GB774284A - Improvements in or relating to the control of gaseous media in manufacturing processes - Google Patents

Abstract

An apparatus comprising in combination a sampling vessel, a vessel provided with condensing means, an evacuating means, a manometer associated directly or indirectly with said sampling vessel and valve means enabling the sampling vessel to be connected firstly to said condensing vessel and said evacuating means, secondly to a source of the gaseous mixture and thirdly to said condensing vessel when isolated from the evacuating means, is used for measuring the proportions of constituents <PICT:0774284/III/1> of a gaseous mixture by observing the pressure change arising in the sampling space as a result of the condensation of one of the components of the mixture. In the preferred apparatus, see Fig. 2, a sampling vessel 1 may be put in communication with a condensing space (preferably smaller than the sampling space) formed in a metal block 12 and comprising the space in a channel 13 around a rod 11, the channel 22 leading to a manometer 9 and a variable volume 46. The block is cooled by a passage of a liquid through a jet pump 8 formed in the block. The suction side of the pump is connected to said channel 13 through which the rod 11 passes. The apparatus is constructed so that said rod also passes through the sampling space 1. The rod contains valve units at 3a, 3b, 7 and 31, whereby the various parts of the apparatus may be put into communication with each other, with the gas to be tested or with the atmosphere. In operation, the rod 11 is actuated by means of a pin 38 moving in a groove 37 in a cam rotated by a knob 41. The sampling space is first opened to the condenser and jet pump and is actuated to a standard pressure, e.g. 27 inches below atmospheric. By rotating the knob the valve rod is positioned so as to isolate the sampling vessel from the condensing space and put it into communication with the source of the gaseous mixture through valve 3a and connection 4 having a filter 45. The valve rod is then withdrawn into the position shown to disconnect the source of gas whilst permitting the gas to flow into the condensing space which is now isolated from the jet pump. The manometer after suitable calibration will then indicate the proportion of the condensable component in the mixture. Finally the valve rod is placed in the extreme right-hand position to put the sampling vessel and condenser into communication with the atmosphere through valves 3b, 7 and 31. In order to keep the sampling vessel above, or preferably at the temperature of the source of the gas mixture, it may be located therein or may be provided with an insulating enclosure or lagging or with electrical heating means such as a spiral electric element (51) controlled by thermostat 52. The manometer preferably indicates differences of pressure from atmospheric-e.g. a Bourden gauge in an unsealed case: it may in an alternative embodiment be permanently or temporarily put in communication with the sampling vessel; in the latter case the temperature should be maintained above the condensation temperature. According to the Provisional Specification, the evacuating means could also be a hand or electrically operated pump. Two embodiments are described, in which the condensing space is a part of the tube connecting the manometer to the sampling space which is surrounded in one case by a widened water supply tube to the jet pump. Means may be provided to operate the jet pump by the movement of a valve rod similar to rod 11 above; a needle valve may be provided in the tube leading to the manometer.