EXHAUSTING MACHINERY
499
the suction side of the machine without letting gas pass back from the pressure side. The machines may be governed by regulating the speed in accordance with the quantity of gas passing, or by means of the by-pass.
A typical Rateau turbo-exhauster is shown in Fig. 311. Although these machines run at high speeds the wear and tear is negligible, the wheels revolving in the casing without
Fig. 309.—Sturtevant Rotaky Exhauster with Automatic By-pass.
touching it. The bearings supporting the
I’ig. 310.— Section through Stübtevant Rotary Exhauster.
impeller shaft are provided with large oil reservoirs and ring lubrication for medium speeds, and with. forced lubrication for high speeds. Where the shaft passes through the casing stuffing boxes of special design are provided, these ensur-ing gas tightness and practically no friction, with the result that little or no loss of power occurs.
The special advantages of the high-speed rotary turbo-exhauster may be enumerated as follows:—
(1) Efficiency at least 70 per cent.
(2) Low wear and tear, due to absence of internal rubbing parts.
(3) Absence of pulsation.
(4) Silent running.
(5) Large ränge in capacity with but small variation in efficiency.