Cylinder Oxygen Cleaning
The proper preparation of a scuba cylinder for use with Enriched Air Nitrox (Nitrox) is essential for the safety of the cylinder user and the person filling the cylinder.
The 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, the issue is the presence of hydrocarbons, or oil, in the scuba cylinder. 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 prior to use in the Nitrox filling operation.
At The Scuba Doctor, we think that proper cleaning of scuba cylinders for use with Enriched Air Nitrox is essential. In addition, we have clear opinions about the methods that should be used in this cleaning process.
Many people, including some scuba store operators, feel that proper cleaning can be accomplished by simply filing the cylinder 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 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 cylinder. 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.
Proper Oxygen Cleaning
Proper 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, we use special cleaners made by a specialist in supplies and chemicals for oxygen cleaning. These special cleaners are basically made of citrus juices, combined with other chemicals and concentrated just for hydrocarbon removal.
We then place the cylinder 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.
In addition, the valves used on the Nitrox cylinder must be 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, an inspection sticker is applied, and the cylinder is ready for use.
Keeping It Oxygen Clean
Maintaining the 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 in 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.
| Oxygen Cleaning Prices | |
|---|---|
| Service Item | Price inc GST |
| Oxygen Clean Cylinders (parts not included) |
|
| Oxygen Clean Cylinder - all sizes (add brush & rumble if required) |
$ 30.00 |
| Oxygen Clean (Nitrox) Wrap | $ 14.00 |
| Oxygen Clean 'In Test' Sticker | $ 4.00 |
| Oxygen Clean Valves (parts not included) |
|
| Standard Valve | $ 30.00 |
| Manifold with Isolator | $ 80.00 |
| Oxygen Clean Regulators (parts not included) |
|
| 1st Stage Only | $ 48.95 |
| 2nd Stage (or Ocy) Only | $ 34.65 |
| Hourly rate for poorly maintained equipment | $ 60.00 |
Full Service Price List
PLEASE NOTE: All prices are correct as of 1st November 2007.
All of the above prices are subject to change without notice.
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