newbie tank question regarding moisture

[Doc C.]

Hope this is not a silly question.
I have read with great interest this forum regarding compressors, tanks, and moisture.
My question is two fold. One, how do we know that the shop who fills our tanks are pumping "dry" air to our tanks. What if they do not let them cool and then top off?
Condensation occurs?
Second, why doesn't anyone use a water trap or separator between the tank and the gun? Or have I missed something obvious?
Doc.

 

[HogKiller]

Those of us that have Tuxing have water separator's, I'm sure some may be getting through, but I hope not. I haven't seen any sign of moisture in my gun, I am concerned about moisture in the tank, now between the tank and the gun....you'd have to keep it under pressure all the time or you'll lose a lot of air

 

[Gerry52]

If you're confident of moisture removal when filling tank you don't have to worry about tank-to-gun. Dive shops (by law) have to have extremely efficient moisture removal as they ONLY deal with BREATHING quality air. The legal ramifications help to keep them doing the right thing.

 

[elwoodblues]

Breathing quality air is NOT DRY, if the moisture content is too low it dries out your respiratory system, The compressed gas companies would love to make reconstituted air from 99.95 nitrogen and 99.95 oxygen but it is too dry for continued use.

 

[Camaro454]

I could not say one way or another about Diving air water content but found this on a Scuba diving page....for what it's worth.


The CGA grade E (scuba air) and grade D (scba air) standards both specify <67ppm water vapor, which is about .007%, or a dew point of at least -50F (not C).

A decently maintained shop air system will produce air this dry, and if it doesn't, then a probablity exists that the filter stack has become saturated, and it is also letting oil and other contaminants by, bad news indeed.

 

[rcs9250]

Dive shop air, in a properly maintained (emphasis on properly maintained) has minuscule water vapor. Dive shops pump Grade E, FD compressors only have to be Grade D. Grade D allows a touch more moisture because their regulator on their breathing apparatus are not subject to potential very cold water that divers can experience which can cause a scuba regulator to freeze and then free flow.
Various dive training agencies that many dive shop operate under are required to have an air sample analyzed quarterly and posted in their operation. If you are curious about their air look for the certificate, it is often posted where the fill tanks. If you don’t see it, ask to see it. Most dive shops, except in third world countries, don’t want to risk pumping wet air. But then they would most likely be the only ones that knew since they do the tank inspections as well. But if I were a store owner it would be idiotic to risk an employee telling someone that they are pumping sub-standard air.

 

[Doc C.]

Thanks for the information.
My concerns come from the fact that the closest dive shop to me,(15 miles) is loacated at and in a boat dock on the lake. Not exactly a dry environment
to compress air. The next shop is 35 miles away.
I was wondering if a water filter on my tank would be a good idea or even necessary.

 

[rcs9250]

Thanks for the information.
My concerns come from the fact that the closest dive shop to me,(15 miles) is loacated at and in a boat dock on the lake. Not exactly a dry environment
to compress air. The next shop is 35 miles away.
I was wondering if a water filter on my tank would be a good idea or even necessary.

The fact that they are located on a dock doesn’t matter. Air compressors for dive shops are located all over the world in the most humid conditions and are able to pump Grade E air, no problem. That of course is if they maintain their equipment. About the only way you can check is to send a sample of the air from your tank to a analysis company.
It requires that you flow air for a specific period of time ( something like five minutes continuous) through a filter disk and bottle. Send in both and they check for oil, water and carbon monoxide. Obviously you aren’t breathing it so all you’re concerned with is water vapor.