Use of O2 clean tanks in remote areas...

[chrisch]

I'm mystified here by the last posting. "most shops in US pump E grade or better" OK so no problem. "E Grade is OK for PP" OK no problem. CO filter not needed as "no CO" - agreed - no problem.
So what is all the BS about high grade filters??

Let's get this VERY clear and in easy to understand language. Two posters; Diverbrian & oharag have asked more or less the same question. They have O2 service tanks and are concerned about contamination from the odd air (21) fill now and then, particularly in remote areas. Pescador775 says all air in US is OK - I cannot argue as that may be true (I live in Europe but I am sure that US air is amongst the best in the world - honest), why not? its a rich country and sues people for spilling hot coffee and so-on, decent compressed air seems reasonable enough to me - I give in - all air in US is OK. So whole issue is BS to start with - contamination will not occur...

Now everyone wants to argue you need mega-filter that takes out everything?

One point of view must be wrong.....

Guys. The "personal air filter" contains activated charcoal and will remove most hydrocarbons. This is adequate for the odd air fill that is a little too much oily for a PP blend. I cannot see in either post where the question is "I am having 300 fills of ****ty air a week".

The personal air filter is adequate. Period. The guy at risk is the blender not the diver. Tanks explode while being filled not being dived. The wo/man at risk is the one pumping pure O2 into a "dirty" tank. S/he takes at face value the (annual) O2 clean sticker and trusts the diver that s/he has not violated the conditions of the sticker.

Diverbrian is being responsable and trying to look after the blender. This is good.

We need more diverbrians.. He (Brian is a bloke's name so forgive me on that one!) gets my vote. I'll fill your tank mate (if you are in Italy any time).

Regards to all from laid-back Italy.
Chris.

 

[pescador775]

My concern is that a carbon filter, for which no technical details are provided, will create a fire hazard. I warned about carbon dust being driven into the tank and you chose to ignore it while claiming that the European filter is 'adequate'. Prove it. Hint, dacron or felt pads are not sufficient protection from this hazard.

Grade E air is OK for partial pressure mixing as long as the tank being filled is examined/cleaned periodically. I have said this once here, now twice. The dive community represented by commercial interests cannot take this position and may deny it. Therefore, the average Nitrox diver may be concerned and have questions about air supplies in general.

A hyper filter is not necessary in most cases but a dive shop may elect to use this device for various reasons. Some do not. Even small portables with Bauer PO or equivalent condensators can produce grade E air. Most dive shops use elaborate 'grade E' systems with cascade storage. This alone acts as additional filtration although not by design. If hyper air is not advertised by the shop quality assurance may be desired by the nervous or skeptical. If so, an inline filter with Lawrence Factor triplex type cartridge or equivalent will clean up any remaining, microscopic contaminants.

A note for compressor owners who hand pack filtrant media: A micronic filter must be inserted in the air line before partial pressure filling. Since you aren't using a commercial cartridge with this feature designed in it is advisable to purchase an inline micronic filter from Compressed Air Specialties or other source.

Pesky

 

[WarmWaterDiver]

Diverbrian,

You may want to ask shops in the area if any use oil-less air compressors - if one does, then the majority of the O2 compatible or not air issue goes away. For diving in the colder waters (since you show a Great Lakes are a address), the moisture content / dew point of the gas in your tank should also be something to examine.

 

[pescador775]

Those are good points. Many years ago, there were compressors lubricated by water/soap mixtures. Haven't seen these lately. It is likely that compressors which might potentially pump a small amount of oil mist could also discharge some water vapor. These two contaminants are dealt with in similar ways by the compressor's filtration system, through agitation, pressurization, condensation and absorption. Hence, my recommendation of the triplex type cartridge. I do not recommend hand packed filters for inline applications. It is extremely important that the filter cartridge and its contents be spring loaded, stablized, and sieved with a 5 micron filter on the output end. Any possibility of breakup of the media and transmission into the SCUBA tank could be hazardous. The dessicant, if driven into the tank, will immediately produce heat if it contacts a drop or two of water. Carbon dust in the presence of oxygen is explosive. The final filter does not have to be elaborate and expensive. It only has to function as a secure housing for a $30 filter cartridge and be able to withstand normal tank pressures. The dive shop may want to be assured of this fact by some traceable means such as test date and service pressure.
Pesky

Diverbrian,

You may want to ask shops in the area if any use oil-less air compressors - if one does, then the majority of the O2 compatible or not air issue goes away. For diving in the colder waters (since you show a Great Lakes are a address), the moisture content / dew point of the gas in your tank should also be something to examine.

 

[WarmWaterDiver]

Technology is always on the move - I don't think soapy water is used in these, nor would I consider soaps and detergents in general to be O2 compatible materials.

http://www.rixindustries.com/general.html

And, I think ChickDiver has the most telling story captured in a thread on this board on compatibility of general lubricants and O2 when the heat from adiabatic compression (such as sudden exposure to full tank pressure, like when opening the tank valve to your first stage) occurs.

http://scubaboard.com/t49915.html

And, dessicant will get warm even when absorbing water vapor - this is when the greatest temperature rise is seen, as the heat capacity of vapor is significantly lower than liquid, as well as the specific volume. Slightly damp dessicant is typically the most troublesome. But the potential for an internal first stage regulator freeze-up is what I was alluding to, no matter if the breathing gas is Grade E air or O2 Compatible air when diving in colder waters - the dew point of the compressed gas must be adequately low for the conditions you're using (including tank pressure). The compressors are compressing ambient air in the scuba shops I've seen, including the absolute humidity of the suction gas (air). Here's a link to a more in-depth discussion.

http://scubaboard.com/t47081.html

 

[chrisch]

Pescator, thanks for the clarification. In respect of carbon dust you have a point - sorry if this was what you were getting at earlier.

The club with whom I used to dive in the UK had a seperate air filter to remove hydrocarbons. I cannot remember which model it was (I accept it was not the Beaver model for which I gave a link). I have been unable to find a link to the relevent filter. As per my first post these are not expensive - the Beaver model being an example. I cannot PROVE it doesn't generate carbon particles - this is for the manufacturer.... However, the concern raises a valid point in that (as I said earlier) the filter can collapse due to constant pressurisation and de pressurisation.
So in practice the thing to bear in mind is that the cheap filter isn't perfect and the solution is to use it only if you are concerned about hydrocarbon contamination.

Filters, like all scuba gear should be well maintained. However, your observation is something to take on board - I agree this is the main problem.

My point again is that the "solution" is not expensive. The personal air filter should meet or exceed all requirements otherwise it should not be sold. If you cannot buy one in the US maybe you have the truth (what scuba gear manufacturers don't tell the truth!!) and my post is wrong therefore. All I can say is that I have seen this solution in use and had no problems.

Oil free compressors are great but do not relate to the original question. Happy to talk about them though..

Best

Chris

 

[iain/hsm]

the Beaver model being an example. I cannot PROVE it doesn't generate carbon particles - this is for the manufacturer.... However, the concern raises a valid point in that (as I said earlier) the filter can collapse due to constant pressurisation and de pressurisation.Oil free compressors are great but do not relate to the original question. Happy to talk about them though..Chris

There are two major problems with PP filling using an oil lubricated compressor and a total reliance on filters.
1. Any oil carry over however small will react with high pressure oxygen at sufficient pressure and temperature.
2. Filters by there very nature FAIL.

This is further complicated by the fact manufactures make no statment on the suitability of there products with Nitrox.
READ THE LABEL (This the manufacturer will use in its defence in court). It is labled either an "AIR" Compressor, and your using this together with a personell "AIR" filter. Fine and OK for AIR, however there is no statement of Nitrox or oxygen compatability, just read the label.

"Nitrox filters" No such product exists (in the UK.)
Reason: Any gas with a percentage of oxygen greater than 23% shall be classed as oxygen and oxygen is "Use no Oil"

The only Nitrox compressors or oxygen compressors are either A. oil free B. oil-less or C. use oxygen compatible lubricants such as Perfluoropolyethers in compressors suitably designed for this type of lubricant. Oxygen compressors compress "dry" gas and as such have no interstage separators and filters only Nitrox compressors that "entrain" ambiant air and LP oxygen require filtration and this is then designed towards the removal of water vapour not long chain hydrocarbons.

On a personel note I thought Beavers made great dams!!
Regards Iain

 

[pescador775]

Chris,
was correct on all points, the solution is relatively simple and neither are we talking about oiless compressors. Nor, Iain, are we talking about 'oxygen compressors'. That is irrelevant to the thread.

Chris hit on a point which relates to the US market. Why are we searching for what seems an obvious solution? Either there is no market for an inline filter or the manufacturers in the US don't make any for their own, other, reasons. Or, the filters are available and we haven't found them yet. Or, the European carbon filter is a possible solution.

Brian has a legitimate question and concerns which should be addressed. Personally, I feel comfortable with grade E air for partial pressure filling but only when I know something about the specific details of the system, in other words the overall compessor system is well maintained and not a junkyard dog. That is not an option for the average diver. One is told that his O2 clean tank must never be touched by unclean, unbaptized systems. He doesn't have the option of making independent decisions without years of experience and study. He needs an edge.

Manufacturers would be happy to sell him a 20 pound, $1500 tank dubbed, 'hyper filter, to lug around. I do not believe that this is necessary but cannot offer links to a reasonably priced, suitable product. My experience has been to come up with my own solutions to intractable problems. It's a generational thing I guess. Today's divers need more hand holding. That's what this board is for.

Therefore, I suggest Brian look for a suitable container, perhaps an 'accumulator' or filter canister from a military surplus system. It may. also, be possible to find a used filter canister on "E Bay" or through some other outlet. "Plans and Kit" sells surplus items of this nature. The catch is that an off the shelf filter cartridge from a reputable concern is available to fit. The connections to the canister may require some thought. It looks like one side, the input, will need a short length of hose with a "yoke block' attached. This requires a 1/4" npt connection, so probably the hose will need 1/4 male connections on both ends. The other side of the canister will probably require a yoke or Din screw in connection, again connected to a short length of 1/4" hose. Anyway, the hoses will need to have the correct screw thread to connect to the filter housing (canister) and to the attachments. Most of the fittings are available from any hydraulics supply store or from Compressed Air Specialties. Hydraulic hoses are rather heavy and stiff so I would make that a last place to shop.

 

[WarmWaterDiver]

The discussion regarding oil-less compressors etc. was my suggestion to diverbrian as alternatives to a "portable" filter, as no one has been able to answer on where to obtain such apparatus easily. A bit of pre-trip research (for me, typically through tools like the Internet and e-mail for example) on exact air quality provided by shops in the area of one's destination has worked well for me on these issues, so I'm sharing my experience to assist the original poster.

Hopefully, no harm done to others in educating and disseminating info on an approach that has yielded success.

To each his own.

 

[chrisch]

Hopefully, no harm done to others in educating and disseminating info on an approach that has yielded success.

Agreed totally - as long as we don't confuse people.

Diverbrian - I hope you have found all this helpfull and not too confusing. In practice one or two fills shouldn't cause problems unless the air is very bad. Without knowing whether that is the case we are all speculating...

Enjoy the diving.

Best
Chris