Heated regenerative desiccant dryer

Shawn_Laughlin · Sep 22, 2020

I’m wanting to build a twin tower heated desiccant dryer for mill air supply but not sure what size I need to make the towers?

I have some 4” aluminum pipe, 2 pcs I cut to 42”, that I plan to use as my twin towers, using one as the other dries.

I’ve been around a couple decent sized units, like twin 100 gallon tanks to supply a lot of air but this will only supply air to a vf4ss, the rotary and a small blast cabinet. Blast cabinet doesn’t get used much.

Reading manufacturers specs i couldn’t find tower size. Now that I think about it I should’ve been looking for desiccant amount used per tower. Ima look for that but if anyone could give me an idea of much desiccant or tower size they think would be satisfactory please I’m all ears?

It should be shipping from the factory in about a week so I need to have this thing built rather quickly. I would buy one but want to save the money for more tooling and another layer of insulation for the shop “Texas summers are a bitch” Plus I’ve always wanted to build one.

Robert R · Sep 22, 2020

Shawn_Laughlin said:
I’m wanting to build a twin tower heated desiccant dryer for mill air supply but not sure what size I need to make the towers?

Does the machine warranty require dried air with a specified dew point or is it sufficient to use a coalescing filter which will remove 99% of 0.1 micron sized and larger drops of water, oil, and grit ?

Desiccant air dryers are needed for laboratory equipment to reduce light attenuation or for air bearings to eliminate corrosion. They can produce air with a -100 deg F dew point.

As long as there is no condensation at the machine tool the water vapor in the air stream should not be a problem. A home made room temperature water cooled condenser after the coalescing air filter should be sufficient.

There is a thread on the forum describing the design of inexpensive condensers. They consist of a copper air coil in a plastic bucket filled with water. The reports are that they will do the job.

If you would still like to know more about pressure swing air dryers or coalescing air filters take a look at the Balston web site. You will need to know your design air pressure, air flow rate and required air dew point.The catalog will show a number of air dryers. There will be one that matches your requirements and it will give you an idea of the required tower sizes and incoming supplied air pressures and flow rates.

The smaller towers are sized for roughly a 5 minute regeneration time between tower transfer at the rated air flow. The short regeneration time is not long enough to allow for a heat up-cool down regeneration cycle of the zeolite in the towers.That is why a pressure swing regeneration process is used.

As a example, a 6 inch diameter 4 foot high tower is rated for a output of 3.0 cfm at 100 psi at -100 deg F dew point. (Balston model 75-62)

You will find that used twin tower desiccant air dryers such as those listed on Ebay are very inexpensive compared to the cost of making your own.

DDoug · Sep 23, 2020

Robert R said:
You will find that used twin tower desiccant air dryers such as those listed on Ebay are very inexpensive compared to the cost of making your own.

Yup....and if the OP "get's it wrong" ?
Haas warranty goes to the lawyers, and some one might just blow you in to OSHA/local code enforcement/insurance company for having qty (2) pressure vessels without "u" stamps.

mjk · Sep 23, 2020

I'd 2nd going to a used working dryer that was sized for your expected shop capacity.
The technology to control with analog timers isn't that hard to recreate, digital if your electronically minded.
Confirming dewpoint from your "homemade" dryer after you have a problem with the vmc.....?
Whether you go with heated or non heated, your tweak time will still be measured in days or weeks.

I worked for a company in the 80's that was a big player in the field. Digital was just coming into play.
Evan when a proven design was being built, simple problems happened

If you go with heated regeneration, your vessel(depending on size) will have to be stamped for (450deg?) as a safeguard in case of heater short inside he vessel

Cole2534 · Sep 23, 2020

A while back I posted a link the Gas Processors Association's trchnical data book. It contains more info on gas dehydration than any reasonable human will ever need to know, tower design is part of that.

Sent via CNC 88HS

Shawn_Laughlin · Sep 24, 2020

I agree with all of y’all and yes I would like to and will read up on pressure swing regeneration. Thank you for that.

I agree with the whole safety deal but it’s me and my dad no employees and if it wasn’t confident in my fabrication skills I absolutely would not do this. I actually build pressure vessels and have been for about 21 or 22 years so I understand Ul and that good stuff but we are only talking about 140 lbs max pressure and that pressure well within the working pressure of any 6xxx series aluminum sch 40 pipe.
If it wasn’t they wouldn’t sell 3000# couplings, socket weld ,aluminum.

If only hearing the name OSHA struck fear into company owners my life would’ve been much better. I’m writing this hoping no one thinks I’m being an ass so please don’t read it wrong, I am not being a smart ass in any way and I wouldn’t ask questions here if I didn’t respect the opinions the you guys just had to put that out there. I work at a company that like I said we build pressure vessels and the shops are right off the side of the highway they sandblast on the other side of the wall from me. A wall that has more cracks between the siding and holes in the tin that you get the grit in your mouth and you can smell the sand it’s so thick. I’ve got a million videos of thick clouds of sand blowing across the highways and people stopped and pulled over so they don’t drive through it. It’s horrible and osha doesn’t do shit about it. People have called and osha does jack shit. Osha is a damn joke. I’m sure they have gotten on some people but for 99.99 percent of the time they do not do their job.

A few years back every single company that sandblasted in the us had to abide by the new laws of 5 micro grams exposure a day for employees. Companies had to have air samplers to monitor air for silica and osha was suppose to do inspections but guess what they have never done shit.

Also if a person calls osha, you have to give your name and it is not confidential like they say it is. Anyways, you call osha, they call the company and tell them to fix it but never even come out to look to see what’s going on and don’t follow up. They only come out if they get another call, that’s bullshit. I have lost all faith in osha and believe they are paid off left and right.

BT Fabrication · Sep 24, 2020

I found a heatless air dryer at auction (brand new) and got it for under $500 for a parker tower dryer. Just waiting on a bigger compressor to hook it up.

DDoug · Sep 24, 2020

Shawn_Laughlin said:
I agree with all of y’all and yes I would like to and will read up on pressure swing regeneration. Thank you for that.

I agree with the whole safety deal but it’s me and my dad no employees and if it wasn’t confident in my fabrication skills I absolutely would not do this. I actually build pressure vessels and have been for about 21 or 22 years so I understand Ul and that good stuff but we are only talking about 140 lbs max pressure and that pressure well within the working pressure of any 6xxx series aluminum sch 40 pipe.
If it wasn’t they wouldn’t sell 3000# couplings, socket weld ,aluminum.

If only hearing the name OSHA struck fear into company owners my life would’ve been much better. I’m writing this hoping no one thinks I’m being an ass so please don’t read it wrong, I am not being a smart ass in any way and I wouldn’t ask questions here if I didn’t respect the opinions the you guys just had to put that out there. I work at a company that like I said we build pressure vessels and the shops are right off the side of the highway they sandblast on the other side of the wall from me. A wall that has more cracks between the siding and holes in the tin that you get the grit in your mouth and you can smell the sand it’s so thick. I’ve got a million videos of thick clouds of sand blowing across the highways and people stopped and pulled over so they don’t drive through it. It’s horrible and osha doesn’t do shit about it. People have called and osha does jack shit. Osha is a damn joke. I’m sure they have gotten on some people but for 99.99 percent of the time they do not do their job.

A few years back every single company that sandblasted in the us had to abide by the new laws of 5 micro grams exposure a day for employees. Companies had to have air samplers to monitor air for silica and osha was suppose to do inspections but guess what they have never done shit.

Also if a person calls osha, you have to give your name and it is not confidential like they say it is. Anyways, you call osha, they call the company and tell them to fix it but never even come out to look to see what’s going on and don’t follow up. They only come out if they get another call, that’s bullshit. I have lost all faith in osha and believe they are paid off left and right.

I think your going to make your own ?

Yes/no ?

Strip out all the chest beating B.S. and repost please.

Shawn_Laughlin · Oct 5, 2020

Yes I completed it. Welds held just fine. but one I forgot how bad I hate working with tapered pipe threads. I have been chasing leak after leak only in the threads and the damn 2 unions I used. Wish I would’ve used a victaulic like I did with the 1” pipe for the dryer blower crossover inlet. I put it on 165 ish psi at about 11:30 pm before going to bed and when I got off from work at 3:30 the next day and got home it was sitting at 135. So not a huge leak but a leak. So I disassembled and I guess bc the stainless valves are a stronger metal than the aluminum, it compressed the aluminum and threads were loose.
I know this is a dumb thing to do if I ever planned on taking apart but I used jb weld not jb quick on tge threads and let it sit for 24 hrs. Pumped it up to about 165 and and this time it dropped about 4 lbs and no leaks.

Now my plan was to use a heat gun to dry the beads but it wasn’t strong enough and I burnt my gun up. I’m thinking about vacuum now and heating the tower.
I found a band heater that would clamp around pipe and heat it to about 150 degrees and then have a vacuum pump, I already have pull a deep vacuum and that should dry it about as much as it can be.
I was going to try a heating element and a stronger blower but with the get blower I would be just trying to dry with whatever humidity the air was that the blower was sucking in.
Sorry if this and my last post was is hard to read I’ve been going to be at 12 or 1 and going to work at 6 for a while now and it’s finally starting to get to me and my posts can sometimes seem grumpy or conceited but I assure that is and never will be the case.

I read up on pressure differentials and thank you for telling me about it. It was some very interesting reading for sure.

I can’t figure out how to post pictures anymore or i would love to post the dryer pictures?

Shawn_Laughlin · Oct 5, 2020

bt fabrication, thats the reason i wanted to build this other than the money, bc my compressor is just a 5hp 80 gallon ingersoll rand piston type. ts pump i believe. i just dont think it suplies enough air for the 10 to 30 perecent needed to dry the desiccant. i think a heat clamp plus vacuum might do the trick and i will surely post my success or failure. looking back i couldve bought a refrigerated dryer for what ive spent so for and that wouldve been better than nothing and probably good enough so i hope im not kicking my self in the ass when its all said and done

Shawn_Laughlin · Oct 5, 2020

Here we go

BT Fabrication · Oct 5, 2020

yep, it uses i think about 15 scfm for one minute at 90Psi. not a ton, but enough. although its a bit oversized and designed for 280scfm flow i believe

Cyclotronguy · Oct 5, 2020

A comment to an earlier post.

A refrigerated air drier at best is only going to give you a dew point approaching the temp of the heat exchanger.

They work great when it's hot and humid, not so much when the ambient temperature starts dropping. So for example, in my regard living where it gets cold in the winter, the refrigerated dryer is pretty useless 4 months out of the year. As a first stage before a desiccant dryer they are great.

Just remember the combined gas laws are your friend. Extract moisture from a compressed air system at as high a pressure and as low a temp as possible. Use the air at as low a pressure and as high a temp as permissible!

Shawn_Laughlin · Oct 8, 2020

cyclotron guy that’s a good piece of info to know

Cyclotronguy · Oct 9, 2020

Shawn

The unspoken outfall of refrigerated dryer operation is that you're never going to get a dew point below the freezing point of whatever you're trying to get rid of. For water +4 deg C dewpoint is pretty good. A desiccant dryer will get you quite a bit lower. That might be a big deal or a who cares, depending upon your need.

Shawn_Laughlin · Oct 14, 2020

Well I have been playing hell trying to get two stainless unions to not leak. So I cut the 1-1/2 pipe off that were welded to the towers and now I’m going with 1” with groove lock/victaulic unions, so much more figuring than a standard threaded union. I got the new pipes with screens tacked in and will weld them out and hopefully no leaks tonight. I will post some pictures. As long as all goes well I’m thinking about buying a 3/4” not process air heater with a blower that won’t burn the motor up, like I did to me new heat gun, to dry desiccant. I just got to go it’s out how the heating element is controlled now.

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