with my 33 gallon craftsman compressor, i have the standard 1/4" quick disconnect fittings for all my air tools. i started to notice 3/8" fittings that are also 1/4" NPT. my hose is 3/8" thick. should i be upgrading bigger fittings? or are those for more ******** commercial applications? I mainly just use the compressor to blow air and to remove lug nuts with the free cheapy Cman impact gun.
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when to use 1/4" NPT 3/8" fittings
- Thread starter maximus96
- Start date
IMO yes, especially if you are using cheap compressor and cheap guns, you will give it more torque to get the job done.. without spending more money.
It was recommended to me by the metal working guys. It won't break to bank to buy just one coupler and few plugs for the air tools, the coupling that comes with your compressor is crappy.. when you get it look at the diameter side by side.
I highly recommend going to napa look for Amflo brand.. home depot doesn't carry it anymore. Or, I heard HVLP fittings are also as good.
It was recommended to me by the metal working guys. It won't break to bank to buy just one coupler and few plugs for the air tools, the coupling that comes with your compressor is crappy.. when you get it look at the diameter side by side.
I highly recommend going to napa look for Amflo brand.. home depot doesn't carry it anymore. Or, I heard HVLP fittings are also as good.
Yes I agree the craftsman couplers are pretty crappy. The one that came attached to the compressor will refuse to accept the plugs sometimes. And the brass one I bought from sears to put on the end of the hose will frequently spit out the tool, be it an air blower or impact gun. I’ve had it happened so often with the blower that I have to press it in after every time so it doesn’t spit it out after the next use blow.
So amflo and HVLP, is there any other brands that I should look into? I was just at home depot and their couplers seem pretty beefy.
So amflo and HVLP, is there any other brands that I should look into? I was just at home depot and their couplers seem pretty beefy.
JayL
Well-known member
I am planning to change my Hose from 1/4" to 3/8" but my fittings are still 1/4 ( compressor side and tool side ). Will this make any difference or better to just keep the hose at 1/4"....
.... unless I change fittings too. Can you please give a link to a 3/8" quick connect coupler that will fit the tools' 1/4" fittings. Prior to my reading this thread, I was with the idea that a 3/8" coupler will need a 3/8" fitting on the tool side.
.... unless I change fittings too. Can you please give a link to a 3/8" quick connect coupler that will fit the tools' 1/4" fittings. Prior to my reading this thread, I was with the idea that a 3/8" coupler will need a 3/8" fitting on the tool side.
Doesn't make sense to change the hose and not the fittings, your flow will be limited by the smallest orffice. Think of it as a garden hose, you could double the size of the hose but if you keep the nozzle at the end the same size you will only get out the same amount of water.
JayL
Well-known member
I think I need to start first with the compressor gate valve becuase what I have is a 1/4" NPT.
Lyaec350
Well-known member
Doesn't make sense to change the hose and not the fittings, your flow will be limited by the smallest orffice. Think of it as a garden hose, you could double the size of the hose but if you keep the nozzle at the end the same size you will only get out the same amount of water.
False. The pressure drop across a restrictive opening is proportional to the length of the restrictive section and inversely proportional to the diameter of that section. You're saying that a 100 ft long 1" air hose with a 1/4" coupler on the end would be the same as a 100 ft long 1/4" air hose with a 1/4" coupler. This is definitely not true.
There are two distinct sizes used in pneumatic plumbing--the hose diameter and the threaded coupler diameter. Most 3/8" air hoses have 1/4" NPT fittings on both ends, because the tiny length of the fitting and coupler (~1/4") is nearly negligable with respect to the overall length of the hose (25, 50, or even 100 ft)
Basically, I would recommend sticking with 1/2" (or 3/4" if you have a big compressor) hard lines to each drop and then a 3/8" hose with 1/4" fittings to each tool. Certain tools like air nailers can get by with 1/4" hoses but its probably not worth the hassle of having multiple diameter hoses hanging around.
Look at your air tool, if the manufacturer put a 1/4" npt fitting in the end of it to attach it to your air hose, having a 1/4" fitting on the other end of the hose is going to be fine.
Air tool ratings are dynamic i.e. while the tool is running. In order to maintain a high dynamic pressure you need flow, a single restriction limits your flow so when you pull the trigger and your tool is trying to use 25 cfm and your quick disconnect can only pass 15 your dynamic pressure drops. Quick disconnect fittings have a body size and a thread size, you can purchase a 3/8" body female QD with a 1/4" NPT for you hose. This alows you to use the 1/4" NPT in the inlet of the tool (refferring to the thread, not the restriction) but not have a small of an ID of a 1/4" body / 1/4" thread QD. That along with a 3/8" hose should be good for most applications unless you are running higher consumption tools or long lengths of hose.False. The pressure drop across a restrictive opening is proportional to the length of the restrictive section and inversely proportional to the diameter of that section. You're saying that a 100 ft long 1" air hose with a 1/4" coupler on the end would be the same as a 100 ft long 1/4" air hose with a 1/4" coupler. This is definitely not true.
There are two distinct sizes used in pneumatic plumbing--the hose diameter and the threaded coupler diameter. Most 3/8" air hoses have 1/4" NPT fittings on both ends, because the tiny length of the fitting and coupler (~1/4") is nearly negligable with respect to the overall length of the hose (25, 50, or even 100 ft)
Basically, I would recommend sticking with 1/2" (or 3/4" if you have a big compressor) hard lines to each drop and then a 3/8" hose with 1/4" fittings to each tool. Certain tools like air nailers can get by with 1/4" hoses but its probably not worth the hassle of having multiple diameter hoses hanging around.
Look at your air tool, if the manufacturer put a 1/4" npt fitting in the end of it to attach it to your air hose, having a 1/4" fitting on the other end of the hose is going to be fine.
In order to maintain a high dynamic pressure you need flow, a single restriction limits your flow so when you pull the trigger and your tool is trying to use 25 cfm and your quick disconnect can only pass 15 your dynamic pressure drops.
I disagree. Assuming the compressor is able to maintain the output, the velocity will increase through the restriction(s) to match the flow on the upstream side of the restriction.
JayL
Well-known member
Can you guys pls provide some links on QD options. I found some but just want to make sure we are talking the same QD fittings.
tks
tks
Theo
Well-known member
A 3/8 coupler and fitting will help deliver more volume (cfm) to your tools, as long as your hose is 3/8" or greater.
This is beneficial for most tools. The trade off is poorer ergonomics due to the weight and bulk of the larger diameter hose.
This is beneficial for most tools. The trade off is poorer ergonomics due to the weight and bulk of the larger diameter hose.
Theo
Well-known member
I disagree. Assuming the compressor is able to maintain the output, the velocity will increase through the restriction(s) to match the flow on the upstream side of the restriction.
Air Pressure will be the same. Air Volume would decrease.
It is real easy to test out the effectitveness of your air system and see if you are getting the required pressure to your tools. Make up a T fitting with a 1/4" NPT male thread on one side that you thread directly into the inlet of your tool and on the opposite side of the T thread in a QD fitting that plugs into your hose. Out the side of the T thread in a cheap pressure guage. Observe the pressure at the guage when the tool is running unloaded and then make changes and see what difference it makes. I've done this in many gargaes and most people are surprised at how low the acutal pressure is at the tool with it running.
Air Pressure will be the same. Air Volume would decrease.
This is false...in fact DPS is right, the same principle that makes airplanes fly makes the air accelerate while going through the orifice and slow again on the other side. At least I think they're both Bernoulli's principle.
Fluid flow (including air) is caused by differential pressure, in this case high pressure in your compressor tank and atmospheric pressure at the outlet of your air tool. Whenever fluid flows through a piping system there will be always be pressure drop at any point downstream compared to upstream. As Lyaec explains that pressure drop is caused by all restrictions in the system, including the piping, however a single 1/4" restriction at a fitting is not the same as a 1/4" ID pipe or hose 100' long (note that 1/4" steel pipe is not 1/4" ID). This is due to increased velocity in the smaller diameter to try to get the same amount of flow. Higher velocity = higher friction = higher pressure drop. The longer distance over which this occurs, the more pressure drop.
It is this pressure drop that robs you of the differential pressure and therefore flow required to properly run your air tools. As Marlin points out, a gaged hooked up at the tool will show this drop for a given system and is exactly what will tell you how well your tools are running compared to their potential.
That being said, I do not have direct experience with the use of 3/8" fittings vs. 1/4" fittings, but it is definitel a myth to say that the system is only as good as the smallest orifice.
Lyaec350
Well-known member
This is false...in fact DPS is right, the same principle that makes airplanes fly makes the air accelerate while going through the orifice and slow again on the other side. At least I think they're both Bernoulli's principle.
Fluid flow (including air) is caused by differential pressure, in this case high pressure in your compressor tank and atmospheric pressure at the outlet of your air tool. Whenever fluid flows through a piping system there will be always be pressure drop at any point downstream compared to upstream. As Lyaec explains that pressure drop is caused by all restrictions in the system, including the piping, however a single 1/4" restriction at a fitting is not the same as a 1/4" ID pipe or hose 100' long (note that 1/4" steel pipe is not 1/4" ID). This is due to increased velocity in the smaller diameter to try to get the same amount of flow. Higher velocity = higher friction = higher pressure drop. The longer distance over which this occurs, the more pressure drop.
It is this pressure drop that robs you of the differential pressure and therefore flow required to properly run your air tools. As Marlin points out, a gaged hooked up at the tool will show this drop for a given system and is exactly what will tell you how well your tools are running compared to their potential.
That being said, I do not have direct experience with the use of 3/8" fittings vs. 1/4" fittings, but it is definitel a myth to say that the system is only as good as the smallest orifice.
Well said. I don't think it's an issue anyway, as just about every 3/8" air hose you buy will have 1/4" couplers, so thats what you'll use. There are a few cases (input of hose reel, output of compressor, input/output of filters, regs etc) where you can use 3/8" fittings but again, I'd use minimum 1/2" for all hard lines and then just switch to 3/8" hose (with 1/4" threads/couplers) for your flexible lines and couplers at the very end.
Disregard all this if you're talking about a 3/4" impact or some other tool that uses very high flow, in that case the back port will be 3/8" or 1/2" already and you should use that type of connector.
They will have 1/4"NPT ends which is the thread size, not the ID. You can have a fitting with 1/4" NPT with a range of different ID's.Well said. I don't think it's an issue anyway, as just about every 3/8" air hose you buy will have 1/4" couplers
With a fixed supply pressure, a given size orfice will only allow a certain flow. Beyond that point the flow will not increase. If that flow is sufficient to run your tool your okay.it is definitel a myth to say that the system is only as good as the smallest orifice.
Info I found on on 1/4" body QD vs 3/8" body QD showed 36 cfm vs 67 cfm at 110 psig.
buening
Well-known member
There is a mix of correct info here. Marlin is correct that a given orifice size will only allow a certain flow. Contraction points such as orifices, along with valves, tees, elbows, etc creat head loss in a hydraulic system. Many of these have tabulated values for K, which is used to determine the head loss. At a contraction point, say at the 1/4" orifice, the velocity will increase because the area decreases. Q (cfm) = V (ft/min) * A (ft^2) Qin=Qout so the air entering the hose at the compressor has the same cfm as when it leaves, unless you have multiple outlets running at the same time. The equation is a bit more complex when you consider head loss and friction factors, but that was just showing that the Q is the same throughout. The volume of air on one side of the disconnect is the same on the other side, its just a raise in air pressure......assuming the 1/4" ID continues throughout the tool.
Orifices, valves, tees, elbows, etc all create head loss, and this head loss reduces the amount of Q (cfm) that leaves the compressor tank and into the hose. There are also friction factors from the pipe and the rubber hose, but that is typically minimal in a small pipe network. So in summary, the cfm will decrease using a 1/4" orifice on a 3/8" ID hose due to head loss. I don't have time to run the numbers, but Marlin appears to have found a website that already has. I don't think a single tool uses more than 36cfm in my garage, so I'll stick with the 1/4" QDs on my 80gal compressor.
Orifices, valves, tees, elbows, etc all create head loss, and this head loss reduces the amount of Q (cfm) that leaves the compressor tank and into the hose. There are also friction factors from the pipe and the rubber hose, but that is typically minimal in a small pipe network. So in summary, the cfm will decrease using a 1/4" orifice on a 3/8" ID hose due to head loss. I don't have time to run the numbers, but Marlin appears to have found a website that already has. I don't think a single tool uses more than 36cfm in my garage, so I'll stick with the 1/4" QDs on my 80gal compressor.