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plunger pump is the volume displaced by the plunger per stroke multiplied by the number of strokes per minute. The actual discharge may be either greater or less than this amount. The ratio of the actual discharge per stroke to the volume displaced by the plunger per stroke is called the co- efficient of discharge of the pump; the difference between these quantities is called the slip. If the actual discharge is less than the theoretical, the slip is said to be positive; if greater, it is said to be negative. Positive slip is due to leakage past the valves and plunger. In a steady-working pump with valves in proper condition, this slippage should be less than 10 per cent, although in a new pump it is seldom more than 1% to 2 per cent. If the size of the pump cylinder and the number of strokes per minute are known, the theoretical amount that such a pump should deliver can be calculated by the following for- mula. Discharge, in gallons per hour = .204 N@?L in which N = single strokes per minute; d = diameter of plunger, in inches; L = length of stroke in inches. The actual capacity will be from 60 to 95 per cent of the figure given by the use of the foregoing formula, de- pending on the tightness of the pis- ton, condition of valves, length of suc- tion pipe, ete. There is a definite limit to the height above the normal level of the liquid to which a pump can lift the liquid by suction; beyond that limit, the pump cannot operate. This height is equal to the length of a column of the liquid of such height that the pres- sure it exerts at its base is the same as the atmospheric pressure, less the loss in head due to friction in the pipe itelf. Atmospheric pressure varies with the altitude, but the pressure existing most generally in the United States is between 14 and 15 pounds per square inch. This corresponds to the pressure of a column of water about 30 feet high. No matter how good a vacuum is obtained, it is im- possible to lift water by suction more than this height above the normal water level. The height to which other liquids can be lifted depends on their specific gravities; for example, strong sulphuric acid could not be lifted by suction above a height of about 16 feet. In actual pumping operations, the distance of the center of the pump above the normal water-level is rare- ly more than 10 or 12 feet. Frequent- ly, the pump suction is below the nor- mal water level, in which case th pump is said to be flooded. The pif limitation on the horizontal length the suction pipe is loss of heaq due 4 friction. If the sum of the loss of a and the height lifted is greatey than the atmospheric pressure, then the stream of liquid in the suction will separate and no liquid wij] e the pump. (Continued in Next Tssue) pipe hter Hoboken Pier Bids The opening of bids on July 23 by the shipping board for purchase of the government-owned piers at Hoboken, N. J. revealed an offer from Paul W. Chapman, New York, of $4,- 282,000 for the entire property. The piers were advertised for sale under authority of the Keane-Auf-der Heide law passed in the last session of con- gress. This property, which former- ly was German owned, was seized by the United States government at the outset of the war and has been used in connection with the opera- tion of shipping board lines. The offer submitted by Mr. Chapman will be taken under advisement by the Merchant Fleet Corp. for recom- mendation to the shipping board. From Philadelphia to Chicago via Water HE diesel barge, BucKEYE STATE, Owned by the Federal Motorship Corp. and operated under charter by the Seaboard-Great The author, Thos. W. Hall, is a mem- ber of the staff of the Fairbanks, Morse & Co., Chicago. 40 Engine Room of the Buckeye State—Control Sid : Two of the Three Diesel B fonts By T. W. Hall Lakes Corp., docked in Chicago at 5:35 a.m. July 5, with more than 1700 tons of sugar from Philadelphia. This method of freight transportation be- tween Chicago and the seaboard is becoming not an uncommon occur- rence and it is of interest to note that the diesel engine is an important ot K of the Starboard Main Engine— ngine Generating Units MARINE REVIEW—September, 1930 factor in making the undertaking both possible and profitable. The elapsed time required to make the trip, in this case less than ten days, compares favorably with fast freight schedules between these two points, but the most important fea- ture is the favorable freight rate. Due to the variety of navigating conditions on a trip of this sort the craft employed must be exceptional- ly versatile. To obtain maximum dis- placement with minimum draft the hull is of the flat bottom type and because of canal bridges, the height above the water line is reduced to a minimum. The craft must also be able to navigate and maneuver easily on the lakes, through canals and rivers as well as on the open sea. The diesel engine is suitable for this type of craft because it gives maximum power in minimum space and with minimum head room. In addition the cost of operating the diesel engine is so low that it permits a margin of profit for the undertaking. The BUCcK- EYE State had been in service less than a month when she undertook her first inland voyage and her per- formance on this trip has been watched with interest by shippers 00 the Great Lakes. The Buckryr State has a length of 246.33 feet, a beam of 43.62 feet and a molded depth of 16.83 feet. Loaded