76 PROGRESS IN TURBINE SHIP PROPULSION. 



full steam pressure at all times on their inner sides. The outer side of the upper 

 one is open to the atmosphere. The lower side of the lower piston receives high- 

 pressure steam through a needle valve. The lower side of the piston is also con- 

 nected with the relay adjacent to the governor which will control the pressure un- 

 der this piston, and hence the position of the valve. 



While the regulating characteristics of this apparatus would hardly meet the 

 rigid requirements for turbines driving dynamos, it is simple and regulates with 

 more than sufficient accuracy for the purpose. 



MANEUVERING VALVES. 



An important detail, at least important to the watch engineer, is the maneu- 

 vering valve. Many shipbuilders — for economy, we presume — are content to merely 

 furnish two throttle valves, one for ahead and the other for astern, with the possi- 

 bility of admitting steam to both the ahead and astern elements at one and the same 

 time. It has been the practice of the Westinghouse Company to furnish a maneu- 

 vering valve operated by a single hand wheel. Motion in one direction gives steam 

 to the ahead, and in the other direction to the astern elements. The design of this 

 valve is as shown in Fig. 29, Plate 56. An important feature is that the valves them- 

 selves are single disc, balanced valves, so that there is but a single ground seat for 

 each valve which may easily be maintained bottle tight. They are balanced by the 

 piston above, rendering their operation easy. With this valve mechanism the tur- 

 bines are easily brought from full speed ahead to full turbine revolutions astern in 

 twenty seconds, or vice versa. 



In all cases the maneuvering valve is arranged so that it is always employed no 

 matter what may be the valve arrangements or what the method of operation ; that 

 is, whether both turbines are operating, or only one of them in case of disablement, 

 as shown in Fig. 5. 



TURBINE GLANDS. 



Most builders of marine turbines have employed a labyrinth type of packing 

 for the turbine glands ; some of them a combination of this with spring packing 

 rings of one kind or another. There is no pretense of these glands being steam 

 tight. To prevent ingress of air, which would interfere with the condenser perform- 

 ance, they are provided with a steam connection for admitting high-pressure steam 

 for sealing so that there shall be a leakage of steam, which will do no harm, rather 

 than one of air. It is found in practice that to absolutely preclude any air leak- 

 age there must be a superabundance of steam admitted which will blow, in consid- 

 erable volumes, into the engine-room. A turbine gland used to be regarded as one 

 of the difficult problems of design detail until in 1903 the Westinghouse Company 

 devised what is known as the water gland. It merely comprises a centrifugal pump 

 runner operating in a casing which, if furnished with water at the axis, would 

 raise that water to some 10 pounds higher pressure than the maximum pressure 



