Snorting with Gilles
Today being a rainy day why not putting it to good use to talk about submarine life! I will cover "snorting" or as the Americans call it "snorkeling". Snorting is to put into action the running of either one or both diesel generators while the submarine is dived at a depth of ±60 feet. The running of diesels either on the surface or dived is done for either charging the main batteries or to aerate the inside of the submarine to clear out the smoke after an on board fire.
While snorting regardless how calm it is above the water, you try to snort with the induction mast head as close as possible to the water to minimize being spotted. The induction mast is a long hollow tube that is located outside the pressure hull. The air sucked in the submarine must pass inside this tube. It is hydraulically operated, but unlike the periscopes, radar mast, ECM mast and communication mast, it does not come through the pressure hull, more on that later.
Induction Mast
On the top of the induction mast is a snort mast head. It is a very large ball shape head, about two and a half feet in diameter. It is covered with an anti-radar material. This ball has two openings around it to allow the air to come in. Each of those openings is fitted with a coil type electric heater. They are used to warm the air coming in, therefore reducing the risk of freezing during operations in the North Atlantic where the water temperature is hovering at the freezing point.
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Ball not a Flap
Inside this ball is fitted a float (not a flap) that goes all around the intake, just like a donut. In normal operation this float drops down. Should the water completely cover this ball, the float will float up, therefore stopping any water from coming in. This is a very important safety feature. Once the ball comes out of the water this float drops down again allowing the air to be sucked back in again.
The Dog House
Since the mast does not penetrate the hull, the base of the mast goes into what we call a "dog house" or a water tight compartment. This compartment is welded to the pressure hull and at the bottom of it enters inside the submarine. Since it is such a large opening, it must go through a massive hydraulically snort induction hull valve. This is the largest hull valve on the submarine. Should this valve fail on a "stop snorting" order, there is another valve fitted immediately under it and it is called the "emergency flap valve" this is also shut by hand from inside the submarine by a very large spring. Should something happen, and the operator is not able to shut it, it will shut itself as soon as it senses a full bore of water coming through.
This valve caused the sinking of the American submarine USS Squalus, since it indicated that it was shut but was not. Now as the air comes through those valves it enters "S" tank. This is called a tank although it just like a chamber that allows the water/air to separate. The air then comes through a grilled opening into the AMS (Auxiliary Machinery Space). Any water that has been separated will fall further into "R" tank where it will be pumped out as necessary to keep a good trim. Once you "stop snorting" any water trapped in the induction system will automatically drain into "R" tank and be pumped out. |
The Barometer is Your Best Friend
Snorting is affected by the sea state. The rougher it is the higher the waves, causing the snort induction mast float head to slam shut as soon as a wave covers it. When this happens, the diesel engines cannot suck the air they require from the outside, therefore they suck it from the inside of the submarine causing a vacuum inside the submarine. If a submariner has a cold, it will cause him great discomfort when the vacuum gets worst since you cannot "clear your ears". That is the reason that we have two big barometers fitted on board; one in the control room and the other one in the engine room. The face of each barometer is divided into three colors. The largest section is green, then a smaller yellow section and finally a red section.
Snorting in the Yellow
The name of the game is to keep the barometer in the green, but as you create a vacuum, the barometer will slowly head toward the yellow, this is acceptable, but only for short periods of time. The engine room chief of the watch will inform the control room "snorting in the yellow" - of course they should know that since they also have a barometer. This message tells them that they better get their ducks in a row because if they continue like that, they will soon reach the red.
They can correct that, either by raising the induction mast higher (if not already fully raised) or by trying to bring the submarine to a shallower depth, keeping in mind that at all times you are trying to stay undetected. One should keep in mind that the use of the induction system will create a restriction of the air flow due to its size as opposed to having the hatches opened like when you are running the engines with full air flow while alongside. |
Stop Snorting . Stop Snorting . Stop Snorting
Red buttons cut off engines quickly.
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Should the barometer go in the red, the engine room chief of the watch will automatically tell the control room over the main broadcast "Stop snorting, stop snorting, stop snorting" and at the same time do an emergency shutdown of the diesel engines, going through the process of shutting all associated hull valves while the control room will do the same.
Of course, if you are in the Gulf Stream, it will get hot in the engine room immediately. Most likely the control room will try to correct their "trim" and ask for a re-start for snorting. |
The Matter of Back Pressure
Other factors affecting "snorting" will come from the engine room chief of the watch. You are allowed a maximum of 10 psi back pressure on the exhaust system. Since your exhaust mast is under water, the deeper you go while snorting the higher the sea pressure on the exhaust system, the higher the pressure the hotter the diesel engines will run. Once you reach 8 psi, the Chief of the Watch will order a "stop snorting". The Chief of the Watch will also order a "stop snorting" should the submarine pass 6° bow down angle; this would clearly indicate that the control room has "lost the bubble". The chief of the watch will also initiate a "stop snorting" at any time he feels they have reached an unsafe situation, i.e. strange noise, oil or fuel leak, flooding, fire etc.
Mind the bubble to keep the boat trim.
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Never Hesitate
As the chief engineer of a submarine I have always instructed my engine room staff to NEVER hesitate if they have any doubt at all, even if they are not sure if they have heard a noise or not. We can always restart an engine once it has been shut down. You would be amazed to see how easy it is to hear "something different" even while you are running two massive V16 diesel engines running fully supercharged, although the superchargers (screamers) sound like jet engines.
Of course the chief of the watch will quickly judge the situation and see if the control room is about to "come out of it" and give them a few extra seconds, even if you have passed certain parameters. It will mean you would not have to shut down and have to conduct a full restart.
Of course the chief of the watch will quickly judge the situation and see if the control room is about to "come out of it" and give them a few extra seconds, even if you have passed certain parameters. It will mean you would not have to shut down and have to conduct a full restart.
Ah! Life in the engineering world on board a submarine… There is no life quite like it. Enjoy!
Gilles
Gilles