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DrDiverDave · 3rd April 2008, 20:23

TDI has a class on this, I also recommend reading what DOT, CGA, luxfer, and other suppliers / manufacturers have to say about this.

About Flash Rusting:

To reduce flash rusting, use Compound "O" according to directions, and dry the cylinder quickly, preferably with Nitrogen gas, or with heated, dry, and filtered air (oxygen clean) if necessary. Alcohol is a bad idea, since significant trace levels (parts per million) may be left behind, and the alcohol may be contaminated with other organics such as denaturants, plasticizers, etc. added during processing and storage.

More on Oxygen Cleaning:

UV light will not show all hydrocarbon contaminants, and does not prove that the tank is safe for oxygen service, but a positive UV test does let you know that additional cleaning is necessary. Since there should only be trace amounts of hydrocarbon present before O2 cleaning, a good hot washing with agitation, followed by through rinsing should remove contaminants.

Thorough rinsing is necessary to remove cleaner, and any hydrocarbons dissolved in the cleaner. Since most cleaners a) foam, and b) are basic, pH>8, rinse water samples can be tested by shaking vigorously and looking for foam, and using pH paper to check for residual cleaner. You need to know the pH of the rinse water that has no cleaner in it to see if its pH shifts toward Basic. The problem is that progressive rinses dilute the cleanser to the point that pH differences can't be observed with pH paper. The "solution" is that progressive rinses also dilute any remaining cleanser and residual hydrocarbons to very low levels.

Note: Carbon dioxide in the air reacts with water to make carbonic acid

which can neutralize some of the cleanser residual if the rinse water has been agitated for very long. So ...(lots of boring chemistry...)

Conclusion:

Unless you have $250,000 + for a GC-MS instrument and the knowledge of how to perform a head-space analysis for hydrocarbons, and the cylinder is not noticeably contaminated with hydrocarbons: wash with an oxygen approved cleanser, rinse multiple times with hydrocarbon free water, checking for foaming, use "Compound O", to prevent flash rusting, and dry with nitrogen or with heated oxygen clean air.

TDI offers training on Oxygen cleaning and servicing. I highly recommend it.

David

Piling it Higher and Deeper every day

3rd April 2008, 20:23	#7 (permalink)
DrDiverDave New Member Current Rebreather/s: Azimuth Other Rebreather/s: Azimuth Join Date: Aug 2006 Location: North Andover, MA Posts: 5	Re: 02 cleaning cylinders using biox TDI has a class on this, I also recommend reading what DOT, CGA, luxfer, and other suppliers / manufacturers have to say about this. About Flash Rusting: To reduce flash rusting, use Compound "O" according to directions, and dry the cylinder quickly, preferably with Nitrogen gas, or with heated, dry, and filtered air (oxygen clean) if necessary. Alcohol is a bad idea, since significant trace levels (parts per million) may be left behind, and the alcohol may be contaminated with other organics such as denaturants, plasticizers, etc. added during processing and storage. More on Oxygen Cleaning: UV light will not show all hydrocarbon contaminants, and does not prove that the tank is safe for oxygen service, but a positive UV test does let you know that additional cleaning is necessary. Since there should only be trace amounts of hydrocarbon present before O2 cleaning, a good hot washing with agitation, followed by through rinsing should remove contaminants. Thorough rinsing is necessary to remove cleaner, and any hydrocarbons dissolved in the cleaner. Since most cleaners a) foam, and b) are basic, pH>8, rinse water samples can be tested by shaking vigorously and looking for foam, and using pH paper to check for residual cleaner. You need to know the pH of the rinse water that has no cleaner in it to see if its pH shifts toward Basic. The problem is that progressive rinses dilute the cleanser to the point that pH differences can't be observed with pH paper. The "solution" is that progressive rinses also dilute any remaining cleanser and residual hydrocarbons to very low levels. Note: Carbon dioxide in the air reacts with water to make carbonic acid which can neutralize some of the cleanser residual if the rinse water has been agitated for very long. So ...(lots of boring chemistry...) Conclusion: Unless you have $250,000 + for a GC-MS instrument and the knowledge of how to perform a head-space analysis for hydrocarbons, and the cylinder is not noticeably contaminated with hydrocarbons: wash with an oxygen approved cleanser, rinse multiple times with hydrocarbon free water, checking for foaming, use "Compound O", to prevent flash rusting, and dry with nitrogen or with heated oxygen clean air. TDI offers training on Oxygen cleaning and servicing. I highly recommend it. David Piling it Higher and Deeper every day
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