Compound O - Oxygen Safe Rust Inhibitor - Gallon
Dilute 1 Ounce to a Gallon
Also called Compound O, is used following the tumbling of steel tanks to prevent flash rust, a reddish film which often forms on the interior walls during drying of the cleaned cylinder. This chemical replaces Compound B, a popular anti-rust agent which is NOT oxygen compatible. Compound O can be used for both air and O2 / Nitrox tanks. GALLON
CONVERTING DIVE TANKS FOR OXYGEN SERVICE WITH GMC OXY-SAFE PRODUCTS © 2002 By Global Mfg. Corp. / Dr. Dick Boyd and Greg Kent Second Edition / January, 2002
This manual describes procedures for converting common scuba air tanks for pure oxygen and / or specialty gas service using Global's Oxy-Safe Products. Presently within the TEK-diving community, many questionable, unresearched, and highly variable methods are being used for oxygen cleaning; some of these techniques are based largely on hearsay and are so poorly documented that they might not withstand legal scrutiny in the aftermath of an accident. Most of the chemicals being marketed for this purpose are sold entirely without specific instructions applicable to scuba cylinders. Thus, GMC has written this expanded manual to not only insure the safe and proper use of our oxy-cleaning products, but also to provide some general information on the overall subject of tank conversions.
The following procedures should give consistently satisfactory results if carried out as explained. However, GMC cannot promise reliable results if users undertake significant variations in the described techniques and / or substitute other chemicals or alter the suggested concentrations.
If you are a novice to tank cleaning in general, doing oxygen preparations is a bad place to start to or to experiment. GMC strongly recommends that in addition to following these procedures, you seek advice and training from an experienced scuba technician or technical diving training agency. We further suggest that you read the GMC Bulletin "Tank Tumbling Tips” (GMC #42130), hereafter referred to as "Tips", to acquaint yourself with general tumbling / cleaning materials and methods. Also, Luxfer's manual, "Guide to Scuba Cylinder Inspection", is a fine reference on aluminum tank maintenance.
As you will note, the methods described in this manual require a certain amount of basic equipment; without it, the procedures become very labor intensive and subject to considerable variation. For example, a tank containing a specific cleaning medium rotated on a tumbler at 25 rpm for 1 hour will give reasonably consistent results tank after tank. When done by hand-rolling and by different individuals, the procedure can give highly random results! Although these new cleaning techniques are simple and similar to those used in the dive industry for many years, certain protocols must still be followed if suitably clean cylinders are to be obtained on a routine basis.
You will be undertaking procedures that are relatively "Big League" when compared to those employed for normal breathing air. They require an elevated degree of cleanliness, operational care, and special equipment. To attempt to shortcut these requirements is flirting with disaster for you, your shop, and your customer.
If you are unable or unwilling to invest in the time and equipment to carry out these procedures properly and safely, you have NO business in the mixed gas arena! Oxygen mishaps are deadly and can be sustained by even experienced experts...consider NASA's Apollo 13 or the Valujet crash in the Everglades.
GETTING STARTED: First, you must assume that the cylinder being cleaned may at some time contain 100% oxygen at high pressure. Once it has been cleaned, unless the cylinder belongs to your shop, you have no control over its future use. Applications could range from holding simple Nitrox I (32% oxygen) to being fully pressurized with pure 02 for an inwater decom bottle! Therefore, any idea of a "fairly clean" cylinder should not be tolerated; immaculate cleanliness is required in all cases!
Next, you must determine the suitability of each cylinder for elevated oxygen service. Just as you have been required to make judgment calls on the serviceability of air tanks, you must now do the same for oxygen vessels. However, here the requirement for cleanliness is far more stringent and the tolerance for error is narrower. In our quick-to-sue society, customers will readily blame the scuba shop for any dive equipment mishaps that they perceive as hi-tech service mistakes! Being conservative with your judgments would seem to make good sense!
TANK SELECTION: Converting brand-new or sparsely used air tanks for 02 service presents relatively few problems. However, divers often resist the idea of dedicating new tanks to singular gas use; thus dive shops will often be asked to resurrect older "salvaged" dive tanks for such purposes. Subsequently, scuba technicians must make judgment calls regarding the suitability of such cylinders for the intended use. Situations will occur where what the customer thinks or wants may be diametrically opposed to what is safe and prudent.
In that regard, one should reject older, STEEL cylinders that contain ANY internal lining. During the late 60's and 70's, various paints, epoxies, and plastics were used to coat the inside of tanks as anti-rust barriers. These internal linings often evolved cracks and pits in which contaminants could develop or collect. Impurities hidden beneath such linings resist removal, creating a potentially dangerous situation when pure 02 is introduced! Remember that under certain conditions, pressurized pure oxygen can react violently and spontaneously with many substances, especially hydrocarbons. Materials of unknown nature trapped under tank linings offer a potentially dangerous situation that should NOT be tested. Moreover, the oxygen-compatibility of the linings themselves, or lack thereof, is completely unknown and unresearched. It is very probable that these materials would burn vigorously in an oxygen environment. Because of such intrinsic hazards, coupled with the fact that linings are nearly impossible to remove by normal, safe methods, lined steel tanks should be rejected for mixed gas service.
Also regarding steel cylinders, the Compressed Gas Association (CGA) recommends special handling and filling procedures for steel tanks containing pure oxygen that may be immersed in salt water. If even small amounts of salty water get into such vessels, corrosion is so rapidly accelerated by the 02 that explosive failure may occur within 60 days! For details, see CGA Special Bulletin SB-7, "Rupture of Oxygen Cylinders in the Dive Industry."
SPECIAL NOTE: GMC IS OF THE OPINION THAT ANY CYLINDER THAT REQUIRES EXTRAORDINARY CLEANING PROCEDURES SHOULD BE REJECTED FOR USE WITH OXYGEN OR HIGH 02 MIXTURES. Whenever heroic measures must be used to restore a cylinder, the possibility of resistant or residual contaminants presents an unacceptable risk for 02 usage.
Having ascertained that a given tank is suitable for elevated oxygen applications, you must next determine what degree of cleaning is required. Obviously, a new aluminum tank does not require the same amount of preparation, as does a 20- year old, rusty, steel vessel. In the case of new aluminum tanks, a TUMBLING WASH (degreasing) is generally all that's needed. On the other hand, the corroded old steel tank will certainly require a standard tumble (PRETREATMENT), followed by a degreasing wash, plus an anti-rust treatment to halt flash rusting during the drying operation.
As already stated, the cleaning procedures to be described require certain special equipment and chemicals. These materials must be oxygen-compatible in nature, i.e. under a specified set of conditions; pure oxygen will not violently react with them. As you will note, these conversion procedures go to great lengths to remove all residues of the cleaning agents after their function has been completed. Nevertheless, should a trace remain and go undetected, one would want that substance to be oxygen-compatible rather than oxygen-reactive!