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Compressed Air Dryer Install

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JimDawson

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About a year ago I decided it was time to dry out my water air lines so started looking around for a solution. Up to then a little water in the air didn't bother too much, and we had one pretty dry line, so the air tools got used on that one. But now have 2 CNC machines in the shop that don't like wet air so time to do something.

I finally settled on a Harbor Freight refrigerated air dryer. The reviews were generally good with the primary compliant being the automatic drain valve. It just doesn't work. The specs allude to automatic operation, apparently via pressure switch, but I find no such provision, turn it on and it runs. I'm working on that, I want it to work on air flow, for the moment I'm operating it manually. Not an easy task to design a flow switch that works from just >0 to whatever flow. I think that will be a project for another thread.
https://www.harborfreight.com/compressed-air-dryer-40211.html

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I have two 5 HP compressors up in the corner and to date they have not been operational at the same time. :rolleyes: A couple years ago a customer gave me the black one because it had a bad motor. Actually pretty low time on it, and it looked like new inside and out. I purchased a 3 phase motor for it and put it up on the shelf beside the red one. Then about 5 months ago the new Baldor motor that I put on the red compressor gave up, so grab the VFD I had been saving for the black one and get it operational. Under some conditions we use quite a bit of air and the air compressor cycles quite a bit, so a 3 phase motor is a much better solution than a single phase because there are no start windings to burn up. The red one is going to get a 3 phase motor also.

The system looks like this, the two tanks are plumbed together with no valve between because the air pressure is sensed only at the red tank so they have to act as one tank. Both tanks are rated at 175 PSI working pressure, but I have the system turned down to 125 PSI
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On the right hand side of the right hand picture, if you follow the pipe down the wall, you can just make out the first moisture trap drop, this has a ball valve on it so it's easy to drain, just below the box fan.

The tank drains are easily accessible, just stick the drain line out the door and turn on the valve. This is the first line of defense for keeping water out of the air.
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From the tanks the airline goes up the wall and across the roll up door.
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And this is one of the places I screwed up the original installation. The pipe is level and should be angled up a bit so the water would flow back toward the air compressors, and the moisture trap drop. Until the last few days everything was hard plumbed in with no unions (another mistake) so too much hassle to fix it.

There used to be a pipe from the elbow above and the tee below, had to cut it out with a Sawzall. I need to do a little re-plumbing up there so I can raise that end of the pipe a bit, the elbow hits the building framework. The other big mistake is that there is no moisture drain at this junction, I will be fixing that. The blue line going to the left goes directly to my front hose reel. When I cut the pipe out, there was quite a bit of moisture in the tee.

Now the blue line from the valve at the top goes to the air drier. Blue line = wet air, Yellow line = dry air.
The Yellow line in the picture below is from the dry air receiver.
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This is an overview of the drier system. Air drier on the far left and a 100 gallon receiver tank in the back. This gives me a total air storage capacity of 260 gallons. That is an 8 x 10 mezzanine above the lathe & mill.

Since air compressors seem to be rated by tank size by the marketing types, does this mean that I have a bigger compressor now? ;):grin:
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I added the filter/drain after the air drier to try to catch anything that the water trap in the dryer fails to take out. https://www.automationdirect.com/adc/shopping/catalog/pneumatic_components/pneumatic_air_preparation_(frl-filters,_regulators,_lubricators)/filters_(af_series)/af-683-a

The 1/4 inch discharge line goes down to the floor
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And the plumbing into the receiver. I almost feel like I should be running the air in on one end and out the other, but I can't figure out why that would be any better. The 1/2 inch poly air lines seem to flow plenty of volume for our needs, and If we do need more volume to run a 1 inch drive impact or something we have another access point near the compressors that is not dry air, but is plumbed in 3/4 pipe.

The blue line on the floor is the tank drain, goes down to a valve I'll show later
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And another view of the system.
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And the guts of the dryer along with the new automatic drain. https://www.amazon.com/gp/product/B00R2110Y0/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 This one seems to work correctly, and I see in the reviews that more than one buyer used one of these to replace the automatic drain in the HD dryer. I just installed it today so not much time on it, but it seems to work correctly. The original HF drain is laying on the floor.

The clear/blue drain line goes down to the floor also.
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The drain lines follow the leg of the pallet rack down to the floor, the floor has a steep slope in this area and the water will just run out under the roll up door. I wanted them here so I can see if the auto drains are working and how much water I'm removing.
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The tank drain is exhausted outside. The small valve center frame.
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Had another little problem when we were trying to sandblast. My poor old, 17 year old VFD, that was not designed for single phase input, was overheating and shutting the compressor down on continuous operation. But this only occured above 70° F, below that it was fine and we had one rather chilly day to finish up the sandblasting. Anyway the old VFD got replaced by a new Huan Yang 7.5KW that is rated for single phase input. https://www.amazon.com/Variable-Frequency-Controller-Converter-HUANYANG/dp/B077KSN4C5/ref=sr_1_3?keywords=7.5+KW+VFD&qid=1561881720&refinements=p_85:2470955011&rnid=2470954011&rps=1&s=gateway&sr=8-3

Seems to work OK once I got all of the parameters set correctly. I do have to say the manual was very readable and a good translation. My biggest complaint is they sell the VFD as 7.5 KW (10 HP) but use the same wiring terminals as a 0.75 KW model. Rather a PITA to get that #10 wire into those little terminals, especially given where I have it mounted. This is mounted on an aluminum plate on the wall behind the compressor and above the door. I'm pretty much out of room anywhere around the breaker panel so this was the only place left to mount it.

The whole system is enabled by a programmable electronic timer switch, https://www.homedepot.com/p/Intermatic-15-Amp-Digital-In-Wall-Timer-White-IW505K/205478790 It is programmed to only manually turn on, but is programmed to turn off at 10:00 PM

As I stated above the pressure switch is set at 125 PSI, along with a safety switch that is set at 150 PSI and if that fails, the pop off valves on the tanks open at 185. Also if the pressure goes too high, the VFD will go over current and kick it's self out. So hopefully one of those safety system will work correctly in the event of a failure.:cautious:

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This is a work in progress and the next step is to get proper air lines run to the machines so we can have our hose reels back, right now we just string airlines across the floor.

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I'll update this thread once I've had a chance to evaluate the system for a while.
 
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rgray

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Since air compressors seem to be rated by tank size by the marketing types, does this mean that I have a bigger compressor now? ;):grin:
By the marketing types there is now more horsepower also. o_O

I have the 2 tanks tied together also, but only one has a compressor. The tank with no compressor stays pretty much water free. That surprised me.
Looks like a great setup there. Interested to hear updates on how much water comes from the new drier.
 

brino

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Thanks for all those details Jim!

It really shows the design effort required to meet all the constraints of pressure, flow, power, moisture, and space required.

I am "watching" the thread for any updates.

-brino
 

mksj

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Nice setup, thanks for sharing.

General question on the placement of air filters, if one has an after cooler, is it reasonable to add a water separator coalescing filter before the air enters the tank to decrease water in the tank. W/O an after cooler the air would be too hot and probably breakdown the filter material. This is similar to the "Franzinator" without all the tubing.
 

astjp2

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I would just let the refrigerated dryer run instead of running it on flow, it may short cycle the unit and cause it damage. We had 3 compressors and dryers at the one plant at work, but we ran about 300 CFM for each compresser.
 

JimDawson

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Nice setup, thanks for sharing.

General question on the placement of air filters, if one has an after cooler, is it reasonable to add a water separator coalescing filter before the air enters the tank to decrease water in the tank. W/O an after cooler the air would be too hot and probably breakdown the filter material. This is similar to the "Franzinator" without all the tubing.
I would think that you want the air as cool as possible prior to entering the filter/tank. A good aftercooler would probably do it.

I would just let the refrigerated dryer run instead of running it on flow, it may short cycle the unit and cause it damage. We had 3 compressors and dryers at the one plant at work, but we ran about 300 CFM for each compresser.
Great point.

And I have considered that. The way I intend to set this up is to turn it on in the morning with the compressor. Then as air is used it will come on, but must stay on for at least several minutes, and when it stops, it must stay stopped for at least 1 minute to keep it from short cycling. I have relays in stock to handle the timing. I'm also trying to figure out a pre-cool scenario that will cool down the air drier before I allow air flow through it.

What I may do is put in a solenoid valve or motorized ball valve upstream of the drier and open it after some time period, or actually read the temperature of the air drier. A motorized ball valve might be the best choice here because they open slowly and would not slam the system with a slug of air.

There is enough reserve capacity in the dry air receiver that a short delay (even a few minutes) in bringing it back up to 125 PSI would not be significant. I may wind up with a PLC controlling the system, haven't decided yet. That would be the easy way once all of the sensors and operating devices are in place, it's very easy to change the PLC program rather than rewiring relays.
 

astjp2

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I would look at doing a latching timer relay, set it for a 5 minute run after the flow stops, PLC's are expensive, a relay is $25
 

JimDawson

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I would look at doing a latching timer relay, set it for a 5 minute run after the flow stops, PLC's are expensive, a relay is $25
True, I do have both in stock. In fact, I have 3 small PLCs within arms reach right now and if I got out of my chair I could scrounge up a few more :grin:
 

extropic

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Very nice write up Jim.
I recommend one change regarding the slope of the pipes. Slope them down in the direction of air flow. Highest near the compressor/receiver and lowest at the longest run. I also pull my tool drops off the top of the supply line and place a drip leg below.

I'll attach the diagram showing the "best practices" that I've always followed. I don't remember from where I got the diagram but I considered it a credible authority.

Thanks again for the write up.

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Larry42

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When I started my current shop I bought a 10hp recip. Noisy! Then needed more air so bought a 2nd 10hp & came by a big (2.5" pipes) air to air cooler. Put the compressors in a room & used the air to air cooler to draw air through filters through the compressor room. Still got water in the lines. Bought a good sized refig drier (1.25" piping.) Bought a coalescing filter & put that in the line. Installed a 1" copper loop around the shop. Not enough air when lots of stuff running. Bought a 25hp screw compressor and set up one of the 10hp ones as a back up & additional storage. Added a moisture drain filter that removes all oil from the condensate. It is needed to comply with federal regulations. Does this seem never ending? We've now got 2 vacuum pumps, 10 & 40 hp. I'd like to put these and all the compressed air system in their own room, some day, maybe.
 

JimDawson

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I haven't updated this thread for awhile. The system is working as planned. The air from the dry air tank has shown no trace of moisture and the humidity has been unusually high for the last month. Once the distribution lines dried out there is no longer any visible moisture in the air lines. The Harbor Freight air dryer seems to be working fine. Still operating it manually, I just turn it on before I fire up the compressor.
 
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