STANDARD LUBRICATING OIL SYSTEM FOR GEARED TURBINES. 273 



Mr. Smith refers to several accidents caused by the defects of the standard gravity sys- 

 tem. I'he instance of damage to the bearings on account of the viscosity of the oil is inex- 

 cusable because the steam coils in the gravity tanks permitted the viscosity of the oil to be 

 brought to the correct point before starting up the units and was put in both gravity tanks to 

 serve the double purpose of controlling the oil viscosity at starting and aiding in the settling 

 of water out of the oil. The same trouble would have occurred with the pressure system 

 if the engineer had not adjusted his automatic appliances so as to increase the pressure to 

 take care of the extra viscosity of the oil. 



The other two instances referred to by Mr. Smith were clearly cases of operating inef- 

 ficiency. In one case the engineer was sent up to close a grating and, instead, closed off the 

 oil supply from the gravity tank. Ordinarily a sight feed or flow indicator in the main, sup- 

 ply pipe from the gravity tank was specified. No satisfactory device was found, and this 

 requirement was later eliminated. It is doubtful if it would have prevented this accident. 

 In the other instances no part of the lubricating oil system failed to function. The vessel 

 was delivered by the shipbuilder with one of his trained engineers to a nearby port for load- 

 ing. At this point the trained engineer left the ship without instructing the new crew, who 

 took the vessel to sea. For some reason the lubricating oil pump failed, and the turbine con- 

 tinued to run on the gravity tank until it ran dry. At this time the chief engineer was in 

 his stateroom. When he reached the engine-room the alarm was still ringing, and the crew 

 was so green that they not only had not stopped the main turbine but they made no effort to 

 start up the spare lubricating oil pump or to switch over to the reserve gravity tank. 



We agree with Mr. Smith that any system may fail and, in the paper, called attention 

 to the limitations of the system in this respect. Even the extra time element for taking care 

 of trouble provided by the gravity system is useless if the crew do not avail themselves of 

 it and ignore v/aming signals. As Mr. Smith's operating experience with this system is 

 limited to trial trips, and as the engineers are trained at his yard, according to his own ad- 

 mission, by using the pressure by-pass (eliminated in the revision), he cannot expect his 

 criticism of the operation of the system to receive serious consideration. 



Mr. Smith's criticism of the 10 per cent loss in the gears is certainly well taken, based 

 on what would be good engineering practice, but, unfortunately, the losses in some of the 

 earlier gears were almost as large by actual test. The excessive losses were due to the use 

 of too close fits in the numerous high-speed bearings. 



Mr. Smith criticises the viscosity of the oil selected and recommends one of lower vis- 

 cosity, but does not submit any reason for this conclusion. The manufacturers of the tur- 

 bines set the amounts of oil that they required, as well as the viscosities; violation of their 

 requirements vitiated their guarantees. We were buying turbines in large quantities, and 

 (using a word popularized by the Shipping Board) we were allocating them to various ship- 

 builders, so that we were responsible to them for the turbines, and in order to- protect our- 

 selves we had to adhere to the stipulations made by the manufacturers, so that we had vis- 

 cosities all the way from 280 to 720 to deal with. 



As a result of operating experience and the modification of bearing designs, it was 

 possible to standardize the viscosity and pressure of the oil and the size of the pumps, cool- 

 ers, etc., taking care of the variation in requirements of different makes of turbines by con- 

 trolling the temperature of the oil in operation and making an initial adjustment of the sup- 

 ply of the oil through reducing flanges or cocks. 



Mr. Smith also raised a number of other points which we believe are already answered 



