Escape Trunk - Operation

Operation

1. The drain valve is opened to ensure any residual water is drained from the compartment and the pressure between the interior of the submarine and the escape trunk is equalized.
2. The drain valve is closed, 6–8 persons climb up through the lower hatch into the escape chamber, and the lower hatch is shut. Before climbing into the chamber, the escapees don a Steinke hood or Submarine Escape Immersion Equipment, which will provide an air supply during the ascent to the surface.
3. The seawater valve is opened to flood the chamber. As the chamber floods, the air in the chamber is compressed until its pressure is equal to the sea pressure. When the pressure in the chamber is equalized with the sea pressure, the flooding of the chamber will stop. The water level must rise above the level of the escape tube (see diagram). Additional air is vented into the chamber from the high pressure air supply to raise the air pressure. A bubble of air at the top of the chamber remains for the persons inside to breathe while awaiting their turns to exit the chamber.
4. The first escapee’s Steinke hood is filled with air from a hose attached to the high pressure air line before departing. Pressure in the hood must be equalized with ambient air/water pressure. The first escapee climbs up through the escape tube and pushes the hatch open. The hatch could not have been opened until the interior pressure of the chamber was equalized with sea pressure. Once outside the chamber, the buoyancy of the air inside the Steinke hood will quickly carry the escapee to the surface. As the person rises to the surface, the ambient water pressure decreases and thus the air in the person’s lungs and in hood expands. Thus escapees must continuously exhale all the way to the surface to release the expanding air from the lungs.
5. One by one, each escapee’s Steinke hood is filled with air and the person climbs out the escape tube and rises to the surface. The last man out must push the outer hatch shut before departing.
6. Inside the submarine, the drain valve is opened to drain the water from the chamber and equalize the pressure to that within the submarine. The pressure inside the chamber will quickly force all water from the chamber out the drain valve. Lowering the pressure inside the chamber will also force the outer hatch shut again because of greater sea pressure outside the submarine. Then the cycle begins again until everyone has left the submarine.