USRE20041E - Process for determining the com - Google Patents

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AS MIXTURE J. A. STEIN PROCESS FOR DETERMINING THEV'COMBUSTIBLE CONTENT IN A G 3 9 l L 2 y m J Original Filed March 19,1952

INVENTOR. 14 6 72/ BY V ATTORNEY Reissued July 21, 1936 Re.

UNITED STATES PATENT OFFICE PROCESS FOR DETERMINING THE COM- ggS'fgIBLE CONTENT IN A GAS MIX- Joseph A. Stein, Pittsburgh, Pa., assignor to Bacharach Industrial Instrument Company, a corporation of Pennsylvania Original No. 1,940,513, dated December 19, 1933, Serial No. 600,044, March 19, 1932. Application for reissue April 11, 1936, Serial No. 13,978

2 Claims. (01. 23-232) The invention relates to a process for measurcatalyzing wire occurs under any condition of ing the combustible content of a gas. Ordinarily use. The range of use of the apparatus is thus the gas to be tested is a gas of combustion in greatly broadened and the cost of operation due order to determine the completeness of combusto replacements reduced to a minimum. 5 tion in the apparatus in which the gas is con- Briefly stated, this result is secured by dilut- 5 sumed, but the invention is applicable to the ing the gas measured with a volume of air which measurement of gases other than gases of combears a definite relation to the volume of gas used, bustion. The apparatus employed in the pracand which will guard the apparatus against failtice of the process is of the general type shown ure of the catalyzing wire regardless of changes in the patent to Max MoellerNo. 1,562,243, wherein the composition of the gas whose percentage 10 in the temperature of a catalyzing wire as afof combustible is under determination. One form ected by the gas burned adjacent the wire is of apparatus suitable for carrying out the procused as the determining factor in ascertaining ess is shown in the accompanying drawing, the percentage of combustible (gas) in the gas wherein: tested. Apparatus of this type has been used The figure is a diagrammatic view partially in 15 with some success in measuring the 00,112 and section. other combustibles in which the amount of com- The construction involves the use of a Wheatbustible is low, that is not over 4 to 8 per cent stone bridge arrangement in which I and 2 are of the gas tested, but serious difficulties have atstandard resistances and 3 and 4 are a pair of retended the use of the apparatus when the comsistance wires located in the chambers or tubes 5 20 bustible content exceeds these percentages, and E. The resistance wires are preferably made which it is the purpose of the present invention of platinum alloy although any other suitable to overcome. One of the main difficulties is the alloy may be used which will act as a catalyzing fact that the apparatus has been unreliable, due agent when exposed to contact with gases of comto the temporary or permanent failure of the bustion and oxygen. The gases to be measured 25 catalyzing wire to function under varying conare caused to pass through the chamber 5 while ditions. A condition referred to as poisoning or the chamber 5 contains atmospheric air, the two contamination of the catalyzing wire arises when wires which are of the same material, length and the combustible in the gas increases above a cercross section thus serving as a basis of comparison tain point. At such time the catalysis may fail as is well known in the art. 30 so that the device ceases to record or indicate The points I and 8 are connected by the wires at all. In other cases, the device continues to 9 and Ill forming a circuit in which is located indicate the percentage of combustible, but does an indicating instrument, such as the galvanomso incorrectly. This failure is ordinarily merely eter ll. Operating current is supplied from a temporary and is remedied when the combustible battery l2 in the circuit l3, l4 and this circuit is 35 content decreases below a certain point, but in provided with a small variable resistance l5 and some cases it becomes permanent and. a new the ammeter l5a for the purpose of adjustment. catalyzing wire has to be substituted. The reli- The gas of combustion to be analyzed is conability of the device is also impaired when the ducted to and from the tubular chamber 5 by the catalyzing wire is overheated due to catalytic pipes 16 and ll, of which I6 is the inlet and I1 40 combustion of high percentages of combustible the outlet, the inlet pipe being provided with the gas which is entirely apart from the failure of the orifice member I8. Connected to the gas inlet wire due to poisoning. These liabilities to failure pipe I6 is an air inlet pipe i9 whose outer end have greatly retarded the introduction and use is provided with a cavity having a cotton filter of the apparatus, which in other respects,both as 20 therein. Admission of air to the cavity is 45 to cost and ease of use, is admirably adapted for afforded by the opening 2|, and the orifice memtesting gases. ber 22 regulates the flow to the pipe Hi. The My invention overcomes the difliculty above filter 20 protects the pipe and its orifice from outlined, making the apparatus entirely reliable clogging with dirt. under any condition of use, so that no poisoning The current supplied to the wires 3 and 4 is 50 of the wire will occur or overheating thereof. such as to heat them to a point where the wire 3 The process may be employed for accurately will ignite the combustible in the stream of gas determining the combustible, when such comby catalysis. The resulting combustion raises bustible ranges from 0 to 100 per cent of the gas the temperature of the wire 3 still further, wheretested, and no poisoning or overheating of the by the resistance of the latter is increased by an 55 amount proportional to the heating efiect of the combustible contained in the gas being tested. The change in resistance of the wire unbalances the circuit of the Wheatstone bridge, of which the catalyzing wire, as heretofore explained.

I have discovered that the range of the apparatus may be increased to any desired extent, without shortening its life, by a proper dilution widely varying conditions of combustible content must be very great, preferably in the neighborhood of twelve volumes of air to one of gas.

Stated difierently, the volume of air should be such that with a maximum in which the combustible never ranges over 16 per cent, the volume of air to that of gas may range as low as 2 to 1. In the particular sired orifice 22 being about l2 times the cross sectional area of the orifice ID. The volume of diluting air thus provided not only prethe particushown, the relative volumes of air and gas are governed by the size of the orifices ner rather than by the size of the orifice.

The apparatus will ordinarily be calibrated to indicate the percentage of CO and H2 or a combination of the two, but may be calibrated to indicate the percentage of any other combustible as.

What I claim is:

1. In a process of gauging the combustible conich has for any type of gas being least twice. the

JOSEPH A. STEIN.

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