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CYLINDERS TANKS
Using the correct scuba diving cylinder is just as important to a diver's success and safety as how they configure their gear. A diver may go to an enormous effort to insure every hose, reel and accessory is exactly right only to 'drop the ball' by making the wrong cylinder choice.
The Scuba Doctor dive shop brings you scuba cylinders from the leading cylinder manufacturers in the world — Faber and Catalina — so you can not only get it done, but can get it done right.
No cylinder is perfect for every diver, or every diving situation. The Scuba Doctor offers the most complete selection of cylinders in the industry, allowing you to choose what is best for your unique needs.
All cylinders from The Scuba Doctor are suitable for nitrox service (i.e. up to 40% oxygen), visually inspected and shipped with a current hydrostatic date (except where indicated).
Australian Standards
In Australia, scuba Tanks must be tested every year (12 months). We always ship cylinders with a current hydro test date. Due to manufacturing and import cycles, the popular sizes of cylinders typically have a factory hydro date less than 12 months old. However less popular sizes of cylinders may have a factory hydro date up to 24 months old as these are manufactured and imported less frequently.
As per the Australian Standards, the cylinders and valves we sell are for Imperial 0.750-14 NPSM (3/4 NPS) neck threads, NOT Metric M25 neck threads, and the valves have overpressure relief devices (burst discs). (Cylinders with Metric M25 neck threads do not comply with Australian Standards.)
The Faber steel cylinders have ISO 9809-1 markings. The Catalina aluminium cylinders have DOT-3AL2957 markings. All of these cyliners comply with Australian Standrads and are suitable for use in Australia. They may, or may not, meet the standards applicable in other coutries.
Choosing Your Scuba Cylinder/Tank
Scuba diving cylinders (USA: tanks, UK: bottles) are awkward and heavy, and if you fall down with one on you'll be lying on your back flailing your arms and legs in the air like a turtle flipped on it's shell.
Without scuba cylinders you can never be like that same turtle 'flying' gracefully through the water, experiencing a world that almost defies explanation.
Like all scuba gear, choosing a scuba diving cylinder/tank/bottle takes more thought and planning than just walking into a dive shop and grabbing the first thing you see.
There are a few different kinds of cylinders, each with their own pros and cons. Plus, not all diving cylinders can be used for all types of diving. The video below may help you to chose which dive cylinder is best for your needs.
Types of Scuba Diving Cylinders
Steel Scuba Cylinders
Steel scuba cylinders have been around since the start of scuba diving, while aluminium diving cylinders came into use in the 1970s. Steel scuba cylinders are typically more expensive than the same capacity aluminium cylinders.
A steel diving cylinder is a lot tougher than an aluminium one, making it less likely to pit or dent. If properly cared for it will last longer than an aluminium cylinder. However, steel rusts with exposure to moisture and thus needs more careful care.
Because steel is stronger it can be handle higher pressures with a thinner wall thickness, making a steel cylinder smaller and lighter than an aluminium one of similar capacity.
Also If you want to use higher pressures (e.g. 300 bar), you will need to use a DIN valve which may make it hard to get refills depending on where you're diving.
Most technical divers use steel scuba cylinders, but they can be a good cylinder for regular recreational scuba diving too. The most common size is a 232 bar, standard 12.2 litre steel cylinder, but many women and those who use less air often prefer a lighter and smaller 10.5 litre cylinder.
Steel cylinders are more negatively buoyant than equivalent aluminium cylinders and only become less negatively buoyant as they are emptied. Thus they are popular in cold/temperate water areas where thick wetsuits and drysuits are used, because a steel cylinder means you can carry less weight on your weight belt.
Aluminium Scuba Cylinders
Aluminium scuba cylinders came into use in the 1970s and are the most common scuba cylinders you'll find in tropical waters for recreational diving. Many dive shop, boat and resort operations use them worldwide.
The most common size used for diving is the aluminium 80 cubic foot (11.1 litre), but they can be smaller or larger depending on what they're meant to be used for.
For example, a bail out or pony bottle is much smaller than a standard size aluminium 80.
Aluminium cylinders being made of a softer, lighter material have thicker walls, making them larger and heavier than steel cylinders of the same capacity. Aluminium cylinders are relatively inexpensive and thus a good choice for most recreational scuba divers.
One downside of the aluminium scuba diving cylinders is that most go from being negatively buoyant to positively buoyant as they empty during the dive, so most divers wear a few extra kilograms (or pounds) of weight to compensate for this. There are a few models of aluminium cylinders that are built specifically to eliminate this problem, but like everything else, the more features it has, the more expensive it is.
Typically aluminium cylinders are certified for use at a working pressure of 200 to 210 bar. But some newer ones are available rated to nearly 230 bar. Again, these cylinders are more expensive and heavier.
Things To Consider When Buying Scuba Diving Cylinders
Here are a few other things to consider before buying.
- Length/height of the cylinder. Is it so long it bumps your butt and the back of your head at the same time?
- Weight of the cylinder. Is it too heavy for you to handle comfortably?
- Type of diving. Do you technical dive or not?
- If it's steel, is it a low pressure (LP) steel cylinder (e.g. 232 bar), or a high pressure (HP) one (e.g. 300 bar)?
- Does it have a DIN valve, or more common A-clamp/Yoke valve, or a valve that can be converted from DIN to Yoke using an insert?
- If it's a used cylinder, when was it last visually inspected or hydro tested?
Our Recommendations
When purchasing scuba cylinders, the long-term advantages of steel's excellent buoyancy characteristics and long life make it the best choice for most divers, but especially those in cold and temperate waters. Choose a 232 bar steel tank size that meets your needs when it is under filled, putting an end to short fill concerns. For most divers this will be a 12.2 litre (100 cubic foot) cylinder, but some may prefer the smaller 10.5 litre (85 cubic foot) cylinder.
If your budget is tight, then aluminium cylinders initially costs significantly less. If going with an aluminium cylinder, avoid paints, and choose the brushed finish.
For both steel and aluminium cylinders you should choose a convertible valve having a DIN outlet with K (yoke) insert, often described as a 'DIN/K' valve. (That's why we provide this as our standard offering.).
Remember, the standard 207 bar aluminium 11.1 litre (80 cubic foot) capacity cylinder with a K valve is not a "one-size-fits-all" tank. Making the right cylinder choice can significantly improve your diving enjoyment. Please use this list as a guide when reviewing scuba diving cylinders and you should be able to find the right cylinder/tank to last you for years of diving.
For more help buying the best diving cylinder (Tank / Bottle) for you, please see our Buying a Scuba Cylinder guide.
The Scuba Doctor dive shop is your best source for scuba diving cylinders.
Cylinder Oxygen Cleaning
The proper preparation of a scuba cylinder and valve for use with Enriched Air Nitrox (Nitrox) is essential for the safety of the tank user and the person filling the cylinder.
The Nitrox Problem
The primary issue here is the introduction, even temporarily, of pure oxygen into the scuba cylinder. Pure oxygen can create flammable or explosive situations that would not be possible in regular atmospheric air. Substances that would not burn in atmospheric air burn freely in the presence of pure oxygen. Routine, everyday substances become ignition sources in a pure oxygen environment. This was demonstrated clearly in the space program fire of Apollo I, where Velcro, a popular and common substance, became explosive when used in a pure oxygen environment during capsule testing.
In the scuba cylinder and its valve, the issue is the presence of hydrocarbons, or oil. When exposed to pure oxygen, hydrocarbons have a much lower flash point. To safely use a scuba cylinder for partial-pressure filling of Nitrox, special precautions must be taken to ensure that all hydrocarbons are removed from the cylinder and valve prior to use in the Nitrox filling operation.
At The Scuba Doctor, we think that proper cleaning of scuba cylinders and valves for use with Enriched Air Nitrox (EAN) is essential. In addition, we have clear opinions about the methods that should be used in this O2 cleaning process.
Many people, including some scuba store operators, feel that proper cylinder and valve O2 cleaning can be accomplished by simply filing the tank with commercial cleaning solutions and rolling the cylinder around for several minutes. The solution is then washed from the cylinder and the cylinder dried. The cylinder is then believed to be ready for Nitrox service.
Actually, a little more is involved. We need to understand that the hydrocarbons we are trying to remove can easily hide in scratches, dents, and other imperfections inside the tank. In addition, hydrocarbons can stubbornly adhere to the cylinder walls by various methods, including static electricity, and may not be adequately broken down by simple exposure to the cleaning chemicals. The proper removal of these hydrocarbons requires special methods.
Plus the valve used on the cylinder needs to be O2 clean as well.
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Proper Cylinder Oxygen Cleaning
Proper cylinder oxygen cleaning requires three basic elements...
- The use of special cleaning solutions designed to degrade hydrocarbons without introducing chemicals that would present a problem in breathing air,
- Some method of agitation that would break the hydrocarbons from scratches, dents, and other areas where it might cling, and
- A complete and tested method of washing the oxygen cleaned cylinder after the cleaning process.
At The Scuba Doctor, special cleaners made by a specialist in supplies and chemicals for oxygen cleaning are used. These special cleaners are basically made of citrus juices, combined with other chemicals and concentrated just for hydrocarbon removal.
The cylinder is then placed on a special rolling machine, where it is tumbled for 15 to 30 minutes. During this time, all stubborn hydrocarbons are removed from the cylinder.
The cleaned cylinder is then placed on special washing stands, where it is flushed with hot running water for five to ten minutes. The cylinder is then tested for the presence of the cleaning solutions using a bubble test, a simple test that involves taking wash water samples from the cylinder and testing it for the presence of soaps.
The cylinder is dried and is ready for oxygen service.
Oxygen Clean In Test StickerIn addition, the valve used on the O2 clean cylinder must be O2 cleaned and prepared with special o-rings, seats, and grease designed for exposure to pure oxygen.
The cylinder is then banded with the familiar yellow and green Nitrox band wrap, an Oxygen clean inspection sticker is applied, and the cylinder is ready for use.
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Keeping Your Cylinder Oxygen Clean
Maintaining the cleanliness integrity of an oxygen cylinder is also critical. Any subsequent introduction of air that is not "oxygen compatible air" contaminates the cylinder and it is no longer suitable for partial pressure filling.
Most scuba stores will not fill a Nitrox banded cylinder with normal air, unless that air comes from a Nitrox production facility, in which case it is identified as 21% Nitrox.
However, the practice of filling Nitrox cylinders with standard breathing air is becoming more common place. This presents a clear problem to a facility that subsequently completes a partial-pressure fill on that cylinder.
We caution our customers to be very careful when obtaining Nitrox fills, or when obtaining air fills or top ups, in their Nitrox cylinders. Cleaning is expensive, and we don't want you to waste additional money because you get an "improper" fill in your oxygen clean cylinder.
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Be Vigilant About O2 Clean
Eventually all pieces of equipment that once were oxygen cleaned will degrade and become contaminated. The problem is that we just don't know when the contamination threshold has been crossed to create a potential dangerous situation. So regular servicing and O2 cleaning of your equipment is a must and it is recommended that any time contamination is suspected, to have the equipment serviced. Hoping that a piece of dive equipment is still clean enough is a thought that only belongs in utopia and fantasy land.
More About O2 Cleaning
If you'd like to know more about Nitrox fills, O2 cleaning of cylinders, Nitrox stickers, banding etc. please also see Nitrox Fills and O2 Cleaning Cylinders.
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