centrifugal force is developed to throw the liquidoutward and away from the center of rotation. Thus theliquid is sucked in at the center, or eye, of the impeller(center of rotation) and discharged at the outer rim ofthe impeller.The centrifugal pump, like the diaphragm pump, isdriven by a single-cylinder, four-cycle, air-cooledgasoline engine. To operate the engine properly, youshould be familiar with its controls.NOTE: Refer to the operator’s manual for specificinstructions for the type of pump you are operating.OPERATION.— The operation of centrifugalpumps is generally similar to the operation of diaphragmpumps. Centrifugal pumps (fig. 14-34) are also fittedwith stuffing boxes and various types of bearings thatrequire periodic operator’s maintenance and inspection.Figure 14-34.—Centrifugal pump.NOTE: Unlike positive displacement pumps, thedischarge stop valve on centrifugal pumps must beclosed before starting the pump.The reason for closing the stop valve is to allow thepump to work against the sealed discharge and buildupan effective pressure head before attempting to moveand distribute the liquid downstream. After the pump isup to speed and the discharge valve is opened, it willcontinue to maintain that pressure head unless theoperating conditions change.There is no danger of building excessive pressurewhile the pump is running with the discharge closed. Ifthe centrifugal pump were permitted to continueoperation with the discharge sealed, it would simplybuild up toward its maximum discharge pressure andthen begin to churn the liquid; that is, the dischargepressure would overcome the suction pressure and theliquid would continually slip back to the suction side ofthe pump. Nothing more would happen, except that thepump would build up heat since the liquid would not beable to carry away heat generated by the moving parts.INSPECTION.— There is little for you to inspectother than routine operator’s maintenance.If youfollow all of the operator’s manual instruction and thepump does not function properly, call for a fieldmechanic or turn it in to the dispatcher with a hard cardfor repair.SWEEPERSMany different types of sweepers are used in theNavy.Some of the most common are the towedsweeper, the street sweeper, and the magnetic sweeper.Figure 14-35.—Towed sweeper.14-30
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