STANDARD LUBRICATING OIL SYSTEM FOR GEARED TURBINES. 247 



the overflow mixture from another, and the sediment remaining in the bowl, from 

 which it may be removed at will. Tests made at Annapolis prove that the rolling or 

 pitching of a vessel will have no ill effects on its successful operation. 



Filtering elements placed in gravity tanks or in the discharge line from pumps 

 to gravity tanks at its connection to gravity tank, unless at sufficient height above, 

 cannot function properly, due to the lack of sufficient head, which results in the oil 

 following the path of least resistance, i. e., through the overflow and not through the 

 straining elements as intended. 



Alarm Systems. — An electric alarm system actuated by a float switch, con- 

 nected to the gravity tanks was provided (and since omitted), which would notify 

 the chief engineer in his room and the engineer officer on watch, by means of an 

 electric gong, that the oil level had dropped below normal operating level. This 

 system, which was so designed as to not only give the necessary notification in case 

 of oil level becoming low but also to automatically increase the speed of the pumps, 

 was later omitted, due to a desire to reduce the cost of the installation rather than 

 because of any belief in a lack of necessity for it. 



Drain Tank. — The capacity of the oil drain tank was required to be from 800 

 to 1,000 gallons for a 3,000 horse-power double-reduction gear turbine unit. 



It was found that most of the drain tanks supplied at the time this system was 

 originated were entirely too small, and resulted in the pumps becoming vapor bound. 

 In most cases of this kind, and also where the suction lift of the pump was high, 

 the oil became very dark in color. Oil experts who were consulted advised that 

 the mixture of air with hot oil frequently resulted in the presence of sulphurous 

 acid (H2SO3) in the oil. For this reason, the drain tanks were made sufficiently 

 large and the pumps placed as low as possible to insure a short suction lift. 



Pumps. — While vertical pumps are more desirable for the purpose of securing 

 low suction lift, it was not possible to procure them in the quantities required. 

 Horizontal pumps were therefore used more extensively. The vertical pump is pre- 

 ferred to the horizontal, not only for the above good reason but also because of its 

 taking less floor space and lending itself to better arrangement generally. 



Oils. — Originally an oil having a viscosity of 300 seconds (Saybolt) at 100° F. 

 was specified, but later this was changed to 500 seconds viscosity. This latter vis- 

 cosity was found to suit conditions better because the high-speed bearings demand 

 oil having a low viscosity and the gears and slow-speed bearings a high viscosity oil. 

 Inasmuch as two separate systems could not be considered on account of their cost, 

 and due to the fact that oils ranging from 300 to 700 viscosity at 100° have prac- 

 tically the same viscosity at temperatures above 140°, and also based on operating 

 results, it was considered that the higher viscosity was more desirable. 



Conclusions. — The results obtained from the system in service have been very 

 gratifying and show that the sizes of equipment specified were in keeping with the 

 requirements, and it is believed that a system of lesser magnitude than that speci- 

 fied would endanger the successful operation of a double reduction gear turbine unit 

 of 3,000 horse-power. 



