PRINCIPLES OF NAVAL ENGINEERING 



8.122 



Figure 4-4.— Members of firefighting party cooling 

 entrance to compartment. 



water admitted by a hole 1 square foot in size 

 in an area located 15 feet below the waterline. 

 Portable submersible pumps used aboard 

 naval ships are centrifugal pumps driven by a 

 water-jacketed, constant- speed a-c or d-c 

 motor. When a submersible pump is being used 

 to dewater a compartment, the pump is lowered 

 into the water and a discharge hose is led to the 

 nearest point of discharge. Since the delivery 

 of the pump increases as the discharge head 

 decreases, dewatering can be accomplished 



faster if the water is discharged at the lowest 

 practicable point and if the discharge hose is 

 short and free from kinks. When it is necessary 

 to dewater against a high discharge head, two 

 submersible pumps can be used in tandem, as 

 shown in figure 4-5. The pump at the lower 

 level lifts water to the suction side of the pump 

 at the higher level. 



The P-500 portable pump, originally devel- 

 oped for firefighting, is also used for dewatering 

 flooded spaces. This pump is of the centrifugal 



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