connected by a flexible conductor 54 to a conductor 59. The tubes 71, 73 are provided respectively with branches 76, 74 which may be hermetically closed by stoppers 77, 75. The space for the piston 43 communicates with atmosphere through a pipe 81 closable by a cap 82. When the device is used to check the liquid level in a container open to the atmosphere the stopper 77 is placed in the branch 76 and the branch 74 is left open to connect the upper chamber 78 with the atmosphere. For containers enclosing air above atmospheric pressure a sheath 83, carried on the outer tube 73 is threadedly engaged with an auxiliary apparatus, Fig. 4 not shown, which is adapted to hermetically seal the sounder tubes 71, 73, within the container by means of a stuffing box. It is also capable of varying the height of the device above the container. When checking the liquid level both of the branches 74, 76 are hermetically sealed the liquid rising in the tubes 7.1, 73 causing a higher pressure to develop in the smaller lower chamber 72 than in the larger upper chamber 78 so that the piston is displaced upwardly to operate the electric contacts as previously described. A small duct 80, leading from the lower end of the chamber 42 to the vertical limb of the passage 79, returns condensate from the chamber 42 to the outer tube 73. When the device is applied e.g. to heated boilers which operate without the presence of air the vapours, trapped in the outer tube 73 when the liquid reaches the lower end of the sounder, cool off in the upper chamber 42 aided by radiating fins 95 and cause a drop in pressure in the upper chamber which corresponds to the difference in temperature between the vapours in the inner and outer tubes 71, 73 so that the piston 40 rises to actuate the device as before. For checking liquids having a lower temperature than that of the atmosphere and in the presence of air, or with extremely high temperatures, the device is inverted so that the tubes point upwards in the container, the inner tube being longer than the outer tube and at high level both tubes being covered so that the diaphragms 42, 46 are subjected to the same pressure. When the level commences to drop the end of the inner tube will project out of the liquid and the pressure on the diaphragm 42 will be lower than that on the diaphragm 46 which will be constant. If pressures are exceedingly high and in order to avoid the use of very thick diaphragms an auxiliary appliance as shown in Fig. 3 has a pipe 110 connected to the pipe 81 of the cylinder 40 and a pipe 111 connected to the interior space of the container a source of compressed air being supplied to the appliance through a pipe 105. A labyrinth type of sounder with a flared lower end is also described. Additional arrangements which subject the device to a sudden high pressure at a predetermined level and which also check exactly the minimum level of liquid can be attached to the lower end of the sounder a remotely controlled installation is also described in which level indicating devices can be raised and lowered in a container to continuously record the height of a liquid.