To scuba divers, the range of pressure for diving cylinders is between two significant figures: 2,600 psi and 3,000 psi. Diving cylinders that exceed the 3,000 mark are newer, more compact tanks that are more expensive, yet offer the incredible advantage of a drastically reduced size.
Manufacturers often pressurize dive cylinders to about 3,000 psi. Because of buoyancy issues, aluminum diving tanks have higher pressures though they are physically more compact than their steel counterparts. This is done to address the issue of positive buoyancy as the contents of the aluminum diving tank dissipate through continuous use underwater.
Dive cylinders that generally have lower pressures (2,000 psi) are used in technical diving. The reason for this is that divers within this niche use mixed gases when underwater. Surprisingly, steel scuba tanks that have been pressurized beyond the 2,000 psi mark are quite compact, but maintain the negative-neutral buoyancy which is the characteristic of even older steel dive tanks.
With all the good news regarding compact and highly-pressurized steel scuba tank cylinders, there are disadvantages to these dive cylinders. For one, the extra pressure takes a toll on the other parts of the underwater breathing equipment. One has to remember that the diver depends not only on the dive cylinder but also on the other parts, such as the valve and mouth piece of the scuba gear.
Logically, if the high pressure dive air cylinder is used extremely well for more than a year, chances are, you have to check whether the other parts of the underwater breathing gear is still functioning perfectly.
According to manufacturers, though it might be avoided in some instance, it is the regulating valve of the gear that first fails when subjected to more than 2,000 psi every use. This sad fact should be a clear warning for those who wish to use high-pressure steel tanks for their underwater adventures.
There is also the small, yet vital issue of seawater contamination. There are some instances that the dive scba cylinder would be contaminated with seawater; because sea water is corrosive, and the steel dive cylinder is a contraption made of steel, the inside of the tank will take damage.
In an independent study conducted by a small commercial firm, it has been found out that high pressure steel tanks take more damage in this scenario than the low pressure variants.
In sports diving, there is a usual practice of "overfilling" a diving cylinder to gain more pressure underwater. Though this is being done continually throughout the fifty states, manufacturers and experts warn people of this practice.
Well technically, the steel and aluminum dive tanks can take the extra pressure. But the problem is that the other parts of the dive cylinder might not be able to handle the extra internal pressure. Because of the risk of device failure underwater, many diving shops refuse customers when they wish for their empty tanks to be "overfilled".
Through multiple tests, manufacturing firms confirmed that such a practice reduces the general durability of the diving cylinders.