Math is an exact science, and there are a few sums that will come in handy as a diver. What is the volume of air in your cylinder? How long will my oxygen supply last? How much oxygen do I need to have at the conclusion of the dive to have a third left?
To calculate your SAC rate, you can determine how long the cylinder will last. If we utilize 20 litres per minute at the surface, a 15 litre cylinder with 200 bars will last 150 minutes (15 X 200 / 20).
You may have overheard someone discussing their SAC rate. What they mean is how much air they would use at the surface, often known as their “Surface Air Consumption” (SAC) rate. In our open water training, we all learned that the further we dive, the more air we need, so we use the surface rate as the control rate.
Read ahead for further information.
How To Determine The SAC Rate?
To determine our SAC rate, dive to a basic depth of 10 meters and record the pressure in your cylinder. Then, for ten minutes, swim about 10 meters and measure your pressure again.
You now know how much air in the bar you consume in ten minutes at ten meters. So, if your starting pressure was 190 bar and your ending pressure was 170 bar, you used 20 bar.
Litres Per Minute
To calculate your SAC rate in litres per minute, you must do four calculations. First, multiply the length of the bar by the diameter of the cylinder. So 20 bars times 12 litres is 240 litres. Second, we calculate a depth value by taking the depth, adding 10, and dividing by 10.
So, 10 metres plus 10 equals 20, divided by 10 is 2. Finally, we divide the first number by the second number. 240 divided by two equals 120. Finally, we divide (120) by the time in minutes (10). Therefore, 120 divided by ten equals 12 litres per minute. Litres per minute = bar utilized X cylinder capacity litres divided by (depth+10)/10 minutes.
The Volume Of Air In Your Cylinder
A 12 litre cylinder filled to 200 bar holds 2,400 litres of air. A 15 litre cylinder filled to 220 psi contains 3,300 litres, whereas dual 12 litre cylinders filled to 210 psi have 5,040 litres.
A simple calculation involving the cylinder size in litres multiplied by the pressure in the bar. 12 x 200 litres = 2,400 litres 15 x 220 litres = 3,300 litres 12 times 2 equals 24 times 210, which equals 5,040 litres.
Watch the video to learn more about tank calculations.
How Long Does a Scuba Tank Last?
The amount of air consumed by a diver is obviously determined by their level of physical effort. However, the depth at which a scuba tank is used has a direct impact on its lifespan.
According to experience, the average open water certified diver on a 40-foot dive with a typical aluminium 80-cubic-foot tank will be able to stay down for roughly 45 minutes before resurfacing with a safe reserve of air.
Scuba Tank Maintenance
Aside from ensuring that no water enters or forms within your tank, you should take the following measures when operating and servicing your scuba tank.
Air
Air-filled tanks should not be stored for lengthy periods of time (no more than 3 months). A tank should be preserved with just enough pressure to keep moisture out (200 psi). Keep in mind that the greater the tank pressure, the more corrosion may occur within.
Visual Check
A visual check of your tank should be performed at least once a year. If the tank is continuously used or filled with salt air, it should be visually examined every three to six months.
The tank must be hydrostatically checked at least once every five years. This should only be done by a professional hydro testing centre that can service your tank completely, including testing, cleaning, drying, zinc coating, and painting.
Water
Before storing your tank, always give it a good cleaning with fresh water. When flowing water over the tank, make sure the tank valve is closed. The quality of the water used to fill the tank must be hygienic and clean.
Capacity
Do not exceed the stamped capacity of your tank. This puts too much strain on the metal, making the tank deteriorate over time. Overfilling a tank repeatedly is dangerous and can corrode the metal.
Handling
Avoid harsh handling, which can result in dents, gouges, or nicks in the tank. This can cause metal corrosion and weakening of the cylinder.
Storage
Unless otherwise directed by a visual inspection, always store tanks vertically. If there is any moisture in the tank, corrosion may begin near the bottom, which is the thickest area of the tank.
Protection
Corrosion or contaminants may be detected if you see or smell anything emanating from the tank valve. If you bang on the tank’s side and hear something rattling around within, the tank must be opened for a visual check.
If water is discovered within the tank, but the corrosion has not yet grown severe, the tank can be washed in steam or fresh water and cleaned before being properly dried with warm air. It is always preferable to leave the extent of the corrosion to a skilled inspection.
If you suspect anything amiss with your scuba cylinder, always get it visually inspected by a competent dive shop or a respected repair facility.
The Longest Dive
After diving for almost 143 hours in the Red Sea city of Dahab, Egyptian diver Saddam al-Kilany has broken the world record for the longest dive.
Kilany, 29, will be inducted into the Guinness Book of World Records, much to the delight of his co-workers, admirers, and Dahab inhabitants. According to his Facebook profile, Kilany began his trek on November 5.
Hundreds of Dahab locals, visitors, and diving communities are waiting for Kilany to emerge from the depths of the water to congratulate him, despite the lack of official media.
The diver has been at the depths of the sea for roughly six days, accompanied by rotating assistance and medical teams and overseen by Adel Taher, director of the HMC.
Conclusion
They employ typical equipment, including an 80-cubic-foot cylinder filled with 200 bar of compressed air. Dives at these elevations are only about 18 meters / 60 feet deep.
According to research, these dives range between 35 and 45 minutes, with 20% lasting up to 60 minutes.
