Venting and Blowing
Yes C., There is a Difference
This image appeared as photo of the day on Friday, October 12, 2012 with a caption that indicated that Ojibwa was ‘blowing’ her tanks. Retired submariner Lucky Gordon, explains
what is really going on. Note: Ojibwa was sporting her pennant number (72) at this date.
Open Main Vents
There are many other factors regarding the state of other tanks, order to the “Planes” and speed of descent desired, in essence, the order from the CO in the control would be “Open Main Vents” at which time the first panel Watchkeeper would switch # s 1, 2, 4, 6 and 7 main vents to open (in that order). This allows sea water to rush in through the free flood holes in the bottom of the main ballast tanks (MBTs) replacing the air in them and forcing it out of the top through the open vents. Think about a paper cup forced upside down into water capturing the air inside, then; poke a hole in the bottom of the cup.
Removing the last bit of air
‘Stand by to blow the mail ballast’
To surface the submarine, the CO will order “Blow” main ballast tanks. Under normal circumstances he would order “Stand by to blow main ballast tanks, Blow 1,.... Blow 2,... Blow 4, 5 and 6 main ballast tanks,” the exact timing & sequence pause and grouping of tanks would be determined by the angle of ascent that he wants and/or the speed