what will happen if ballest tanks in a submarine are rapidly with high pressure air?
Answers
Explanation:
First off, you don’t blow air to submerge; you open the Main Ballast Tank vents (they’re operated hydraulically normally, but can be cycled manually if needed), which lets water come in through the bottom of the MBT’s, forcing air out through the vents on the main deck topside. Viewed from outside, it may appear the air is being blown out, but in reality it’s being forced out rapidly from the extreme pressure of the seawater coming into the tanks from the open, grated bottoms of each MBT.
It’s similar to a cork in a wine bottle with no bottom, filled with air. Put the bottle into a pool of water down to the bottle’s neck, then pull the cork.
As far as surfacing, high pressure air is stored in air tanks in each ballast tank, but they’re for emergency use only. For normal surfacing a Submarine will use main propulsion to get to Periscope Depth, raise the snorkel mast, then use a device called a Low Pressure Blower (essentially just a large air blower) that takes air from the snorkel mast and routes it to the MBT’s, to force the water out of the bottom of the MBT’s. The blower takes more time to surface the boat, but it conserves valuable HP air should an emergency occur.
As to how the HP air is replenished, most boats usually have 2 High Pressure Air Compressors that are run at PD during “housekeeping operations ”(dumping trash, blowing sanitary tanks, getting radio messages, getting navigational fixes, etc.).
During an emergency blow to get to the surface quickly, high pressure air is dumped into the MBT’s, forcing the water out the bottom of the tanks. Depending on depth at the time, and propulsion speed, it can up to 90 seconds to get to the surface. If you’re really deep, the air will still be compressed by sea pressure as it enters the MBT’s; as the boat slowly rises, the air in the tanks will begin to expand as the pressure decreases and the depth gets shallower, increasing buoyancy faster and faster as the boat heads to the surface, eventually so fast that the bow of the boat will literally come out of the water. This doesn’t actually keep you on the surface; you’ll sink back down to Periscope Depth or a bit further depending on surface weather/water conditions. You’ll then need to push to PD and use the LPB, or any compressed air left in the MBT air storage tanks, to force out any remaining water in the MBT’s, to fully surface if a serious casualty requires it. The diesel generator (Nuclear Powered boats) can also be lined up to force exhaust into the MBT’s if the Blower isn’t working.
Major casualties like a fire can spread quickly and affect other systems very rapidly. In the case of the battery fire aboard USS BONEFISH (SS-582) in 1988, the fire ruptured a nearby high pressure hydraulic line and freon line, rapidly compounding the efforts to extinguish it. They were lucky; they were fairly shallow and working with several Navy Surface ships that were able to assist once they were on the surface. The time between the initial report of the fire to the CO ordering all hands to Abandon Ship was just under 29 minutes. We still lost 3 Submariners in that accident, one of whom was a friend of my cousin when they were stationed on the same boat.