Using Scuba Diving Tanks
Transporting Scuba Tanks, Filling Tanks, Checking Air Fill Quality
Sep 12, 2008
As basic maintenance, a scuba tank, including the valve assembly, should be washed in fresh water after every dive. For long periods, a scuba tank should be stored standing upright.
Transporting Tanks
When transporting a tank by car, the valve should face the rear so a sudden stop won’t send the tank forward, damaging the valve. Tanks shouldn’t be left in a car parked in the hot sun. The air in the tank could expand, blowing the burst disk.
Always secure tanks on a boat. Lie them down or use a proper rack. This protects the tank, and could save a crushed foot or smashed mask. A tank should be carried by the valve or with a proper tank holder. Never on the shoulder as it could easily fall.
Tanks are solid and can take a few knocks, but this strength comes from the pressure they are designed to hold. They weren't meant for a diver to throw around. Excessively rough treatment can weaken the tank and lead to premature failure or rejection at testing time.
Filling Tanks
If possible, always have a look around the filling station. If the area is clean and tidy it suggests the air will be clean. If there are old dirty rags, tools and a generally unkempt appearance it can suggest the operator is a bit lax. They might also be lax about regularly cleaning the compressor’s filters.
Air Quality
The most common contaminates in a fill are carbon monoxide, carbon dioxide, water vapour and oil.
Carbon monoxide usually comes from the exhaust of a petrol engine driving the compressor. The air inlet for the compressor should be well away from the exhaust of the engine.
Water occurs in a fill when air is compressed pressing the oxygen molecules together with hydrogen molecules to form water. The compressor’s filters and fluid traps get most of this water, but if not cleaned and maintained regularly water can get into the tank
Water in a tank can start corrosion - especially important with steel tanks. Rust not only weakens the tank but also uses the oxygen.
Checking A Fill
To do a rough check of the air quality, bleed off a small amount and smell it. There shouldn’t be any odour. Blow some through a white handkerchief. If the material discolours there is a problem with the fill. Also check for discolouration around the air outlet.
These are not reliable checks. If wary about the fill, re-fill at another filling station.
Tank O Rings
Divers often hold the O ring with the fingers and crack the air before fitting the regulator to clear the airway of any foreign material. This is a bad practice. If there is any dirt, the force in the tank can propel it into the skin.
At a resort or dive shop where a tank is in continuous use there is little need to worry about dirt in the valve. If the tank has been sitting for some time then it is worthwhile to clean out the airway before fitting the regulator. Hold the O ring on the side and beware of the power behind a full tank.
A couple of spare tank O rings should always be handy. The failure of a simple, inexpensive item can ruin a dive. Some divers carry spares on the string of the regulator dust-cap. It is common for dive-masters to have spares on their watchbands.
A scuba tank appears robust as if it can take rough treatment, but it is used to provide life-sustaining air so must be treated with respect.
For further information on scuba tanks, refer to:
Design And Testing Of Scuba Tanks
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