Need advice for compressed air lines in shop
#21
Safety Car
I absolutely disagree with the notion that either a refrigerated or desiccant dryer is overkill. In any compressed air system, the air inside the pipe will be completely saturated. That is to say, that the air inside the line will be at 100% relative humidity at all times. All the good advice about nice long runs and metal pipe to help condense water out of the air line, is very good advice, but the fact remains that the air is still going to be at 100% relative humidity, unless you introduce a process that drops more moisture out. You might ask why this is important, so here we go.
Assume that the temp of you shop is 80 degrees, and therefore the air lines and the air inside them are all 80 degrees, and the air is at 100% Relative humidity. As soon as that air passes through an air tool, a blast cabinet nozzle, or the nozzle of a spray gun, that temperature will drop dramatically, and moisture will condense to whatever moisture level equates to 100% humidity at that temp. This will leave little drops of moisture in your blast stream, or in the paint you are shooting. It is not at all uncommon for the temp at these points to drop to 40 degrees F, or even lower. When I use air tools for an extended period of time, I have to wear gloves, because the tool gets so cold!
Keep in mind, that relative humidity, is exactly that, RELATIVE. It is a measure of how much moisture air can hold at a given temperature. As the temp goes up, air can hold way more moisture, and as the temp goes down, it can hold way less. When the temp goes down, the moisture has to fall out of the air stream, until it reaches the saturation point (100%).
What a refrigerated air dryer does, is to drop the temp to just above freezing, to drop out the excess moisture, and then when the air warms back up to 80 degrees, the temp drops to less than 2% relative humidity!
This makes it almost impossible to condense moisture out inside an air tool or nozzle.
I have both a refrigerated air dryer and a desiccant dryer in my shop. The Hankinson refrigerated dryer drops the dew point to about +40 degrees F in most of the shop, and then I use the desiccant dryer for the painting regulator, and it drops the dew point to -40 degrees C on that line. Air used for painting can never be too clean, or too dry. Most commercial paint shops use this same level of dryness, and for good reason.
The desiccant dryer is kind of a pain to regenerate, as I have to bake the desiccant in the oven until it turns blue again, to drive the moisture out. Fortunately, this dryer is large enough, and with the already dry air from the refrigerated dryer feeding it, I only have to regenerate about twice a year. The refrigerated dryer is very low maintenance, as it automatically drains out the water as it accumulates. I pull the moisture trap off once a year to clean it, but otherwise it is zero maintenance. If you keep an eye on Ebay and Craigslist, you can find a clean, used 10-15 CFM unit for a few hundred dollars, and it is money well spent.
Regards, John McGraw
Assume that the temp of you shop is 80 degrees, and therefore the air lines and the air inside them are all 80 degrees, and the air is at 100% Relative humidity. As soon as that air passes through an air tool, a blast cabinet nozzle, or the nozzle of a spray gun, that temperature will drop dramatically, and moisture will condense to whatever moisture level equates to 100% humidity at that temp. This will leave little drops of moisture in your blast stream, or in the paint you are shooting. It is not at all uncommon for the temp at these points to drop to 40 degrees F, or even lower. When I use air tools for an extended period of time, I have to wear gloves, because the tool gets so cold!
Keep in mind, that relative humidity, is exactly that, RELATIVE. It is a measure of how much moisture air can hold at a given temperature. As the temp goes up, air can hold way more moisture, and as the temp goes down, it can hold way less. When the temp goes down, the moisture has to fall out of the air stream, until it reaches the saturation point (100%).
What a refrigerated air dryer does, is to drop the temp to just above freezing, to drop out the excess moisture, and then when the air warms back up to 80 degrees, the temp drops to less than 2% relative humidity!
This makes it almost impossible to condense moisture out inside an air tool or nozzle.
I have both a refrigerated air dryer and a desiccant dryer in my shop. The Hankinson refrigerated dryer drops the dew point to about +40 degrees F in most of the shop, and then I use the desiccant dryer for the painting regulator, and it drops the dew point to -40 degrees C on that line. Air used for painting can never be too clean, or too dry. Most commercial paint shops use this same level of dryness, and for good reason.
The desiccant dryer is kind of a pain to regenerate, as I have to bake the desiccant in the oven until it turns blue again, to drive the moisture out. Fortunately, this dryer is large enough, and with the already dry air from the refrigerated dryer feeding it, I only have to regenerate about twice a year. The refrigerated dryer is very low maintenance, as it automatically drains out the water as it accumulates. I pull the moisture trap off once a year to clean it, but otherwise it is zero maintenance. If you keep an eye on Ebay and Craigslist, you can find a clean, used 10-15 CFM unit for a few hundred dollars, and it is money well spent.
Regards, John McGraw
I read this post because I knew the pcv thing would pop up. I didn't know was I was going to run across info like this. Thanks for posting it. On the last car I painted We had a dryer and a water trap plus the little orange one on the gun. I thought that would be enough. After reading your post I now know I've got work to do before I paint my car.
#22
Melting Slicks
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I have had this set-up for 25 years, I use a blast cabinet without moisture problems, but I don't paint often. I also run a dehumidifier in my shop all summer.
#23
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I'm not trying to be picky or be word police, just trying to be sure I understand what we are talking about. I'm not an expert on plastics and am learning a lot from this thread.
#24
Safety Car
White pvc as you use for plumbing. My friends compressor is outside. He hooked it to the inside via a rubber air line. As I was changing the pressure switch the pvc adapter he used to screw the air line in broke. I hadn't even paid any attention to it being pvc until it broke. I replaced it with a metal fitting.
Last edited by Robert61; 06-17-2018 at 06:43 PM.
#25
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White pvc as you use for plumbing. My friends compressor is outside. He hooked it to the inside via a rubber air line. As o.o was changing the pressure switch the pvc adapter he used to screw the air line in broke. I hadn't even paid any attention to it being pvc until it broke. I replaced it with a metal fitting.
#26
Tech Contributor
A lot depends on what you are going to use it for. I don't paint so I am blasting or using tools. I just setup a little shop to tinker in and bought a new Eastwoods super quiet 12 cfm compressor. So far, after a couple of start up issues, it's been great. I would love to have a refrigerated air dryer but so far I haven't needed it. I ran 1/2 & 3/4 black pipe, it is surplus I had, I have all the dies to thread so it wasn't too bad. I ran 6" 1/2 hose from the 30 gallon tank to 4- 5' risers into the 80 gallon tank, out with another 6' hose into dry filter and tapered the run away from the tank with blow offs by the blaster and end of line- so far never had any moisture at either one. I blow down the tanks and lines 1-2 times a day depending on Rh and hours I am working. I was going to go with copper but I had more black pipe and like it. It's all I use for air lines going back 45 years. I expect this setup will be fine until I stop building vette parts, retire, or die.
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Railroadman (06-17-2018)
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That's quite the set-up, GTR, I like it. Before I retired I had access to a shop where I could do all the pipe threading I wanted (and probably get most of the pipe and fittings I need in return for a dozen donuts) but that's no longer an option. I might see if anybody I know has a thread cutter but offhand I can't think of anyone.
#28
Safety Car
Our local hardware plumbing supply house will thread for customers.
#29
Tech Contributor
Home Depot will cut threads as well. I had to thread mostly because of dead ends on the pipe I had. I have boxes of plumbing and electrical supplies so I was able to pick what I needed, I did buy a few lengths and fittings but I gave away a lot supplies moving my shop. I used Tees with plugs in place of some elbows so I can tap into the line if I need to run a line to my Bridgeport, lathe or surface grinder. The Sears hose reel at the end of the line actually cover the floor and 20 ' outside the shop easy.
#30
I have a heavy duty 5hp 2 stage compressor. Water trap right at the compressor and at the end of the line. Copper tubing with sweat joints. I paint, sand blast and use air tools all the time including full car paint jobs. Not having any trouble in WI. with moisture ruining paint jobs but I do use a ball filter at the spray gun just in case. This has been working for me for over 30 years.
#31
Le Mans Master
Pvc
Great information. I used to use PVC for my air lines until an elbow shattered. Happy to say that no one was hurt. I own a medical imaging company and asked my radiologist if, in the event of a failure, can PVC shards be seen on an X-ray. He said no. I would hate to think what a surgeon would be faced with trying to find and remove plastic pieces from who knows where on my body. That did it for me. I replaced the PVC lines, elbows etc. with black pipe. I figure the pipe will outlast me. Jerry
#33
Burning Brakes
I used Transair:
http://www.ecompressedair.com/access...g-systems.aspx
in my old shop. It's powder coated aluminum pipe, uses compression fittings on the joints. It can be bent easily with a conduit bender to help the installation.
For drops, the air is tapped off the top of the horizontal lines so no water runs down the drop into your tools.
I have an auto drain on the compressor that you can vary the length and frequency of the auto bleed for moisture removal. The whole system has been in use for 11 years now with no problems. I do no paint work. The main air valve is turned off every night.
Thomas
http://www.ecompressedair.com/access...g-systems.aspx
in my old shop. It's powder coated aluminum pipe, uses compression fittings on the joints. It can be bent easily with a conduit bender to help the installation.
For drops, the air is tapped off the top of the horizontal lines so no water runs down the drop into your tools.
I have an auto drain on the compressor that you can vary the length and frequency of the auto bleed for moisture removal. The whole system has been in use for 11 years now with no problems. I do no paint work. The main air valve is turned off every night.
Thomas
Last edited by BB767; 06-19-2018 at 11:01 AM.
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Railroadman (06-19-2018)
#34
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I used Tansair:
http://www.ecompressedair.com/access...g-systems.aspx
in my old shop. It's powder coated aluminum pipe, uses compression fittings on the joints. It can be bent easily with a conduit bender to help the installation.
I have an auto drain on the compressor that you can vary the length and frequency of the auto bleed for moisture removal. The whole system has been in use for 11 years now with no problems. I do no paint work. The main air valve is turned off every night.
Thomas
http://www.ecompressedair.com/access...g-systems.aspx
in my old shop. It's powder coated aluminum pipe, uses compression fittings on the joints. It can be bent easily with a conduit bender to help the installation.
I have an auto drain on the compressor that you can vary the length and frequency of the auto bleed for moisture removal. The whole system has been in use for 11 years now with no problems. I do no paint work. The main air valve is turned off every night.
Thomas
Father's Day brought two Home Depot gift cards which would go a fair way toward pipe. But just when I thought I had decided to go that route, you post this. What a great arrangement! Decisions, decisions!
#35
Tech Contributor
That sir is one nice shop setup.
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The blast cabinet will be using a lot of air so 1/2" line to that? What about going to the rest of the shop, for air ratchets, etc? Is 3/8" adequate for those? The inlet on the tools is only so big, and the pressure will be whatever I set it at, so it would seem I don't need 1/2" to all 4 corners of the building. Or am I wrong?
#37
Melting Slicks
Go all the way with 3/4" lines. I used 3/4" in my shop and eventually had to change it to 1 1/4"
Air takes a while to move inside of a pipe, short burst of an air hammer will not be as effective with 1/2".
When I built my shop, the city wanted to instal 1/2" water pipe, they said I would have to pay for the 3/4" if I wanted it. I paid, but now I wished that I had insisted on 1" pipe. To late now for me, but not you.
Air takes a while to move inside of a pipe, short burst of an air hammer will not be as effective with 1/2".
When I built my shop, the city wanted to instal 1/2" water pipe, they said I would have to pay for the 3/4" if I wanted it. I paid, but now I wished that I had insisted on 1" pipe. To late now for me, but not you.
Last edited by Roger Walling; 06-19-2018 at 03:43 PM.
#38
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The blast cabinet will be using a lot of air so 1/2" line to that? What about going to the rest of the shop, for air ratchets, etc? Is 3/8" adequate for those? The inlet on the tools is only so big, and the pressure will be whatever I set it at, so it would seem I don't need 1/2" to all 4 corners of the building. Or am I wrong?
An example is the calculated cfm of 100 feet of unrestricted 1/2 inch pipe, ~18 cfm for airflow capacity.
Elbows and tees with a tight 90 degree airflow direction change adds restriction, and a reasonable rule is each tight 90 degree airflow direction change adds the restriction equivalent of about ten feet of pipe.
If you have twenty tight 90 degree changes in flow direction between the compressor outlet and your shop's main distribution manifold pipe you figure 20*10=200, or 200 additional feet of pipe restriction.
Use the calculator and the flow capacity for the equivalent 300 feet of pipe changes to ~10 cfm (100 feet of pipe and twenty fitting restrictions added together).
Fitting losses add up quickly.
Add in the drop. A drop that comes off the top of the manifold pipe main line has three to five 90 degree airflow turns before dropping down the wall. The outlet for the tool hookup has two more 90 degree airflow direction changes. The total restriction can be equivalent to 70+ feet of additional pipe , from a main line at seven feet up the wall, to a tool hookup at four feet above grade (dropping the capacity down to ~9 cfm, before the additional restriction of your 3/8" hose to the tool).
Go back and look at the cfm chart, and note an impact gun needs 15 cfm. The 1/2 inch system above only delivers ~9 cfm to the tool hook up hose.
Time to redesign is before you buy.
Changing to an all 3/4 pipe size with 400 equivalent feet of restriction has a capacity of ~37 cfm (enough to use a blast cabinet and an impact gun at the same time). Mixing a 3/4 main with 1/2 inch drops gets you somewhere in the middle, with ~43 cfm capacity in the 300 foot equivalent main, and the 3-5 cfm loss in airflow capacity through the drop (enough to tee out to two tools with no loss of airflow).
I trust this helps.
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#39
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Wow, NOTHING is simple, is it?
The compressor itself has a 1/2" outlet. Does going up to 3/4" gain me anything or does that initial limitation affect the whole system?
I was considering making the part from the compressor to the blast cabinet out of 1/2" iron pipe with verticals, like GTR1999 shows in post #26. Then using the RapidAir hose in either 1/2" or 3/8" downstream of that. Thoughts about that concept?
I will add that this is for a hobby application, not commercial production. Unless my son is in town or a buddy is over, it's a 1-man operation (me) and if I'm blasting I won't be using an impact gun and vice versa.
You mention the pump scrolling up to meet demand. I was hoping the 60 gallon tank would be a hedge against instant pressure drop. The compressor output is listed as 18.1 CFM at 90 psi, while the blast cabinet says it takes 9.1 CFM @ 90 psi. In theory that sounds like it should work, but there are a lot of 90 degree bends in that pipe setup in the pic so maybe not.
Later tonight I'll look on that RapidAir flow calculator you suggest. In the meantime, does this post's additional info change any of your recommendations?
Thank you!
The compressor itself has a 1/2" outlet. Does going up to 3/4" gain me anything or does that initial limitation affect the whole system?
I was considering making the part from the compressor to the blast cabinet out of 1/2" iron pipe with verticals, like GTR1999 shows in post #26. Then using the RapidAir hose in either 1/2" or 3/8" downstream of that. Thoughts about that concept?
I will add that this is for a hobby application, not commercial production. Unless my son is in town or a buddy is over, it's a 1-man operation (me) and if I'm blasting I won't be using an impact gun and vice versa.
You mention the pump scrolling up to meet demand. I was hoping the 60 gallon tank would be a hedge against instant pressure drop. The compressor output is listed as 18.1 CFM at 90 psi, while the blast cabinet says it takes 9.1 CFM @ 90 psi. In theory that sounds like it should work, but there are a lot of 90 degree bends in that pipe setup in the pic so maybe not.
Later tonight I'll look on that RapidAir flow calculator you suggest. In the meantime, does this post's additional info change any of your recommendations?
Thank you!
#40
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Wow, NOTHING is simple, is it?
The compressor itself has a 1/2" outlet. Does going up to 3/4" gain me anything or does that initial limitation affect the whole system?
I was considering making the part from the compressor to the blast cabinet out of 1/2" iron pipe with verticals, like GTR1999 shows in post #26. Then using the RapidAir hose in either 1/2" or 3/8" downstream of that. Thoughts about that concept?
I will add that this is for a hobby application, not commercial production. Unless my son is in town or a buddy is over, it's a 1-man operation (me) and if I'm blasting I won't be using an impact gun and vice versa.
You mention the pump scrolling up to meet demand. I was hoping the 60 gallon tank would be a hedge against instant pressure drop. The compressor output is listed as 18.1 CFM at 90 psi, while the blast cabinet says it takes 9.1 CFM @ 90 psi. In theory that sounds like it should work, but there are a lot of 90 degree bends in that pipe setup in the pic so maybe not.
Later tonight I'll look on that RapidAir flow calculator you suggest. In the meantime, does this post's additional info change any of your recommendations?
Thank you!
The compressor itself has a 1/2" outlet. Does going up to 3/4" gain me anything or does that initial limitation affect the whole system?
I was considering making the part from the compressor to the blast cabinet out of 1/2" iron pipe with verticals, like GTR1999 shows in post #26. Then using the RapidAir hose in either 1/2" or 3/8" downstream of that. Thoughts about that concept?
I will add that this is for a hobby application, not commercial production. Unless my son is in town or a buddy is over, it's a 1-man operation (me) and if I'm blasting I won't be using an impact gun and vice versa.
You mention the pump scrolling up to meet demand. I was hoping the 60 gallon tank would be a hedge against instant pressure drop. The compressor output is listed as 18.1 CFM at 90 psi, while the blast cabinet says it takes 9.1 CFM @ 90 psi. In theory that sounds like it should work, but there are a lot of 90 degree bends in that pipe setup in the pic so maybe not.
Later tonight I'll look on that RapidAir flow calculator you suggest. In the meantime, does this post's additional info change any of your recommendations?
Thank you!
Input one foot of 1/2 inch pipe into the calculator, and you will see the airflow is length and diameter dependent (and the outlet is not a problem if you increase the pipe downstream).
I expect a 3/4 inch system out to 1/2 inch risers and drops will work best for airflow and economics.