Molecular Sieve Orientation

[shamu]

Here is a picture of my shoebox setup. My Dewalt compressor feeding the large air dryer is off to the side so not in the picture. My question is Why do some people say that my Diabolo sieve (red filter) at the Shoebox outlet needs to be placed in the vertical? I cannot figure what difference it would make compared to it lying on its side.
Just curious.

 

[Trucker3573]

You want the water to collect in the bottom not in the molecular media itself as it (the media) is really only meant to filter vapor. The media will become full very fast on its side.

 

[Trucker3573]

This video explains filters well.

 

[shamu]

Thanks Trucker, very informative

 

[rcs9250]

I had the same drier that Brancato showed in the video. In the photo below I show how it is vertically mounted on my bench. The airflow is shown with the red arrows show the airflow direction. The air actually enters into a tee fitting at the bottom. One side of the tee threads into the drier. One side is the air entry. And the very bottom of the tee has a purge valve that I used to crack open every couple minutes to drain any collected water. The green arrow is the purge valve.

 

[shamu]

Very nice setup. What compressor do you have. Is there another dryer in the system?

 

[nervoustrig]

If lying on its side, the beads settle and leave a gap at the top where humid air can simply bypass them. That cannot happen when the canister is oriented vertically.

 

[rcs9250]

Very nice setup. What compressor do you have. Is there another dryer in the system?

That drier was on my Omega Air charger. The compressor also had a drain it as well. I now own an Alkin W31 because I anticipated more use. I fill two 74 cu ft carbon fibers with the Alkin.

 

[JimD]

When the air comes out of the compressor it is hot. It can carry more water when it is hot. As it goes through the lines and the filter it cools and water condenses. If you lay the filter on it's side, the water condenses in the filter and loads up the dessicant. If you put the filter vertical, the water drains back to the compressor where you can vent it. I vent every 5 minutes and my dessicant lasts a long time.

 

[shamu]

I understand most of the above feedback and really appreciate your help. Here is what I have found with over 400 hours of shoebox use. My Dewalt compressor feeds the shoebox with 125 psi air which goes through a large Wilkerson air dryer. As you may know the air flow is quite low. My Diablo molecular sieve is at the outlet of the Shoebox. I recharge the Wilkerson dessicant when it turns orange about 1/3 of the way up. I also open the Diablo and recharge the molecular sieve at the same time. In the past 5 years I have never found a hint of moisture in the Diablo. The only explanation I come up with is that the Wilkerson must put extremely dry air into the Shoebox. Any other thoughts?

 

[rcs9250]

It sounds like you have a good effective set up, along with your vigilance.
The Wilkersons seem to be taking every bit of moisture out of the air that they are designed to.
I went back and looked at your Wilkerson. That is a big one. I wonder if that is the secret. To my knowledge, that type of separator relies on the air to swirl and centrifugally sling moisture to the bowls wall. In addition, your shoebox pulses the air as it used by the workings which adds some dwell time to help the air cool additionally, allowing more moisture to drop out.
Nice job.

 

[Smudgerii]

Hi

I’ve recently bought the GX3 and wondered if it is possible to add a drier to the intake, it is WET here in Manchester UK even on our best summer days…

if it is possible, what do you guys recoomend as a set up?

 

[rcs9250]

Basically worthless, but people do do it and claim it helps. YMMV.
For a molecular sieve to work, it requires a “dwell” time in the beads. The compressor breathing at intake is a slightly negative pressure. The beads work in positive pressure... like 1600psi.
I worked 10 years in a dive shop maintaining their compressor. Their were times when humidity was in the 90%
vicinity. I was required to test for humidity, CO and oil and never once in 10 years did it fail. The intake was a filter like on a lawn tractor.
The best way to insure dry intake is to use nitrogen. Problem solved.

 

[AlanMcD]

I use the exact same Wilkerson dryer on my Shoebox set up, and like you there has never been a hint of water on the exit. I don't run any post compression desiccant filtration because once the water vapor has been removed from the air to a sufficient level, it is gone and there is no way for water vapor to re-enter the compression path. That filter is rated to dry the air to an atmospheric pressure dew point of -45 degrees F while flowing air at 10 cfm, and we are flowing air through it at less than 0.25 cfm, so it is more than up to the challenge. I've verified that no water makes it into my tank by inspection after flowing more than 50 cubic meters of compressed air into and through a Guppy tank, and there were zero signs of water ever being in there. Mathematically there could have been a bit of water in there (based on the -45 F dew point, about 0.01 gram per cubic meter of air might be possible), but I attribute the lack of it to the extremely slow air flow rate and thus very high dwell time in the filter.

The one thing that I might suggest you do to your set up is to add a ball valve as a shut off on the input to the filter that you can close between uses - these filters will suck moisture out of the air feeding them so efficiently that they will draw moisture out your shop compressor and shorten the time you get on them between recharges. We can also shut off the air flow on the compressor end by just pushing in the pistons when the compressor is done - that way your desiccant will last longer. I get hundreds of hours of runtime out of mine this way. Also, it can be good for the o-rings to include a micron filter as the last step before air enters the Shoebox - desiccant beads can throw off dust, especially if any liquid water comes into contact with them (they basically explode from the heat of rapid water absorption). This can help your Shoebox run longer between rebuilds.

 

[AlanMcD]

Hi

I’ve recently bought the GX3 and wondered if it is possible to add a drier to the intake, it is WET here in Manchester UK even on our best summer days…

if it is possible, what do you guys recoomend as a set up?

As others have implied, removing all water vapor from air before compression is difficult because there can be so much of it (but it is not impossible). A cubic meter of air like you describe could have close to 20 grams of water vapor in it, even though you can't see it! It would take a huge amount of desiccant to accomplish the task.

That said, if I wanted to do it, I would do it this way: the first thing I would do is try to draw my air source from a cold place, because when air is chilled water vapor is removed (most commercial high flow air driers use chillers). If you could draw the air out of a freezer that is running, that might remove about 75% of the water vapor right there - of course that does mean that it will form frost in the freezer, so more defrosting (or defrost cycles) will be needed on the freezer. And also air would need to be able to get into the freezer to replace what is being sucked out. The best way to do this might be with a closed path of air flowing through a cooling coil or radiator placed in the freezer - then there would be no buildup of frost in the freezer either . . .

Then I would feed that air through a still large desiccant filter that I would make with PVC pipe - may 3 to 4 inch in diameter and about 2 feet in length, thus holding several pounds of desiccant. And I would put a regular filter after it to trap any dust or dirt too. Part of the reason for for going so big is to reduce the airflow resistance into the compressor - I'm sure that if the resistance is too large it would be bad for the compressor . . . but I don't know. Worst case one could feed the air path going into the hose going into the freezer at a few psi, perhaps regulated from a shop compressor . . .

Of course if one were to do that (feed with a shop compressor), they could just use the shop compressor as the first stage of drying just like us Shoebox users do - once the air has cooled off after being compressed to about 100 psi, about 90% of the water will condense out there. That is one of the things that makes getting dry air so easy with a Shoebox, as we have easy access to dry the air after the first stage of compression, which is probably the most efficient place to do it overall (it dramatically reduces the amount of desiccant needed, without increasing the time needed to compress air into the tank by "wasting" time spent filling the desiccant filter with fully pressurized air). So if you could regulate it low enough at the right flow rate, you could feed it into the same dryers we Shoebox users are using - that Wilkerson unit is great.

Anyways, that is how I would go about it. Hope it helps

 

[shamu]

Wow, you guys have done your homework. All makes great sense, thanks. Only wish a reliable source of shoebox parts was still around.

 

[rcs9250]

As others have implied, removing all water vapor from air before compression is difficult because there can be so much of it (but it is not impossible). A cubic meter of air like you describe could have close to 20 grams of water vapor in it, even though you can't see it! It would take a huge amount of desiccant to accomplish the task.

That said, if I wanted to do it, I would do it this way: the first thing I would do is try to draw my air source from a cold place, because when air is chilled water vapor is removed (most commercial high flow air driers use chillers). If you could draw the air out of a freezer that is running, that might remove about 75% of the water vapor right there - of course that does mean that it will form frost in the freezer, so more defrosting (or defrost cycles) will be needed on the freezer. And also air would need to be able to get into the freezer to replace what is being sucked out. The best way to do this might be with a closed path of air flowing through a cooling coil or radiator placed in the freezer - then there would be no buildup of frost in the freezer either . . .

Then I would feed that air through a still large desiccant filter that I would make with PVC pipe - may 3 to 4 inch in diameter and about 2 feet in length, thus holding several pounds of desiccant. And I would put a regular filter after it to trap any dust or dirt too. Part of the reason for for going so big is to reduce the airflow resistance into the compressor - I'm sure that if the resistance is too large it would be bad for the compressor . . . but I don't know. Worst case one could feed the air path going into the hose going into the freezer at a few psi, perhaps regulated from a shop compressor . . .

Of course if one were to do that (feed with a shop compressor), they could just use the shop compressor as the first stage of drying just like us Shoebox users do - once the air has cooled off after being compressed to about 100 psi, about 90% of the water will condense out there. That is one of the things that makes getting dry air so easy with a Shoebox, as we have easy access to dry the air after the first stage of compression, which is probably the most efficient place to do it overall (it dramatically reduces the amount of desiccant needed, without increasing the time needed to compress air into the tank by "wasting" time spent filling the desiccant filter with fully pressurized air). So if you could regulate it low enough at the right flow rate, you could feed it into the same dryers we Shoebox users are using - that Wilkerson unit is great.

Anyways, that is how I would go about it. Hope it helps

I like it. One thing you could do is maybe use a shop vac hose inside to freezer, maybe six or eight feet long. Room permitting of course in your freezer box.
Typically the sidewalls of a freezer are just insulation but you want to verify before boring a hole. Then work out your connection to your compressor intake.
One thing I would also add is a Magnahelic gauge or U tube manometer to assure you aren’t pulling a negative pressure. Good job.

 

[Ca_Varminter]

 

[Bleudg]

For my air charging system, I am also using a Shoebox compressor. It is fed from an oil-less air compressor at 125 psi. The air flows from the compressor and travels through a coalescing filter, air/water separator, a refrigerated air dryer with an auto moisture drain. The air then passes through a large Wilkerson desiccant dryer and into a small filter to catch any carryover desiccant dust and then into the Shoebox suction. As mentioned by AlanMcD the Shoebox being a booster, allows you to use more methods/devices on the inlet side to remove water from your system before the air is compressed to High pressure.

I have around 200 hours on my system. I use to check my filters, tank and gun internals at regular intervals (25 hours). Since I never had any observed problems I slacked off and haven’t done an inspection for several intervals.

When I saw this thread I decided to inspect my Diablo filter. I found no signs of water or corrosion of any kind. Although the pictures show my Diablo filter laying horizontally, I agree with Joe, and have since installed it vertically to prevent air bypassing and possible moisture saturation of the filter beads. I also included a picture of my Diablo filter internal bore.

 

[Beer Nap]

Also a filter such as the Tuxing has a air in and a air out end. The aluminum cap looking part of the inner filter is the air out end.