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Appendix C

Snorkel Exhaust System

Made available by Bob Emery of the Submariners Association of Canada West

The snorkel exhaust mast is a vertical telescoping mast housed in the conning tower sail and mounted abaft the snorkel induction mast.

A central snorkel exhaust line extends from the base of the snorkel exhaust mast within the superstructure to the vicinity of the forward engine room. At this point the line divides into two branch lines, one line going toward the forward main engines 1 & 2, and the other line going toward the after main engines 3 & 4. Each branch line further divides into two more lines with each division going to an engine exhaust system. These lines connect to the engine exhaust lines between the inboard and outboard exhaust valves. The connection is made in the forward, vertical face of the outboard exhaust valve housing.

Located in the horizontal piping near the base of the exhaust mast is the main snorkel exhaust valve (Able Valve) which serves as the sea valve in the Snorkel Exhaust System.

Capping the exhaust mast is an exhaust gas diffuser plate that aids in reducing a telltale plume of water while snorkelling.

The Snorkel Exhaust System consists of the following pieces of equipment:

  1. the snorkel exhaust mast.
  2. the snorkel exhaust diffuser plate.
  3. the main snorkel exhaust valve (Able Valve).
  4. the forward engine room snorkel exhaust valve (Baker Valve).
  5. the after engine room snorkel exhaust valve (Charlie Valve).
  6. the exhaust piping.

EXHAUST MAST

The snorkel exhaust mast is made up of a fixed base pipe structure designed to receive a second telescoping section of pipe. This mast is designed for snorkel operations at induction mast operating depth. The lower lip of the fully extended telescoping section of the exhaust mast forms a metal to metal bevel seat with a built up lip surrounding the top of the fixed base pipe. At the lower position a close fit between the base pipe and the telescoping section exists. No seal is formed, but the proximity of the two pipes precludes rapid flooding. The water that does enter the mast is rapidly vaporized and blown out by the engine exhaust gases.

The snorkel exhaust mast is geared to the induction mast and raises and lowers with it.

The exhaust mast does not raise as high as the induction mast, thereby permitting the exhaust to be ejected below the surface of the sea. Such an arrangement reduces the amount of snorkel engine exhaust and spray that may be visible to a searching ship or aircraft.

At the start of snorkelling all the water in the snorkel exhaust mast (approx. 3000 lbs) is blown to sea by engine exhaust pressure.

EXHAUST DIFFUSER PLATE

The diffuser is designed to break up the exhaust gas stream and radially eject the gases into the surrounding water. It consists of a cylindrical framework with vertical vanes mounted around the periphery of this framework. The forward side of the framework is shielded by a circular piece of sheet metal. This shield prevents dynamic water pressure, due to own ships' motion, from impeding exhaust injection. A large deflector plate is mounted on top of the diffuser, and exhaust gasses ejected from the snorkel exhaust mast are radially discharged through the vanes and forced to bubble to the surface around the periphery of the deflector plate.

MAIN SNORKEL EXHAUST VALVE (ABLE VALVE)

The main snorkel exhaust valve is located in the snorkel exhaust piping near the base of the snorkel exhaust mast.

This valve seals the after Snorkel Exhaust Systems from the free flooding exhaust mast, acting as the snorkel equivalent of an engine outboard exhaust valve.

This valve is a 15 inch hinged flapper type unit housed in a cylindrical metal structure.

The main snorkel exhaust valve is designed for hydraulic or manual operations, the operating gear being located in the overhead of the ship's galley.

The main snorkel exhaust valve is also known as Able Valve and is designed so that a combination of hydraulic pressure and engine back-pressure is required to open it.

It is opened hydraulically by concurrence of all of the following conditions:

  1. Able Valve in the 'Power Position' and hydraulic power available.
  2. control room lever in 'Control in Engine Room' position.
  3. engine safety circuit energized.
  4. exhaust back pressure 17 psi or above.
  5. Able Valve control lever in engine room is opened.

Able Valve may also be operated by hand from the after battery compartment.

FORWARD ENGINE ROOM SNORKEL EXHAUST VALVE (BAKER VALVE)

The forward engine room snorkel exhaust valve is located in the snorkel exhaust piping above the forward engine room. It can be operated hydraulically from the snorkel hydraulic manifold located in the forward engine room, or manually at the valve operating gear in the forward engine room. This valve receives the exhaust gases from 1 & 2 main engines. The forward engine room snorkel exhaust valve is shut when surface cruising. If the valve was opened, or was not installed, engine noises would be magnified by the resonance of the exhaust piping and carried as far as the main snorkel exhaust valve. Spaces such as the bridge area and the radio room would be difficult to work in under these circumstances. The valve also serves as an additional safety factor in the Snorkel Exhaust System. The forward engine room snorkel exhaust valve is also known as Baker Valve.

AFTER ENGINE ROOM SNORKEL EXHAUST VALVE (CHARLIE VALVE)

The after engine room snorkel exhaust valve is located in the snorkel exhaust piping above the after engine room. It is designed for hydraulic or manual operation, the operating gear being located in the after engine room. This valve receives the exhaust gases from 3 & 4 main engines. It serves the same purpose as the forward engine room snorkel exhaust valve and it is shut when not snorkelling. The after engine room snorkel exhaust valve is also known as Charlie Valve.

SNORKEL MAST HOISTING MECHANISM

The snorkel hoist mechanism is designed to raise the snorkel induction and exhaust masts simultaneously. When the masts are in either of the two operating positions, the exhaust mast is at a preset distance below the snorkel head valve. This places the snorkel head valve above water and the top of the snorkel exhaust mast beneath the surface of the water.

Hoisting power is supplied by main hydraulic pressure, driving a modified 5 A End hydraulic motor, which in turn drives gears meshing with rack gearing on the induction and exhaust masts.

By using a different gear ratio, the induction mast travels a greater distance than the exhaust mast for the same number of turns of the hydraulic motor. This permits the two masts to be in the proper relative height positions although starting from the same initial level.

SNORKEL EXHAUST PIPING

The snorkel exhaust piping, valves and fittings between the main snorkel exhaust valve (Able Valve) and the four main engine outboard exhaust valves are designed for maximum submergence pressure, with drain lines installed to indicate flooded piping.

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Appendix BAppendix D