Filling tanks with enriched air

[wunat]

Ok, I am going to ask this stupid question......

When filling tanks with enriched air, does the filling station uses the same air compressor (same one they used for filling air) with special filter/adapter? Or does the station need to have a specialy enriched air compressor dedicated for filling Nitrox?

Is there a device (filter or adapter) which would allow us to fill enriched air into the tank simply by attaching it to the typical air-filling compressor. :huh:

 

[hunter991]

I have one compressor for all my needs. It produces OCA or oxygen compatible air that allows me to partial pressure blend nitrox in the tank by mixing a certain quantity of pure oxygen into the tank and then filling with air. This is one of the ways to product nitrox. If your compressor does not product a high enough quality of air you can buy a special hyper filter that filters the air to the needed level, these are expensive.

Brent

 

[dannobee]

Some will use the "partial pressure" fill method, where pure oxygen is added to the tank, then the tank is topped up with air (hyperfiltered to remove any hydrocarbons). Some shops use a "nitrox stick" where the oxygen is added to the compressor's inlet, along with air. A couple of oxygen sensors are added in the mix to ensure the mix is correct. Some shops will fill up some cascade bottles with, say, 36% mix, then fill your bottle from the cascade system. The latter two methods don't require your tank to be oxygen cleaned. The first method requires the tank and valve to be oxygen cleaned, otherwise the tank might go boom.
They all can use the same compressor.

There are two other methods which can be used, but are less commmon, pressure swing absorption and nitrox membrane. They both involve pushing low pressure air (~150 psi) through a medium and removing the nitrogen from plain old air, then feeding that mixture into the compressor. These methods don't require oxygen bottles from a cascade or otherwise, but are more expensive initially.

 

[kjundvr]

From my experence it depends on wht type of system the shop is using. If they are filling Nitrox via partial pressure blending they they ususaly have a seperate filling station. However some areas which use a continuious flow blending system (basicly filters nitrogen out to achieve a higher O2%) can use the same filling station for both air and nitox. This is the system that you were hinting at. several companys make these systems

 

[pescador775]

In order for a compressor to pump Nitrox, this gas must be fed to the machine's inlet port which is then compressed like normal air before being fed to the Scuba tank. There is no device or filter which can be attached to the compressor output which will then produce Nitrox from high pressure compressed air.

 

[SparticleBrane]

continuious flow blending system (basicly filters nitrogen out to achieve a higher O2%)

I have always been under the impression that "continuous blend" to make nitrox is when oxygen is added to the input of the compressor at a predetermined rate, ie continuously blending the oxygen into the air, thus making nitrox. I believe you are referring to membrane separation.

 

[oxyhacker]

Membrane separation is essentially the same process as continuous mixing as far as the compressor is concerned. Only difference is where the extra O2 is coming from, whether it's being selectively filtered from the air or coming from a bottle. Either way, the mix goes into the input of the compressor, and through the compressor.

I have always been under the impression that "continuous blend" to make nitrox is when oxygen is added to the input of the compressor at a predetermined rate, ie continuously blending the oxygen into the air, thus making nitrox. I believe you are referring to membrane separation.