134 1. Power generating system

134 1. Power generating system.

2. Floods and vents.

3. Periscope and radio mast hoists.

4. Forward and after service lines.

5. Emergency systems.

FigureA-19 shows a schematic view of the main hydraulic system in the submarine.

B. POWER GENERATING SYSTEM

12B1. General arrangement. The i. The accumulator air flask, located in

power generating system comprises a group of units, the coordinated action of which provides the hydraulic power necessary for the operation of the main hydraulic system. It consists of the following principal parts:

a. The IMO pumps, located in the pump room, which supply hydraulic power to the system.

b. The main supply tank, located in the control room, which contains the oil needed to keep the system filled.

c. The accumulator, located in the pump room, which accumulates the oil from the pump and creates pressure oil which is maintained at a static head for instant use anywhere in the system.

d. The main hydraulic manifolds, located in the control room, which act as distribution and receiving points far the oil used throughout the system.

e. The pilot valve, a two-port, fitted lap-fitted trunk, cam-operated slide valve, located in the pump room, which directs the flow of oil that causes the automatic bypass valve to open or shut.

f. The automatic bypass and nonreturn valves which are located in the pump room. The automatic bypass valve directs the flow of pressure oil in obedience to the action of the pilot valve. The nonreturn valve prevents the oil from escaping through the open automatic bypass.

g. Cutout valves, serving various purposes throughout the system and nonreturn valves which allow one-way flow.

the pump room, which serves as a volume tank for the accumulator, allowing the air to pass to and from it when the accumulator is loading or unloading.

12B2. IMO pump. Hydraulic systems need, in practice, some device to deliver, over a period of time, and as long as required, a definite volume of fluid at the required pressure.

The IMO pump (Figure 12-1) is a power-driven rotary pump, consisting

essentially of a cylindrical casing, horizontally mounted, and containing three threaded rotors which rotate inside a close-fitting sleeve, drawing oil in at one end of the sleeve and driving it out at the other end.

The rotors of the IMO pump, which resemble worm gears, are shown in Figure 12-1. The inside diameters of the spiral threaded portions of the rotors are known as the troughs of the thread; the outside diameters or crests are known as the lands. The troughs and lands of adjacent rotors are so closely intermeshed that as they rotate, the meshing surfaces push the oil ahead of them through the sleeve, forming, in effect, a continuous seal so that only a negligible fraction of the oil that is trapped between the lands can leak back in the direction opposite to the flow.

The center rotor is power driven; its shaft is directly coupled to a 15-hp electric motor which drives it at 1750 rpm. The other two rotors, known as idlers, are driven by the center rotor which, through the intermeshing of its threads with the idlers, communicates the shaft power to the idlers and forces them to rotate in a direction opposite to the center rotor. The

h. The back-pressure tank, or volume tank, located in the control room and containing compressed air at a pressure of 10 to 25 psi, provides the air

pressure on top of the oil in the main supply tank which keeps the entire system full of oil.

rotation of the center rotor is clockwise as viewed from the motor end of the coupling shaft, while the two idler rotors rotate counterclockwise.

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Figure 12-2 Hydraulic accumulator.

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The end of the power rotor nearest the motor rotates in the guide bushing; the rotor shaft extends out through the end plate, where it couples to the shaft of the electric motor which drives it.

Leakage around the shaft is prevented by five rings of 3/8-inch square flexible metallic packing which is held in place by a packing gland. Oil which leaks through the packing gland falls into the drip cup.

12B3. The main supply tank. Fluid is supplied to the pumps from the main supply tank. (See FigureA-9). The shape of this tank varies in different installations. Its total capacity is 50 gallons, but the normal supply maintained is only 30 gallons; the 20-gallon difference is an allowance made for discharge from the accumulator and thermal expansion of the oil.

When the system is operating, the fluid circulates through the power system, returning to the supply tank. However, the fluid will not remain in the supply tank for any length of time, but will be strained and again

pumped under pressure to the accumulator and the manifolds.

Glass tube sight gages mounted on the side of the reservoir, or supply tank, give minimum and maximum readings of the amount of oil in the tank. A drain line and valve near the bottom of the tank provide a means for draining water that may have accumulated there.

The back-pressure tank is connected by a length of pipe to the top of the supply tank (air inlet). It maintains an air pressure of 10 to 25 psi on the oil in the supply tank. This forms an air cushion between the top of the tank and the body of the fluid and maintains the system in a filled condition. An air relief valve set to lift at 40 pounds prevents the building up of excessive air pressures in the supply tank.

12B4. Accumulator. The 1,500-cubic inch air-loaded hydraulic accumulator is located in the pump room. (See FigureA-19.) Figure 12-2 shows a schematic view of the accumulator.

Figure 12-3. Main hydraulic control station.

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