What is the maximum time you can get out of a scuba tank?
I have a friend who knows everything about everything. However, this time I think he has overstepped his boundries. He has assured me that it doesnot matter what type of SCUBA tank you are using that the maximum time is one hour. I think he has let his alligator mouth overload his hummingbird ***. Thanks for the help
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Re: What is the maximum time you can get out of a scuba...
There are four main variables affecting this:
1. The (total) internal volume of the tank(s)
2. The pressure to which that tank has been filled
3. The ambient pressure at depth
4. The rate at which the diver uses the air out of that tank for their breathing and buoyancy control (including drysuit inflation).
The first three are simply a matter of physics and will be the same for everyone under the same circumstances.
The major variation comes from the last one, which is usually a function of the diver's experience/ competence (not the same thing!). One who is less so will go through air quicker than one who is more so.
So the best answer for your question is "It depends..."!
However, many resorts and guides set a maximum dive time of one hour, so they know when to expect a diver back on the boat (or, when they have to call out the Coastguard!). This might be the source of your friend's assertion.
FYI: The current world record for breathing off a single tank of air while sitting at the bottom of a swimming pool is a little bit short of 8 hours. The divers in question were using 12-litre cylinders charged to 200B and breathing verrrry slowly! (approximately 12 x 200 litres / 460 minutes = 5.22 l/min)
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A scuba tank is design to hold a certain volume of air, at a particular at a particular temperature. In the US, the standard tank is an aluminum 80 CF tank. At room temperature and 3,000 psi, the tank holds 72 CF of air (yeah, I know they round up calling it 80 CF tank).
When you are filling the tank, the air and tank will become warm/hot. If you check the pressure guage while the tank is warm, it will give you a reading of X. Once the tank cools, it will give you a reading that is less than X. They put the tanks in the water in the hopes of keeping the temperature do, and filling the tanks closer to the design pressure and temperature.
Some examples that you can see...
In Mexico, many of the tanks will be sitting in the sun while on the boat. The tank may have a reading of 3,200 psi. Once you jump in the water, and the tank cools down, the new reading may be 2,800 psi without ever breathing any of the air.
I have been ice diving, the tank was acutally colder than the water. Since the water temperature was warmer than the tank, me pressure reading was slightly higher.
The scuba regulator is employed in an open-circuit scuba set. Said scuba equipment reduces high air pressure conveyed by the diving cylinder to the first stage and feeds breathable gas to the diver through the second stage's mouthpiece. Also called pressure regulator or demand regulator, the scuba equipment is one of the essentials to diving that determines breathing quality and inhalation effort during the dive. But given the different types of regulators and the pertinent design of its first and second stage components, how should a neophyte diver - or even a seasoned diver at that, choose a scuba regulator that incorporates user adjustment and delivers a venturi-assisted air flow in its features? Consider your diving purpose and frequency. Better yet, take note of the following criteria to guide you in your purchase:
1. The Scuba Regulator's Mouthpiece. Check the specifications if the regulator is outfitted with a patented orthodontic mouthpiece. This implies that it is ergonomically-designed to accommodate an overbite or underbite by the human mouth. An ergonomic mouthpiece helps reduce fatigue in the mouth and jaw area, particularly in the cruise of lower depths and extended dives.
2. User Adjustment Settings. There are optimally-designed scuba regulators that are outfitted with adjustment levers to therefore allow divers to finetune valve settings in order to provide the least possible inhalation effort throughout the dive. One notable scuba equipment is the Aeris AT 400 Pro Regulator that is equipped with an adjustable second stage.
3. Weight of the Scuba Regulator. Visualize yourself on a dive and using just any other type of scuba regulator. Is the regulator bulky to considerably increase drag and cause jaw fatigue or is it buoyant enough for you to carry around with your mouth? Lightweight scuba regulators use polycarbonate thermoplastics for its housing to make the scuba equipment compact, sturdy and corrosion-resistant that makes them fit for extended use.
4. Nitrox Compatibility. This entails an ocular inspection of the cylinder tank (Nitrogen and Oxygen proportions) and scuba regulator (Nitrox compatibility) specifications. As a matter of convention, most regulators are suited for nitrox mixture use out of the box; containing the standard, maximum proportion of 40% Oxygen (in terms of volume) but then again, there are gas mixes supporting leaner proportions of oxygen such as the trimix. Therefore, check if the scuba regulator supports the gas mixture configured for your diving cylinder prior to purchase.
5. No-Contaminant Feature. As much as possible, choose a diving regulator that has been manufactured using Dry Valve Technology (DVT). DVT operates through an automatic valve that prevents contamination of the first stage mechanism to thus prevent regulator flooding and the entry of moisture or dust particles. This likely improves scuba regulator performance and extends its useful life.
6. Air-Sharing Feature. This feature often associated with octopus regulators (used as a spare demand valve or alternate second stage) will prove to be most helpful during diving emergencies such as a free flow or during diver rescues. High performance octopus regulators such as the Aeris Gyro Octopus Regulator are designed lightweight and with air-sharing feature, while sporting an inline swivel for convenience mounting and flexibility
Scuba gauges give a diver three very important pieces of information:
3. Air Consumption
This information enables a diver to stay within safe time and depth limits and avoid running out of air. There are many different devices on the market to help with this, from simple gauges to complex digital consoles.
If a diver is not using a dive computer to monitor their nitrogen, they dive according to approved dive tables. To use dive tables properly, a diver needs to track their downtime. This can be done with a good dive watch. Two things make a good dive watch: water resistance and a rotating bezel.
1. Water Resistance. Good dive watches are rated to a depth in meters or feet (e.g. 200 feet) or a pressure rating in atmospheres (e.g. 4atm). Even though most divers probably won’t dive below 130 feet (the recreational dive limit), a good dive watch should be rated to 200 feet. Note: There is a difference between “water resistance” and “waterproof”. A “waterproof” watch is what you would wear in the shower, but would probably start leaking at 15-20 feet.
2. Rotating Bezel. A bezel is an adjustable ring on the face of the dive watch with a pointer indicator. At the beginning of a dive, the pointer on the bezel is aligned with the minute hand where it stays though out the dive. At the end of the dive, you compare the difference between the bezel and the minute hand to find out the length of the dive. The bezel should only move “counterclockwise”. It is possible to accidently move the bezel during a dive. Because of this, watchmakers make sure any accidental movement will turn the time in a conservative direction, making the dive longer rather than shorter.
Another important part of scuba gauges is a depth gauge. A depth gauge enables a diver to keep track of their depth even if they cannot see the water’s surface. Gauges can be either an analog (needle-and-dial) device or a digital device. Both work in the same way. They measure the surrounding water pressure and convert this into an accurate reading of your depth. Another feature of a good depth gauge is a maximum depth indicator. This tells a diver their maximum during a dive and must be reset after each dive.
Another equally important part of scuba gauges is a submersible pressure gauge (SPG). This is connected to the first stage with a high-pressure hose and measures the pressure of the air in the tank. The SPG is much like the gas gauge on a car. At the beginning of a dive, a diver starts with a full tank. This should be about 3000 psi or 200 bars. As the diver breathes during the dive, the gauge will move slowly downwards. This allows the diver to have enough air left in the tank to:
1. Make a slow, safe ascent
2. Make any necessary decompression stops
3. Inflate their BCD once at the surface
4. Breath from the regulator if the surface conditions are rough
A submersible pressure gauge also allows a diver to stop diving with air still in the tank. This keeps contaminants from entering the tank due to no air pressure.
Wrist Depth Gauge
Scuba gauges come in two basic styles. Stand alone gauges or gauge consoles. Stand alone gauges such as a wrist mounted depth gauge or a submersible pressure gauge attached to the first stage of a regulator are great backups when using digital gauges. Gauge consoles allow divers to have all their gauges in one place.
Although less easy to read, analog gauges sometimes give slightly more accurate readings than digital gauges, particularly at shallow depth.
Submersible Pressure Gauge
Choosing Scuba Gauges
When choosing scuba gauges, remember to look for:
1. Easy-to-read numbers
2. Luminescent dial or back lighting options
3. Rotating/swivel mounting
4. Easy disassembly for cleaning or replacing parts
5. Good warranty
"The scuba tank is one of the most important pieces of dive equipment. It must be looked after. A well-maintained tank could give 20 or 30 years service. A neglected tank can fail with the force of a hand grenade. It pays to care for a scuba tank, not only for economy, but also for safety and diving enjoyment.
The following ten tips can help ensure a scuba diving tank will provide many years of faithful diving service.
1) Never completely empty a scuba tank. Always leave at least 1000 kPa to ensure moisture doesn’t enter.
2) Always rinse the scuba tank and valve in fresh water after use.
3) If the scuba tank is to be stored for a few months, drain the air down to around 1000 kPa. This is to decrease the amount of oxygen that can cause corrosion.
4) A scuba tank should be stored standing up out of direct sunlight.
5) A scuba tank should be carried with care and attention. They shouldn’t be carried on the shoulder as a fall can lead to the valve getting smashed off and the tank taking off like a rocket.
6) A scuba tank should be regularly tested in accordance with statutory regulations.
7) A scuba tank should not be left in a closed car in the heat of the day. It can heat up and explode or the burst disk can rupture; both scenarios leading to damage to the car. When in the car the tank should be carried with the valve towards the back. If the car brakes suddenly the tank valve won’t be damaged as the tank moves forward with its momentum.
8) The scuba tank valve should not be turned off too tightly. It only has to be just nipped closed enough to stop the air flow.
9) A scuba tank should be filled with clean, dry air. Any discolouration around the air outlet or bad odour should be treated with suspicion. If there are any doubts that a tank has been filled with bad air, it should not be used for scuba diving and should be checked immediately. A bad fill can lead to damage to the tank, as well as pose a threat to a diver.
10) If painting a tank, ensure no heat curing paints or strippers are used as these could affect the strength of the tank."
The scuba regulator has two parts: a 1st stage and a second stage connected by a hose. The 1st stage connects right to the tank; the 2nd stage is the contraption behind your mouthpiece. Both have an important function in regulating air flow throughout your scuba system.
"A diver relies on scuba gauges to know three things:
Depth and Time are vital for nitrogen and air management. A scuba diver needs to know how deep he has been and for how long in order to judge the necessity and length of decompression stops and to calculate residual nitrogen for repetitive dives. The time of a dive is easily tracked using a scuba diving watch and the depth is tracked using a depth gauge. "
"A diver relies on scuba gauges to know three things: 1.-Depth 2.-Air Consumption 3.-Time Depth and Time are vital for nitrogen and air management. A scuba diver needs to know how deep he has been and for how long in order to judge the necessity a