AFS Foundry Sand Testing Equipment Operating Instructions Manual

RIDSDALE GAS DETERMINATORIGENERAL PRINCIPLESThis method of determining the gas content of sands depends upon the introduction of aweighed sample into a heated tube filled with an inert gas and measurement of the increasein pressure due to the gas evolved from the sample.Pressure readings are converted to volumes by means of a calibration graph prepared at theoperating temperature.The tube is heated in a furnace with an inclined heating chamber which ensures that theevolved gases remain in the hot zone and only the inert gas passes into the pressurerecorder.IIDESCRIPTIONA fused silica tube, 18 in long x 2½ in outside diameter, sealed at one end is heated bymeans of a thermostatically controlled electric furnace. The open end of the tube is fittedwith a water cooled metal closure to which is attached a spring-gun assembly, the lattercontaining a trigger mechanism designed to eject the sample into the hot zone of the tube.An inconel tube which extends to the closed end of the silica tube, is fitted to sweep theapparatus out with nitrogen* which is supplied from a cylinder via a pressure reducing valve.A further tube connects the interior of the silica tube to the pressure recorder. The metalclosure is secured to the silica tube with high melting-point wax, henceWATER MUST ALWAYS BE PASSING THROUGH THE COOLING JACKETWHEN THE TUBE IS HOT(ie, when the furnace temperature is over 200 °C).*It is recommended that oxygen-free (white spot) nitrogen be used as commercial gradenitrogen may contain a trace of oxygen which would give false readings.115