Hello all,
Going to pipe my work shop for compressed air.
1) Compressor is rated at 10.5 SCFM @ 90 PSI. & 135 PSI max.
The biggest thing I’ll ever likely use is a 1/2″ drive impact wrench or maybe down the line I’ll get an air powered sander.
I’ve decided to use Type L copper, forget the actual numbers but working pressure is something like 900 PSI. Plenty strong for my intentions.
So my long winded question is do I go with 1/2″ or 3/4″?
From what I read 1/2″ pipe will do the job just fine, But my head keeps thinking 3/4″ is the way to go.
Went to the copper org web site but I don’t have a clue to using the engineering formulas they offer.
What do you guy’s think?
Replies
If you have long runs, the larger diameter would have less pressure loss. That said, the choke point is probably going to be the connectors between your compressor & the fixed piping/tubing. You're supposed to use something flexible between the compressor & the rigid pipe/tubing. Most people end up using some sort of readily available air hose & some brass connectors. If the connectors are only 3/8" in diameter, not much sense in running 3/4" line.
for the flexible piece between compressor and disrtibution plumbing large diameter hyrdaulic hoses work great.
I laugh every time I see someone running 1/2" air line but the hole in the QD fittings is 1/4" I mean really whats the point, unless they all share the same size fittings. You could run 6" pipe but put 1/4" fittings on it and thats whats you got.Make sure sure you size the fittings to your pipe.ML
Depending on the length of the run, running a 1/2 hose fpor a 1/4" tool can be a very good idea. I run 250' (or more) of flex hose to run 1/4 air tools all the time, if I run 3/8 line that far I won't get the volume necessary to run tools.
Agreed my shop is small enough that I didn't even bother hard piping in my air lines. I run 150' of hose and just coil it back up on the hose reel at the end of the day. unless your running real air hogs a 1/4" fitting is going to work fine.ML
Depending on the length of the run, running a 1/2 hose fpor a 1/4" tool can be a very good idea. I run 250' (or more) of flex hose to run 1/4 air tools all the time, if I run 3/8 line that far I won't get the volume necessary to run tools.
ITA, it's an excellent idea. Depending on the tools, necessary even...and it's not just for 250' runs.
Restriction to flow volume and it's resulting ressure drop adds up over distance, the same way you need heavier gauge wiring for long runs.
The 1/2" long restriction to 1/4" in the connector is nothing compared to 20' (or more) of 1/4" restriction.
Don't forget the restrictions in all the tees and elbows too.
The friction loss in the fluid (air in this case) is proportional to the velocity of the fluid through the pipe or hose. The velocity for a given volume of air is dependent upon the diameter of the pipe or hose. Thus if you have a smaller pipe or hose you have higher velocity through it and higher friction losses. If you have 1/4" couplings and a 1/2" hose, you would get higher friction losses for a short distance through the couplings, but then proportionately lower losses over the span of the 1/2" hose. Thus using a larger hose even with small couplings allows for a larger volume of air over a given distance than would be the case with a small hose for the same distance. Other factors such as the surface smoothness of the inside of the hose would also play a role as would some other factors. Some one with more background in fluid dynamics would be needed to calculate the difference between a quarter inch hose and a half inch hose with the same couplings, howeer.
The frictional pressure loss is proportional to the SQUARE of the velocity in the pipe or hose- that's why the line size matters so much! Doubling the air flow in a given line increased the frictional pressure loss roughly four-fold...
If your line is a little small, it's a good idea to put the pressure regulator right at the point of use, so the velocity and hence pressure loss in the line and hose is as low as possible. That is, provided your hoses and lines are rated for the full output (relief) pressure of your compressor. They should be, just in case your pressure regulator fails- they DO fail open sometimes!
Continuous users such as air sanders, die grinders and spray equipment are going to be your biggest concern for line sizing. These devices have a given air flow requirement and a required pressure at the inlet. You can find charts which will give you the recommended linesize for that flowrate which you can use for guidance. A rough guideline is you want the velocity in the line no more than about 4000 ft/min- at actual conditions (ie. the volume has to be calculated at the flowing pressure).
Unless you've got more than one simultaneous user, a really huge shop or a really complicated line with lots of elbows (each elbow is about 4' of equivalent length), 1/2" copper (5/8" OD) is probably fine. At 5.5 ACTUAL cfm at 75 psig (~33 scfm), velocity in 1/2" copper is about 4000 ft/min and pressure loss is about 10 psi per 100 ft equivalent length. For comparison, an air die grinder takes about 3.5 cfm. 1/2" sch 40 pipe will give you more than required capacity, with about 2600 ft/min velocity and only ~ 4 psi/100 ft loss. Copper's nice because it's smooth and clean inside and won't corrode due to condensate- no need for point of use filters on all your tools.
Impulse devices such as nailers can get by with a smaller linesize than you'd think, because there may be enough air stored in the hose and header itself for a single shot of the gun. That local air storage gives the system time to recover pressure from the tank before the next shot. Chances are, whatever you're doing in your shop is not going to require rapid-fire use of the gun.
There is no way you will use more air than a body shop does. A very good friend is running a screw compressor feeding a 3 man (very busy) shop with 1/2.
the pipe is plenty strong enough but the solder?
Don't forget that compressed air is hot air and the heat will soften the connection. It's not uncommon to get 150 degree compresseed air from a compressor more is certainly possible..
>>the heat will soften the connection..... get 150 degree compresseed air from a compressor...<
Uhhhhh...... 150 degrees softening the solder connection......
Edumacate me re: solder softening at 150 degrees. Domestic hot water at 125 or so........
Jim Never underestimate the value of a sharp pencil or good light.
jusr braze the joints or just weld the joints
consider using silver solder due to the combination of temperature and pressure, commonly used for refrigeration lines.
Plant spec is copper with regular solder. 1/2" will flow all you will want. Pitch to a low point and put a bucket style steam trap in to auto puke the condensate. At far end put a 10 gal or so air tank, will serve as a surge tank.
Oversize piping will serve as an aux air tank for surge and deliever slightly cooler, hence dryer air. Over size piping will be more costly.
Please do not consider PVC, it will craze/crack with time and shatter/explode with considerable force.
Auto body paint applications or cold weather applications you should consider an air dryer.
I agree with ErnieD. I used 1/2" copper in my garage and have had no problem. Its been in for 4 years.
Your outlet line you could use a rubber hose used for heavy truck brake lines. 1/2"id. or stainless steel braided teflon hose which is used on the air compressors on heavy trucks which produce temps up to 225 degrees.
think about this,all your air tools have 1/4" inlet. 1/2 copper at 150 psi will deliver every thing any hand tool can use.guys around const run air hoses with 1/4 and 3/8 half way around the block.
i once had a 250' long line,1/2",i was scared of presure drop.ther wasn't any, i guess when your pushing air at high pressure there isn't much resitance in the line?larry
if a man speaks in the forest,and there's not a woman to hear him,is he still wrong?
wow, you guy's are great!
Ok so 1/2" it will be, forget who said it but I certainly won't use as much air as a body shop!
Type L copper, no PVC!
I'm looking at having a short, flexible connection from the tank to my hard piping. We have a local fab shop that can make something up with out breaking the bank. Or maybe just a short piece of quality rubber pipe. I'll get a regulator / water filter in there too.
I'm thinking about drip legs ( like you see on natural gas lines ) with a ball valve to easily drain any water that accumulates.
I'm was thinking regular solder will be sufficient, never thought about Brazing ( haven't done that in years ). Never brazed copper either, can you do that with a Mapp gas? Could be an easy upgrade.
Thanks again,
Bill
Don't braze- ordinary solder will work fine. No need for silver solder- period. This is air at 150 psig, not refrigerant at up to 400 psig. Solder is perfectly fine for this duty.
If your compressor has a storage tank (it should!), then the line between the compressor and the storage tank is the only thing that will get hot to any significant extent, and it's pre-plumbed for you. The line from the storage tank to your distribution header can be ordinary airline hose (rubber hose with fiber reinforcement between the layers).
I recommend downloading the copper tube handbook from copper.org.It has lots of useful information about the temperature and pressure ratings of the various types of copper pipe and tubing.It tells you the ratings you can expect with solder and if I recall correctly, brazing.Follow the link below to down load the handbook.http://www.copper.org/applications/plumbing/techref/cth/cth_main.html
was over checking out copper.org and also talked to a couple of maintenance plumbers here at work.
I'm going to go ahead and use regular solder. Mapp gas works just fine and I'm experienced with it.
Thanks again for all that answered my post!
Bill
regular hydraulic hose with 1/2" pipe threads on the fittings works perfectly for the connection between the tank and the supply line.
you can pick them up cheap at Fleet Farm or stores like that.
Plumbing safe silver bearing solder is stronger than plain old plumbing safe solder without silver.
Harris StaBrite #8 is at the top of the list, and it requires their flux.
The silver content creates a higher melting temperature and a better joint. The wicking action is better and is far less prone to leaks or pinholes if the joint properly prepared.
Regular solder melts around 450F and the silver solders are around 530F.
Either will work in your application, just a matter of preference.
Brazing occurs at 1200F (IIRC) and the process creates oxides inside the pipe at the brazed joint unless a nitrogen purge is used. These oxides will flake off. A brazing alloy with a high silver content like Harris #15 flows better than the 5% stuff. You will have a difficult time brazing even 1/2" line with a MAPP torch, and things like valve bodies will be especially difficult.
I'd slope the tubing each way from your drip leg or two so they do double work for you. Of all places, I found part of a coil of 1" copper tubing at a neighborhood garage sale. I plan to leave it in an elongated spiral just above the compressor and connected to the compressor with short lengths of air hose. Any immediate condensation will cool in the spiral and drain back into the compressor tank. Harbor Freight has an "Automatic" pressure water drain you add in place of the drain cock at the bottom of the tank. You can get it for about $20.
Also consider some of those metal support clamps that have a rubber grommet inside to keep down any buzzing vibes or corrosion.
Finally, consider 'hiding your exposed copper" along the long runs or on the visible ends with ugly duct tape or those lengths of foam insulation tube lengths, so the bad guys don't come in and steal all your copper....;>)
Bill
Edited 11/6/2008 10:09 pm ET by BilljustBill
Edited 11/6/2008 10:45 pm ET by BilljustBill
"Automatic" pressure water drain you add in place of the drain cock
I'm going to check that out, thanks!
from http://www.McMaster.com pg 936
Compressed-Air-Activated Moisture Drain Valve
View Image
Piston-powered valve automatically drains moisture each time your compressor cycles. It is activated by compressed air via an 1/8" NPT female pilot port (no electricity required). Connect to your aftercooler, moisture separator, compressed air tank, dryer, or filter. Body has
a rugged cast aluminum construction. Max. temperature is 150° F. Max. pressure is 200 psi. Inlet and outlet connections are NPT female.
4919K13
$49.00
cool,
got that bookmarked
Piston-powered valve automatically drains moisture each time your compressor cycles. It is activated by compressed air via an 1/8" NPT female pilot port (no electricity required).
I'm trying to figure out where you'd plumb in that 1/8 port to activate it, yet not have it open whenever there's pressure in the lines.
I'll start off by saying I didn't installed the one I was familiar with, but it sat at the bottom of the tank and I think a sense line drove the actuation of the valve. I know the guy who installed is not a rocket scientist (not a dumby either) so it couldn't have been too difficult.
That's ok man, I'm just trying to figure it out.
I'm guessing it uses the slight pressure difference between the comp outlet and the tank or lines to detect when the compressor kicks on. But then it would also open whenever tool use caused a pressure drop in the lines too...
I've used a ton of the automatic drip legs like A, C, and D, just below that one in the link, and manual valve on the tank, but never that one. If it's an improvement I'll use it on the tanks. I still like the drip cup for pipe runs though.
Edited 11/7/2008 1:06 pm by deadman1
trying to clear a foggy memory but somethings telling me when the tank pressure began to rise it opened briefly to bleed out anything that collected at the bottom. Might've been all internal and no sense lines.
Bill,
Our shop is all 1/2" copper soldered with regular plumbing solder. Have never had a problem. Make sure all the lines slope back to the compressor, and it helps tremendously to have a riser, then go down the wall at each drop. This helps keep water out of the drop. Expect to have a water seperator at every outlet.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
Mr Bill
Not shore what you mean by a riser?
Kind of like a drip leg facing up??
Bill,
Sorry it took me a while to find the link I was looking for. Look at this diagram and you will see what I mean by running the pipe up, then down to the outlet.
http://www.tptools.com/StaticText/airline-piping-diagram.pdf
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
Good stuff Bill, thanks for the link.
I'll put that one to use. Eventually I want to learn to spray finishes so moisture will be an issue.
Bill
Is copper any cheaper than galvanized pipe these days? That is what I used, 3/4 on the trunk and 1/2 to the outlets. It just screws together.
Even though every auto repair or body shop I've ever worked in or seen uses galv or iron pipe, I can't see why copper wouldn't do.
The only downsides I can think of are wear from vibration/motion on hangers, etc., and impact resistance.
That and if some knucklehead decides he needs to get 51' out of a 50' hose, he's not bending iron pipe pulling on the hose. Copper...
I was surprised.
Did a quick fly by at Home depot. Black pipe vs copper was not much different in price.
I'll stick with copper. No rust issues and I can sweat a fitting any place I want, I'm not tooled up to thread pipe.
I used galvanized and just made everything come up on a standard size. I got lucky that 10' sections with 4' down pipes and a few short nipples got me the 5 outlets I needed. I also used an SSR (Solid State Relay) to control the compressor and low voltage switches with an indicator LED at each outlet.