246 STANDARD LUBRICATING OIL SYSTEM FOR GEARED TURBINES. 



ditions, still this size of cooler provided for a considerable drop in the efficiency 

 of the cooler, due to the fact that the tubes would in time become covered with a 

 deposit which would materially decrease the efficiency of the cooler as compared 

 with a clean one. 



Results obtained in operation have demonstrated that the size of cooler speci- 

 fied satisfies average operating conditions. 



Gravity Tanks — Sise and Location of. — During the time the designs of the 

 new system were in the course of preparation, one manufacturer claimed that it was 

 necessary to have 12 pounds oil pressure on the turbine bearings and gear oiling 

 devices on equipment manufactured by them, and still another used spray nozzles of 

 such size as to make it almost impossible to maintain a higher pressure than 4 or 

 5 pounds. The rest of the builders' requirements averaged about 10 pounds pres- 

 sure at the oil manifold. 



Due to the above facts, and based on the assumption that it was best to satisfy 

 the higher pressure requii-ements, and also owing to the fact that all of the vessels 

 on which installation of the system was contemplated would permit of the location, 

 it was specified that the gravity tanks be located at a height of- 30 feet above center 

 line of turbine in the engine-room casing. This location of the gravity tank has 

 proved very satisfactory in service, and no trouble has been experienced in securing 

 the required pressure. 



The size of the gravity tank, which is of 600 gallons capacity, was based on 

 having three or four minutes reserve supply of oil available for the gears in the 

 event of the oil supply to the gravity tanks being interrupted. This, it was thought, 

 would provide sufficient time for action on the part of the operating personnel. 



Kingsbury Thrust Bearing. — Inasmuch as, on most of the various types of tur- 

 bines purchased by the U. S. Shipping Board, the Kingsbury or similar type of 

 thrust bearing is used, it is essential that there be a constant supply of cool, clean 

 oil. Failure or interruption of the supply has caused the thrust bearing to burn out 

 on several occasions, with consequent serious damage to the turbine. 



This same type of thrust bearing was employed in the majority of cases for 

 the main propelling shaft thrust, and therefore the same necessity for cool, clean 

 oil obtained in this case. 



Strainers. — As a precautionary measure against sabotage, a twin suction 

 strainer having a coarse mesh strainer basket was installed, but eventually omitted 

 in the revised specifications at the end of the war. 



A strainer having approximately i /64-inch mesh was placed in the discharge 

 line, and this is considered sufficient to remove all sediment incidental to ordinary 

 operation after the system has been thoroughly cleaned before the trial trip as 



specified. 



Filters and Separators. — ^While all of the filters and separators specified are 

 satisfactory for the purpose, it is considered that the results obtained from the cen- 

 trifuo-al type of separator show greater efficiency, inasmuch as the oil, water and 

 sediment are separated — the oil flowing from one nozzle, the water from another. 



