MPA Logo, San Francisco Maritime National Park Association, USS Pampanito, Historic Ships at Hyde Street Pier, Education Programs Maritime Park Association Home Page Maritime Park Association Home Page Events Maritime Park Association Home Page Maritime Park Association Home Page Maritime Park Association Home Page Volunteer Membership Donate Maritime Park Association Home Page USS Pampanito Submarine Historic Ships at Hyde Street Pier Education Programs About Maritime Park Association Home Page Directions to Maritime Jobs at Maritime Facility Rental at Maritime Trustees of the Association Calendar Press Room Store Maritime Map
3
THE 600-POUND MAIN BALLAST TANK
BLOWING SYSTEM
 
A. GENERAL DESCRIPTION
 
3A1. Introduction. The main ballast tanks are normally 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 chapter deals with 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. It is discussed in Chapter 5.

Figure 3-1 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, described in Section 3B, 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 1000 psi, or 166 percent of the maximum working pressure.

3A2. Hammer valves. Air at bank pressure (1500 to 3000 psi) passes 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

  the one does not supply enough air or in case of failure, the other hammer valves can be used. The group stop check valves permit the blowing of tanks by groups. The manifold is protected by a sentinel valve and two relief valves (Figures 4-8 and 4-9) set to blow when the pressure in the 600-pound system reaches 750 psi. The 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 excess 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 3000 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 psi.

3A3. Operation. 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 will build up the pressure within the system more rapidly at greater depths than it will on the surface. Since the hammer valve regulates the volume of 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

 
12

Figure 3-1. THE 600-POUND MAIN BALLAST TANK BLOWING SYSTEM.

FBT. From the after section of the manifold, blow lines 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 tank valves, are open, as are the two group stock check valves. (See Section 3B.) 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.

At the point where each blow line enters the tank, it is provided with a regulator valve. 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.

Detailed instructions for blowing specific tanks or combination of tanks are given in Chapter 8.

 
B. THE 600-POUND MAIN BALLAST TANK BLOW MANIFOLD
 
3B1. Description. The 600-pound MBT blow manifold directs the flow of air within the 600-pound MBT blowing system. It is located on the starboard side of the control room, adjacent to and aft of the low-pressure (225-pound) manifold, with the connecting piping directly above it (see Figure 3-2).

The 600-pound MBT blow manifold is made up of two parts, the forward section and the after section. The upper half of Figure 3-2 shows the construction of the forward section of the manifold. The after section is of similar construction (lower half of Figure 3-2) except that it contains one additional blow valve. The forward section has four blow valves and the after section of the manifold has five blow valves.

The blow valves and the two group stop check valves have no permanently attached handles, but are provided with square-ended stems. A double-handled socket wrench is supplied to fit these stems, and the valves are opened and shut by applying the valve wrench to one stem at a time. This lessens the possibility of accidentally opening or shutting the wrong valve.

The stems of the blow valves for the fuel ballast tanks are furnished with chain-attached locking caps and padlocks as a safe guard against accidental blowing of the tanks when they contain fuel oil.

  Both sections of the 600-pound MBT blow manifold, as well as the lines carrying the 600-pound air, are capable of withstanding depth pressure.

High-pressure air, controlled* by one or both manually operated hammer valves, passes through the group stop check valves into the two sections of the 600-pound MBT blow manifold. From there it is directed by the blow valves into the blow lines connecting with the main ballast tanks. When all the tanks are to be blown simultaneously, the tank blow valves on the manifold, the two group stop check valves, and a hammer valve are opened in the order given. When the tanks in either the forward or the after group are to be blown, the blow valves, the group stop check valve for that group, and the hammer valve are opened. When the tanks are to be blown separately, the individual tank blow valves, the corresponding group stop check valve or valves, and the hammer valve are opened in the order given.

When the ship is rigged for diving, all individual tank blow valves on the 600-pound MBT blow manifold, as well as the two group stop check valves, are open.

Detailed instructions for main ballast tank blowing operations are given in Chapter 8.

*Hammer valves are not automatic reducers. They control air pressure only by regulating the volume of air admitted to the system.

 
13

Figure 3-2. The 600-pound MBT blow manifold.
Figure 3-2. The 600-pound MBT blow manifold.
 
14

Previous chapter
Previous Chapter
Sub Air Home Page
Sub Air Home Page
Next chapter
Next chapter


Copyright © 2013, Maritime Park Association
All Rights Reserved
Legal Notices and Privacy Policy
Version 1.10, 22 Oct 04