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THE MAIN HYDRAULIC SYSTEM
 
A. INTRODUCTION
 
3A1. Functions. The main hydraulic system performs the bulk of the hydraulic work aboard a submarine. Lines from the central power source radiate throughout the ship to convey fluid under pressure for the operation of a large variety of services. The vent valves of the main ballast, fuel oil ballast, bow buoyancy and safety tanks, and the flood valves of the negative and safety tanks are hydraulically opened and closed by power from the main system. It also operates the air induction valves, the outer doors of the torpedo tubes, the bow plane rigging gear, the forward windlass-and-capstan, the echo-ranging and detecting apparatus (sound heads), and the main engine exhaust valves on earlier classes of   boats. (In some of the latest installations the main engine exhaust valves are operated by pneumatic-hydraulic, or air cushion, units.) In an emergency the main hydraulic system is also called upon to supply power for the steering system and for the tilting of the bow and stern diving planes, although these systems normally have their own independent power supply units.

On the latest classes of boats, the periscopes and antenna masts are also hydraulically operated as units of the main hydraulic system. In earlier classes, they are electrically operated.

3A2. Component parts. In order to perform these numerous tasks, a variety of valves,

Figure 3-1. Schematic piping diagram of power generating system.
1) IMO pumps; 2) 18-horsepower motors; 3) automatic bypass and non-return valves; 4) accumulator; 5) pilot
valve; 6) main supply tank; 7) main supply manifold; 8) main return manifold; 9) accumulator air flask;
10) back-pressure air, or volume, tank; 11) non-return valves; 12) air-loaded relief valve.
Figure 3-1. Schematic piping diagram of power generating system.
1) IMO pumps; 2) 18-horsepower motors; 3) automatic bypass and non-return valves; 4) accumulator; 5) pilot valve; 6) main supply tank; 7) main supply manifold; 8) main return manifold; 9) accumulator air flask; 10) back-pressure air, or volume, tank; 11) non-return valves; 12) air-loaded relief valve.
 
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actuating cylinders, tanks, and manifolds is required, as well as the pumps for building up the required power. The units of the main hydraulic system fall conveniently into five groups:

a. Power generating system.
b. Floods and vents.
 
c. Periscope and radio mast hoists.
d. Forward and after service lines.
e. Emergency systems.

A schematic view of the main hydraulic system in the submarine may be seen in Figure 7-1 at the back of the book.

 
B. POWER GENERATING SYSTEM
 
3B1. General arrangement. The power generating system consists of a group of units whose coordinated action provides the hydraulic power necessary for the operation of the main hydraulic system. It consists of the following principal parts (see Figure 3-1):

a. The IMO pumps (1) supply hydraulic power to the system.

b. The main supply tank (6) contains the oil needed to keep the system filled.

Figure 3-2. Main supply tank.
Figure 3-2. Main supply tank.

  c. The accumulator (4), as the name implies, 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 supply and return manifolds (7 and 8) act as distribution and receiving points for the oil used throughout the system.

e. The pilot valve (5) is a two-port, lap-fitted trunk, cam-operated slide valve, which directs the flow of oil that causes the automatic bypass valve to open or close.

f. The automatic bypass and nonreturn valves (3). The automatic bypass valve directs the flow of pressure oil in response to the action of the pilot valve. The nonreturn valve prevents the oil from escaping through the open automatic bypass.

g. Cut-out valves, serving various purposes throughout the system and nonreturn valves to permit one-way flow.

h. The back-pressure tank, or volume tank (10), contains compressed air at a pressure of 10 to 25 pounds per square inch, which provides the air pressure on top of the oil in the main supply tank and maintains the entire system full of oil.

i. The accumulator air flask (9) serves as a volume tank for the accumulator, allowing the air to pass to and from it when the accumulator is loading or unloading.

3B2. Detailed description. a. Pumps. Power is developed for the system by means of two IMO pumps. The power rotor of each pump is direct-coupled to an 18-horsepower electric motor which drives it at about 1750 revolutions per minute. The two IMO pumps were described in Sections 2B1 to 2B3. They may be operated either singly or both at once, depending upon the volume of oil required by the system at a given moment. Ordinarily a single IMO pump is sufficient to supply the

 
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required volume of oil. However, when operation of the hydraulic units creates a heavy enough demand, the driving motor of the second IMO pump is switched on. The switch can be set on either manual or automatic control.

b. The main supply tank. Fluid is supplied to the pumps from the main supply tank (see Figure 3-2). The shape of this tank varies in different installations. Its total capacity is 50 gallons, but the normal supply maintained there is only 35 gallons; the 15-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.

Figure 3-3 shows another view of a main supply tank with some sections partly cut away to show the internal structure.

Glass-tube sight gages (1) mounted on the side of the reservoir give minimum and maximum readings of the amount of oil in the tank. A drain line and vale (5) near the bottom of the tank provide a means for draining water which may have accumulated there.

The back-pressure tank is connected by a length of pipe to the top of the supply tank (air inlet [2]), It maintains an air pressure of 10 to 25 pounds per square inch 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 full condition. An air relief valve set to lift at 48 pounds per square inch prevents the building up of excessive air pressures in the supply tank.

c. Accumulator. ( See Figure 3-4.) 1. Basic principles of operation. Oil which is discharged by the IMO pumps is directed to the accumulator until the required quantity is obtained. The accumulator receives and stores fluid under pressure and transmits it to the system as it is needed. Actually, the

  accumulator serves the same purpose as a storage battery in an electric system which retains an electrical charge until it is used. Then the charge must be replaced or the battery becomes discharged, or exhausted.

2. Principal parts. The accumulator has three principal working parts: the oil cylinder, the air cylinder, and the plunger. The cutaway view (Figure 3-5) shows the internal structure of the unit.

The oil cylinder (1) receives oil from the IMO pumps through the passage (8) at the top of the cylinder.

Air is admitted into the lower end of the air cylinder (3) through the inlet (9), from the accumulator air flask.

Figure 3-3. Cutaway of main supply tank. 1) Gage; 2) air inlet; 3) hand hole for strainer; 4) strainer mounting base; 5) valve.
Figure 3-3. Cutaway of main supply tank.
1) Gage; 2) air inlet; 3) hand hole for strainer; 4) strainer mounting base; 5) valve.

 
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Air pressure is exerted against the inner surface of the plunger (2) while oil pressure acts on its outer surface. Therefore, its position in the accumulator varies in relation to the differences between the air pressure on the inner surface and the volume and pressure of the oil acting on the outer surface.

Leakage past the inner and outer surfaces of the plunger is prevented by chevron, or C-type ring packing (4 and 6). These packing rings nest together and are held in place by the packing glands (5 and 7). Note that both the air cylinder and the oil cylinder are

Figure 3-4. Accumulator shown with pilot valve.
1) Oil seal fill; 2) oil cylinder drain; 3) oil seal drain;
4) cam roller; 5) pilot valve operating arm; 6) pilot
valve.
Figure 3-4. Accumulator shown with pilot valve.
1) Oil seal fill; 2) oil cylinder drain; 3) oil seal drain; 4) cam roller; 5) pilot valve operating arm; 6) pilot valve.

  equipped with drain valves. The oil packing is shown assembled in Figure 3-6. The air packing is illustrated in Figure 3-7.

A gage connected to the oil line leading to the accumulator indicates the oil pressure on the pressure side. The air system is also

Figure 3-5. Cutaway of accumulator.
1) Oil cylinder; 2) plunger; 3) air cylinder; 4) oil
cylinder packing; 5) packing gland; 6) air cylinder
packing; 7) packing gland; 8) oil inlet; 9) air inlet;
10) oil seal fill; 11) oil seal valve.
Figure 3-5. Cutaway of accumulator.
1) Oil cylinder; 2) plunger; 3) air cylinder; 4) oil cylinder packing; 5) packing gland; 6) air cylinder packing; 7) packing gland; 8) oil inlet; 9) air inlet; 10) oil seal fill; 11) oil seal valve.

 
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equipped with a gage for indicating the air pressure in the air side of the accumulator. In order to prevent leakage from the air side of the accumulator, an oil seal is provided. The oil filler connection (10, Figure 3-5) attached to the plunger supplies oil to a narrow space between the air cylinder and plunger, above the packing. Since the packing will not retain high pressure air, the oil seal is placed on top of the packing. Therefore the high-pressure air acts against the oil seal instead

Figure 3-6. Accumulator packing (oil).
Figure 3-6. Accumulator packing (oil).

Figure 3-7. Accumulator packing (air).
Figure 3-7. Accumulator packing (air).

of the packing. Oil is poured through a pipe and funnel in the oil filler until its level reaches the mid-position of the funnel. The oil filler pipe is mounted in a trap which catches water. A stop valve is fitted to the oil filler to retain the oil seal within the accumulator; also, a needle-type drain valve (3, Figure 3-4) is provided to empty the trap and the oil seal from the air cylinder packing gland.

3. Operation. The oil cylinder and the air cylinder are stationary. The plunger,

  however, can slide up or down inside the oil cylinder and over the air cylinder. Before the IMO pumps are started, the accumulator air flask and the air cylinder are charged with compressed air to a pressure of 1750 pounds per square inch from a connection to the high-pressure air system. The cut-out valve for opening the high pressure service line is shown at the extreme right of the piping diagram, Figure 3-1, on the line leading off from the accumulator air flask (9, Figure 3-1).

When the pumps are stopped, air pressure holds the plunger at the top of its travel, ready to receive the charge of pressure oil from the pumps. Since it is the charge of pressure oil that determines the load conditions of the oil cylinder, the cylinder will, therefore, be under no-load when the pumps are not running. In starting the system, it is desirable but not necessary to maintain the no-load condition until normal operating speeds have been attained. Therefore, the hand bypass valve on the main supply manifold is opened, and one of the IMO pumps is switched on. The opened hand bypass valve allows the oil from the discharge side of the pump to flow back to the supply tank, relieving the pump of any load, until it has attained normal operating speed.

The hand bypass valve is then closed, and the oil from the discharge side of the pump begins, to fill the oil cylinder in the accumulator.

When the hand bypass valve is open, the plunger is held at the top of the cylinder by air pressure. Therefore, closing the hand bypass valve forces sufficient pressure oil from the pump into the oil cylinder, on the outer surface of the plunger, to meet and overcome the force exerted by the air upon the inside of the plunger, thus pushing the plunger down in the oil cylinder. The oil pressure in the line between the discharge side of the pump and the accumulator will rise immediately to a value sufficient to overcome the air pressure that tends to force the plunger up.

The two operating diagrams, Figures 3-8 and 3-9, illustrate the action which takes place.

 
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Figure 3-8. Accumulator In fully loaded position.
1) Plunger; 2) automatic bypass valve piston; 3) pilot
valve; 4) air chamber; 5) cam roller; 6) pilot valve
operating arm; 7) automatic bypass valve; 8) from
pump; 9) bypass to pump suction; 10) nonreturn valve
spring; 11) nonreturn valve.
Figure 3-8. Accumulator In fully loaded position.
1) Plunger; 2) automatic bypass valve piston; 3) pilot valve; 4) air chamber; 5) cam roller; 6) pilot valve operating arm; 7) automatic bypass valve; 8) from pump; 9) bypass to pump suction; 10) nonreturn valve spring; 11) nonreturn valve.
 
Figure 3-9. Accumulator in unloaded position.
Figure 3-9. Accumulator In unloaded position.
 
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The force of 600 to 700 pounds exerted by this oil upon the outer surface of the plunger (1, Figure 3-8) will force it to travel downward until it has reached the limit of its downward stroke, tripping-the pilot valve operating arm, as shown in Figure 3-8.

The pilot valve (3) which hydraulically operates the automatic bypass valve will cause the automatic bypass valve to open when a column of oil is sent from the pressure side of the system to the underside of the automatic bypass valve piston (2). The oil coming from the discharge side of the pump through the line (8) is now bypassed directly back through the line (9) to the pump's suction side. This allows the nonreturn valve (11) to close, shutting off the line between the pump and the accumulator so that the pressure oil in the accumulator will not returns through the open bypass valve.

In practice, the pump can either be run continuously or switched off automatically by the use of a toggle switch as the plunger approaches the bottom of its stroke. However, the automatic bypass valve serves as a further precaution to guarantee that no more pressure oil will be forced into the accumulator line after the accumulator is fully charged. In this condition, the full charge of oil will be maintained under pressure in the accumulator. However, this is only theoretically true. In practice, the accumulator will not remain fully charged indefinitely, even when no hydraulic mechanisms are being operated, since there is always a slight oil leakage at various points in the system.

If a control valve were opened at some point in the system, utilizing some of this stored oil to operate a hydraulic mechanism, the force exerted by the compressed air at 1750 pounds per square inch upon the inner surface of the plunger would immediately cause the plunger to travel upward.

When enough of the oil charge has been used, the plunger cam roller, as in Figure 3-9, will trip the pilot valve, closing the automatic bypass valve, and again directing the oil from the discharge side of the IMO pump through the nonreturn valve to the accumulator. The pressure oil will again begin to charge the accumulator, forcing the plunger downward.

  4. Automatic switches and contact makers. The cam roller on the plunger actuates the pilot valve operating arm, which not only operates the pilot valve, but also at different intervals throws two electrical contact makers which switch on the IMO pumps as the plunger is traveling upward and switch them off again as the plunger travels downward.

Figure 3-10 shows schematically how the contact makers, switches, and electrical wiring are arranged. The cam roller (2, Figure 3-10) is shown in a position intermediate between the highest and lowest limits of its travel. As it moves in either direction from

Figure 3-10. Contact makers for pump controls.
1) Accumulator; 2) cam and cam roller; 3) pilot
valve; 4) pilot valve control arm; 5) contact makers;
6) motor switches.
Figure 3-10. Contact makers for pump controls.
1) Accumulator; 2) cam and cam roller; 3) pilot valve; 4) pilot valve control arm; 5) contact makers; 6) motor switches.

this intermediate point, it actuates the pilot valve operating arm, which throws the contact makers (5) connected to the motor switches (6). The wiring is so arranged between the contact makers and the manual push-buttons that, when required, either or both pumps can be automatically switched on or off by the motion of the cam roller. This arrangement permits each pump to be used in turn at continuous service, so that both pumps will receive equal wear.

5. Explanation of pressure differential. The oil pressure on top of the plunger varies

 
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between 600 and 700 pounds per square inch, while the air pressure underneath it is maintained at 1750 pounds per square inch. Since the air pressure is so much greater than the oil pressure, the oil, to be able to exert a force sufficient to overcome that of the air beneath it, allowing the plunger to travel downward, must be acting over a greater area than the air.

This is in fact true. The area on the oil side of the plunger is much larger than the area on the air side, the ratio between the two areas, being approximately 3 to 1. Since the total force exerted by a fluid at a given pressure is proportional to the area over which it is exerted (see Section 1B3b), it follows that an oil pressure of 600 pounds per square inch exerted on the larger area of the oil side of the plunger will be sufficient to overcome an air pressure of 1750 pounds per square inch exerted against the smaller air side of the plunger, which is only about one-third as large as the oil side.

  6. Function of the air-loaded relief valve. In Figure 3-1, an air-loaded relief valve (12) is seen just beyond the top of the accumulator. This valve contains a double-ended piston, one end of which is air-loaded by a small secondary line running from the accumulator air flask. The other end of the piston is in contact with the high pressure oil from the oil cylinder in the accumulator.

The ratio between the area of one surface of the piston and the area of the other surface is approximately 3 to 1, or about the same as the ratio between the area of the oil side of the plunger to the area of the air side.

This ratio will not allow for an oil pressure overload of more than 10 percent. In other words, if the oil pressure increases to a value which is more than 10 percent over one-third of the air pressure, the valve piston will lift, allowing oil to escape from the accumulator back to the return side of the system until the 3:1 ratio between air pressure

Figure 3-11. Main supply manifold.
1) Bypass; 2) service aft; 3) service fore; 4) emergency planes; 5) emergency steering; 6) quick-throw cutout; 7) relief valve; 8) to control manifolds; 9) to pilot valve supply; 10) to gage and vent.
Figure 3-11. Main supply manifold.
1) Bypass; 2) service aft; 3) service fore; 4) emergency planes; 5) emergency steering; 6) quick-throw cutout; 7) relief valve; 8) to control manifolds; 9) to pilot valve supply; 10) to gage and vent.
 
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and oil pressure is restored. For example, if the air pressure, because of leakage, fell off to 1500 pounds, the oil pressure to maintain the correct ratio would be about 500 pounds. If now the oil pressure were to exceed 550 pounds per square inch (one-third of the air pressure plus 10 percent), the valve would lift, allowing the oil to escape from the accumulator back to the return side of the system.

The valve will function correctly regardless of variations in the value of the air pressure.

This air-loaded type of relief valve is currently installed only on Portsmouth built boats. It is intended to furnish additional protection since the existing relief valves in the high pressure side of the system are not adequate to handle an overload when both IMO pumps are running.

On submarines of Electric Boat Company design, the line from each IMO pump is provided with its own relief valve, making unnecessary the inclusion of an air-loaded relief valve in the high pressure side of the system.

d. The main supply and return manifolds. 1. Hydraulic fluid discharged by the accumulator is conveyed to the main supply manifold (see Figure 3-11) where its flow is distributed to the supply lines and also to the control valve manifolds. The returning fluid flows through lines to the main return manifolds which then deliver it back to the oil supply tank.

The supply manifold consists of a series of valves combined into a single unit. The opening or closing of any of the valves either permits or interrupts the flow of hydraulic fluid controlled by that valve without affecting the other valves in the manifold. The valves are all connected into a common fluid channel, but distribution of the oil is made through pipe lines attached to those valves which supply a group of hydraulic units. The return manifold is similar in design to the supply manifold.

2. The main supply manifold has seven valves, a bypass valve (1, Figure 3-11), four supply valves (2, 3, 4, and 5, Figure 3-11), a quick-throw cut-out (6), and a relief valve

  (7). The four supply valves are connected to the forward and after service lines and to the emergency systems for steering and plane tilting.

A flanged port (8) connects with the flood and vent control manifolds. A small opening under the relief valve at the end of the fluid channel (9) provides a connection to the pilot valve. A small opening (10) in the hand bypass valve body provides for a gage and vent connection. Both the pilot valve and the gage and vent connections are always open to the common oil passage in the manifold.

3. The bypass handwheel (1, Figure 3-12) is attached to the collar (2). The upper end of the stem (3) is square, to fit into the collar inside the squared hub of the handwheel (1). The lower end, passing through the packing (4), is attached to the short stem which is attached to the disk (5). When the handwheel is turned to the left, the disk (5) is raised off its seat, opening a passage between the central fluid channel and the port at the bottom. At the time the IMO pumps are started, the bypass is opened so that the oil will flow freely from the pump back to the supply tank until the pumps attain their maximum speed. Then the bypass is closed so that hydraulic pressure will build up.

4. Starting from left to right in Figure 3-12, the bypass valve appears first. The next four valves supply hydraulic fluid to:

a) After service line.
b) Forward service line.
c) Emergency bow and stern planes system.
d) Emergency steering system.

The internal mechanism of these valves is identical with that of the bypass valve. The valve is operated by a double-ended wrench. The small end fits over the turn-nut (8) to rotate the inner mechanism. Before the turn-nut can be moved, the locking cap (7) must be backed off slightly with the large end of the wrench. After each operation, the lock cap is tightened to prevent accidental turning of the valve stem.

5. A quick-throw cut-out valve is provided on the supply manifold. This is a

 
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tapered plug-type valve. Its method of operation is somewhat different from that of the disk valves. The plug valve has an elliptical hole cut through its center. It can be turned by the lever (9) through the stem (10) so that the hole is in line with the fluid passage in the manifold, or turned in the opposite direction, thereby cutting off the flow of oil to supply valves and manifolds. The valve is spring-loaded and must be lifted off its seat by the handle before it can be turned. The plug valve is provided as a means for rapidly blanking off the oil lines from the power group to the rest of the units in the main hydraulic system.   6. A relief valve of conventional type is installed on the manifold for relief of excessive pressure. The normal operating oil pressure for the main hydraulic system is 600 to 700 pounds per square inch. The relief valve, however, is adjusted to open when the pressure reaches 750 pounds per square inch, since pressures in excess of 750 pounds per square inch may cause damage to the equipment. The valve (15) is held on its seat by spring (14) until oil pressure overcomes tension on the spring. When this occurs, the valve is lifted off and passes through port (16) to the supply tank. The tension on the spring is regulated by the
Figure 3-12. Cutaway main manifold. 1) handwheel; 2) collar; 3) stem; 4) packing; 5) disk; 6) seat; 7) locking cap; 8) turn-nut; 9) handle; 10) 11) spring; 12) plug valve; 13) cap; 14) relief valve spring; 15) valve; 16) connection to supply tank; 17) main fluid passage; 18) flood vent manifold; 19) adjustment nut.
Figure 3-12. Cutaway main manifold.
1) handwheel; 2) collar; 3) stem; 4) packing; 5) disk; 6) seat; 7) locking cap; 8) turn-nut; 9) handle; 10) 11) spring; 12) plug valve; 13) cap; 14) relief valve spring; 15) valve; 16) connection to supply tank; 17) main fluid passage; 18) flood vent manifold; 19) adjustment nut.
 
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adjusting nut (19). The retaining cap (13) prevents leakage from valve.

7. The main return manifold, illustrated in Figure 3-13, has four valves which are connected to the following lines:

a) After service line.

b) Forward service line.

c) Emergency bow stern planes system.

d) Emergency steering system.

Each valve is identical with disk-type valves contained in the main supply manifold, and operates in the same way. Oil returned to this manifold is directed back to the oil supply tank.

Figure 3-13. Cutaway of main return manifold.
1) Turn-nut; 2) lock cap; 3) valve body; 4) stem; 5) valve; 6) seat.
Figure 3-13. Cutaway of main return manifold.
1) Turn-nut; 2) lock cap; 3) valve body; 4) stem; 5) valve; 6) seat.

In submarines which have hydraulically operated radio mast and periscope hoists, the return manifold has six valves, instead of only four. On this installation, however, the two necessary additional supply valves are not attached directly to the main supply manifold, but adjacent it.

8. Both the supply and return manifolds are flexible in size, in the sense that additional

  valves may be welded to the units when required.

The quick-throw cut-out at the main supply tank suction lines and main supply tank suction lines and main supply manifold are normally kept open. They are closed only when it is desired to isolate these units from the rest of the system.

All supply and return valves on both manifolds are normally open, making power instantly available in any part of the main hydraulic system.

e. Pilot valve. The pilot valve (see Figure 3-14) is used in the main hydraulic system to operate the automatic bypass valve by directing oil under pressure to the automatic bypass valve piston when the accumulator is fully charged, thereby opening the bypass and then venting off this oil when the accumulator is discharged, allowing the bypass to close again.

3-14. Pilot valve.
3-14. Pilot valve.

Figure 3-15 shows a cutaway view of this valve. It is mounted on or near the accumulator in such a way that the operating arm (6) is actuated by a cam roller mounted on the accumulator plunger. Hydraulic fluid from the accumulator under pressure enters the valve at the supply port (7). As the accumulator is charged, the plunger moves downward, carrying with it the cam roller. As the plunger approaches the bottom of its stroke, the cam will bear against lower end of the pilot valve operating arm, pushing the piston (2) up within cylinder (1). In this position, the flat-milled surface (2) cut along side of the piston will allow a column of oil to pass from the supply port (7) through the

 
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port (8) leading to the automatic bypass valve.

This will open the automatic bypass valve, bypassing the pressure oil from the discharge side of the IMO pump back to the suction side of the pump and allowing the nonreturn valve to close. No more oil will be delivered to the accumulator as long as the pilot valve remains in this position.

When the oil charge in the accumulator is depleted either by the use of oil required for operation of various units in the system, or by leakage, the plunger rises. This causes the cam roller to bear against the upper end of the pilot valve operating arm, thus depressing the pilot valve piston until the land between the two flat-milled surfaces on the piston blocks off the supply port (7) from the port (8) leading to the automatic bypass valve. At the same time, the upper flat surface (10) now aligns the port (8) with the escape

Figure 3-15. Cutaway of pliot valve.
1) Body; 2) piston; 3) packing; 4) gland nut; 5) pin;
6) pilot valve operating arm; 7) port from high pressure line;
8) port to automatic bypass; 9) to oil
supply fank; 10) flat-milled passage; 11) Mounting
bracket; 12) flat-milled passage.
Figure 3-15. Cutaway of pilot valve.
1) Body; 2) piston; 3) packing; 4) gland nut; 5) pin; 6) pilot valve operating arm; 7) port from high pressure line; 8) port to automatic bypass; 9) to oil supply tank; 10) flat-milled passage; 11) Mounting bracket; 12) flat-milled passage.

  port (9), and the oil trapped under pressure in the line leading to the automatic bypass piston is vented out through the port (9) to a vent line which bleeds into the main supply tank.

This removes the pressure from under the valve piston of the automatic bypass, permitting the loading spring to reseat the automatic bypass valve and thus shut off the bypass line.

Immediately pressure oil from the IMO pump, once more directed against the underside of the nonreturn valve, opens this valve, allowing the oil to flow to the accumulator.

A packing gland with chevron packing (3) prevents oil leakage past the pilot valve piston at its point of entry into the valve body.

The foregoing description applies only to the latest types of pilot valves, since earlier pilot valves are different both in design and installation. The earlier type valve, while serving the same purpose and designed on the same general principle as the later type, has two structural differences. (1) it uses a spool piston and has its accumulator and automatic bypass line reversed from the later pilot valve installation; and (2) the drilled passage in the center of the piston actually allows the venting and releasing of the oil pressure from the automatic bypass valve. This reversal of lines uses the automatic bypass line to be blanked off as the piston rises rather than when the piston descends as in the later type. The purpose of this change in the later pilot valve is to have the toggle switch, that automatically starts and stops the pumps, operated by the cam attached to the pilot valve bracket arm. This change also provides for more positive action of the pilot valve.

f. Automatic bypass and nonreturn valves. 1. The automatic bypass and nonreturn valves (see Figure 3-16) are installed between the IMO pumps and the accumulator. There is one on each pump pressure line. The automatic bypass valve bypasses hydraulic oil when the accumulator is fully charged. The nonreturn valve prevents back-flow of the oil to the pump.

 
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2. As seen in Figure 3-17, the valve body (1) contains two valve parts. One is the bypass valve (2) which is held on its seat by the valve spring (3). The other valve is of the disk-type (4) which is also seated by a spring (5).

Figure 3-16. Automatic bypass and nonreturn valve.
Figure 3-16. Automatic bypass and nonreturn valve.

3. During the intervals when the accumulator is being charged, hydraulic oil is delivered by the pump into the pressure line (8). The oil pressure unseats the spring-held nonreturn valve disk (4) and oil under pressure goes into the line (7) to the accumulator. When the accumulator is fully loaded, the pilot valve is tripped and oil enters the bypass valve at port (9). The force of this pressure opens the bypass valve (2) and the oil from the pumps is bypassed back to the suction side of the pumps through port (6). When this occurs, there is not enough pressure to keep the nonreturn valve (4) off its seat, so the disk valve spring (5) returns the disk to its seated position, thus blocking the back-flow of oil from the accumulator. Oil pressure from the accumulator also assists in the seating of the valve.

g. Miscellaneous valves. Brief mention should be made of a group of cut-out and check valves found in the main hydraulic system as well as in the steering and planes systems.

  1. Sound isolation: supplementary nonreturn valves. If the noise of the IMO pumps in operation were transmitted to the hull of the submarine, it would greatly increase the danger of detection by enemy listening devices. The pumps are therefore mounted on rubber. This precaution, however, would be of comparatively little value if rigid pipelines connected the pumps with the rest of the system, since then the piping would carry the vibration to the framework and thence to the hull.

Accordingly, the pump noise is isolated by inserting short lengths of flexible rubber tubing in the hydraulic pipelines between the automatic bypass and nonreturn valves and the accumulator.

Rubber hose is, of course, subject to deterioration and lacks the strength of the rigid parts of the system. Hence, the flexible connection represents a weak point in the piping. An examination of the schematic piping diagram (Figure 3-1) will show that if either of those connections were to give way, and no

Figure 3-17. Cutaway of automatic bypass and
nonreturn valve.
1) Body; 2) bypass valve; 3) bypass valve spring;
4) nonreturn valve disk; 5) nonreturn valve spring;
6) to pump suction; 7) to accumulator; 8) from pump;
9) from pilot valve.
Figure 3-17. Cutaway of automatic bypass and nonreturn valve.
1) Body; 2) bypass valve; 3) bypass valve spring; 4) nonreturn valve disk; 5) nonreturn valve spring; 6) to pump suction; 7) to accumulator; 8) from pump; 9) from pilot valve.

 
53

provisions were made for shutting off the lines between the accumulator and the automatic bypass and nonreturn valves, oil stored in the accumulator would instantly be discharged into the pump room with accompanying hazard and inconvenience. To prevent backing up of oil from the accumulator in this eventuality, an additional nonreturn valve is placed in each of these lines. The schematic piping diagram shows the location of these valves (11, Figure 3-1).

Figure 3-18, the internal structure of a nonreturn valve, shows that this valve is practically identical with the nonreturn valve which forms part of the automatic bypass and nonreturn valve assembly (see Figure 3-17), except that it has no return spring. The pressure oil coming from the automatic bypass and nonreturn valve enters these nonreturn valves at the intake port (2), pushing the valve disk (1) off its seat and allowing the oil to flow out through the outlet port (3),

Figure 3-18. Cutaway of nonreturn valve. 1) Valve disk; 2) inlet port; 3) discharge port.
Figure 3-18. Cutaway of nonreturn valve.
1) Valve disk; 2) inlet port; 3) discharge port.

into the line leading to the accumulator. The instant that the pressure through this valve is reversed, oil flowing in through the outlet port (3) would immediately force the disk (1) back against its seat, shutting off the line.

2. Quick-throw cut-out valve. This valve (see Figure 3-19) is similar in operation to the cut-out valve in the main supply manifold described in Section 3B2d. The handle (1) rotates a stem (2) which is attached to a

  valve plug (5), either to line up the port in the plug with the fluid flow or to turn the plug to prevent flow. The plug is tightly held on its seat by a spring (4). The handle must be raised to allow the plug to lift far enough to be rotated and then released so it can be reseated. This type of quick-throw cut-out valve is located in the pump supply lines from the supply tank.

3. Hydraulic cut-out valves. A smaller type of cut-out valve is illustrated in Figure 3-20. The nonrising stem (2) is rotated by a wheel fitted with finger knobs (1). Both ends of the stem are square, the top end fitting into the finger wheel from which the knobs extend and the bottom end fitting into a threaded piece which bears against the valve disk (4).

Figure 3-19. Cutaway of quick-throw cut-out valve.
1) Handle; 2) stem; 3) packing; 4) spring; 5) valve
plug.
Figure 3-19. Cutaway of quick-throw cut-out valve.
1) Handle; 2) stem; 3) packing; 4) spring; 5) valve plug.

 
54

The top of this disk forms a collar, which fits into a groove cut in the interior of the male threaded piece. As this piece screws

Figure 3-20. Cutaway of hydraulic cut-out valve. 1) Handle; 2) stem; 3) packing; 4) valve disk.
Figure 3-20. Cutaway of hydraulic cut-out valve.
1) Handle; 2) stem; 3) packing; 4) valve disk.

up or down as a result of being turned left or right by the squared lower end of the stem, the disk will ride with it. Therefore, rotating this stem by means of the finger wheel will cause the male threaded piece to be screwed downward, seating the valve disk and shutting off the flow of oil.

The valve disk has a hole drilled partially through its center into which fits a small cylindrical rod, extending downward from the squared lower end of the stem. This rod serves as a guide upon which the valve disk slides up or down with the rotation of the threaded piece.

Oil leakage past the stem is prevented by packing (3), held in place by a gland.

An indicator plate at the top of the valve (not shown in the illustration) shows which way to turn the wheel in order to open or close the valve.

4. Hydraulic Silbraz valves. Several of these valves (see Figure 3-21) are located throughout the hydraulic system. They range in size from 1/8-inch to 1/4-inch. This valve is of the on-and-off type in which the valve position is secured by a lock cap. It

  consists essentially of a valve body, or bonnet, containing an upper and lower chamber which can be opened to each other by raising the valve disk (5, Figure 3-21), or closed by lowering the disk down into its seat. The disk is moved up and down by a traveling stem (4), the top end of which is squared, and the lower end threaded. The square top of the stem fits loosely inside the turn-nut (1). The lower end of the stem is formed into a double collar to hold the valve disk (5), within which it can turn freely. Turning the stem left or right, therefore, will cause it to travel up or down, thus raising or lowering the valve disk, which rides on its lower end.

The turn-nut is secured in any required position by screwing the locking cap (2) down tightly to it, using for this purpose the large-end hex-wrench. Therefore, before the turn-nut can be moved, the locking cap must be backed off a little, until the turn-nut is freed. The small end of the hex-wrench is then applied to the turn-nut. Turning the turn-nut all the way to the right will screw-the stem down to its lowest position,

Figure 3-21. Cutaway of hydraulic Siibraz valve.
1) Turn-nut; 2) locking cap; 3) packing; 4) stem;
5) valve disk.
Figure 3-21. Cutaway of hydraulic Silbraz valve.
1) Turn-nut; 2) locking cap; 3) packing; 4) stem; 5) valve disk.

 
55

seating the valve disk and blocking off the upper and lower chambers from each other, thereby shutting off the line through the valve. Turning the turn-nut to the left will raise the disk, opening the valve.

Oil leakage is prevented by packing (3), held in place by the packing gland.

It should be noted that though it is the turn-nut to which the wrench is applied, the turn-nut itself does not travel up or down, it merely turns left or right, while the stem rides up or down within it.

3B3. Operation. a. Preliminary steps. With all units arranged in place as shown in Figure 3-1, the following steps must be taken before the power generating system is started.

1. The entire system must be filled with oil and the accumulator fully charged. An additional 35 gallons, over and above the amount necessary to fill the entire system, must be placed in the main supply tank.

2. The back-pressure, or volume, tank must be charged with compressed air at a pressure of from 10 to 25 pounds per square inch, from the 200-pound air service line. (Not all classes of submarines have this unit.)

3. All hand levers on the control manifolds must be placed in the HAND position.

4. The quick-throw cut-out valves at the main supply tank and main supply manifold must be opened.

5. The air cylinder in the accumulator and the air bottle must be charged with compressed air to a pressure of 1750 pounds per square inch from its high pressure service line, raising the plunger in the accumulator to its top position.

6. The hand bypass valve on the main system manifold may be opened if required.

b. Starting pumps. Turn on the motor switches which start the pumps. In a few seconds, the pumps should be operating at full speed and the hand bypass valve (if opened) can be closed, making possible full development of oil pressure.

c. The accumulator (see Figure 3-8) is charged with oil under pressure. As this

  occurs, the plunger (1) is forced down until it reaches the fully loaded position shown in this illustration. The cam roller (5) moves downward with the plunger and changes the position of the pilot valve operating arm (6). The piston of the pilot valve (3) moves up so that the port which allows oil to flow to the automatic bypass valve is uncovered. This oil acts upon the automatic bypass valve (7), forcing it upward off its seat. Hydraulic oil which enters the automatic bypass and nonreturn valve from the pump pressure line (8) is bypassed to the suction side of the pump through the port (9). In the meantime, the nonreturn valve (11) is seated because of the reduction in pump pressure caused by bypassing the oil, and the flow of oil from the IMO pumps to the accumulator is shut off.

d. When the accumulator is discharged, nearly all its contents being used in the operation of the hydraulic system, the plunger again rises to the position shown in Figure 3-9. The cam roller, acting upon the arm of the pilot valve, lowers the piston so that oil no longer flows to the bypass valve (7), while the small quantity of oil under pressure trapped in the line between the bypass and

Figure 3-22. Contact makers for pump controls.
1) Accumulator; 2) cam and cam roller; 3) pilot
valve; 4) pilot valve control arm; 5) contact makers;
6) motor switches.
Figure 3-22. Contact makers for pump controls.
1) Accumulator; 2) cam and cam roller; 3) pilot valve; 4) pilot valve control arm; 5) contact makers; 6) motor switches.

 
56

the pilot valve vents off through the pilot valve vent line back to the main supply tank. The spring will then reseat the automatic bypass valve. Oil from the pressure side of the pump unseats the-nonreturn valve (11) and once more charges the accumulator.

e. During the periods when pressure is being built up in the accumulator, the two IMO pumps can be operated jointly, if required. In more recent classes of boats, this is accomplished automatically. Figure 3-22

  shows a typical installation. A pair of contact makers, one for each pump, is mounted so that they are in contact with the bracket arm of the pilot valve. When the accumulator is in the unloaded position, the cam on the pilot valve operating arm releases both contact makers, and both pump motors are switched on at proper intervals. In the fully loaded position, the cam presses in both of the contact makers, shutting off both pumps at proper intervals.
 
C. FLOOD AND VENT CONTROL SYSTEM
 
3C1. General. The ability of a submarine to attain neutral buoyancy, so that by suitable manipulation of its diving planes it can submerge, surface, or maintain a given depth, is effected by a series of tanks built around the pressure hull. These tanks are divided into separate compartments, which can be filled with sea water to submerge the vessel, and emptied by compressed air to restore positive buoyancy. The tanks are classified and named according to their normal functions as follows:

a. Main ballast tanks. The main ballast tanks (M.B.T.) comprise e principal group. They contain air when the vessel is surfaced, sea water when it is submerged.

b. Fuel ballast tanks. The fuel ballast (F.B.) tanks normally carry fuel for the Diesel engines. When the fuel has been consumed, they can be converted for use as normal ballast tanks.

c. Negative and safety tanks. 1. The negative tank. The negative tank is a special-purpose tank located under the control room, just forward of amidships. When opened to the sea, it fills up with water. It is used to get the vessel under rapidly, or if the vessel is already submerged, to make a quick descent to greater depth. It is called the negative tank because its purpose is to, provide negative buoyancy.

2. The safety tank. The safety tank is another special-purpose tank, located amidships. Its function is the opposite of that of the negative tank; that is, it provides positive buoyancy in an emergency situation. Specifically, it is designed to hold a quantity of

  water equal to the quantity which would flood the conning tower as a result of enemy action. In such case, the amount of positive buoyancy supplied by blowing the safety tank would just compensate for the amount lost by the flooding of the conning tower.

A special feature of both tanks is that they are constructed as strongly as the pressure hull itself, and hence can withstand full sea pressure at any working depth. Therefore, whenever it is necessary either to surface or to attain a shallower depth, the full working pressure of the high pressure air line can be let into these tanks, rapidly expelling the water.

d. The bow buoyancy tank. The bow buoyancy tank, as its name implies, is located in the bow of the vessel, and controls-its buoyancy. When the ship dives, this tank is flooded first to make the ship nose-heavy; when surfacing, it is blown out first, to make the ship rise by the bow.

3C2. Detailed description. a. Flood valves and vent valves. All main ballast tanks have flood ports; the fuel ballast tanks have hand-operated flood valves. All have hydraulically operated vent valves.

The vent valve on the safety tank and the flood valves on the safety and negative tanks normally are hydraulically operated, but if necessary, can also be operated by hand.

The vent valve on the negative tank is hand-operated and is vented inboard.

When the submarine is surfaced, the vents are closed, and the water is kept out of the tanks by keeping them filled with air at about 10 pounds pressure. Since the flood

 
57

ports of the main ballast tanks are always below the waterline, the sea exerts a constant upward pressure, but is prevented from entering because the imprisoned air cannot escape. To submerge the vessel, therefore, it is necessary only to open the vents, allowing the imprisoned air to escape, and the sea water will enter the tanks.

To surface again, the vents are closed, and air is forced into the tanks from the top, blowing the water out through the flood ports in the bottom.

b. Flood and vent control manifolds. The main ballast, fuel ballast, and safety tank vent valves, and the bow buoyancy and the two hydraulically operated flood valves (safety and negative tanks) are controlled from two flood and vent control manifolds, the six-valve manifold and the three-valve manifold, both located in the control room.

  1. The main vent control manifold. a. Portsmouth installation. Figure 3-24 shows the main vent control manifold, commonly called the six-valve manifold, as installed on boats of Portsmouth design. It is a housing containing six identical control valves, each one of which is separately operated by individual hand levers.

Reading from right to left (Figure 3-24), these six levers operate the following vent valves:

1) Bow buoyancy tank
2) Main ballast tanks No. 1 and No. 2
3) Fuel ballast tanks No. 3 and No. 5
4) Main ballast tank No. 4
5) Main ballast tanks No. 6 and No. 7
6) Safety tank

b. Electric Boat Company installations. The main vent control manifold on boats

Figure 3-23. Piping diagram of flood and vent system and periscope and antenna mast hoists.
1) Main supply manifold; 2) main return manifold; 3) two-valve addition to main supply manifold, for periscope hoist and antenna hoist (in practice welded to lower end of main manifold); 4) main vent control, or six-valve, manifold; 5) flood and hull ventilation control, or three-valve, manifold; 6) vent valve operating gear, bow buoyancy tank; 7) main engine air induction and hull ventilation; 8) periscope vent line; 9) antenna vent line; 10) settling tank; 11) settling tank.
Figure 3-23. Piping diagram of flood and vent system and periscope and antenna mast hoists.
1) Main supply manifold; 2) main return manifold; 3) two-valve addition to main supply manifold, for periscope hoist and antenna hoist (in practice welded to lower end of main manifold); 4) main vent control, or six-valve, manifold; 5) flood and hull ventilation control, or three-valve, manifold; 6) vent valve operating gear, bow buoyancy tank; 7) main engine air induction and hull ventilation; 8) periscope vent line; 9) antenna vent line; 10) settling tank; 11) settling tank.
 
58

built by the Electric Boat Company houses seven control valves instead of the six found in the Portsmouth installation.

Reading from right to left, these seven valves operate the following vent valves:

1) Bow buoyancy tank
2) Main ballast tanks No. 1 and No. 2
3) Fuel ballast tanks No. 3 and No. 5
4) Main ballast tank No. 4
5) Safety tank
6) Main ballast tank No. 6
7) Main ballast tank No. 7

c. Operation of the valves. Each valve has four positions, which are shown on indicator plates next to the hand levers:

1) CLOSE, which closes the vent.

2) OPEN, which opens it.

3) HAND, which bypasses the oil allowing hand operation.

4) EMERGENCY, which shuts off the lines to the hydraulic unit cylinder, so that if there is a break in the local circuit, oil will not leak out of it from the main system, and only the oil in the local circuit will be lost.

Figure 3-24. Main vent control manifold (six-valve manifold).
Figure 3-24. Main vent control manifold (six-valve manifold).

The frame mounted on the manifold has notches cut into it for each valve position. The hand lever is firmly latched into these notches by a lateral spring. Once placed in any position the lever remains there until moved by the operator.

Each of these control valves operates a flood or vent valve, at some point remote from the manifolds, by directing a column of pressure oil to one side or the other of a hydraulic unit cylinder whose piston is connected,

  through suitable linkage, to the valve operating mechanism.

Figure 3-25 shows the internal construction of one of these valves, as it would look from the left end of the manifold. (The illustration shows the three-valve manifold, but the internal structure of its valves is identical with those in the six-valve manifold.) It is a spool-type valve, so called because of the spool (11) which, when moved by the hand lever (2), shaft (15), arm (14), and connecting link (13), opens and closes the required combinations of ports and channels in the body (1) of the valve. The pressure line (7) and the return line (8) form channels which run lengthwise through the whole manifold; the threaded port (9) on the bottom of the manifold goes to the upper end of the hydraulic unit cylinder; a similar port just behind it (not shown) goes to the lower end of the cylinder. The latching spring (10) holds the hand lever firmly in place. The individual locking arms (5) swing freely on the pivot rod, making a sliding fit against the side of the hand lever, just tight enough to prevent the lever from being pulled out of the notch. Therefore, the hand lever cannot be moved from any of the four notched positions while its locking arm is down, that is, horizontal. The lock hole (6) is just above the top of the locking arm when it is horizontal so that, to secure a valve in any position, it is necessary only to place the hand lever in the desired notch, drop the locking arm, and slip a padlock through the locking hole. In this view, Figure 3-25, the three locking arms are viewed from the left end of the manifold and shown in the dropped position. Reference to Figure 3-24, in which they are shown partly raised, and viewed from the right end, will make the arrangement more easily understood.

2. The flood and hull ventilation manifold. Figure 3-26 shows the flood and hull ventilation manifold, usually called the three valve manifold. Its three control valves are identical in structure and operating principles with those on the six-valve manifold just described (see Figure 3-25). Its hand levers are all shaped differently, however, and its functions differ in important ways from those of the six-valve manifold.

 
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Reading from right to left (Figure 3-26), its three hand levers operate the following units:

a) Main engine. Engine air induction and hull ventilation supply and exhaust. (Ball-shaped handle; name plate V.)

b) Negative tank flood valve. (T-shaped handle; name plate N.)

c) Safety tank flood valve. (Straight handle; name plate S.)

As on the six-valve manifold, each valve

  has four positions, shown on indicator plates next to the hand levers:

a) CLOSE, which closes the hydraulically operated unit.

b) OPEN, which opens it.

c) HAND, allowing hand operation.

d) EMERGENCY, which shuts off the lines to the hydraulic unit cylinder in case of a break in them, so that the oil in that circuit only will be lost.

Figure 3-25. Cutaway of safety and negative flood, engine air induction and hull ventilation control manifold (three-valve manifold).
1) Valve manifold body; 2) hand lever for flood valve of safety tank; 3) hand lever for flood valve of negative
tank; 4) hand lever for hull ventilation valve and engine air induction valve; 5) locking arms; 6) hole for
padlock; 7) hydraulic port from supply line, main hydraulic system; 8) hydraulic port to return line; 9) hydraulic port to hydraulic cylinder of operating gear; 10) latching spring; 11) spool; 12) bypass channel in
valve; 13) link; 14) arm; 15) shaft; 16) drain plug; 17) bracket; 18) mounting hole.
Figure 3-25. Cutaway of safety and negative flood, engine air induction and hull ventilation control manifold (three-valve manifold).
1) Valve manifold body; 2) hand lever for flood valve of safety tank; 3) hand lever for flood valve of negative tank; 4) hand lever for hull ventilation valve and engine air induction valve; 5) locking arms; 6) hole for padlock; 7) hydraulic port from supply line, main hydraulic system; 8) hydraulic port to return line; 9) hydraulic port to hydraulic cylinder of operating gear; 10) latching spring; 11) spool; 12) bypass channel in valve; 13) link; 14) arm; 15) shaft; 16) drain plug; 17) bracket; 18) mounting hole.
 
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The units operated by this manifold are extremely important to the safety of the vessel and the following precautions have been taken to prevent errors in its operation:

a) As already shown, its handles are so shaped as to be instantly identifiable, even in the dark.

b) The safety and negative tank flood valve levers throw in opposite directions from each other for CLOSE or OPEN (see name plates in Figure 3-25).

c) The main engine air induction and hull ventilation valve lever (with ball-shaped handle) is fitted with a spring-loaded pin which will lock it when placed in the CLOSE position (see Figure 3-26). In order to move this lever to OPEN, this pin must be pulled out and held out while the lever is being moved. In other words, it takes both hands to move this lever out of either position.

In addition, the three-valve manifold has the regular latching and locking devices described in connection with the six-valve manifold.

c. The vent valve operating gear. All vent valves on the main ballast tank system and the valve on the safety tank and bow buoyancy tank are hydraulically operated.

Figure 3-26. Safety and negative flood, engine air
induction and hull ventilation control manifold (three-valve manifold).
Figure 3-26. Safety and negative flood, engine air induction and hull ventilation control manifold (three-valve manifold).

  The operating gear is shown in Figure 3-27. It consists essentially of a hydraulic unit cylinder and suitable linkage connecting it to a vertical operating shaft which opens and closes the vent. It can also be operated by the hand lever (shown projecting downward in the illustration).

Figure 3-27. Vent valve operating gear and hydraulic
unit cylinder.
Figure 3-27. Vent valve operating gear and hydraulic unit cylinder.

 
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A cutaway view of the same mechanism is shown in Figure 3-28. Fluid under pressure is admitted from the control valve into the hydraulic unit cylinder (1) through the ports (4). As the piston head (2) moves, it actuates the crankshaft (6). This moves the cam, which, bearing against the groove in the slotted link (8), causes that link to push up or pull down on the flat link (9), thereby moving the crosshead (10) up or down. Into   the top of the crosshead is screwed the lower end of the operating shaft (11). This shaft goes up through a packing gland in the pressure hull, to the superstructure, where the mechanism which opens and closes the vent is located. Figure 3-28 shows the mechanism as it would look with the vent closed.

The mechanism is furnished with a locking pin (15), attached to the framework by a chain. This pin is placed in one of three holes,

Figure 3-28. Cutaway of vent valve hydraulic unit cylinder and operating gear.
1) Hydraulic unit cylinder, 2) piston; 3) connecting rod; 4) hydraulic pressure ports; 5) double crank;
6) crankshaft; 7) crank arm; 8) slotted link; 9) connecting link; 10) crosshead; 11) operating shaft; 12) locking holes, LOCK position; 13) locking holes, HAND position; 14) frame; 15) locking pin.
Figure 3-28. Cutaway of vent valve hydraulic unit cylinder and operating gear.
1) Hydraulic unit cylinder, 2) piston; 3) connecting rod; 4) hydraulic pressure ports; 5) double crank; 6) crankshaft; 7) crank arm; 8) slotted link; 9) connecting link; 10) crosshead; 11) operating shaft; 12) locking holes, LOCK position; 13) locking holes, HAND position; 14) frame; 15) locking pin.
 
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Figure 3-29. Diagram of vent control valve and cylinder, OPEN.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end
of cylinder; 7) port to lower end of cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing
bypass; 11) upper port in cylinder; 12) lower port in cylinder; 13) hydraulic unit cylinder; 14) piston;
15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting link; 20) operating shaft; 21) locking
pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) handle
locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve.
Figure 3-29. Diagram of vent control valve and cylinder, OPEN.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end of cylinder; 7) port to lower end of cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing bypass; 11) upper port in cylinder; 12) lower port in cylinder; 13) hydraulic unit cylinder; 14) piston; 15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting link; 20) operating shaft; 21) locking pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) handle locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve.
labeled respectively POWER, HAND (13), and LOCK (12), and identified by adjacent indicator plates.

When the pin (21, Figure 3-29) is placed in the POWER hole (23), the hand-operating lever (24) is locked in the stowed position, and the vent is operated by the hydraulic unit cylinder.

When placed in the lock holes for the HAND position (26, Figure 3-29), the pin bolts the hand-operating lever solidly to the linkage, so that moving the lever (24) will actuate the mechanism and operate the vent.

When placed in the lock hole for the LOCK position-which can be done only when the valve is closed and the hand lever stowed-the pin locks the operating shaft so that it cannot be moved.

d. The hydraulic flood valve operating gear. The flood valves on the safety and

  negative tanks are hydraulically operated by the mechanism shown in Figure 3-30. The crossarm and hand grips shown are for hand operation in case of failure of the hydraulic power.

Figure 3-30. Flood valve operating gear and hydraulic
cylinder.
Figure 3-30. Flood valve operating gear and hydraulic cylinder.

 
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Figure 3-31 is a diagram of this mechanism. It is essential to understand that the main piston rod (3) and the tie rods (6) are yoked rigidly together through the crosshead (4). Impelled by the hydraulic pressure against the piston head (2), all three rods move inward or outward as a unit.

Two positions, OPEN and CLOSE, are shown in the diagram. Oil under pressure

  from the control manifold is shown in red, return oil in blue; direction of flow is indicated by arrows.

1. To open the valve, hydraulic fluid from the control valve is admitted through the port (13), moving the piston head (2) outward ( up in the diagram). The motion is communicated through the crosshead (4). The tie rods (6), screwed rigidly into this crosshead, are

Figure 3-31. Diagram of flood valve operating gear and hydraulic cylinder in OPEN and CLOSE positions.
1) Hydraulic unit cylinder; 2) piston; 3) main piston rod; 4) crosshead; 5) yoke; 6) tie rod; 7) guide cylinder;
8) guide piston; 9) outboard connecting rods; 10) crank; 11) operating shaft; 12) hydraulic port, pressure
to close flood valve; 13) hydraulic port, pressure to open flood valve; 14) half-nut; 15) hand grips; 16) crossarm; 17) threaded shaft.
Figure 3-31. Diagram of flood valve operating gear and hydraulic cylinder in OPEN and CLOSE positions.
1) Hydraulic unit cylinder; 2) piston; 3) main piston rod; 4) crosshead; 5) yoke; 6) tie rod; 7) guide cylinder; 8) guide piston; 9) outboard connecting rods; 10) crank; 11) operating shaft; 12) hydraulic port, pressure to close flood valve; 13) hydraulic port, pressure to open flood valve; 14) half-nut; 15) hand grips; 16) crossarm; 17) threaded shaft.
 
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pushed outward; the outboard connecting rods (9), through the crank (10), push the operating shaft (11) out, opening the flood valve (not shown). Return oil meanwhile flows out through the other port and back to the control valve.

2. To close the valve, the flow of hydraulic fluid is reversed, pushing the piston inward ( down in the diagram).

3. To operate the mechanism by hand, the hand grips (15) are pulled outward (to the position shown in Figure 3-30). This meshes the half-nut (14) with the threaded shaft (17). Turning the crossarm (16) will then cause the shaft to travel.

  4. The guide cylinders (7) are watertight. The guide pistons (8) slide through greased packing into the tank.

e. Operation of vent valves. Figures 3-29, 3-32, 3-33, and 3-34 illustrate the operation of a vent by any valve on the six-valve manifold (see Figure 3-24). In all cases, oil from the supply line of the main hydraulic system is shown in red, oil to the return line in blue, and inactive oil in lighter red. Direction of flow is indicated by arrows.

Figure 3-29 shows the hand lever (1) of the control valve (2) in the OPEN position. The spool (9) directs oil from the supply port (4) to the port (6) into the line leading to the upper port (11) of the unit cylinder

Figure 3-32. Diagram of vent control valve and cylinder, CLOSE.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end of
unit cylinder; 7) port to lower end of unit cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing
bypass; 11) upper port in cylinder; 12) lower port in cylinder; 13) hydraulic unit cylinder; 14) piston;
15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting shaft; 20) operating shaft; 21) locking
pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) hand lever
locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve; 28) locking hole for LOCK
position.
Figure 3-32. Diagram of vent control valve and cylinder, CLOSE.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end of unit cylinder; 7) port to lower end of unit cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing bypass; 11) upper port in cylinder; 12) lower port in cylinder; 13) hydraulic unit cylinder; 14) piston; 15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting shaft; 20) operating shaft; 21) locking pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) hand lever locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve; 28) locking hole for LOCK position.
 
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(13). The pressure lowers the piston head (14) turning the crank (16), which actuates the cam (17). The cam rides down in the slot of the slotted link (18), pulling the flat link (19) downward. This in turn pulls down the operating shaft (20), opening the vent. Return oil, forced from the lower port (12) in the unit cylinder, flows through the port (7) to the return channel (5) in the control manifold body. Note that for power operation, the hand-operating lever (24) is in the stowed position, locked into the bracket (25) by the locking pin (21).

Figure 3-32 shows the control valve in the CLOSE position. The spool (9) directs oil from the supply port (4) to the port (7) into the line leading to the lower port (12) of the hydraulic unit cylinder, pushing the piston up and pulling the cam (17) up through

  the slotted link (18). This raises the operating shaft (20), closing the vent. Return oil, forced through the upper port (11) of the unit cylinder, flows through the port (6) back into the return channel (5) of the manifold. Note that the hand-operating lever (24) is again in the stowed position, and the locking pin (21) is placed in the POWER hole (23) in the bracket (25). In this position, with the vent closed and the hand-operating lever stowed, the locking pin can be placed, if required, in the locking hole for the LOCK position (28), thus preventing accidental opening.

Figure 3-33 shows the lever in the HAND position. Here the bypass channel (8) in the control valve connects the two ports (6 and 7) leading to the unit cylinder. This allows bypassing of the oil between the upper and the

Figure. 3-33. Diagram of vent control valve and cylinder, HAND.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end of
unit cylinder; 7) port to lower end of unit cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing bypass; 11) upper port in cylinder; 12) lower port in cylinder; 13) hydraulic unit cylinder; 14) piston;
15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting link; 20) operating shaft; 21) locking
pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) hand
lever locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve.
Figure. 3-33. Diagram of vent control valve and cylinder, HAND.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end of unit cylinder; 7) port to lower end of unit cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing bypass; 11) upper port in cylinder; 12) lower port in cylinder; 13) hydraulic unit cylinder; 14) piston; 15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting link; 20) operating shaft; 21) locking pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) hand lever locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve.
 
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lower sides of the unit cylinder (13) permitting hand operation. At the same time, the lands on the control valve (2) have cut off the pressure port. A special feature of the HAND position is the small extra channel, 3/16-inch in diameter, called the equalizing bypass (10). This permits a very small flow of oil from the bypass channel (8) back into the return line when the valve is operated at CLOSE. It also permits replenishment of oil when the valve is in the OPEN position to compensate for the unequal areas of the two sides of the piston. Without this compensation, opening and closing the valve by hand would meet with considerable resistance, because the top of the hydraulic unit cylinder's piston (14) presents a greater effective area to the contained oil than does the bottom side, whose effective area is practically negligible because of the   piston guide sleeve (27) cast integral with the piston. Note that for hand operation the locking pin (21) is placed in the HAND locking hole (26), so that when the hand-operating lever (24) is moved, the linkage also moves.

Figure 3-34 shows the lever in the EMERGENCY position. The control valve lands completely blank off the supply port (4) and the return channel (5) from the ports (6 and 7) which lead to the hydraulic unit cylinder. These lands also close the 3/16-inch equalizing bypass (10). Thus the oil to the hydraulic unit is completely isolated from the rest of the system. In case of a broken line, hand operation is possible, since the cylinder ports are bypassed to each other. However, some resistance will be encountered because of the difference in area between the lower and upper sides of the piston, which was explained in the preceding paragraph.

The locking pin (21) is shown here in the lock hole (26) for HAND operation.

Figure 3-34. Diagram of vent control valve and cylinder, EMERGENCY.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end of
unit cylinder; 7) port to lower end at unit cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing bypass; 11) upper port, in cylinder; 12) lower part in cylinder; 13) hydraulic unit cylinder; 14) piston;
15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting link; 20) operating shaft; 21) locking
pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) hand lever
locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve.
Figure 3-34. Diagram of vent control valve and cylinder, EMERGENCY.
1) Hand lever; 2) control valve; 3) return port; 4) supply port; 5) return channel; 6) port to upper end of unit cylinder; 7) port to lower end at unit cylinder; 8) bypass channel of control valve; 9) spool; 10) equalizing bypass; 11) upper port, in cylinder; 12) lower part in cylinder; 13) hydraulic unit cylinder; 14) piston; 15) piston rod; 16) crankshaft; 17) cam; 18) slotted link; 19) connecting link; 20) operating shaft; 21) locking pin; 22) chain for locking pin; 23) locking hole for POWER position; 24) hand-operating lever; 25) hand lever locking bracket; 26) locking hole for HAND position; 27) piston guide sleeve.
 
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Figure 3-35. Diagram of periscope hoist approaching
fully raised position.
1) Hydraulic cylinders; 2) piston; 3) piston rods; 4) yoke for periscope;
5) periscope; 6) eyepiece; 7) control valve; 8) control valve spool;
9) tapered center of spool; 10) control valve hand lever; 11) automatic
trip; 12) actuating spindle for automatic trip; 13) supply port, from main
supply manifold; 14) return port, to main return manifold; 15) port to
hydraulic cylinders; 16) cylinder ports; 17) upper section of hydraulic
cylinders (no oil in upper section); 18) shaft; 19) packing.
Figure 3-35. Diagram of periscope hoist approaching fully raised position.
1) Hydraulic cylinders; 2) piston; 3) piston rods; 4) yoke for periscope; 5) periscope; 6) eyepiece; 7) control valve; 8) control valve spool; 9) tapered center of spool; 10) control valve hand lever; 11) automatic trip; 12) actuating spindle for automatic trip; 13) supply port, from main supply manifold; 14) return port, to main return manifold; 15) port to hydraulic cylinders; 16) cylinder ports; 17) upper section of hydraulic cylinders (no oil in upper section); 18) shaft; 19) packing.
 
Figure 3-36. Diagram of periscope hoist in fully
raised (tripped) position.
1) Hydraulic cylinders; 2) piston; 3) piston rods; 4) yoke for periscope;
5) periscope; 6) eyepiece; 7) control valve; 8) control valve spool;
9) tapered center of spool; 10) control valve hand lever; 11) automatic
trip; 12) actuating spindle for automatic trip; 13) supply port from main
supply manifold; 14) return port, to main return manifold, 15) port to
hydraulic cylinders; 16) cylinder line; 17) upper section of hydraulic
cylinders (no oil in upper section; 18) shaft; 19) packing.
Figure 3-36. Diagram of periscope hoist in fully raised (tripped) position.
1) Hydraulic cylinders; 2) piston; 3) piston rods; 4) yoke for periscope; 5) periscope; 6) eyepiece; 7) control valve; 8) control valve spool; 9) tapered center of spool; 10) control valve hand lever; 11) automatic trip; 12) actuating spindle for automatic trip; 13) supply port from main supply manifold; 14) return port, to main return manifold, 15) port to hydraulic cylinders; 16) cylinder line; 17) upper section of hydraulic cylinders (no oil in upper section; 18) shaft; 19) packing.
 
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D. PERISCOPE AND VERTICAL ANTENNA HOISTS
 
3D1. General arrangement. On some later classes of submarines, the periscope and the vertical antenna are hydraulically operated, as units of the main hydraulic system. Their location is shown schematically in Figure 3-23.

Each is raised and lowered by a hydraulic hoist. This consists essentially of a pair of long, vertically mounted hydraulic cylinders of small diameter, bracketed in the fairwater above the conning tower. Two piston rods emerge from the lower ends of the cylinders are yoked together and carry between them, in the yoke, the periscope or vertical antenna. Control valves for each are located in the conning tower. Since these units are raised by hydraulic power and lowered by gravity, an automatic trip arrangement reduces the hydraulic pressure before the unit reaches the mechanical stop at the top of its travel, while a spring bumper at the bottom cushions its descent.

3D2. Detailed description. a. The periscope. 1. Arrangement of hoist mechanism and distribution of pressure. The general arrangement of the periscope hoist and hydraulic lines is illustrated schematically in Figure 3-35.

A pair hydraulic-cylinders (1) is bracketed into the periscope fairwater, at the top of the conning tower. The piston heads (2) and piston rods (3) are bolted to a yoke (4) which carries the periscope (5). In other words, the pistons and periscope are rigidly connected and travel as a unit. As the pistons are raised by hydraulic pressure admitted to the undersides of the piston heads, the periscope extending through the center of the fairwater rises from its well and is projected upward.

A distinctive feature of this type of hoist is the fact that the control valve (7 ) admits hydraulic fluid only to the lower ends of the cylinders. No oil is present on top of the piston heads except that which leaks past the piston from the pressure side. Overflow lines and a settling tank (not shown), located in

  the conning tower, are provided to catch any oil that may leak up past the piston heads.

To lower the periscope, the lines from the ports (16) at the lower ends of the cylinders are opened to the return line (14) and the periscope and pistons are allowed to descend by their own weight, forcing the oil out of the cylinders into the return line.

2. The control valve. The control valve (7) is a three-position spool-type valve. The spool itself (8) has a center channel (9) with a very fine taper (40-30), and hence the lands do not rise at a sharp angle from the center channel.

This tapered cut-off has the effect of opening and closing the valve ports gradually, preventing sudden shocks and so-called hydraulic hammer which might affect the delicate optical instruments in the periscope.

The position of the spool is controlled by the hand lever (10). As shown in Figure 3-35, this lever has three positions, RAISE, LOWER, and NEUTRAL. At RAISE, the spool is pulled toward the left, admitting pressure from the supply port (13) into the discharge port (15) leading to the cylinder ports (16). The return line (14) is blanked off.

At NEUTRAL, the spool is in the intermediate position, blanking off all the ports and hydraulically locking the periscope at any given height.

At LOWER, the spool is pushed to the right, blanking off the supply port (13) and opening the cylinder line (16) to the return port (14). This allows the oil to escape from the cylinders into the return line by the weight of the periscope assembly. Note that, because of the lack of a hydraulic line to the upper end of the cylinder, this valve needs only three ports instead of the usual four.

3. The automatic trip. To prevent the periscope from jolting against the mechanical stop when it reaches the top of its travel, an automatic trip (11) is attached to the same shaft (18) as the hand lever (10).

This automatic trip is operated by the spindle (12) bolted onto the yoke (4). The

 
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height of the spindle and the angle of the trip are so adjusted that, as the periscope approaches the fully raised position, the spindle pushes up the trip, automatically moving the tapered spool (8) toward the intermediate, or NEUTRAL, position. This gradually cuts off the flow of oil to the cylinders, bringing the periscope to an easy stop.

The trip and the hand lever are solidly connected to the same shaft (18) so that if the operator should try to hold the lever at the RAISE position after the spindle has reached the trip, the trip, mechanically impelled by the upward movement of the periscope, will pull the hand lever out of his grasp. This simple arrangement therefore acts as a quick, sure, automatic cut-out.

4. Explanation of Figures 3-35 and 3-36. In Figure 3-35, the control valve is at RAISE and the periscope has almost reached the top of its travel. The spindle (12) is almost at the automatic trip.

  In Figure 3-36, the periscope is fully raised and the spindle has pushed the trip and hand lever, moving the valve to the NEUTRAL position, blanking all ports, cutting off the flow of oil, and locking the periscope in that position. Oil under pump pressure is shown in red; return oil in blue; inactive oil in lighter red. Direction of flow is indicated by arrows.

b. The vertical antenna. The vertical antenna hoist need not be discussed in detail, as it is almost identical to the periscope hoist in arrangement, structure, and operating principles.

In addition to the automatic trip arrangement for preventing a sudden stop at the top of its travel, the vertical antenna hoist also has a dash-pot arrangement and a piston head with tapered grooves cut toward its underside, which help to bring it to an easy stop at the bottom.

Figure 3-37. Piping diagram of forward and after service lines.
1) Main supply manifold; 2) main return manifold; 3) main engine exhaust actuating cylinder; 4) main engine
exhaust gear and exhaust valve; 5) main engine exhaust control valve; 6) torpedo tube outer door control
valve; 7) torpedo tube outer door actuating cylinder; 8) echo-ranging control valve; 9) echo-ranging cylinder;
10) bow plane rigging control valve; 11) forward service line, supply; 12) forward service line, return; 13) after
service line, return; 14) offer service line, supply; 15) control valve for forward windlass-and-capstan.
Figure 3-37. Piping diagram of forward and after service lines.
1) Main supply manifold; 2) main return manifold; 3) main engine exhaust actuating cylinder; 4) main engine exhaust gear and exhaust valve; 5) main engine exhaust control valve; 6) torpedo tube outer door control valve; 7) torpedo tube outer door actuating cylinder; 8) echo-ranging control valve; 9) echo-ranging cylinder; 10) bow plane rigging control valve; 11) forward service line, supply; 12) forward service line, return; 13) after service line, return; 14) offer service line, supply; 15) control valve for forward windlass-and-capstan.
 
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E. FORWARD AND AFTER SERVICE LINES
 
3E1. General arrangement. There are two sets of hydraulic lines extending from the main supply manifold and the main return manifold to both ends of the submarine. These lines, known as the forward and after service lines, furnish power to a miscellaneous group of hydraulically operated submarine equipment; specifically, these hydraulic lines supply   necessary power to the following apparatus:

a. The after service lines supply power for the operation of:

1. Main engine drowned-type exhaust valves.

2. Outer doors of the four after torpedo tubes.

Figure 3-38. Cutaway of main engine drowned-type exhaust valve operating gear and hydraulic cylinder.
1) Cylinder; 2) piston; 3) connecting rod; 4) crank, 5) worm gear; 6) drive gear; 7) power shaft; 8) indicator dial; 9) pointer; 10) locking pin; 11) hand gear; 12) frame; 13) crosshead; 14) operating lugs.
Figure 3-38. Cutaway of main engine drowned-type exhaust valve operating gear and hydraulic cylinder.
1) Cylinder; 2) piston; 3) connecting rod; 4) crank, 5) worm gear; 6) drive gear; 7) power shaft; 8) indicator dial; 9) pointer; 10) locking pin; 11) hand gear; 12) frame; 13) crosshead; 14) operating lugs.
 
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b. The forward service lines supply power for the operation of:

1. Bow rigging.

2. Forward windlass-and-capstan.

3. Two echo-ranging and sound detection devices, known as the sound heads.

4. Outer doors of the six forward torpedo tubes.

Each of the above items of equipment is operated by a hydraulic cylinder to which oil under pressure is directed by a control valve. The remainder of this section is devoted to a description of the hydraulic cylinders and control valves for the equipment listed above.

Hydraulic pressure is distributed to the service lines at the main supply manifold by two valves. One line is marked SERVICE FORWARD, the other, SERVICE AFT. The return lines terminate in two similarly named valves of the main return manifold.

A schematic diagram of the forward and after service lines is shown in Figure 3-37. The diagram shows the rigging control valve but not the equipment which operates the bow rigging and the forward windlass-and-capstan. Although that equipment receives its power from the forward service lines, its description has been included in Section C of Chapter 5.

3E2. Main engine drowned-type exhaust valve. a. General arrangement. When the submarine is surfaced and the main engines are running, the engine exhaust is vented outboard. Each main engine has an exhaust which must be opened before the engines start and closed when the engines are stopped. These valves are hydraulically operated as units on the after service lines.

b. Detailed description. The control valve is of the conventional spool type, having three positions: OPEN, CLOSE, and HAND. A control valve is provided for each hydraulic cylinder. As the piston (2, Figure 3-38), is moved backward or forward in the cylinder (1) by hydraulic pressure, the connecting rod (3) which is attached to a crank (4) rotates the operating lug (14). The operating lug, in turn, moves the power shaft (7)

  up or down to open or close the main engine exhaust valve through a set of linkage arms and cranks.

In the event of hydraulic power failure, the hand gear (11) can be used to rotate the drive gear through a worm (5). A locking pin (10) holds the hand gear in place when it is not being used.

The motion of the drive gear is indicated by the pointer (9) which moves with it and shows on the indicator dial (8) whether the exhaust valve is in the OPEN or in the CLOSE position.

c. Operation. The installation and arrangement of the hydraulic equipment for operating the main engine drowned-type exhaust valves vary with different classes of submarines.

Some earlier classes of submarines have five exhaust valves: four main engine outboard exhaust valves and one outboard exhaust valve for the auxiliary engine. The control valves are arranged in two manifolds. The after engine room has a manifold of three control valves, and the forward engine room, a manifold of two valves.

The more recent type of submarine, however, has only four main engine outboard exhaust valves. There is no separate exhaust valve for the auxiliary engine, its exhaust being expelled through one of the main engine exhaust valves-main engine No. 4 on the Electric Boat Company submarine and main engine No. 3 on the Portsmouth submarine. The control valve for both main engine outboard exhaust valves in each engine room is located near the throttle, on the port side of that engine room, so that the engine operator can manipulate both exhaust valve controls simultaneously.

Figures 3-39 and 3-40 show a main engine drowned-type exhaust valve in the CLOSE and OPEN positions, as well as the connecting linkage between it and the hydraulic cylinder.

When the control valve handle is brought to the CLOSE position, the exhaust valve and actuating cylinder are in the condition shown in Figure 3-39. Hydraulic pressure pushes

 
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the piston (1) to the left, rotating the crank (3) so that it pulls down the cam lever (4). This action moves the power shaft (5) and shaft linkage (6) downward, and forces the exhaust valve (8) upward by means of the connecting linkage (7).

Moving the control valve handle to OPEN admits fluid into the hydraulic cylinder to move the piston to the right as shown in Figure 3-40, the OPEN position. This rotates the crank (3) so that the cam lever (4) is raised, lifting the power shaft (5) and the

  shaft linkage (6) which pulls the exhaust valve (8) downward by means of the valve linkage (7), thus opening it.

The valve operating gear just described will be found in all later classes of Portsmouth submarines. On the Electric Boat Company submarines, the main engine exhaust valves are operated by a hydropneumatic system, consisting of a small independent hydraulic system for each valve, to which pressure is provided by compressed air.

Figure 3-39. Diagram of main engine drowned-type exhaust valve operating gear and hydraulic cylinder, CLOSE.
1) Piston; 2) drive gear; 3) crank; 4) cam lever; 5) power shaft; 6) shaft linkage; 7) valve linkage;
8) exhaust valve; 9) exhaust valve housing; 10) hand gear.
Figure 3-39. Diagram of main engine drowned-type exhaust valve operating gear and hydraulic cylinder, CLOSE.
1) Piston; 2) drive gear; 3) crank; 4) cam lever; 5) power shaft; 6) shaft linkage; 7) valve linkage; 8) exhaust valve; 9) exhaust valve housing; 10) hand gear.
 
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To operate the valve, the air is admitted on top of an oil reservoir, which in turn is connected to the hydraulic cylinder.

The air, acting upon the oil, forces it into the cylinder where it moves the piston to open or close the exhaust valve.

3E3. Torpedo tube outer door mechanism. a. General. The torpedo tube outer doors are hydraulically operated as separate units from the fore and aft service lines. There are ten torpedo tubes in all, six forward and four aft. Their location is shown schematically in

  the fore and aft service line piping diagram, Figure 3-37.

The outer door operating mechanism consists essentially of the hydraulic cylinder, piston, and power shaft; the control valve and operating handle; and a jackscrew for hand operation. All parts are mounted on the torpedo tube itself and controlled from its breech.

1. The control valve. The control valve is a three-position spool-type valve. Figure 3-41 shows its internal structure. The operating lug (7) is moved back and forth when

Figure 3-40. Diagram of main engine drowned-type exhaust valve operating gear and hydraulic cylinder, OPEN.
1) Piston; 2) drive gear; 3) crank; 4) cam lever; 5) power shaft; 6) shaft linkage; 7) valve linkage;
8) exhaust valve; 9) exhaust valve housing; 10) hand gear.
Figure 3-40. Diagram of main engine drowned-type exhaust valve operating gear and hydraulic cylinder, OPEN.
1) Piston; 2) drive gear; 3) crank; 4) cam lever; 5) power shaft; 6) shaft linkage; 7) valve linkage; 8) exhaust valve; 9) exhaust valve housing; 10) hand gear.
 
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the handle is pushed in or out. This in turn moves the slotted link (6), rotating the shaft (5) and the arm (4). The arm moves the connecting link (3) which moves the valve (2) inside the valve body (1), opening and closing the required combination of ports. The ports (9) lead to opposite ends of the hydraulic cylinder; the return port (10) leads to the fore and aft service lines. The supply port is not shown in this view.

Figure 3-41. Cutaway of outer door control valve.
1) Valve body; 2) valve; 3) connecting link; 4) arm;
5) shaft; 6) slotted link; 7) operating lug; 8) connecting rod (to handle); 9) cylinder ports; 10) return
port (to main hydraulic system); 11) channel from
supply port (from main hydraulic system; port not
shown in this illustration); 12) mounting bracket.
Figure 3-41. Cutaway of outer door control valve.
1) Valve body; 2) valve; 3) connecting link; 4) arm; 5) shaft; 6) slotted link; 7) operating lug; 8) connecting rod (to handle); 9) cylinder ports; 10) return port (to main hydraulic system); 11) channel from supply port (from main hydraulic system; port not shown in this illustration); 12) mounting bracket.

Figure 3-42 shows the control valve in each of its three positions: OPEN, in which the pressure line (7) is opened to the inner, or breech, end of the hydraulic cylinder, and the return line (8) is opened to the outer end; CLOSE, in which these connections (pressure and return) are reversed; and HAND, in which the pressure ports leading to the cylinder (9) are connected to each other, bypassing the oil in the cylinder. The pressure side is shown in red, the return side in blue; inactive oil is shown in lighter red. The direction of flow in each position is shown by arrows.

  2. General arrangement. The considerably simplified general arrangement of the mechanism as a whole is shown in Figure 3-43. The hydraulic cylinder (1) contains a piston (2) which is moved by hydraulic power. It is connected rigidly to the power operating shaft (3) whose motion opens or closes the outer door. The hydraulic power is directed to one side or the other of the hydraulic cylinder by the control valve (18). This allows flow of hydraulic power from the supply side (20) of the forward or after service lines

Figure 3-42. Diagram of outer door control valve in
three positions.
1) Valve body; 2) valve; 3) link; 4) arm; 5) shaft;
6) bypass channel in valve; 7) channel to supply port
from main hydraulic system; 8) return port (to main
hydraulic system); 9) cylinder ports (to actuating
cylinder).
Figure 3-42. Diagram of outer door control valve in three positions.
1) Valve body; 2) valve; 3) link; 4) arm; 5) shaft; 6) bypass channel in valve; 7) channel to supply port from main hydraulic system; 8) return port (to main hydraulic system); 9) cylinder ports (to actuating cylinder).

 
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Figure 3-43. Schematic diagram of outer door operating mechanism.
1) Hydraulic cylinder; 2) piston; 3) power operating shaft; 4) jackscrew or threaded portion of shaft; 5) jack-nut; 6) hand shaft driving gear; 7) hand-operated shaft; 8) rack on power operating shaft; 9) spur gear; 10) sprocket chain; 11) rack on outer slide (breech and outer door interlock);
12) inner slide; 13) operating lug; 14) operating handle; 15) trigger; 16) spring; 17) ready-to-fire interlock tube; 18) control valve; 19) linkage
on control valve; 20) supply from forward or after service line; 21) return to forward or after service line; 22) lines to hydraulic cylinder; 23) ports
in hydraulic cylinder.
Figure 3-43. Schematic diagram of outer door operating mechanism.
1) Hydraulic cylinder; 2) piston; 3) power operating shaft; 4) jackscrew or threaded portion of shaft; 5) jack-nut; 6) hand shaft driving gear; 7) hand-operated shaft; 8) rack on power operating shaft; 9) spur gear; 10) sprocket chain; 11) rack on outer slide (breech and outer door interlock); 12) inner slide; 13) operating lug; 14) operating handle; 15) trigger; 16) spring; 17) ready-to-fire interlock tube; 18) control valve; 19) linkage on control valve; 20) supply from forward or after service line; 21) return to forward or after service line; 22) lines to hydraulic cylinder; 23) ports in hydraulic cylinder.
 
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and feeds it back to the return side (21). The control valve is operated by the operating handle (14), a push-pull arrangement which slides in and out lengthwise through the ready-to-fire interlock tube, a section of which (17) is shown. The operating handle is connected to the control valve by the inner slide (12) which is attached to the control valve linkage (19) by the operating lug (13).

3. The interlocks. Safe operation of a torpedo tube is a delicate and complicated process. It involves several different conditions which cannot be allowed to occur simultaneously. For example, it is obvious that when the outer door is opened to the sea, the inner door must be locked shut, and vice versa. The tube must not be made READY-TO-FIRE unless different interlocks, not shown in full detail in the schematic diagram, are properly engaged. At the end of the power operating shaft (3) is a spur tooth rack (8) which, through a pair of spur gears (9), sprocket chain (10), and a similar spur tooth rack (11) on the outer slide, operates the ready-to-fire interlock (not shown). The ready-to-fire interlock is connected to the tube (17) which rotates around the inner and outer slides and also serves as a guide tube.

4. Hand operation of outer doors. For hand operation of the outer doors, a hand-operating shaft (7) is provided, with a squared end over which fits an operating crank. This turns the hand shaft driving gear (6). This gear is meshed with the jack-nut (5), which in turn is threaded into the threaded portion (4) of the power operating shaft. Therefore, as the jack-nut is turned, the power operating shaft will travel through it, opening or closing the outer door. In order to operate this by hand, the control valve (18) must be in the HAND position, so that the fluid trapped in the hydraulic cylinder (1) will not act as a hydraulic lock against the motion of the piton (2).

The operating handle (14), therefore, has three positions:

a) OPEN (handle pulled all the way out toward the operator), in which the power operating shaft moved by hydraulic power will open the outer door.

  b) CLOSE (handle pushed in all the way away from the operator), in which the power operating shaft will close the outer door.

c) HAND (handle in intermediate position), in which the lines from the hydraulic cylinder are bypassed through the control valve.

3E4. Echo-ranging and detecting apparatus. a. General arrangement. The echo-ranging and detecting apparatus is contained in a metal sphere, called the sound head, fixed to a cylindrical tube. This tube is extended downward through an opening in the underside of the vessel in much the same way that the periscope is extended upward through the top and is hydraulically operated by power from the forward service line of the main hydraulic system.

The hydraulic part of the apparatus consists essentially of three hollow tubes one within the other, so arranged that the two inside tubes act as a stationary piston fixed to the frame of the vessel. The outer tube, actuated by hydraulic pressure, acts as a movable cylinder which slides up and down over it, raising and lowering the sound head. A control valve directs the oil pressure to one side or the other of the piston head to raise or lower the cylinder.

A hand pump is installed in the lines for hand operation.

b. Detailed description. Figure 3-44 shows two views of the apparatus. A is a schematic diagram of the echo-ranging and detecting apparatus showing its operation; B is a cutaway view of the tube in its correct proportions. Wherever the same part is shown in both views, it has been given the same index number. The control valve appears only in the cutaway view, where its location with respect to the rest of the apparatus has been schematically indicated.

1. Stationary piston and traveling cylinder. The traveling hydraulic cylinder (1) is free to slide up and down in the bracket bearing (7). This bearing is bracketed solidly to the deck plate (8).

The outer tube (3) of the piston rod assembly (20) is the stationary member and is bracketed solidly to the overhead frame (14) through the trunnion yoke (12) and trunnion bearing (13).

 
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Figure 3-44. Cutaway and diagram of echo-ranging and detecting apparatus.
1) Hydraulic cylinder; 2) piston; 3) outer piston tube; 4) oil ports in outer piston tube, to top of piston head;
5) inner piston tube; 6) oil port, to underside of piston head; 7) bracket bearing; 8) deck plate; 9) sound
head; 10) upper port of piston rod assembly, to inner piston tube; 11) lower port of piston rod assembly, to
outer piston tube; 12) trunnion yoke; 13) trunnion bearing; 14) overhead frame; 15) indicator dial; 16) control
valve; 17) control valve hand lever; 18) supply line, from main supply manifold; 19) return line, to main return
manifold; 20) piston rod assembly.
Figure 3-44. Cutaway and diagram of echo-ranging and detecting apparatus.
1) Hydraulic cylinder; 2) piston; 3) outer piston tube; 4) oil ports in outer piston tube, to top of piston head; 5) inner piston tube; 6) oil port, to underside of piston head; 7) bracket bearing; 8) deck plate; 9) sound head; 10) upper port of piston rod assembly, to inner piston tube; 11) lower port of piston rod assembly, to outer piston tube; 12) trunnion yoke; 13) trunnion bearing; 14) overhead frame; 15) indicator dial; 16) control valve; 17) control valve hand lever; 18) supply line, from main supply manifold; 19) return line, to main return manifold; 20) piston rod assembly.
 
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2. Distribution of oil pressure. The piston rod assembly itself actually consists of two hollow tubes one inside the other. Both of these tubes are rigidly connected to the piston head (2). The inner piston tube (5) runs from the top of the piston rod assembly down through a hole in the center of the piston head itself to a port (6) which opens to the underside of the piston head. The outer piston tube (3) runs down from the top of the piston rod assembly only as far as the top end of the piston head, where two oil ports (4) open out of it just above the point at which it attaches to the top of the piston head. Thus, as can be seen in the schematic diagram, the inner and outer piston tubes form a pair of oil passages from the top of the piston rod assembly to the piston head, the inner tube opening underneath the piston head, the outer tube opening on top of it.

Since the hydraulic cylinder is free to slide up and down over the stationary piston head, admitting oil under pressure to the underside of the piston head will cause the cylinder to move downward, while admitting the pressure to the top of the piston head will force the cylinder upward.

3. The control valve. The control valve (16) is a three-position, spool-type valve fitted with a straight hand lever (17). The supply line (18) of the valve is connected to the main supply manifold of the main hydraulic system; the return line (19) is connected to the main return manifold. The location of the control valve with respect to the rest of the sound head hydraulic apparatus is shown schematically in Figure 3-44A. Its actual location varies to suit installation requirements in the various classes of submarines.

4. Location of electrical equipment. The echo-ranging and detecting apparatus itself is contained in the sound head (9), a large

  metal sphere bolted to the lower end of the tube where it emerges from the watertight hull and extends downward into the sea. A cable (not shown) connects the electrical equipment in the sound head with the electrical controlling and detecting devices.

c. Operation. Oil is admitted under pressure from the main hydraulic system through the control valve to the upper port (10) or the lower port (11), depending upon whether the operator desires to lower or raise the sound head. The upper port leads into the innermost tube and to the underside of the piston; the lower port leads into the outer tube and to the top of the piston.

In Figures 3-44A and 3-44B, the hand lever of the control valve is pulled all the way out, toward the operator, in the position to RAISE the sound head. Oil under pressure from the main hydraulic system enters the supply line (18) of the valve, goes through the valve body, and into the lower port (11) of the piston rod. Here it enters the outer piston tube (3) and flows out on top of the piston (2), through ports (4), forcing the hydraulic cylinder to slide upward through the bearing (7).

Meanwhile, as the cylinder space above the piston (the red area) is increased by the upward movement of the cylinder, the space under the piston (the blue area in the diagram) decreases, forcing the oil in through the port (6) upward through the innermost piston tube (5), and out through the upper port (10) in the top of the piston rod assembly. To LOWER the sound head, the hand lever (17) is pushed all the way in, away from the operator and the flow of oil is the reverse of that just described for raising.

Placing the hand lever at NEUTRAL (intermediate position) will blank off all ports in the valve, and hydraulically lock the sound head in any given position.

 
F. EMERGENCY STEERING AND PLANE TILTING SYSTEMS
 
The steering and plane tilting operations are usually performed by their own individual hydraulic systems. To provide assurance against failure, it is possible to use the pressure in the main hydraulic system to power the gear which actuates the rudder and the planes. In the main hydraulic system, this is provided for by connecting lines to both   systems from the main supply manifold and the main return manifold.

A group of valves located in the steering and the plane systems directs the flow of emergency power to whichever service requires it. A full description of utilization of emergency power is given in Chapters 4 and 5.

 
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