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11
AIR SYSTEMS
 
A. GENERAL DATA
 
11A1. Importance of the air systems to submarines. The importance of the air systems to a submarine cannot be overemphasized, for virtually every function in the diving and surfacing procedure stems initially from air provided by one or more of the air system; to cite a few:

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,

  more operations than any other single system.

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.

 
B. TYPES AND RELATIONSHIPS OF AIR SYSTEMS
 
11B1. General information. There are five air systems on the submarine: the 3,000 pound high-pressure and torpedo impulse system; the 600-pound main ballast tank (MBT) blowing system; the 225-pound service air system (ship's service air); the 10-pound main ballast tank (MBT) blowing system; and finally, the salvage air system. (See FigureA-13.)

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

  salvage air system is dependent upon the 225-pound service air system, while the external compartment salvage air system is entirely dependent upon an outside source for its supply of air.

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.

 
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The 3,000-pound air system also supplies air to the hydraulic accumulator air loading manifold and to the forward and after 600 pound Grove reducing valves which supply the forward and after torpedo tube impulse charging manifolds.

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

  aboard the submarine. The 225-pound system consists of the 225-pound service air manifold, interconnecting piping, and various valves.

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.

 
C. HIGH-PRESSURE AIR AND TORPEDO IMPULSE AIR SYSTEMS
 
11C1. General description. FigureA-14 shows the location and relationship of the individual units that comprise the high-pressure 3,000-pound air system. It should be noted that 3,000 pounds is the maximum working pressure of the system end not a constant pressure. Actually, the pressure may vary between 1,500 and 3,000 psi. The system is hydrostatically tested to 4,500 psi or 150 percent of the working pressure. The system extends from the high-pressure air compressors in the pump room to the receiving and distributing manifolds in the control room, and from there forward to the torpedo impulse air system in the forward torpedo room, athwartship to the air banks, and aft to the after torpedo room.

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.

  11C2. Manifolds and lines. The high-pressure manifold, made up of a receiving manifold and two distributing manifolds, is mounted on the starboard side of the control room. The receiving manifold receives air up to 3,000 psi from two high-pressure air compressors, and directs it to the air banks where it is stored. The capacity of each compressor is 20 cubic feet per hour at 3,000 psi. As the air is needed, it flows back through the same piping to the receiving manifold where it is directed to the distributing manifold. This operation is controlled by the valves on the manifold.

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

 
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Schematic drawing of compressed air systems.
Figure 11-1. Compressed air systems.
 
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hydraulic accumulator air flask, the high-pressure air bleeder, the bow buoyancy tank blow line, the 225-pound service air system, and the forward and after 3,000-pound service air lines.

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

  charging manifolds and six impulse flasks connected by lines to the manifolds. The impulse flasks are mounted above the pressure hull in the superstructure forward. One impulse flask charging manifold is located on the port side of the torpedo room and the other on the starboard side. Each manifold is used to charge three flasks with 600-pound air.

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.

 
D. THE 600-POUND MAIN BALLAST TANK BLOWING SYSTEM
 
11D1. General description. The main ballast tanks are filled with sea water when the submarine is submerged. These tanks cannot be pumped. Therefore, when the submarine is surfacing, compressed air must be used to blow the water out through the flood ports to the sea.

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

  distribution control unit of the system. It is located on the starboard side of the control room with its pressure gage next to it. The piping mounted directly above the manifold connects the MBT blowing manifold with the high-pressure air manifold through two hammer valves.

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

 
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group stop check valves permit the blowing of tanks by groups. The manifold is protected by a sentinel valve and two relief valves set to blow when the pressure in the 600-pound system reaches 750 psi. A sentinel valve is set to blow at a pressure of 610 psi. When the sentinel valve opens, it acts as a relief valve for comparatively small rises in pressure and gives notice of excessive pressure in the system.

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

  maintain the required pressure. When blowing is finished, the hammer valve is shut.

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.

 
E. THE 225-POUND AIR SYSTEM (SHIP'S SERVICE AIR)
 
11E1. General description. The 225-pound service air system, known as the ship's service air system, performs or controls many operations other than those discussed in the sections dealing with the 3,000-pound, the torpedo impulse, and the 600-pound air systems. The 225-pound air system provides the air for approximately 100 operations. The system extends from the forward torpedo room to the after torpedo room, with service connections in every compartment of the vessel, and supplies air at pressure ranging. from 225 psi to 8 psi. The center of direction   of the system, the 225-pound service air manifold, is located in the control room. The 225-pound system is hydrostatically tested to 350 psi, or 155 percent of its maximum working pressure of 225 psi.

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

 
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procedure is followed for each of the compartments of the vessel, proceeding first forward and then aft of the control room.

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

  supplies 225-psi and air to the hydraulic oil supply volume tank, the signal ejector, the drain pump air domes, the negative tank blow valve, and the sea pressure and depth gage blows.

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

 
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tank, the sanitary tank, the QC and JK sea chests, the underwater log, the compartment air salvage valve, and the fuel oil blow and vent manifold. Two other branch lines, equipped with reducing valves and bypass lines, furnish air to the pneumatic tool connection at 100 psi, and to the No. 1 and No. 2 fresh water tanks at 12 psi. The line to the escape trunk supplies air for the ship's diver's air, connection, and a blow and vent line for the escape chamber. The forward trim tank blow and vent line from the 225-pound manifold in the control room terminates at the forward trim tank and connects with the forward trim tank blow and vent line from the forward torpedo tube blow and vent manifold.

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,

  with a relief valve set to open at 15 psi. In addition, the forward engine room is provided with a pneumatic tool connection equipped with a 100-pound reducing valve and a bypass for emergency. A relief valve, set to open at 110 pounds, safeguards the line against excessive pressure.

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

 
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on either side of the bulkheads to permit a reading of air pressure in the adjoining compartment.

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

  with pressure gages. All fuel oil, lubricating oil, collecting, expansion, sanitary, and variable tanks are provided with pressure gages located in the various rooms and compartments.
 
F. THE 10-POUND MAIN BALLAST TANK BLOWING SYSTEM
 
11F1. General description. The 10-pound MBT blowing system is used to remove water from the main ballast tanks when the submarine is on the surface. It completes the work started by the 600-pound MBT blowing system, thus saving high-pressure air.

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.

  The list control dampers are used to correct a list during blowing of the main ballast tanks. The list control dampers adjust the amount of air admitted into the port or starboard ballast tanks of the No. 2 and No. 6 MBT group, increasing or decreasing the rate at which the tank is blown. The dampers are located at the Y outlet connections on the 10-pound blow manifold.

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.

 
G. SALVAGE AIR SYSTEM
 
11G1. General description. The submarine is provided with a salvage air system for use, in salvage operations.

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.

  FigureA-18 shows in schematic form the location and relation of the component parts that comprise the salvage air system.

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

 
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COMPARTMENT SALVAGE DECK PLATE MARKINGS *
CompartmentNumber of Screw Heads
HIGH CONNECTIONLOW CONNECTION
Officers' quarters12
Forward torpedo and control room34
Crew's quarters56
Forward engine room78
After engine room910
Maneuvering room1112
After torpedo room1314
TANK SALVAGE DECK PLATE MARKINGS
TankNumber of Lugs
MBT 2A and 2B1
MBT 12
MBT 2C and 2D2
MBT 6A and 6B3
MBT 6C and 6D4
MBT 75
10-POUND DECK PLATE BLOW MARKING
TankNumber of Lugs
MBT 2A and 2B2
MBT 2C and 2D4
MBT 6A and 6B6
MBT 6C and 6D8
* The markings used for a particular submarine may be obtained from the vessel's air salvage systems plans.
 
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inside the vessel to the 600-pound blow manifold for use in blowing the main ballast tanks. and to the 225-pound service air manifold for use in blowing water from flooded compartments by means of the compartment salvage air valves.

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

  outside or by a handwheel from within the compartment. In salvaging operations, air hoses can be attached to the valve fittings to supply the ship with air for breathing, pumping, or circulating purposes.

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.

 
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