Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGFigure 4-4.— Members of firefighting party coolingentrance to compartment.8.122water admitted by a hole 1 square foot in sizein an area located 15 feet below the waterline.Portable submersible pumps used aboardnaval ships are centrifugal pumps driven by awater-jacketed, constant- speed a-c or d-cmotor. When a submersible pump is being usedto dewater a compartment, the pump is loweredinto the water and a discharge hose is led to thenearest point of discharge. Since the deliveryof the pump increases as the discharge headdecreases, dewatering can be accomplishedfaster if the water is discharged at the lowestpracticable point and if the discharge hose isshort and free from kinks. When it is necessaryto dewater against a high discharge head, twosubmersible pumps can be used in tandem, asshown in figure 4-5. The pump at the lowerlevel lifts water to the suction side of the pumpat the higher level.The P-500 portable pump, originally developedfor firefighting, is also used for dewateringflooded spaces. This pump is of the centrifugal70