Modern Gasworks Practice

EXHAUSTING MACHINERY Fig. 298.— Complets Exhausteb Installation suitable for a Small Works. accordingly, tlie holder bell drops and operates through its link motion to open the by-pass valve. In this way gas is sucked back from the outlet to the inlet, and compensates for the falling off in the quantity coming from the retorts—thus the original vacuum is maintained. In the same way, as the quantity of gas passing along the foul main increases the vacuum momentarily decreases, with the result that the holder bell rises and closes down the by-pass valve until the normal “ draw ” is given. The method is certainly effective, but care is necessary to see that the exhauster is rumiing at a sufficient speed to deal with the maximum quantity of gas likely to pass at any time from the retorts, for the govemor cannot increase the speed of the engine should this be insufficient at any period. Fig. 298 shows a