Filter Stack Plans/Design

[divingtactics]

Thanks again Iain,

What is the benefit of two short double stacked filters in series within the 33-inch tower? Is is that you could replace the first one more often than the second? Would you have the first one with only dessicant 13x and the 2nd with dessicant 13x and activated carbon? I too like building stuff but as I mentioned, external casings I'll just buy to be safe.

I suppose the little compressor will just have to run for a few minutes before the cracking pressure of the 2nd PMV is achieved - I do tend to run it for at least an hour now anyway when I'm filling the banks. I generally fill the banks and then the tanks off the banks, not the compressor.

How long would you suggest to flush for and how long is a long lay off?

So from what I am understanding, it should be fine to use the non anodized aluminium filter insert that I had made for the Hopcolite only filter then and check it every year or so.

I bet there are a heap of divers out there using their little compressors/filters well beyond their expected lifespan, never knowing what the real air quality is like and not having any additional filtration beyond their P21's. Where I initially thought that the little Undersea filter would be better than nothing - without a downstream PMV, it has no dwell time and is fairly useless. I certainly am learning a lot. Do you think it is okay to mod the P21, so it has an empty cartridge in it and is used as a separator only if a 33-inch tower is used?

Thanks again for your time.

Jason

 

[iain/hsm]

I should say all this is my personal opinion and nothing to do with the works.

1. Double stacking needs a lot more discussion, later
2. Hopcalite needs to be very dry so a non anodised holder is fine.
3. From memory the 33 inch tower is about a 1.3 ltr water capacity cylinder.
So about a 10 cubic foot factor in say 2-3 minutes flush after standing idle.
but do it at working pressure 3000psi and drain at your panel drain.

With my personal 3cfm compressor (Rix SA-3) I am more interested in a balanced system, one that maximises the efficiency of the filter but also at the lowest running cost. I still stick to a 5 filter per year change out regardless of use.

So in your case, a low hours user I would stick with the P21 as a chemical filter.
Using the P21 as a separator IMHO only really kicks in with high hours use. Your 40 hours use per year it is pretty much perfect for the four (4-5) filter changes a year.

Now we could argue the benefit of using cheaper throw away cartridges or even the even cheaper repack route but for that again IMHO you have to factor in not only the cost of the chemical but the type brand and source.

For example most 13X molecular sieve from China is pretty poor, most others are more suited for glass applications. Same again with activated carbon or charcoal most we see in UK is designed for aquarium use, it works OK but only half as well as the coconut husk carbon at the same price.

I of course make no comment on the US suppliers but in the UK we are plagued with low cost supplies, and the independent throw away cartridge suppliers don't help by putting in rubbish cheap ineffective chemical. Then again on disposable cartridges there is little incentive for them to provide any long lasting chemicals.

Although its a dollar and cents call on the chemical cost, I would also work to factor in a regular four to five times a year maintenance with a filter change. Also don't even it out, say a new filter at the start of the season say Easter, then every 5-6 weeks during summer then trail off to say 10-12 weeks during autumn winter. A compressor log and a visual water vapour indicator is essential.

I mark the filter stainless steel rain cap with a black Chinagraph pen the date done and below in big letters the month I will change. The visual indicator give me the purity of each fill at the point of dispensation and the compressor log history the validation of the system.

With a dedicated filter change out and the hours run you compressor does should give you the information needed to size up the perfect size filter.

On the large 33 inch it 's cost for length is the attraction half the price of the Bauer
but the MAKO male spigot may be a pain in Australia. You can also get them with the Bauer female spigot, and a small Bauer to MAKO adaptor so best of both.

But the idea for consideration of a long 33 inch filter tower with inside with a short self packed cartridge or throw away. The empty space to fill is the issue. I cant remember the water capacity of the 33 inch tower but I can easily fill one with water and let you know. As for stacking there are a few more factors that need discussing before you go ahead.
Iain Middlebrook

 

[divingtactics]

Okay, all good information, thanks again Iain.

So I am thinking of adding the following in this order:
* P21 output
* Check valve (to keep pressure in tower when P21 is bled)
* 33-inch tower (for main filtration - filled with 13X MS and AC)
* Bleed valve (for bleeding when I change the tower filter)
* Moisture visual indicator 20/40/60 (to indicate earlier change of filter as required - I thought it better here to keep ensure the Hopcalite is always dry)
* Hopcalite in Undersea filter housing (to remove ambient CO)
* PMV set to 150 bar (to increase dwell time in tower)
* Check valve (currently there already to stop Oxygen travelling to filters when PP filling through manifold)

Is there anything you would add or any order you would change? I think that I should be able to drain my panel manifold down to zero bar at the end of filling and the final PMV should close at 150 bar, thereby keeping the tower under constant pressure.

I do have an electronic hour meter on the compressor and a log to signal filtration changes. To date, I've been changing the filters every 15 hours, which is double what I should be doing but none of the 13X MS has been wet and only the first felt pad has ever been a little damp, but not saturated. This has become less and less since I fitted the auto dump solenoid valves. Do you think I should still stick with 15 hours or change them every 7 as suggested by Gabe Kaplan and IyaDiver in the other post on filtration?

All of my chemicals, I get here locally in Australia from Pro Diving Services but I don't know their original origin. These guys do a lot of commercial work, so I'd hope they use high quality materials but will check. The 13X MC is small round balls about 1.3mm diameter I suppose and the AC is chips of irregular size but nothing longer than probably 5mm. The Undersea filter uses MC which are tubes and the AC are small balls about 4-5mm diameter.

Having high quality breathing air is more important than the cost of maintaining it in my case, which is why I bought the Kitigawa system and started this quest for better filtration. Money is no good to a dead man.

Thanks,

Jason

 

[divingtactics]

Another concern is your media. You should check the activity of your desiccant (should be using 13x desiccant) go outside and put a spoonful of 13x in your plam, then add 1/2 spoonful of water. If you can hold the media in your hand for longer then a second or two, the media is bad.

Hi Gabe,

I did the tests that you suggested on the 13x MC, and did three tests:

1. Tested old used 13x MC from the P21 repack - result was that it generated no heat and I could hold it in my hand indefinitely.
2. Tested old used 13x MC from Undersea inline filter original - result was that it generated no heat and I could hold it in my hand indefinitely.
3. Tested new unused 13x MC that I have had for 2 years stored in a plastic container - result was that as soon as I poured it into my hand, I could feel it warming - then as soon as I tipped the first water droplet on to it, I had to throw it on the ground as the heat was intense and instant. So from this test, I can see that the 2 year old stuff is still okay by the look of it - although some seem to suggest that it is no good after a few months. I'd be interested to learn any other testing methods for 13x MC.

The old used 13x MC has been sitting in a rubbish bin for a month or so, so it may have expired there too. Funny thing is that visually, the new stuff and the old stuff looks that same, so you can't tell by looking at it if it is okay or not but this has been a worthy test.

The other thing that I can confirm is that there is no channeling going on in the repack. It is a dedicated repack cartridge, not an old Bauer one. It has a stainless mesh, felt pad, AC, felt pad, stainless mesh, 13x MS, felt pad, stainless mesh, spring, cap. When I fill it, I do it slowly and tap it gently to ensure that every gap is filled. Then I push the felt pad down firmly with some pipe and then do the same again for the 13x MC. When I remove the cap for repacking, the 13x MC is indented quite deeply on the felt pad, same with the AC. So I think all good there.

Thanks,

Jason