Air line issue

[KELLHAMMER]

I installed a new air line in my garage. I ran and the lines in 1/2 inch diameter black iron. The system works like this : My compressor connects to the a hard line system by a flexible line 3/8" in diameter about 4 feet long The main system consists of a 1/2" main line that runs up vertically about 8 feet then starts to go horizontal for about 18' then turns 90 degrees and goes for about 4 feet and ends with a cap. Off the main branch there is one drop I used a tee and went up vertically 8 inches then horizontal 4 inches and then turned down for 4 feet to a moisture separator. The moisture separator has a outlet I can plug my air line into to go to my tools.

Problem: I don't get constant pressure. If I attach the air gun and pull the trigger the pressure drops really fast. Then it builds back up until I pull the trigger again. So if I want to run a small siphon feed sand blaster I probably would not get good constant pressure to run it properly. Which I know from experience I can run my blaster right off the compressor satisfactorily.

My thought is the hard lines need to be larger like 3/4 or even 1 inch in diameter to supply constant pressure. The 1/2" lines are too restrictive to allow the stored air from the tank to get to the tool . Just my thought
I would appreciate any comments on how to improve my system



Compressor spec 4 hp 18 gal tank oiless compressor

 

[lockness]

The diagram everyone posts recommends 1/2 is fine for under 75'. Id try bypassing the moisture seperator just to test that it isnt restricting the flow.

I ran 1/2 copper from the garage to my shop... about 50' and Im getting great flow using a DA sander.

 

[5wndwcpe]

The first thing I'd lose is that 3/8" feed line and switch to a 3/4". I've run 1/2" black pipe in my last three garages and never had a problem.

 

[Uncle Buck]

The first thing I'd lose is that 3/8" feed line and switch to a 3/4". I've run 1/2" black pipe in my last three garages and never had a problem.

I agree 100%

 

[Steve in Mi]

Yes increase the size of the flex line and be sure to open all the valves wide open.

 

[Charles (in GA)]

Classic example of a restriction, probably that 3/8 line.

Charles

 

[RAYJAY]

how big is your air compressor ???? what size is the ouput fitting ???

the 3/8 line looks like your problem, pictures would help

Jeff

 

[JCByrd24]

What are the connection sizes of the moisture separator. I'd be that's right up there with the 3/8" line. The other thing to consider is that running vs. not running there will always be less pressure with any amount of fittings/normally sized piping/devices in the system. Systems are not designed for no pressure drop, they are designed for the proper amount. In a shop air system I'd shoot for no more than 10 psi, meaning tank gage reads 100, a gage at the tool while running reads 90 (would read 100 while not running).

 

[Bill K]

The 3/8 hose is your problrm. The larger black pipe acts as storage. When you plug in a tool a use it the air dumps quickly from the back pipe but cannot be replaced fast enough thru the 3/8 line.
Think of your air system like this. The compressor tank is the movie theater, the flex connector is the exit doors into the hallways and the hallways to the front doors are the black pipe. Fill up the theater and hall with people then open the front doors with only one door from the theater to the hall open. The hall will empty quicker as the folks are jammed up leaving the theater trying to get thru just one door.
Bill

 

[KELLHAMMER]

Sorry it a craftsman 4 hp 18 gal horizontel
I was thinking the flex 3/8" commpressor to hard line could be the culprit

Bill
I love analogies like that. My dad was a Mech. engineer (rest his soul) and I grew up with him explaining very complex thing in terms like yours.

 

[KELLHAMMER]

I have seen those flex lines in braided. They are like 30 bucks. Anyone have a cheaper solution? The braided one is way too heavy duty for my hobby shop.

 

[Steve in Mi]

If you have a Tractor Supply Co nearby, they have 1/2" X 2' premade hydraulic hose with 1/2" NPT male on each end for ~ $6.00

 

[FourthHrsmnn]

Get ready for rust. I know It's too late now but you should of used galvanized pipe and @ least 1" diameter, larger vibration hose, and a tee below every air coupler w/ ball valve for drain, oh and slope your mainline back towards compressor. my .02

 

[tuned10]

The 1/2" pipe should be fine. I think the 3/8" hose could be your bottle neck.

Those hydraulic hoses from Tractor Supply work very well and are very durable.

 

[Charles (in GA)]

I have seen those flex lines in braided. They are like 30 bucks. Anyone have a cheaper solution? The braided one is way too heavy duty for my hobby shop.

Actually, with this size compressor, you probably have a 3/8 fitting on the tank. You are simply not going to get much air from this compressor tank, no matter how large the line. You air nozzle probably passes more air than the siphon blaster does.

Charles

 

[Uncle Buck]

Sorry it a craftsman 4 hp 18 gal horizontel
I was thinking the flex 3/8" commpressor to hard line could be the culprit

Bill
I love analogies like that. My dad was a Mech. engineer (rest his soul) and I grew up with him explaining very complex thing in terms like yours.

I don't think any of us realized the size of compressor you were supplying that system with!

 

[Steve in Mi]

Problem: I don't get constant pressure. If I attach the air gun and pull the trigger the pressure drops really fast. Then it builds back up until I pull the trigger again.

My guess is you don't have a pressure regulator in the system but rather one of those flow restrictor valves w/gage. Get yourself a REAL pressure regulator and you will get constant pressure at least for the period of time when your compressor tank pressure is equal to or greater than the regulator setting (90 - 100 psi for blasting).

 

[RAYJAY]

Get ready for rust. I know It's too late now but you should of used galvanized pipe and @ least 1" diameter, larger vibration hose, and a tee below every air coupler w/ ball valve for drain, oh and slope your mainline back towards compressor. my .02

never use galvanized pipe. black or copper is the way to go.( I used black not rich enuf for the copper) as galvanization can come off the inside of the pipe,separators and regulators.

jeff

 

[Kong]

The problem is not the air lines, it's the compressor. The reason the pressure drops so fast is you are using all the air stored in the lines, then the tank (18 gallon) and then your 4 HP compressor ( probably really a true 1.5 HP - the manufacturers lie a lot about HP ratings. Take a look at how much electrical power it takes to run it your compressor. A true 5 HP motor will draw about 24 amps on a 220 volt circuit, most hobby type compressors will run on a normal 15 amp 110 volt circuit which is only capable of running about 2 HP. If you can plug it into a normal wall plug, it can’t be more than 2 HP.) tries to refill the lines. However it will take about 5 minutes for that to happen.

You need a bigger compressor, with a bigger tank if you want to run higher volume air tools, especially if they are "budget" air tools (they use more air).

Sorry dude.

KongBastard

 

[KELLHAMMER]

I've heard about the galvanizing coming off and clogging parts of the system thats why I chose black pipe.
Also, I think it is wise to tilt the main line away from the compressor so that any moisture in the line will run away from the compressor. Thats why there is a vertical leg at each tee off the main branch to lessen the ability of that liquid to reach the tool. The main line has a drain leg at the end to allow the run-off to collect there and be blown out. True, the compressor is small but I agree the stored air in the tank can't refill the air line due to the choke point created by the 3/8" flex line. I going to try switching to 1/2" and see if it improves. The compressor didn't even turn on when I ran the system and notice the instant pressure drop. It took allitle time before it came on.

Tip Tools has a very descriptive diagram how to layout a air system. www.tptools.com. It's pretty much how mine is setup

 

[Uncle Buck]

I've heard about the galvanizing coming off and clogging parts of the system thats why I chose black pipe.
Also, I think it is wise to tilt the main line away from the compressor so that any moisture in the line will run away from the compressor. Thats why there is a vertical leg at each tee off the main branch to lessen the ability of that liquid to reach the tool. The main line has a drain leg at the end to allow the run-off to collect there and be blown out. True, the compressor is small but I agree the stored air in the tank can't refill the air line due to the choke point created by the 3/8" flex line. I going to try switching to 1/2" and see if it improves. The compressor didn't even turn on when I ran the system and notice the instant pressure drop. It took allitle time before it came on.

Tip Tools has a very descriptive diagram how to layout a air system. www.tptools.com. It's pretty much how mine is setup

While I do think you are undersized on the compressor, I think the situation might be improved by playing with the limit switch adjustment that controls when the compressor pump kicks on and off. It may not cure your problem; but it might help some. My thoughts were to adjust it so that the compressor kicks in earlier than it previously did. Just a thought.

 

[shocksystems]

I've heard about the galvanizing coming off and clogging parts of the system thats why I chose black pipe.
Also, I think it is wise to tilt the main line away from the compressor so that any moisture in the line will run away from the compressor. Thats why there is a vertical leg at each tee off the main branch to lessen the ability of that liquid to reach the tool. The main line has a drain leg at the end to allow the run-off to collect there and be blown out. True, the compressor is small but I agree the stored air in the tank can't refill the air line due to the choke point created by the 3/8" flex line. I going to try switching to 1/2" and see if it improves. The compressor didn't even turn on when I ran the system and notice the instant pressure drop. It took allitle time before it came on.

Tip Tools has a very descriptive diagram how to layout a air system. www.tptools.com. It's pretty much how mine is setup

That is pretty comprehensive diagram, thanks for the link. I notice they explicitly recommend against copper piping for air. The conclusion I had reached based on discussion on this forum was that Copper was the best for air lines, the tradeoff was the expense. I also did not realize how important "risers" could be.

Cheers!

Jim M

 

[KELLHAMMER]

They also say to not use galvanized. Which may be wise. But, I would not tell someone to trash their system if it was galvanized. Get some filters at the appropriate points and it could work just fine.

I realize my compressor may not be huge but I wanted to pipe air around my garage so I could incorporate different things into it easily. First, I wanted a moisture trap to cure the moisture problem. Now, I can do a small sandblast job or use my HVLP gun and know it should not have any moisture problems.

 

[FourthHrsmnn]

You will absolutely have water inside the line, which absolutely cause rust, which absolutely leads to clogging lines, correct? I have installed, repaired, sold, and designed automotive service equipment for 10+ years and we ALWAYS use galvanized pipe. I have NEVER had a clogging issue. As a matter of fact you will probably get scale from inside the compressor tank itself. Let's face it, air systems are dirty and can build a lot of moisture. Daily draining and maintenance are required. You have been given incorrect information regarding piping material. Your compressor guy should have asked how many drops, cfm's per tool, distance VS. horsepower/cfm output. Also, I have never seen a copper system, way overkill expense wise. totally unneccessary. Also, if you "loop" your mainline around your shop you won't have a "dead-end" and the extra pipe will also act as suspended tank volume. I know these things.