GB953665A - Method and apparatus for detecting the presence of hydrogen-containing combustible gases or vapors - Google Patents

Abstract

953,665. Measuring electrically. GAS DETECTOR S.p.A. April 28,1961 [March 2, 1961], No.15420/61. Heading G1N. To detect the presence in air of hydrogencontaining combustible gases such as vapours of alcohols, aldehydes, ketones, organic acids, or H 2 S, PH 31 the air is passed through a tube containing a heated resistance of, or coated with, an oxidation catalyst so as to cause any such gas to form water vapour which is then caused to humidify a solid hydrophilic substantially dry electrolyte in which are immersed a pair of electrodes which are connected to conductivity measuring apparatus. As shown, Fig. 1, the air under test is drawn by a pump P through a tube M1 containing a moistureabsorbing substance D such as CaCl 2 ; M is an alternative drying tube; each tube contains a heater H, H 1 for regenerating substance D. The dried air is filtered at F, then passed via a tube I to a combustion tube C containing a heated resistance RC coated with, an oxidation catalyst such a platinum black (alternatively the resistance may be made of a metal of the platinum group), and an electrolyte S, e.g. KCl, in which are embedded two electrodes E; the air is finally discharged through outlets U. Variations of conductivity of the electrolyte due to changes of humidity of the air impinging on it are used to actuate an indicator X and, through amplifying and/or relay means (which may be comprised within indicator X) if necessary, to operate an alarm such as a lamp N or a bell Z, or a suction fan, when the resistance of S is reduced below a predetermined limit. In Fig. 3, the dried, filtered air is passed to two tubes C, C1, the former containing a catalytic resistance RC and the latter containing a non-catalytic resistance R. The electrolyte S in each tube forms an arm of a Wheatstone bridge device, energized by A.C., with a rectifier W in the output circuit. In an alternative embodiment, the air is divided between two concentric tubes, the inner tube only containing a catalytic resistance, before being passed to two tubes containing electrolyte. The air may alternatively be dried by being passed through a liquid drying agent such as conc. H 2 SO 4 , or by being cooled. Instead of being dried, the air may wetted by being bubbled through water or an aqueous liquor.