• About
• Education
• Events
• USS Pampanito
• Support
• Visit

a. The main hydraulic system operates because of the air pressure maintained in the air-accumulator flask.

b. Torpedoes are discharged from the submarine by air.

c. Tanks are blown by air.

d. The main propulsion engines are started by air.

Air, or more specifically, compressed air, is necessary to surface, submerge, attack, and cruise. In addition, compressed air together with oxygen is used to revitalize the air in the ship after long periods of submergence. Pressure in the boat, a test for tightness, utilizes air.

The air systems represent, therefore, the most versatile of all systems aboard a submarine, in that they are capable of performing, either as primary or secondary functions,

11A2. Basic principles of compressed air. The actuating force of the air systems is compressed air, which, as the name implies, is air under pressure confined within the limits of a container. The force required for compression of the air is provided by the high-pressure air compressors, a simple machine that compresses air by means of a series of pistons designed so that one or more pistons discharges air into another for further compression and finally through lines to banks for storage. Air can be compressed easily aboard a submarine, as it requires a relatively small plant and comparatively simple equipment. It can be stored at any convenient place and is always ready for use. Its action can be regulated to produce a low or high-pressure, and yet it has enough elasticity or compressibility to cushion its impact against the equipment it operates. It consumes no valuable materials and can be supplied to any part of the submarine simply by extending a line from the air supply. Air, once stored, requires no further expenditure of energy for operation, but rather is a source of power to other equipment.

The 600-pound MBT blowing system and the 225-pound service air system receive their supply of air from the 3,000-pound air system. The 10-pound MBT blowing system is an independent system with its own low-pressure blower. The internal compartment

11B2. The 3,000-pound and torpedo tube impulse air system. This system consists of the 3,000-pound high-pressure compressors, the high-pressure manifold, the interconnecting piping, valves, and compressed air banks. The main function of the 3,000-pound air system is to compress, store and supply air at the maximum pressure of 3,000 pounds per square inch for use within the 3,000-pound, the 600-pound, and the 225-pound systems.

The 3,000-pound air system is equipped with air external charging connection so that the system may be supplied with air from an outside source.

11B3. The 600-pound MBT blowing system. The only function of the 600-pound MBT blowing manifold and system is to remove water ballast front the main ballast tanks or the fuel ballast tanks when used as main ballast tanks. It receives its supply of compressed air from the high-pressure system through the distributing manifold.

11B4. The 225-pound service air system. The 225-pound service air system or, as it is sometimes called, ship's service air, is so called because, in addition to blowing the variable group of tanks, it provides the compressed air for all the miscellaneous services

11B5. The 10-pound MBT blowing system. When the submarine has surfaced, the 10-pound main ballast tank blowing system is used to conserve the compressed air stored in the ship's air banks. The system consists of its own low-pressure blower, control manifold, and piping to the various main ballast tanks. The 10-pound system is operated only after the submarine has, surfaced sufficiently to permit the opening of induction valves and hatches.

11B6. The salvage air system. This system is actually three separate systems: the MBT external salvage, the compartment external salvage, and compartment internal salvage. The external salvage connections permit compressed air from an outside source to be supplied to the tanks and/or compartments, while the internal salvage system utilizes the ship's air for, compartment salvage only.

In Sections 11C1 through 11C4, a more detailed description is given of the general layout of the high-pressure air system. The control room, the air banks, and the torpedo impulse air system fore and aft of the control room are discussed.

The 3,000-pound service air lines supply air at a pressure up to 3,000 psi to the forward and after torpedo rooms, to the engine starting flasks, and to the reducing valves in each engine room which furnish 500-pound air used in starting the diesel engines.

The distributing manifolds distribute air to the safety and negative tank blow lines, the main ballast tanks blow manifold, the

11C3. Air banks. Each of the five air banks consists of seven flasks, with the exception of the No. 1 air bank which has eight. Each flask is provided with a drain valve. The total capacity of the air banks is 560 cubic feet.

The No. 1 air bank is located inside the pressure hull, with four flasks in each battery, compartment. The other four air banks are located in the main ballast tanks. (See FigureA-14.)

11C4. Torpedo impulse air system. The torpedo impulse air system stores and controls the air used to discharge the torpedoes from the tubes.

The 3,000-pound air service line forward, extending from the distributing manifold, ends with a 3,000-pound to 600-pound reducing valve, from which a line leads to the forward torpedo impulse air system. This system is composed of two impulse flask

The 3,000-pound air service line aft, extending from the distributing manifold, ends with a 3,000-pound to 600-pound reducing valve, through which air is furnished to the after torpedo impulse air system. This system consists of one impulse flask charging manifold with lines leading to the four impulse flasks provided for the four after torpedo tubes. The impulse flasks are mounted below the after torpedo room deck; the manifold is located on the starboard side.

In both the forward and the after sections of the torpedo impulse system, a bypass valve and line are provided, leading from the 3,000-pound air service line to the charging manifold. The bypass valve and line allow the charging of the impulse flasks in the event of failure of the reducing valves.

Two separate systems are provided to blow the main ballast tanks. This section describes the first of these, the 600-pound MBT (main ballast tank) blowing system. The second system, the 10-pound MBT blowing system, is used only when the ship is surfaced.

FigureA-15 shows the location of the lines and component parts of the 600-pound MBT blowing system. The system is inside the pressure hull and extends from the MBT blowing manifold in the control room fore and aft along the starboard side to the main ballast tanks and fuel ballast tanks.

The MBT blowing manifold is the

The maximum working pressure of the 600-pound main ballast tank blowing system is 600 psi. It is tested hydrostatically to a pressure of 1,000 psi, or 166 percent of the maximum working pressure.

Air at bank pressure (1,500 to 3,000 psi) passed through two manually operated hammer valves and two group stop check valves to the 600-pound MBT blowing manifold. The flow of the air is regulated by the hammer valves so that it is delivered at the required pressure. Normally, only one hammer valve is used for blowing; in case one does not supply enough air or in case of failure, the other hammer valve can be used. The

To supply air to the 600-pound MBT blowing system, one of the hammer valves is opened. The valve permits air from the 3,000 pound manifold to enter the MBT blow manifold at a reduced pressure. The pressure gage of the MBT blow manifold is closely watched to guard against the pressure exceeding 600 pounds.

The depth at which the submarine is operating will have a direct effect on the resistance offered to the air in blowing the main ballast tanks and, therefore, the pressure will be built up within the system more rapidly at greater depths than it will on the, surface. Since the hammer valve regulates the volume of the air entering the 600-pound MBT blowing system, while the resistance offered to this air varies with submerged depth, it follows that, when submerged at great depths, the hammer valve must be opened cautiously, otherwise the pressure within the system will build up rapidly and exceed the safe working pressure. When the gage indicates that the pressure is dropping, the hammer valve is opened wider to

Blow lines extend from the forward section of the 600-pound MBT blow manifold to tanks No. 1 MBT, Nos. 2B and 2D MBT. Nos. 2A and 2C MBT, and Nos. 3A and 3B FBT. From the after section of the manifold, blow lines extend to tanks Nos. 4A and 4B FBT, Nos. 5A and 5B FBT, Nos. 6B and 6D MBT, Nos. 6A and 6C MBT, and No. 7 MBT. Any tank or any combination of tanks can be blown by opening the required individual tank valve, or valves, the group valves, and finally the hammer valves.

When the submarine is rigged for diving, all the blow valves on the manifold, except the fuel ballast tanks valves, are open, as are the two group stop check valves. The individual regulator valves at the main ballast tanks are open, while the MBT blow hammer valves on the 600-pound manifold are shut. The two supply valves to the 600-pound MBT blow manifold on the distributing manifold are open.

To operate the 600-pound MBT blow system, the hammer valve is opened and air is admitted to the blow manifold, from which it is directed to the main ballast tanks by the lines of the system.

Each blow line is provided with a regulator valve at the point where it enters the tank. The regulator valve acts as a combination stop and check valve and is equipped for securing the stop in any position required to equalize the flow of air into the tanks.

FigureA-16 shows the, location and relationship of the parts of the system, as well as their nomenclature.

The discussion of the ship's service air system starts with the control room, describing each component part of the system located there, and explaining its function in the operation of the submarine. A similar

11E2. Control room. The 225-pound service air manifold is located in the control room on the starboard side aft of the high-pressure manifold. This manifold receives its supply of air through two Grove pressure-reducing valves which reduce the high-pressure air from 3,000 psi to 225 psi. Stop valves are provided on the low-pressure side of the 225-pound Grove reducers, cutting them off the 225-pound system. This permits removal of a Grove reducer without impairing the operation of the 225-pound system. The 225-pound service air manifold can also be supplied from the 225-pound bypass which is controlled by a manually operated 225-pound bypass valve located at the high-pressure distribution manifold. Where the 225-pound bypass is used, the high-pressure air bypasses the reducing valves and is admitted directly into the 225-pound system. The bypass valve is only partly opened so that the pressure can be built up gradually. The 225-pound manifold pressure gage must be constantly watched and the pressure must never be allowed to go beyond 225 psi.

The 225-pound service air system is protected by one sentinel valve and two relief valves located on the line between the Grove reducers and the 225-pound manifold.

When the air within the 225-pound system reaches a pressure of approximately 250 psi, the sentinel valve opens, allowing the excess air to escape into the compartment. The sentinel valve has a comparatively small capacity and serves primarily to warn that the normal working pressure is exceeded. If the rise in pressure is rapid and above the capacity of the sentinel valve, the two relief valves, set to operate at 275 psi, open and allow the excess air to escape into the compartment.

The relief valves and the sentinel valve shut automatically when the normal working pressure is restored.

The supply line from the Grove reducing valves has two branches. One branch

The other branch of the line from the Grove reducing valves supplies air to the 225-pound service air manifold. This air is directed by means of valves to the forward and after service air mains, the auxiliary tank blow and vent lines, and the forward and after trim tank blow and vent lines. A hose connection to the manifold provides for air supply from the shore or tender.

A reducing valve from the forward service air main furnishes air at pressure of 100 psi to a connection for pneumatic tools. A bypass is provided for emergency operations, with a relief valve set to open at a pressure of 110 psi as a protection against excessive pressure. It also carries a connection supplying air to the whistle and siren.

The after service main has branch connections to the sea pressure gage and to the compartment air salvage. It also supplies air through a reducing valve at a pressure of 12 psi to fresh water tanks No. 3 and No. 4. A bypass is provided for emergency operation, with a relief valve set to open at a pressure of 15 psi.

11E3. Forward battery compartment. In the officers' quarters, the forward service air main supplies the compartment air salvage valve mounted on the after bulkhead. This valve can be operated from either side of the bulkhead. A branch of the service line, passing through an 8-pound reducing valve, supplies air at a pressure of 8 psi to the four battery water tanks Nos. 1, 2, 3, and 4 in the forward battery compartment. A bypass line is provided for emergency operation, with a relief valve set to open at a pressure of 10 psi.

11E4. Forward torpedo room. In the forward torpedo room, the forward service air main extends to the torpedo tube blow and vent manifold. The service main is also provided with branch lines to the torpedo stop cylinders, the escape trunk blow, the volume

11E5. After battery compartment. The galley and mess room compartment has one connection from the after service main which supplies air to the blow and vent manifold for fuel ballast tanks 3A, 3B, 4A, and 4B. A second connection enters an 8-pound reducing valve and supplies air at 8 psi to the four battery fresh water tanks Nos. 5, 6, 7, and 8 located in the after battery compartment. Bypass is provided for emergency use with a relief valve set to open at 10 psi. The lines for blowing and venting the auxiliary ballast tanks connect from the 225-pound manifold to the auxiliary ballast tank and stop valves located at the tank top in this compartment.

11E6. Crew's quarters. In the crew's quarters, the after service main supplies air to the crew's forward water closet and the No. 2 sanitary tank blow line. The sanitary tank is equipped with a relief valve set to open at 105 psi.

11E7. Forward engine room. The forward engine room has direct connecting lines from the after service main to the compartment air salvage valve, the No. 5A and No. 5B fuel ballast tank manifold, the exhaust valve operating gear, and the lubricating oil tanks blow and vent manifold. The supply to the fuel oil manifold is protected by a relief valve set to open when the pressure exceeds 15 psi. The air for the lubricating oil manifold is reduced to 13 psi by a reducing valve. A bypass is provided for emergency operation,

11E8. After engine room. In the after engine room, the after service main has direct connections to the compartment air salvage valve, the auxiliary engine shutdown, and the air manifold which controls the blowing and venting of the Nos. 6 and 7 normal fuel oil tanks, the expansion and the collecting tanks. A relief valve, set to open at 15 psi, protects No. 6 and No. 7 normal fuel oil tanks and the collecting and expansion tanks against excessive internal pressure. A pneumatic tool connection is also provided, equipped with a 100-pound reducing valve, 110-pound relief valve, and a bypass line, to supply air at 100 psi.

11E9. Maneuvering room. The maneuvering room contains lines extending from the after service main to the after water closet, the compartment air salvage valve, and the main engine shutdown connection.

11E10. After torpedo room. In the after torpedo room, the service air main has branches leading to the 225-pound compartment air supply valve for escape hatch, the torpedo tube stop cylinders, the volume tank, and the pneumatic tool connection. The pneumatic tool connection is provided with a 100-pound reducing valve and a bypass protected by a 110-pound relief valve. The service air lines terminate at the after torpedo tube blow and vent manifold.

The after trim tank blow and vent line, which extends from the 225-pound manifold in the control room, connects with the after trim tank by a branch line extending to the torpedo tube blow and vent manifold, similar to that of the forward torpedo room.

The compartment air salvage valves are so mounted on the transverse bulkheads of each compartment that they may be operated from either side, releasing air into the compartment from which they are worked, or into the adjoining compartment. The compartment air pressure gages are also mounted

All manifolds and lines equipped with reducing valves and blow valves are provided

The 10-pound MBT system (FigureA-17) consists of a low-pressure blower located in the pump room, a manifold, and blow lines to each of the tanks serviced by the system. The low-pressure blower furnishes compressed air to the manifold in the control room at a pressure of approximately 10 psi. The manifold distributes the air supplied by the blower to the ballast tanks through nine pipe lines which pass through the hull directly above the manifold and extend outside the pressure hull under the superstructure deck.

The air supply to the manifold is controlled by the flapper valve. The manifold and the valves are designed to withstand sea pressure if any of the blow lines fail.

The nine low-pressure lines have lever-operated flapper valves (10-pound blow valves) at the point where they pass through the hull, and swing check valves where they join the main ballast tank (MBT) vent risers.

Gate valves, controlled from the superstructure deck, are installed in the lines leading to main ballast tanks 2A, 2B, 2C, 2D, 6A, 6B, 6C, and 6D.

Both list dampers are attached to a shaft which runs through the manifold chamber. The shaft is operated by a hand lever at the after end of the manifold. The handle assembly consists of a push rod at the top of the handle, a handle, a spring, a latch, a name plate, and a bracket. Pressing down the push rod releases the spring, lifting the latch, and leaving the lever free to move inboard or outboard. As the shaft turns, the list dampers are swung to shut one port or open both ports of the Y.

The movement of the lever and the attached connecting rod turns the shaft by means of an offset arm. Outboard movement of the lever causes the damper to restrict the flow of air to the starboard side. Inboard movement of the lever causes the damper to restrict the flow of air to the port side. The normal position of the damper is neutral, allowing equal flow to both sides.

The salvage air arrangements provide external salvage facilities for use by outside salvage agencies (divers, and so forth) and also internal facilities for use by the crew of the submarine or by a diver, after he succeeds in entering the vessel.

Two external high-pressure air connections, located on each side of the conning tower, provide a means of supplying high-pressure air from the salvage ship to the high-pressure (3,000-pound) receiving manifold. This air can be directed by personnel

Each main ballast tank has an external salvage valve with a blow line connection extending up to a plate set in the deck. In salvaging, air hose lines from the salvage ship are attached to the pipe fitting and the valve is opened, thus enabling the rescue vessel to blow the ballast tanks free of water.

Each compartment of the submarine has two external compartment salvage valves, one at either end of the compartment. A salvage line from each valve extends through the hull to a deck plate where it is provided with a capped male fitting, similar to those of the main ballast tank salvage lines. The valve can be operated by a socket wrench from the

Compartment salvage air valves are located on each bulkhead between compartments, for use in blowing individual compartments. The 225-pound air is supplied to these compartment salvage air valves by lines extending from the forward and after service air lines. The arrangement of the valves permits the release of air from either side of the bulkhead into the adjacent compartment. Pressure gages are installed on both sides of the bulkhead near this valve arrangement to indicate the pressure in the adjoining compartment.

All external salvage valve deck plates are identified by lettering and round screw heads, and special lugs cast on the plates for touch identification.