Pseudo Partial Pressure Blending using HP 300 cuft rented tank?

[nadwidny]

So this is one off and I could not find a thread that was similar.

It makes sense to me why the tank needs to be Oxygen Clean - you will be filling directly from the O2 to the Scuba Tank - slowly and cleanly.
What I don't understand is why the compressor or fill station if it is pumping Grade E air after the O2 has been transferred but is not O2 Clean is required... Is there a resource or a simple explanation for why the fill system to be O2 Clean?

Grade E is a s*** standard to go by. I can produce Grade E from my bicycle pump. Something like the Canadian CSAZ275 will give you a better idea of whether or not the air is OK. However you would need to see a recent air report to see whether or not the compressor is capable of producing OCA air (which is a made up standard by the scuba agencies BTW).

 

[rcontrera]

Just a silly FYI ... while many fire station air systems will put out grade E air, they are only required to meet grade D.

 

[KDAD]

@tbone1004 would @Basking Ridge Diver be able to make up a semi portable stick system as his compressor is at a location other than where he may be storing the O2 tank? An adapter from his stick system to the compressor can be added in when in use? In the thread title he mentions using a 300 cu ft tank for the o2. Seems to be a large tank to transport around to fill tanks and I suspect he won't be able to leave that tank at the station. Would this make pp blending a better method in this situation.

 

[tbone1004]

@tbone1004 would @Basking Ridge Diver be able to make up a semi portable stick system as his compressor is at a location other than where he may be storing the O2 tank? An adapter from his stick system to the compressor can be added in when in use? In the thread title he mentions using a 300 cu ft tank for the o2. Seems to be a large tank to transport around to fill tanks and I suspect he won't be able to leave that tank at the station. Would this make pp blending a better method in this situation.

yes he will have to PP blend. Unfortunately that is what I'm doing as well but it is because I have an O2 generator/compressor that gets me basically free O2 up to 2600psi *works same as a membrane so there is a bit of argon in there*, and then I have free access to an SCBA fill station at a fire department that is across the street from the plant where I'm engineering manager. I have a great relationship with the Fire Chief as well as his compressor mechanic so it's actually much more convenient for me to PP blend and fill my tanks there than it is to run my gas compressor at home.

If I had more foresight when I bought my trailer, it would have twin axles and I'd put the storage bottles in there, but alas, it's only a single axle

 

[Basking Ridge Diver]

thread title he mentions using a 300 cu ft tank for the o2.

Reading my mind... lol I used 300 cu ft as it was the largest tank they had at $43 a cylinder. They scale back from 300 cu ft but I wanted to see where and from whom I can get the tank - I am closing in on my sources.

But I would have to transport anyway I believe - I would not want to put 100% into the scuba tanks at this point due to multiple failure points including the scuba tank - (cross contamination of O2 clean) .
What appears to be the safest method is to mix the O2 with air using a "mixing stick" and then introduce that less than 40% into the compressor leading into perhaps a 300 cu ft 6000 PSI tank for storage. Take that storage tank and use it to fill scuba tanks off a whip with a pressure gauge. I am still learning and I need to read up further... but it appears I can avoid Oxygen Clean scuba tanks and regs using this method.

 

[Basking Ridge Diver]

so it's actually much more convenient for me to PP blend and fill my tanks there than it is to run my gas compressor at home

So I may have missed it - you do all the mixing at the firehouse? or you mix at home and top off with air at the firehouse?
Thanks

 

[KDAD]

With pp blending (including a booster so that you can use the remaining 1000 psi in his oxy tank) you would use an o2 tank at home connected to a booster to partially fill the tanks and then bring the tanks to the compressor to complete the pp blend ensuring that that air rhere is OCA?

Take a look at this page and see where your compressor is and how you an add in the oxygen and other components to make nitrox. Seems like pp blending.

Different Methods to Make Nitrox

 

[Basking Ridge Diver]

With pp blending (including a booster so that you can use the remaining 1000 psi in his oxy tank) you would use an o2 tank at home connected to a booster to partially fill the tanks and then bring the tanks to the compressor to complete the pp blend ensuring that that air rhere is OCA?

Take a look at this page and see where your compressor is and how you an add in the oxygen and other components to make nitrox. Seems like pp blending.

Different Methods to Make Nitrox

I have looked at that site and determined it is still a "risk" using 100% O2 and you are "cross contaminating" the tank using Grade E and O2 - but this maybe easier and more efficient. Oh and the "The Nitrox Stik is available for purchase for $2300 (up to 30 CFM compressors)" pricing is a bit higher than I wanted...

Mixing Stick

 

[tbone1004]

So I may have missed it - you do all the mixing at the firehouse? or you mix at home and top off with air at the firehouse?
Thanks

I mix at home and fill at the firehouse since my O2 compressor is SUPER slow, so it stays on overnight to fill a single bottle all the way up and then I transfill. I'm trying to find some O2 storage bottles that I can use since I'm not looking forward to trying to take the valves off and replacing them for the CO2 storage bottles thta I have

I'm trying to work on getting a key to the second fire station, and if I can, then I will set up a mix stick on their second compressor, and set up my own set of bank bottles at the fire house. It's a liability risk for them to have any modifications to the new compressor which is the one they use for SCBA filling. Realistically though, that's going to be more trouble than it is worth

 

[KDAD]

Could a portable OCA filtration system be made up that can be added onto the end of the fill whip at the firehouse to ensure OCA air goes into the tanks? Doesn't seem too difficult. Once that is made up the ongoing part of o2 cleaning valves and tanks would have to be done but that isn't too bad either.