Filter Stack Plans/Design

[divingtactics]

Just wondered if anyone had some plans that I could use to have a filter stack made. I currently have a P21 (PZERO) and an inline Undersea personal filter with a similar capacity connected permanently in my panel being supplied with a Bauer Oceanus. I did some air tests with Kitigawa tubes and found that CO2 was high and moisture levels were higher than spec.

Filling inside a room that is part of my garage, so will route air intake from outside to hopefully cut the CO2 down - it was around 2300ppm, should have been 480ppm.

Water vapour was over 160, should have been 50.

Using medical regulator with variable flow rate, have checked flow rates are correct in accordance with the Kitigawa requirements.

Test was done at 15 hours life of filters just before a change. So I'm thinking that I will add another much larger filter in.

Plans, recommendations, suggestions all welcome.

 

[GKaplan]

Hi DivingTactics,

I work for Lawrence Factor and I reviewed your post with our Filtration Technical Manager Mike Casey. Here are his thoughts. The Oceanus is rated 4.9CFM and your P21 Filter system should provide enough filtration to produce clean air, so long as you are replacing your filter according to a proper schedule. If you are over using your filter, this could be the cause for high moisture and CO readings. Now, here is the kicker, Colormetric Tubes are unreliable for testing your air quailty and also do not provide back up documentation if a law suit should ever arise. Here is a link to some more information on this. http://www.lawrence-factor.com/Library/ColormetricTubes.pdf . Here is another thought, you explained that you added another tower, if you did not add a check valve between the two towers as well as a priority valve after the final filter then your system is open to ambiant air and has moisture bleeding between the two filters. So that could be another cause for your irregular readings. All in all, your test is unreliable and that is the first place to start. There are many scientific air testing labs that can provide this service for you, we are one of them.

I hope this helps, Contact Mike Casey at mcasey@lawrence-factor.com to look further into your filter schematic and possible issues.

Thanks!
Gabe

 

[divingtactics]

Thanks Gabe,

I appreciate your response and advice. The paper makes interesting reading but I'm located in Australia, so it's not practical for me to send you an air sample for testing. I change all my filters at 15 hours and the average filling temperature of the room is around 25 degrees C. I will add a check valve and additional pressure maintaining priority valve into the system as suggested.

Kind regards,

Jason

 

[Peter_C]

I change all my filters at 15 hours

:shocked2:

You realize there are business that run their compressors more than that in a day? You are probably over servicing your compressor.

 

[divingtactics]

Filter life is proportional to filling temperature, so at 25 deg C, they don't last as long as they would at 10 deg C. I refill my own anyway, so I don't mind being a little on the cautious side. I am actually thinking that I may change them every 10 hours, given what I've been learning lately. My filter media is not wet at change time, but I like to err on the side of caution. I tend to think that a lot of shop compressors are not serviced nearly enough, despite regulations, so using a shop is maybe not the best example to compare.

 

[ErikH]

:shocked2:

You realize there are business that run their compressors more than that in a day? You are probably over servicing your compressor.

They use a different kind (larger and designed for longer runtimes) of compressor and filter. The P21 is indeed only for ±15 hours of use. They are relatively cheap though.

 

[GKaplan]

Hi Jason,

Thanks for the additional information. Actually, changing the filter every 15 hours is not often enough. I will show you the math for your single P21 tower only. If you want us to adjust for your second tower, I will need to see a schematic of your system.

So, Bauer's suggested calculation for filter life is Processing Capacity (3200 at 68'F for your P21) Divided by CFH (the CFM of your compressor times 60). This shows you the maximum life of your filter at 68'F. Then you adjust for tempurature (multiply by .65 at 80'F, .58 at 86'F, .455 at 95'F, and .34 at 104'F).

Your max filter life is 7 hours and you must change out your P21 filter every 7 running hours so long as the system is functioning properly without leaks and all peripherals are adjusted properly. Again, I will need to see a schematic to account for your second tower and adjust your processing capacity.

Now, the next issue that comes up is repacking. very seldom is filter repacking done properly. The easiest way to check if you are packing your media tight enough is by checking the filter during removal. If the old filter has a gap between the media and the top of the filter then you will get air channeling. Simply put, the air will not be forced through the media and instead will find a channel to pass through without being cleaned.

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.

Any or all of these might be contributing to your test results.

I'd be interested in seeing the schematic if you want to email it. My email is gkaplan@lawrence-factor.com

Thanks,
Gabe

 

[IyaDiver]

Hi Gabe & Jason,

Jason, your P21 uses a 68 grams cartridge ( no hopcalite ) and at 25C ambient and 40C final temperature, indeed it is only 7.4 hours filter life at ur 140 liters per minute Oceanus.

Depending how much you are pumping a month, if I were you and if I do 40 hours a month, I will use LF65247 filter cartridge size and this has hopcalite for CO removal. Its 27" size and best bang for the buck and not to mention higher air quality a small P21 can not ever deliver no matter how healthy your compressor is.

Jason, LF65247 is equivalent in size to Bauer P61 ( your market ) or a P2 ( USA market ).
No it is not too big if you can use it up within 3-4 months. Its life is 134 hours at 25C ambient and final 40C temp with 140 liters per minute compressor. Its approx 16 times more media ( and has hopcalite ) compared to a P21. Price wise its so cheap for its size/capacity. In fact I like it better than Bauer 58827 ( used in P61, has Hopcalite ) because it has more activated carbon.


Gabe,
You don't need his schematic for his Oceanus with a P21 output. The output is a Unimam fitting for all Bauer except USA market ones. In a Bauer USA version that fitting outputs a 1/4" NPT female.

Design him a wall mounted tower or stand alone tower with all the PMV etc etc and humidity plug. Supply him that Bauer USA version of male BSPP to 1/4" female NPT and the USIT ring for his P21 output. 2 meter hose with 1/4" NPT male hose ends, one swiveling & one static for connection of his P21 to bigger tower.

Add bleed valve at bigger filter tower entry before check-valve for input hose removal.
Add adjustable relief valve after check valve as insurance if his P21 final safety jammed up.
Bauer P21 used as water separator only with a dummy emptied out P21 cartridge.

At the output of the bigger filter tower PMV add a line valve to make sure air pressure can be kept ( Bauer filling assy may leak a bit over time ).
After line valve get a 1/4" male to 1/4" BSPP female fitting for Jason to use his original Unimam fitting ( the one removed from P21 ) and he may then use his Bauer original filler assy ( US$500 value ). Talk to Porter at August Industries, he knows what I mean on this 1/4" male to 1/4" BSPP female and that Bauer USA version of P21 output fitting with female 1/4" NPT.

Good luck guys........

IYA

 

[divingtactics]

Very interesting discussion, thanks Gabe and Iya for your useful information.

If it makes it easier, attached is my current set up.

As mentioned, I do intend to add a PMV after the Undersea filter, but I'm inclined to get rid of the Undersea filter and use a larger one like you have suggested Iya.

I should add that the intake to the compressor is only connected to the Nitrox stick if I am using the sticks, but with the booster now, I tend not to bother with the sticks. Air intake will be routed from outside using 3 inch pipe in about a weeks time.

 

[IyaDiver]

300 feet dive......02 booster pump and all......dang, scare the crap out of me.......

Good luck shopping and dive safe Jason.
.