The tubes have individual impulse tanks of 69.4 litres volume. Impulse pressure was not indicated. Two and three sixteenth copper impulse pipes lead from the tanks directly to the firing valve. On the valve housing is a small reducer with two copper service lines to the tube firing system. It is not possible to give a detailed account of the firing system without dismantling the entire torpedo room. It appears that there is a system of air piston interlocks operated by service air for each setting spindle and leading to the control room so that when tube is fired, service air goes to a "stop cylinder", lifting the stop bolt and releasing impulse air built up against the firing valve. Mechanical lugs and screws prevent operation of the stop cylinder unless the stop bolt and tripping latch are in the proper position. The action of the firing valve follows: The main valve of steel and cup shaped, is about two and three sixteenths inches in diameter and is held on its flat seat by impulse air, gravity and a large spring. This valve has a one inch hole in the center of its face and provides a flat seat for a brass, so called, "auxiliary" piston valve. When air is released in the chamber of the piston valve, the valve lifts, thereby destroying the balance of forces holding the main valve on its seat and causing it to lift. A tapered lug integral with the lower face of the piston valve, controls the tube pressure and too rapid lifting of the main valve. A mechanically operated screw sleeve in the valve bonnet closes the line leading to the "stop" cylinder, when it is in the down position. An arrangement like this is necessary to charge the impulse line and in addition acts as a safety stop valve, no impulse stop being provided.

It is understood that the Captain of the submarine tried to fire the tubes but couldn't. The above mentioned screw sleeve was found in the closed position, preventing firing of the tube.

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