Check Valve - Need Help Installing on Alkin W31

[realdiver7]

Hoosier....thanks for the first-hand info. I understand adding extra filtration can cost quite a bit and be somewhat involved when trying to keep a system as small as possible. My filling operation is very small-scale and for personal use only, so I don't fill that many tanks. I'll make sure to keep a close eye on moisture issues, especially when I VIP my steel tanks. I have a large thermometer with a relative humidity gauge in my garage and I pump fresh air from outside of the garage, so I know about how high the humidity is every time I pump air. I am prepared to change filter media hopefully not less than every 15 hours, but will change more often if needed, i.e., every 15-20 fills.

You seem to be on the right track with your summations as an Alkin dealer told me that adding larger filtration accomplishes much more than keeping the stock filtration canister pressurized.

If you ever run across a good extra filtration deal, please let me know. I'm willing to make reasonable improvements to my system whenever possible.

Thanks!

 

[Waterskier1]

realdiver7: Very nice job. Which check valve did you get and where did you get it? I think I want to put one in my system.

I think there was a problem with the Alkin's was moisture and maybe even a recall? The moisture problem can be handled with a good separator. Yes, you do have to change the filters a bit more often than if you had a huge canister, but you loose some portability (added weight) and many of us don't fill 100's of hours a year for our personal use. And, keeping the filter under pressure (I'm told that 500 psi is sufficient) your filter will last up to 4 times as long.

You do not need hyper filtered (O2 compatible) air to continuous blend, unless you are filling the same O2 cleaned tanks that will also be used for partial pressure mixing. If that is the case, then you want clean air in those tanks regardless of the O2 percentage. I plan to CB eventually, and will not hyper filter the air afterthe O2 is mixed. That seems silly unless you fall into the above situation. I'll just fill my regular tanks, marked with Vance's Stickers indicating VooDoo Gas, and the MOD, as applicable. That way, if I need to fill them somewhere that doesn't have O2 compatible air (hyper filtered) I can get air fills with no worries. For me, having NITROX is an added benefit, not a requirement. So far, I'm not doing the multiple dives for multiple days or need the additional bottom time when diving in the mountains. When I really like the NITROX is when diving in Caribbean, for 30+ dives a week!

If I am misstating anything above, please correct me.

 

[Hoosier]

One thing.

It has been discussed many many times on the board, but the simple adding 2nd chamber doesn't produce a hyper filtered air.

The simple 2nd chamber is enough for PPB?

Yes. it is, but it isn't a hyper filtered air TECHNICALLY.

To add 2nd chamber isn't ONLY to get a hyper filtered air, but to ensure your air quality. So, it isn't pointless to use the 2nd chamber with CBing set up.

Filtration: filtering a gas.
CBing: Mixing a gas

It is a totally different job.

Just my 2 bar.

 

[rjack321]

I have a WD31 without autodrains. I would say the check valve was completely unnecessary. But hey its done, no biggie.

As far as the supplied "P0" filter goes...

Its too small, way too small. You will go from fairly dry gas to soaking wet gas in less than one tank. I use a 10/20/30% relative humidity disk to gauge when to change the filter (and change it when the 20% turns). I have had my gas analyzed several times and there is significant water breakthru at that time and it happens very fast. The gas is still breathable with no substantive oil breakthru at this time, just off the analytical scale wet with a slight odor.

If you have steel tanks you will be tumbling them often.
If you ice dive you will have significant freeflows.
You may have odors due to wet activated charcoal not working very well.

I would not try to be cheap here, this is part of your life support system. A 2nd filter is a pretty important addition even if you chose to avoid partial pressure blending. It need not be very large since it only removes a fraction of the moisture bypassing the primary filter towards the end of its life.

 

[oxyhacker]

The problem isn't the fact that you have to change the filters more often, it's that the breakthrough comes so quickly that it is easy to miss it - you just don't have much leeway. Just skipping one drain cycle is enough to wipe out some of the smaller stacks, and that means that the odds are very high that, if you use the system long enough, you will at some point be getting some very bad air. Can't remember what the rating is for the PO, but the little Coltri cartridge, which is smaller, is good for about 18OO cf, and a standard one pound (short) filter stack about 13,000 (both under standard, ideal conditions (5000 psi 80F inlet temp), Hoosiers real life numbers would work out to 2,000 to 3000 cf per cartridge ,which seem reaonable as the PO cart is about half again to double the size of the Coltri.

BTW I don't worry much about whether my air is hyper or not. Grade E or better is fine with me, even for PP mixing. I have added an extra media chamber to my compressor, but I make no claims that it produces "genuine" OCA. Just that it produces considerably better air that it would without, and, because if its longer life, gives me a greater cushion apporaching breakthrough.

I don't doubt that keeping a stack pressurized may somewhat improve performance, but the 4x figure seems unlikely. Can anyone substantiate it?

The moisture problem can be handled with a good separator. Yes, you do have to change the filters a bit more often than if you had a huge canister, but you loose some portability (added weight) and many of us don't fill 100's of hours a year for our personal use. And, keeping the filter under pressure (I'm told that 500 psi is sufficient) your filter will last up to 4 times as long.

 

[realdiver7]

After all of the discussion above, I am now convinced that I need extra filtration for my Alkin W31 for my own peace of mind. Where can I buy a new or used 16-32 inch tower that will accept 1/4 inch fittings and Lawrence Factor, or similar filters without spending a small fortune?

Thanks!

 

[rcontrera]

... without spending a small fortune?

That's the real kicker!

Global has a nice little 16 inch tower that can take a LF filter cartridge for about $800-900 depending on dealer mark-up. LF sells the same housing but only in a complete system so it is quite a bit more. In fact there is no shortage of the companies that sell those housings all made by the same guy (who wishes to remain anonymous).

Realistically, you can put together a system by yourself for about $500-700 depending on buzzers and bells.

When I have a customer that asks for installed filtration upgrade on the small compressors, that is a $700 job and I use the same filtration components that the big guys use.

Anything less than that and you are looking at some of the used or custom built systems off Ebay.

Good hunting!

 

[realdiver7]

I found and ordered an unopened surplus 16 in. canister filtration system today that uses Lawrence Factor filters and should work just fine. There have been some very good discussions here, and I appreciate everyone's input.

Edited to add: See details of my purchase in my next post below.

Thanks!

 

[pescador775]

Realdiver, share-- we like deals, too.

Hacker, I know of no theory or experiment which demonstrates that a pressurized filter canister will preserve the contents longer than one which is merely sealed off from the environment. I would like to hear from someone who can explain this. If true, it might be useful to know. My initial impression is that someone has ripped off the 500 psi "rule" for Scuba tanks and misapplied it.

As I see it, the problem with hybrid filters is the bottom section containing the coalescer, a source of humid evaporate. This problem can not be eliminated by pressurizing the canister. That is just wishful thinking.

My compressors use staged filtration with separate coalescer tanks and filters. They are isolated from each other by a back pressure valve. However, a check valve would also do the job. Anybody who wants to know why the BP valve is upstream of the final, don't ask. Tired of explaining it (word).

 

[realdiver7]

Realdiver, share-- we like deals, too.

Ooops, sorry! I got in a hurry and forgot to post the info on my deal today because I had company and was trying to finish up some work for the week. Waterskier1 hooked me up with Jim at Sheldon Sporting Goods, Inc. in Wichita, Kansas. Jim is very knowledgeable and helpful. I believe he said he's been in the dive business since 1954, so he really knows his stuff and I developed a sense of trust in him right from the start.

Check out the filter system at: Shelden Sporting Goods Inc. - High Pressure Air Compressors

It's the third item from the bottom of the page and the canister with fittings is $126. My complete deal with filter, all fittings, high pressure hose and shipping was only $236, which I consider to be very reasonable. I have included a picture below. The updated Lawrence Factor filter is #X282417; not the one Jim has listed right now, but he plans to update the web site soon. He sells all fittings and hoses that are needed to work with various compressor systems. The overall system is approx. 16 inches, but that's all I need for my filling applications.

By the way, following some of the discussions above....Jim did not seem to be a proponent of having to keep the final filtration canister pressurized to prolong filter life. He says if you're going to keep anything pressurized, it's more important to pressurize the on-board factory filter before air reaches the final filter so that moist air does not enter the final filtration stage. He advised me to keep my check valve, priority regulator, and moisture/CO indicator on my small on-board factory filtration canister. I can check for moisture at the final stage on my Lawrence Factor filter moisture monitor strip. Kinda makes sense to me, but I'm sure others will have varying opinions.