268 STANDARD LUBRICATING OIL SYSTEM FOR GEARED TURBINES. 



Mr. Parker M. Robinson, Visitor: — Experience has undoubtedly shown that the oil- 

 ing system on a geared turbine unit is a most vital factor, and a great deal of credit is due 

 to Messrs. Schmeltzer and Femald for recognizing this fact at an early date and taking 

 the necessary steps to develop a reliable system. 



Technical Order No. 75, vifhich has now become famous, received a large amount of 

 adverse criticism and all sorts of gibes were pointed at it; yet on the whole it was a big 

 step in the right direction. 



The question as to whether the gravity or the pressure system should be used was set- 

 tled in favor of the gravity system, and that seems logical because of its more inherent 

 reliability. The pressure system is used in the Navy, because it is undesirable to have any 

 vital part of- the machinery above the protective deck; and in the case of destroyers the 

 headroom necessary for installing the gravity system is not available. However, the pres- 

 sure system operates quite satisfactorily on these vessels became of the much larger person- 

 nel in the engine-room force, and because of the fact that the periods, of full power opera- 

 tion are rather infrequent and of short duration. 



The service required of a vessel in the merchant marine is entirely different, requiring 

 practically continuous full-power operation while the ship is at sea. This fact, coupled with 

 the small size of the engine-room crew, makes the more reliable gravity system the proper 

 choice. 



As to the details of the system described in the paper, there are one or two points on 

 which I would like to comment. 



The first is in regard to the strainers. The type of strainer shown is the familiar type 

 of twin-basket strainer. This has many good features, but it has the one disadvantage of 

 not being fool-proof. If the engineer neglects to change over the valves at the proper time, 

 either the flow of oil will be completely shut off, or else the basket will burst and all the 

 accumulation of dirt, together with parts of the broken basket, will be carried on through 

 the system. This will result in more harm than if the dirt had not been separated from the 

 oil at all. 



To guard against such an occurrence a by-pass should be installed around the strainer, 

 in which is located a spring loaded relief valve. Then, when the oil pressure reaches a cer- 

 tain point due to the clogging up of the strainer basket, the relief valve would open and 

 the flow of oil continue uninterrupted. To inform the engineer when the oil is flowing 

 through the by-pass, a simple indicator could be provided, and he would then know when 

 it was time tO' change over to the other strainer basket. 



iVs a further safeguard against misoperation a by-pass with a relief valve can be in- 

 stalled around the coolers, so that it is impossible to shut off the supply of oil by incorrect 

 manipulation of the oil cooler valves. 



One other point on which I desire to comment is in connection with the gravity tanks. 

 Two tanks are shown, either of which can be used as the supply tank while the other is used 

 for settling purposes. This requires the duplication of float control devices, heating coils, 

 etc., which could be avoided by having only one gravity tank with a settling tank located 

 just below. Any water or dirt which collects in the bottom of the gravity tank can be drained 

 directly into the settling tank, from whence it can be passed through the purifice and back 

 into the system. This would seem to be a somewhat better arrangement than the one shown 

 in the paper. 



