GB862150A - Liquid level float and apparatus for testing the same - Google Patents

Abstract

862,150. Indicating liquid levels. AMERICAN DISTRICT TELEGRAPH CO. July 2, 1959 [Oct. 9, 1958], No. 22741/59. Class 123(1) A low level alarm for tanks, &c., in which the correct level must be maintained but which are difficult of access, for example, a roofmounted, fire sprinkler water storage tank for a building, comprises a float 25 mounted on a shaft 26 passing through a flexible seal on the inner face of a housing 15 secured in an aperture in a wall 19 of the tank 10. The shaft 26 carries a contact 27 which closes on a fixed contact 29 when the water stands at its normal level to energize a coil 33 at a remote station. The apparatus incorporates means for testing at the remote station the operability of the float. For this purpose a casing 20 secured to the housing 15 surrounds the float. The casing has a large aperture 30 in its underside for the entry of water and an opening 22 near its top into which is connected a conduit 21 leading from a source 35 of an inert gas such as nitrogen. The conduit has a three-position, solenoid-operated valve 221 therein. When a test of the operability of the float is to be made the valve 221 is moved from its first, i.e. closed, position to its second position by closing a switch at the remote station. In this second position gas enters the casing 20 forcing the water therein downwards. If the apparatus is functioning properly the coil 33 is de-energized when the float reaches the preset "low" level and the alarm is given. On completion of the test the valve 221 is moved momentarily to its third position to vent the casing to atmosphere allowing it to refill with water and then returned to its closed position.