HNSA Crest with photos of visitors at the ships.
Figure 4-1. THE 225-POUND AIR SYSTEM.

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THE 225-POUND AIR SYSTEM
 
A. GENERAL DESCRIPTION
 
4A1. Introduction. The 225-pound compressed air system, known as the ship's service air system, performs or controls many operations other than those discussed in the chapters dealing with the 3000-pound, the torpedo impulse, and the 600-pound air systems. The 225-pound air system provides the air for approximately 100 operations which are discussed in later sections of this chapter and in Chapter 9. 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 pressures ranging from 225 to 8 psi. The center of direction of the system, the 225-pound service air manifold (see Section 4B) 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.

Figure 4-1 shows the nomenclature, location, and relationship of the parts of the system. Detailed descriptions of the main components of the system are given in later sections of this chapter.

Discussion of the ship's service air system will start 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 procedure will be followed for each of the compartments of the vessel, proceeding first forward and then aft of the control room.

4A2. 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 air supply through two Grove pressure-reducing valves, which reduce the high-pressure air from 3000 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 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 distributing manifold. When 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 opened only partly, so that the pressure can be built up gradually. The 225-pound manifold pressure gage must be watched constantly and the pressure must never be allowed to go beyond 225 psi.

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

If 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-pound 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 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 line, and the forward and after trim tank blow and vent lines. A hose connection to the manifold provides for air supply from the dock or tender.

 
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Figure 4-2. Pneumatic tool connection.
Figure 4-2. Pneumatic tool connection.
A line from the forward service air main is provided with a reducing valve which furnishes air at a pressure of 100 psi to a connection for pneumatic tools. (See Figure 4-2.) A bypass is provided for emergency operation, with a relief valve set to open at a pressure of 110 psi as protection against excessive pressure.

The after service air main carries a connection supplying air to the whistle and siren.

The after service air main has branch connections to the sea pressure gage and to the compartment salvage air. It supplies air through a reducing valve, at a pressure of 12 psi, to fresh water tanks Nos. 3 and 4. A bypass is provided for emergency operation, with a relief valve set to open at a pressure of 15 psi.

4A3. 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 air line, passing through an 8-pound reducing valve, supplies air at a pressure of 8 psi to the four battery fresh 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.

4A4. Forward torpedo room. In the forward torpedo room, the forward service air main extends to the torpedo tube blow and vent manifold ( Figure 4-1.). The service air main is also provided with branch lines to the torpedo stop cylinders, the escape trunk blow, the volume tank, the sanitary tank, the QC and JK sea chests, the Pitometer 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 at 100 psi to the

 
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pneumatic tool connection, and at 12 psi to the No. 1 and No. 2 fresh water tanks. The line to the escape trunk supplies air for the ship's diver's air connection, and a blow and vent line supplies 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.

4A5. After battery compartment. The galley and mess room compartment has one connection from the after service air main, which supplies air to the blow and vent manifold for fuel ballast tanks 3A, 3B, 4A, and 4B. A second connection through an 8-pound reducing valve supplies air at 8 psi to the four battery fresh water tanks, Nos. 5, 6, 7, and 8, located in the after battery compartment. A 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 angle stop valves, located at the tank top in this compartment.

4A6. Crew's quarters. In the crew's quarters, the after service air 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.

4A7. Forward engine room. The forward engine room has direct connecting lines from the after service air 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.

  4A8. After engine room. In the after engine room, the after service air 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 the Nos. 6 and 7 normal fuel oil tanks and the expansion and collecting tanks against excessive internal pressure. A pneumatic tool connection is also provided; it is equipped with a 100-pound reducing valve, a 110-pound relief valve, and a bypass line to supply air at 100 psi.

4A9. Maneuvering room. The maneuvering room contains lines extending from the after service air main to the after water closet, the compartment air salvage valve, and the main engine shutdown connection.

4A10. After torpedo room. In the after torpedo room, the service air main has branches leading to the 225-pound compartment air supply valve for the escape hatch, the torpedo tube stop cylinder, 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 after torpedo tube blow and vent manifold, similar to that of the forward torpedo room. The compartment air salvage valves are mounted on the transverse bulkheads of each compartment so 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 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

 
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Figure 4-3. The 225-pound service air manifold.
Figure 4-3. The 225-pound service air manifold.
 
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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 as shown in Figure 4-1.   The main parts and controls of the 225-pound system are described in detail in the following sections of this chapter.

Step-by-step instructions in the use of this system will be found in Chapter 9.

 
B. THE 225-POUND SERVICE AIR MANIFOLD
 
4B1. Description. The 225-pound service air manifold which was introduced in the preceding section controls the blowing and venting of the forward and after trim tanks, the No. 1 and No. 2 auxiliary ballast tanks, and the air supply to the forward and after service air mains.

Figure 4-3 shows the mechanical construction of the manifold as well as the proper nomenclature of its parts. The manifold is located on the starboard side of the control room, just aft of the 3000-pound air manifold. Gages indicating the air pressure in the manifold, in the forward and after trim tanks, in the No. 1 and No. 2 auxiliary ballast tanks, and a gage registering sea pressure are mounted on the gage board directly above the manifold.

The body of the manifold is a one-piece bronze casting, divided into eight compartments. There is one large rear compartment provided with a flanged inlet for connection to the 225-pound air supply. Each of the seven smaller front compartments is provided with a flanged port for connection to one of the lines of the 225-pound system. There are four vent ports in the bottom of the manifold, one from each of the four lower compartments. A drain pan is mounted directly below the manifold to catch any drain water.

4B2. Valves. Eleven valves are provided on the front (or inboard) side of the manifold, each with a bolted bonnet on which a name plate designates the function of that particular valve. The ends of the rising valve stems

  are shaped to fit the special wrench provided for their operation.

The valves are arranged in three horizontal rows. Reading from left to right, the first valve on the top row directs the air supply to the forward service air line, the middle valve is a spare, and the end valve directs airflow to the after service air line. These valves lead to the forward and after service air mains and are normally locked open to insure an uninterrupted air supply. The locking caps and padlocks are used to lock the valves in the open position.

The middle row contains the valves controlling the blowing of the forward trim tank, the auxiliary tank No. 2 blow, the auxiliary tank No. 1 blow, and the after trim tank blow. The bottom row of valves controls the venting of the forward trim tank, the auxiliary tank No. 2, the auxiliary tank No. 1, and the after trim tank.

4B3. Operation. In operation, the air supply from the two 225-pound reducers enters the rear compartment of the manifold. When any one of the blow valves (the middle row) is opened, the air in the rear compartment passes to the front part of the manifold leading to the line in which the valve is open.

In venting, the opening of any vent valve (the bottom row) allows the air in the corresponding line to flow into the front passage and out the vent port, which discharges into the drain pan.

Step-by-step instructions for the use of the 225-pound service air manifold will be found in Chapter 9.

 
C. GROVE REDUCER
 
4C1. Description. The 225-pound service air system is supplied with air by the 3000-pound air system. In turn, the 225-pound system supplies air at 100, 12, 13, 10, and 8 psi to the various service lines, such as the pneumatic   tool connections and the fresh water tanks. This reduction or lowering of air pressure is accomplished by a device known as the Grove reducing valve, (See Figure 4-4.)
 
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Figure 4-4. Grove reducing valve.
Figure 4-4. Grove reducing valve.
 
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Both the high-pressure and the 225-pound service air systems are provided with pressure reducing valves. There are two 3000-to-600-pound reducing valves for charging the torpedo tube impulse flask, and two 3000-to-500-pound reducing valves for the main engine starting air. Two 3000-to-225-pound reducers are used on the supply line to the 225-pound service air manifold.

The other reducing valves (a total of 12 on the 225-pound air system) are distributed throughout the submarine as follows: five supplying the pneumatic tool connections with 100-pound air; two supplying the battery fresh water tanks with 8-pound air; one supplying the lubricating oil manifold with 13-pound air; one delivering 10-pound air for the distillate tank; one delivering 40-pound air to the brine tank; and two supplying 12-pound air to the fresh water tanks.

Figure 4-4, which illustrates a typical reducing valve, shows that it consists principally of an air dome, a diaphragm, a regulating valve, and a body provided with both a high-pressure inlet and a low-pressure outlet.

4C2. Operating principle. The reducing valve acts on the balanced pressure principle. As the air is used, and the pressure on the

  discharge side decreases, the diaphragm is forced down and the valve admits high-pressure air until the correct pressure is restored.

The dome chamber is charged by a loading channel, controlled by two needle valves as shown in Figure 4-4. The dome is loaded as follows:

1. Place the loading wrenches in the dome and body needle valves.
2. Back off the dome valve, to vent the pressure in the dome.
3. Shut both needle valves.
4. Shut the inlet line stop valve.
5. Shut the outlet line stop valve.
6. Open the body needle valve one half turn.
7. Watching the outlet pressure gage, carefully open the dome needle valve. When the desired delivery pressure is shown on the outlet gage, shut the dome needle valve.
8. Shut the body needle valve.

The reducer is now ready for service.

The reducing valve provides a close, accurate control of air pressure. If the delivered pressure rises or falls, it is necessary to correct it, by reloading the dome, as described above.

 
D. AUXILIARY BALLAST TANK BLOW AND VENT STOP VALVE
 
4D1. Description. The connection from each blow and vent line of the 225-pound system to the auxiliary ballast tanks serviced by it is made through a blow and vent stop valve, a typical example of which is shown in Figure 4-5. The flange on the discharge end of the valve body is bolted to the tank opening, and the pipe flange is bolted to the flange on the inlet side of the valve. Thus the flow of air between the pipe and the tank can be stopped by operating the valve.

The valve is of the disk and seat type with a rising stem. The valve body is a one-piece bronze casting with the bonnet bolted

  on it to give access for inspection or repair. The seal between bonnet and body is made by an asbestos gasket. An adjustable packing gland and braided flax packing prevent leakage.

The blow and vent stop valves are opened and shut by a manually operated handwheel.

Counterclockwise rotation of the handwheel raises the valve disk from the seat and allows the passage of air for blowing or venting. Figure 4-5 shows the flow of air through the valve when blowing. In venting, the flow of air is reversed.

 
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Figure 4-5. Auxiliary ballast tank blow and vent stop valve.
Figure 4-5. Auxiliary ballast tank blow and vent stop valve.
 
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Figure 4-6. WRT BLOW AND WRT OVERFLOW INTERLOCKING SYSTEM.
Figure 4-6. WRT BLOW AND WRT OVERFLOW INTERLOCKING SYSTEM.

 
E. WRT BLOW AND WRT OVERFLOW INTERLOCKING SYSTEM
 
4E1. Description. The purpose of the WRT overflow interlocking system (see Figure 4-6) is to prevent blowing from the WRT tank to the trim tank by way of the overflow piping and overflow valve. This precaution is necessary in order to assure that needless and useless air pressure will not be put on these two tanks without actually transferring the water ballast from the WRT tank to the trim tank.

To prevent this condition, the quick-acting blow valve for the WRT tank, located in the WRT blow and vent line, is mechanically interconnected with the overflow valve in such a way that the opening of the overflow valve automatically shuts the blow valve, and vice versa.

The interconnection consists of a single lever which operates both valves, with connecting links to cams actuating the valves. The linkage is shown in Figure 4-6.

The operating lever for the forward system is located adjacent to the torpedo tubes in the forward torpedo room. The lever for the after system is located forward of the tubes on the port side of the after torpedo room.

The upper diagram of Figure 4-6 shows water being blown from the torpedo tubes and

  entering the WRT tank through the open torpedo tube drain stop valve to the WRT tank. Assuming that the WRT tank is already filled, it therefore cannot hold the entering water which forces the excess water into the overflow pipe, past the open overflow valve, and into the trim tank.

The flow arrows in the lower diagram of Figure 4-6 trace the path of flow and the valve line-up required to get air to the WRT tank and transfer water from the WRT tank to the torpedo tubes or the trim system by way of the torpedo tube drain stop valve to the WRT tank.

The lower diagram also shows the conditions existing when blowing the WRT tank to the torpedo tubes or the trim system. The quick-acting blow valve is open, allowing air to enter the WRT tank and to force the water in it to the torpedo tubes, via the open torpedo tube drain stop valve to the WRT tank.

If the system were not protected with an interlock during this operation, the overflow valve could be opened, allowing the water to be blown from the WRT tank to the level of the overflow pipe, and then the air would rush into the trim tank, through the overflow pipe, and exhaust itself through the trim tank vent.

 
F. TORPEDO TUBE BLOW AND VENT MANIFOLD
 
4F1. Description. When a torpedo is fired, sea water rushes in and fills the empty tube. Before the breech door can be opened for reloading, this water must be removed by blowing or draining the tube.

Similarly, after loading and before firing, the excess air in the tube must be vented and the tube flooded with water.

The basic function of the torpedo tube blow and vent manifolds is to direct the 225-pound air used to blow the tubes during draining, and to vent the tubes during flooding. It also provides for blowing and venting the WRT tank and the trim tank when the water from the tubes is transferred to or from either of these tanks.

Each manifold consists of a bronze

  casting, fitted with blow valves with bolted bonnets, and provided with flanged connections. The cutaway illustration, Figure 4-7, shows the mechanical construction typical of all three manifolds. All blow valves are provided with extended stems and manually operated handwheels. The vent valves are lever-operated. The access plates on the bottom permit inspection and repair of the vent valves.

Figure 4-7 illustrates the port side manifold in the forward torpedo room. Two hundred and twenty-five pound air is supplied through the upper flanged connection on the side, filling the upper longitudinal compartment. When any of the blow valves is opened, air is permitted to enter the corresponding

 
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Figure 4-7. Torpedo tube blow and vent manifold (port side).
Figure 4-7. Torpedo tube blow and vent manifold (port side).
 
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rear compartment, or passage, to the desired torpedo tube blow and vent line. Shutting the blow valve will stop the flow of air.

The lower flanged outlet on the side connects the lower longitudinal compartment of the manifold to the torpedo tube vent line. Opening any one of the vent valves allows air from the desired tube or tank to flow into the vent line.

4F2. Location. There are three torpedo tube

  blow and vent manifolds in the submarine. (See Figure 4-1.) Two are mounted aft of the torpedo tubes in the forward torpedo room; the manifold on the port side servicing torpedo tubes Nos. 2, 4, and 6, and the forward WRT tank. The starboard manifold services torpedo tubes Nos. 1, 3, and 5, and the forward trim tank. The third manifold is mounted in the after torpedo room just forward of the torpedo tubes and services tubes Nos. 7, 8, 9, and 10, and the after trim and WRT tanks.
 
G. PNEUMATIC TOOL CONNECTIONS
 
4G1. Description. Among the functions of the 225-pound service air system is that of supplying air under pressure to the pneumatic tool connections (Figure 4-2) which provide air pressure to operate the grease guns and other air-driven tools necessary to service the vessel.

There are five such connections, located one each in the forward torpedo room, the control room, the forward engine room, the

  after engine room, and the after torpedo room. Each connection is supplied with 100-pound air through a Grove reducer which receives 225-pound air from the forward or after service air main. In addition, each pneumatic tool connection is provided with a bypass which permits the use of the connection even if the reducing valve is not functioning. The connection is opened or shut by a manually operated handwheel.
Figure 4-8. Sentinel valve.
Figure 4-8. Sentinel valve.
 
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Figure 4-9. Relief valve.
Figure 4-9. Relief valve.
 
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H. SENTINEL VALVES
 
4H1. Description. If the working pressure of the 225-pound service air system rises to a pressure of approximately 250 psi, the sentinel valve (Figure 4-8) opens automatically, allowing the excess pressure to escape. It will close when sufficient air has been exhausted to lower the pressure below 250 pounds.

The discharge capacity of the sentinel valve is limited and hence it serves principally as a warning that excess pressure is being built up in the system. If the pressure in the system becomes so great that the sentinel valve is unable to discharge fast enough to lower it, the two relief valves automatically open and reduce the system pressure. The relief valves are discussed in detail in Section 4I.

  Figure 4-8 is an illustration of the sentinel valve. Its internal construction is similar to that of the relief valve shown in Figure 4-9. The sentinel valve is set into the line by the threaded male inlet. Air from the 225-pound line fills the lower chamber and exerts pressure against the valve disk which is held shut by the spring. The spring is preset to allow the disk to open when the pressure in the lower chamber approximates 250 psi. The rising of the valve disk allows excess air to escape through the side outlet. When the line pressure drops below 250 pounds, the spring closes the valve. The hand lever permits manual operation of the valve when necessary.
 
I. RELIEF VALVES
 
4I1. Purpose. Relief valves are used to protect the lines of the 225-pound service air system from excessive pressure. Placed directly in the lines, they are set to open at a predetermined pressure, thus allowing air to escape from the lines into the boat, and so relieve internal pressure. When normal pressure in the lines is restored, the valve shuts automatically.

4I2. Description. The construction of a typical relief valve is shown in Figure 4-9. The arrows indicate the flow of air when the valve is blowing, or relieving pressure.

The bottom outlet is fitted to the line or manifold to be protected, thus allowing the air to enter the lower chamber and push against the bottom of the valve disk. The valve disk is held against the valve seat by the tension of the spring, which is adjusted to exert a downward force equal to the maximum allowable pressure in the air line. When

  the pressure in the air line exceeds this limit, it forces the valve disk up and allows air to escape into the boat through the side outlet. As soon as enough air has escaped to lower the pressure, the spring forces the disk downward and shuts off the flow through the escape outlet. The regulating ring controls the rate of escape by opening or closing the blowdown vents. The hand lever allows the valve to be operated manually. Lifting the lever will raise the valve disk and allow the escape of air.

The cap, body, and bonnet of the valve are made of bronze with a steel spring and valve assembly.

4I3. Location. Relief valves are located throughout the 225-pound service air system as outlined, in the table on page 28, which also shows the service performed and the pressure at which the valve is set to blow.

 
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LOCATIONSERVICE SETTING (psi)
Forward torpedo room Sanitary tank
Fuel oil manifold
Fresh water tanks
Pneumatic tool connection
105
15
15
110
Forward battery compartment Battery fresh water tanks 10
Control room Pneumatic tool connection
225-pound manifold
Fresh water tanks
110
275
15
Galley and mess roomBattery fresh, water tanks
Fuel oil manifold
10
15
Crew's quartersSanitary tank 105
Forward engine room Pneumatic tool connection
Fuel oil manifold
Lube oil manifold
Brine tank
Distilling tank
110
15
15
44
12
After engine roomPneumatic tool connection
Fuel oil manifold
110
15
After torpedo roomPneumatic tool connection110
 
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