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CHAPTER 9, FLOOD AND DRAIN SYSTEM

The Tube Flood and Drain System-General116
Flooding the Tube118
Draining the Tube119
Roller Bracket Drains120
 
115

The Tube Flood and Drain System
 
GENERAL
 
As explained in the opening chapter of this pamphlet, when a torpedo has been loaded into the tube and the breech door is closed and-locked, the tube is flooded with water to equalize the pressure inside the tube with the pressure from outside, so the muzzle door and shutter may be opened against the resistance of the sea water outside. The tube is flooded from tanks within the submarine. As the tube is being flooded, the air from the tube is vented through the forward and after vents. After the torpedo has been launched from the tube, the muzzle door and shutter are closed, and the water which has entered the tube is drained off. As the water is being drained off, air is blown into the tube through the vents, forcing the water out by filling the tube with air.

The tube flood and drain system provides the means for this flooding, venting, and draining of the tube, before and after firing a torpedo.

  Variations will be found in the tube flood and drain systems on different submarines, and for detailed information pertaining to the installation in any particular vessel, reference should be made to the plans as well as to the General Information book supplied to each vessel. The purpose here is to give

Figure 214
Figure 214 The tube drain valve with operating lever in valve open position.

Figure 213
Figure 213 The tube drain valve, with operating lever in valve closed position. (A) Operating lever; (B) Valve; (C) Lead to drain.
 
116

the basic principles of operation of the system. Once thoroughly familiar with the fundamentals, the student of submarine operation should readily recognize any changes he may encounter on submarines to which he may be assigned.

A typical tube flood and drain system consists of drain, vent, and blow valves, these being arranged in manifolds; also piping, and the related interlocking mechanism, the latter having already been described in detail in Chapter 4, in the section dealing with the Tube Flood and Drain Interlocking Mechanism, on page 42 of this pamphlet.

There are two drain lines for each tube, forward and aft, these leading to the drain and flood manifold. The manifold controls flooding and draining tubes from or to the trim line, trim tank, torpedo compensating tank, or W.R.T. (water round tube) tank.

Each tube has two vent and blow connections,

  one toward the breech end, the other toward the muzzle end, these leading to an individual vent and blow manifold. The manifolds have a three-way plug cock to the blow and vent line from each tube, a three-way plug cock to the blow and vent line from the W.R.T. tank, and a stop valve to the 200-pound air service line.

Each tube is vented inboard by means of the three-way plug cock connection to the blow and vent line from the tube. When this connection is in the blow position it permits blowing the tube from the 200-pound air service line. When it is in the vent position it permits venting the tube through another three-way plug cock valve, which permits venting inboard through a two-inch line, or outboard through a one-inch line which is clear of the bow buoyancy tank. The tube is vented outboard only when it is believed that noxious gasses or vapors are present in the tube.

Figure 215 The drain valve
Figure 215 The drain valve, view from the side opposite to that shown in Figures 213 and 214, showing (A) Valve operating lever, in valve open position; (B) Rod extending down from the interlock lever to interlock collar; (C) Connection for pipe to drain roller bracket (one of four); (D) Valve; (E) Interlock collar on stem of valve operating lever; (F) Connection to drain.
 
117

 
FLOODING THE TUBE
 
The procedure for flooding the barrel, preparatory to opening the muzzle door after a torpedo has been loaded into the tube, is as follows:

(a) The breech door must be closed and locked, as described in Chapter 3, see Figure 33, page 28.

(b) The tube is then vented, either inboard or outboard as determined necessary.

(c) The drain valve interlock lever is moved to "Muzzle Door Closed" position, as described in

  Chapter 4, see Figure 77 on page 42.

(d) The W.R.T. tank and barrel drain valves are opened.

(e) Blow the W.R.T. tank until the tube is flooded.

(f) Close the W.R.T. tank, barrel drain, and tube vent valves, and vent the W.R.T. tank until the gage shows atmospheric pressure.

To flood a tube from the trim tank, the trim

Figure 216
Figure 216 The W.R.T. (water round tube) tank vent lever, the one at the left, shown in open position.
 
Figure 217
Figure 217 The W.R.T. tank vent lever, shown in closed position.
 
118

 
DRAINING THE TUBE
 
tank blow and vent valves are used instead of the W.R.T. tank valves. To flood a tube from the sea, the trim pump, trim line valve, and the tube vents are used.

For draining the barrel after a torpedo has been launched, the procedure is as follows:

(a) The firing interlock lever is moved to the "Muzzle Door Unlocked" position, as described in Chapter 4, see Figure 81 on page 44.

(b) Close the impulse stop valve, if one is installed on the tube.

(c) Close the muzzle door.

(d) The drain valve interlock lever is moved to "Muzzle Door Closed" position, as shown in Chapter 4, see Figure 77 on page 42.

(e) Open the barrel drain valve.

(f) Open the W.R.T. tank valve in the drain manifold.

(g) Vent the W.R.T. tank.

(h) Blow the barrel until free of water.

(i) Close the tank vent.

(j) Vent the tube until the gage shows atmospheric pressure in the tube.

Note-In submarines of the Portsmouth design, to drain a tube to the trim tank, the trim tank drain and vent valves are used instead of the W.R.T. tank valves. To drain to the sea, the trim pump, trim line valve, and the tube vents are used.

In submarines of the Electric Boat Company design, a W.R.T. tank overflow valve to the trim tank is provided for the purpose of blowing the tubes to the trim tank when the W.R.T. tank is full. An interlock to close a quick operating valve in the W.R.T. tank blow line when the overflow valve is open, prevents accidental blowing of the W.R.T. tank to the trim tank. A loop around the quick operating valve is provided with a check valve for venting purposes. When the overflow valve is closed, normal blowing and venting of the W.R.T. tank is accomplished, and, when the overflow valve is open, water from the tube is transferred to the trim tank by way of the W.R.T. tank.

  Figure 218 Venting the tube (first vent to right).
Figure 218 Venting the tube (first vent to right).

Figure 219 Venting the W.R.T. tank.
Figure 219 Venting the W.R.T. tank.

Figure 220 Flooding the tube from the W.R.T. tank.
Figure 220 Flooding the tube from the W.R.T. tank.

 
119

 
ROLLER BRACKET DRAINS
 
The roller brackets, of which there are four on the under side of the tube-these brackets containing the rollers on which the torpedo rides as it passes through the tube-are drained by three-eighths inch I.P.S. lines to the tube drain line (see C in Figure 215, page 117) entering that line above the drain valve, i.e., between the tube and the drain valve.

These drain lines from the roller-brackets must be kept free of any obstructions. This is important inasmuch as the shell of the torpedo is steel, and the tube barrel rollers with their associated parts are principally bronze, hence the presence of sea water in the roller bracket pockets may cause

  galvanic action, with resulting pitting and corrosion of the torpedo. In order to prevent this, the installation of phenolic compound rollers in late vessels has been authorized, to facilitate extensive service test. If successful, such rollers will be issued to all submarines.

Where bronze rollers are installed, pieces of zinc may be placed in the roller brackets to minimize electrolytic corrosion. As the zinc is electro-positive to both steel and bronze, it should be attacked by the sea water instead of the steel or bronze. These pieces of zinc should be inspected regularly and renewed whenever necessary.

Figure 221
Figure 221 The No. 1 tube blow valve-watching water level gage preparatory to closing the tube blow valve.
 
120

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