Air coupler types

[spectre6000]

I'm setting up my new air system, and trying to figure out couplers. The Euro/Milton-V flows more air than the standard industrial/M-type that are easy to find everywhere in a variety of materials. I've read up on the Stedlin quick connect, and really like the idea and feedback/reputation of their orbital quick connect, save that it only seems to work with their proprietary connector (at $10/ea and only available direct) or industrial/M ($1, available everywhere). There's lots of stuff out there from Stedlin about how high flow connectors usually aren't, but there's also a direct comparison between the Stedlin and Prevost connector, and they flowed the same. Prevost MAKES a high flow safety disconnect, so logically it follows that the high flow with the Prevost would check all the boxes (except a swivel, which I haven't looked into yet).

What I want to know is what the pressure/flow drop is between the MALE sides of the high flow vs. industrial connectors at low CFM rates available to most home gamers; ie. 10 CFM or less. The high flow is attractive, and safety quick connects exist that can take advantage of it, but does it matter at such low pressures/flow rates?

 

[spectre6000]

Found this:

For ballpark purposes, we're looking roughly at the two lines/grid intersections circled in pink. Industrial/M is 3/16", and high flow is closer to, but not quite 3/8", so these would be a bit optimistic, but representative for napkin math purposes. Ditto 100psi compared to what the tool is hopefully seeing at 90psi. About a 15cfm difference between the two at 100psi, but both still flow more than the 10cfm comparison point identified above. It's not like resistance is on or off, but that seems like a meaningful difference...

 

[txvwnut]

For couplers and fittings get Stedlins. I’ve got them in my personal shop and the shop for the day job.

 

[spectre6000]

I really like the Stedlins (especially the swivel), but it seems like I would be missing an appreciable amount of airflow by doing so over high flow + Prevost. I can't tell if that amount of foregone flow actually matters at <10CFM though... Trying to acquire that data in order to make a decision.

 

[spectre6000]

Swivel testing:

The high flow ball swivel won the race, but I wonder what the block swivels would have looked like with high flow fittings. The difference between the high flow and industrial swivel fittings was not huge at ~4%. Not sure how that translates to other things, but it's at the very tail end of a very specific test that I don't know how to translate to daily use for other tools.

 

[The Cobbler]

I have some Stedlin couplers & I really like them too. They have done tests ( available on you tube & here at GJ ) of flow and they are comparable to high flows IIRC

 

[spectre6000]

I have some Stedlin couplers & I really like them too. They have done tests ( available on you tube & here at GJ ) of flow and they are comparable to high flows IIRC

I've seen where he tested the female COUPLERS, but not the male *******. That seems like the choke point. How much more restrictive are the industrial ******* compared to the Euro/V *******?

 

[The Cobbler]

I'm not sure but if he was testing the couplers he had to have had a plug in it ?I thought his tests were done on couplers & plugs?
the couplers ( that I have taken apart) have only 2 small holes for the air to pass thru . volume wise I'm not sure how they compare to the plugs .

 

[spectre6000]

As I recall (from earlier today, but not in front of me now), he tested a Milton quick disconnect with high flow ****** against his coupler with industrial or his own ******. In a different video, he tested his vs. Prevost with both being industrial, and they performed the same.

Transitive equality being what it is (if A=B and B=C, A=C), it seems that the high flow Prevost would be the best of all. They also have the benefit of being more widely available. Of course, that said, industrial fittings are the most widely available of all...

Then for swivels, the block swivels are rebuildable for the cost of a few O-rings, and the Stedlins... I assume they're not. No rebuild kits on the site at any rate. Block swivels are also the standard you see in every shop everywhere, can be had for under $5, and are so stone simple those <$5 examples are likely to be usable and decent.

 

[GeoBruin]

To answer you ultimate question, no, there will be no noticeable difference between fittings of really any conventional type at 10 CFM at the pressure ranges were talking about*.

To back that up, I'm willing to test it for you. I have various styles and ranges of flowmeters capable of measuring flow at the pressures and temperatures were talking about. I have standard industrial couplers and plugs, stedlin quick connects and full flow plugs (and a swivel adapter) and I'm willing to purchase a high flow connector/plugs.

So you design the experiment. What do you want to see?

*You keep saying 10 cfm, but is that really the air flow you're looking at? I realize your compressor makes 10 CFM, but that's just refilling the tank. Typically, when using a high flow tool or blast cabinet etc... the instantaneous air flow is higher than 10 cfm and it's only because you take brakes to reposition or whatnot that the compressor is able to "keep up" with demand. If you really are only flowing at 10 cfm in actual use, it doesn't matter what fittings you buy. They will all work with minimal pressure drop.

 

[spectre6000]

10 CFM is a round number ceiling for home gamer compressors. Mine doesn't actually make that much.

The most directly applicable test for my own application would be flow/pressure drop across Stedlin w/ industrial vs high flow (i.e. Milton-V) Prevost at 90psi, and something between 5-10 CFM, etc. The most scientifically granular test would be the same across just the male fittings to isolate that specific variable, but that might be difficult depending on what you have available for testing.

 

[GeoBruin]

10 CFM is a round number ceiling for home gamer compressors. Mine doesn't actually make that much.

The most directly applicable test for my own application would be flow/pressure drop across Stedlin w/ industrial vs high flow (i.e. Milton-V) Prevost at 90psi, and something between 5-10 CFM, etc. The most scientifically granular test would be the same across just the male fittings to isolate that specific variable, but that might be difficult depending on what you have available for testing.

Okay, but I must refer you to the asterisk in my last post. 5, 10, or 20 cfm compressor has nothing to do with the air supplied to the tool in use, unless you have drained the tank to below the regulated pressure. In other words, I could turn my compressor on, fill the tank, then completely turn off the compressor motor/pump, rendering my compressor effectively a 0 cfm compressor. I can then plug in an impact to the outlet on the tank and rattle out a nut/bolt no problem.

So what I'm asking you is, what is the actual recommended air consumption of the tool you want to use, and at what pressure. If you have a really high demand tool that needs (for example) 50 cfm at 90 psi, and you are unable to bump the static pressure up high enough to maintain the necessary flow rate or the necessary working pressure, then you can consider chasing demons in your air delivery system. But testing at 10 CFM just because your compressor pump is capable of filling the tank at that rate doesn't enter into the discussion.

 

[dnschmidt]

Buy the Prevost couplers and the Milton V ******* as they're dirt cheap. The so called high-flow couplers have been the standard in Europe for a very long time. Americans seem to believe them to be a relatively new invention and that's simply not true. I get my ******* from JB Tools. Having over 60 air tools I'm not paying big bucks 60 times for something made on a screw machine at about 100 per minute. The Prevost couplers are the best I've used along with Dixon. Prevost also makes a air releasing coupler that's a good idea as it makes disconnecting and connecting the tool easier.

 

[spectre6000]

Oh. I gotcha. The tool is theoretical at this point. I'm just starting out with shop air in my own shop. I have an air hammer, die grinder, ratchet, impact, some paint guns, and a compressor. Don't even have a hose yet. At this moment, my switching cost is zero, so I'm trying to do the best I can for what I have now, but also what I will have down the road as the system expands and evolves. I know that at SOME point, the differences between these things will manifest, but it may be 30CFM (which I will likely never see even way down the road). If the ******* are moot, and it's really just down to the quality of fittings, then that's one thing. If it matters in some range that I might conceivably be working in, since the cost difference is nothing now, I might as well try to start off in the right direction.

If I go the Stedlin route, I'm tied into industrial fittings (I wouldn't do the $10 a pop male fittings regardless, it's just too expensive and only available from the one source rather than everywhere for a buck). If I go the high flow route, they seem to be becoming more popular and more readily available, but I'd still be ordering things online. I live in the mountains, so that's how I get most things anyway, and I'm not sure it's really a demerit. The Prevost couplers likewise are available (at about the same cost as the Stedlins for the simple quick connects, but the Stedllin swivel connects are much cheaper) to order. The swivel is something I care about, and the Stedlin design looks pretty great and seems to flow well, but the block swivels are cheap, everywhere, and rebuildable. Might even be comparable flow with high flow connectors.

 

[cvairwerks]

I've switched to the Milton 5-in-1's for all my air tools. The only one that won't get that is the blast cabinet. It will get hard plumbed.

 

[GeoBruin]

Oh. I gotcha. The tool is theoretical at this point. I'm just starting out with shop air in my own shop. I have an air hammer, die grinder, ratchet, impact, some paint guns, and a compressor. Don't even have a hose yet. At this moment, my switching cost is zero, so I'm trying to do the best I can for what I have now, but also what I will have down the road as the system expands and evolves. I know that at SOME point, the differences between these things will manifest, but it may be 30CFM (which I will likely never see even way down the road). If the ******* are moot, and it's really just down to the quality of fittings, then that's one thing. If it matters in some range that I might conceivably be working in, since the cost difference is nothing now, I might as well try to start off in the right direction.

If I go the Stedlin route, I'm tied into industrial fittings (I wouldn't do the $10 a pop male fittings regardless, it's just too expensive and only available from the one source rather than everywhere for a buck). If I go the high flow route, they seem to be becoming more popular and more readily available, but I'd still be ordering things online. I live in the mountains, so that's how I get most things anyway, and I'm not sure it's really a demerit. The Prevost couplers likewise are available (at about the same cost as the Stedlins for the simple quick connects, but the Stedllin swivel connects are much cheaper) to order. The swivel is something I care about, and the Stedlin design looks pretty great and seems to flow well, but the block swivels are cheap, everywhere, and rebuildable. Might even be comparable flow with high flow connectors.

I ordered a Prevost high flow safety coupler and some Milton v style plugs. They'll be here Sunday.

In the mean time, figure out your highest flow tool.

 

[spectre6000]

I ordered a Prevost high flow safety coupler and some Milton v style plugs. They'll be here Sunday.

In the mean time, figure out your highest flow tool.

Well that's exciting!

I don't know what the highest flow tool I currently have is (probably impact or paint gun if I were to guess), but I am just barely getting started. The highest flow tool I intend to have (which will require a larger second tank among other things) is a blast cabinet. I haven't had time to see what I can get away with on that front, but I imagine it'll be very close to 10 CFM. Again though, that was just a round number ceiling for the home gamer sized setups.

If we're designing experiments though, a specific tool doesn't matter so much as the curve. More to the intent of answering the initial question in a way that's the most beneficial to the most people would be to try to establish curves (like the image I posted above) for the two (or more if you've got 'em) most common types of connectors at low pressure, low flow rates. Set up so that there's 90 psi at the tool (a more or less constant pressure requirement), then test for drops at a range of low flow rates from 0-10 cfm. At least three different flow rates, but more is more better. A single tool with a variable speed trigger and maybe a band clamp or something to keep it steady with proper instrumentation would probably give us all the information we need to plot curves.

I don't know what you have at your disposal exactly, but in my head the test rig looks like:

air => shutoff valve* => pressure gauge => connector in test => pressure gauge => flow gauge => tool with variable trigger and clamp

* to allow swapping of fittings and changing of trigger clamp setting without losing a ton of air in order to keep the source constant.

 

[GeoBruin]

Well that's exciting!

I don't know what the highest flow tool I currently have is (probably impact or paint gun if I were to guess), but I am just barely getting started. The highest flow tool I intend to have (which will require a larger second tank among other things) is a blast cabinet. I haven't had time to see what I can get away with on that front, but I imagine it'll be very close to 10 CFM. Again though, that was just a round number ceiling for the home gamer sized setups.

If we're designing experiments though, a specific tool doesn't matter so much as the curve. More to the intent of answering the initial question in a way that's the most beneficial to the most people would be to try to establish curves (like the image I posted above) for the two (or more if you've got 'em) most common types of connectors at low pressure, low flow rates. Set up so that there's 90 psi at the tool (a more or less constant pressure requirement), then test for drops at a range of low flow rates from 0-10 cfm. At least three different flow rates, but more is more better. A single tool with a variable speed trigger and maybe a band clamp or something to keep it steady with proper instrumentation would probably give us all the information we need to plot curves.

I don't know what you have at your disposal exactly, but in my head the test rig looks like:

air => shutoff valve* => pressure gauge => connector in test => pressure gauge => flow gauge => tool with variable trigger and clamp

* to allow swapping of fittings and changing of trigger clamp setting without losing a ton of air in order to keep the source constant.

I think the biggest problem were going to have is the inability to actually detect a difference on the gauges, given the gauges have such course gradations. I might have to find some ******/more granular gauges, or else some that have a smaller range centered around 90 psi.

Most of my flow meters are the differential pressure variety. They function (as I understand it) by doing exactly what were doing... measuring the pressure before and after a restriction of known dimensions and then translating that to flow. But I suspect the pressure measuring components are dialed in to a very narrow range. Thats why the meter is rated at either 90 or 100 psi, because pressures outside that narrow range will be outside the sensitivity range of the meters.

Anyhow, if my hypothesis is correct, and the pressure difference is so small as to go undetected (or within experimental error), I figure you will have your answer that it doesn't matter.

I think what could possibly be magnifying the potential issue in your mind is that chart above. My impression is that chart is for a (relatively) long run of pipe or hose, where the friction (and whatever other forces I don't understand) are magnified. For a very short restriction like a fitting, I just don't think it's going to make a big difference at the flow ranges were talking about.

 

[FredWanaker]

I have standard HF, HD, Napa generic Automotive Interchange fittings. The two parallel compressors can flow close to 12 CFM @ 90 PSI. I can drain the 2 x 25-gallon tanks using the blast cabinet to where I am running just on the two compressors. I see no need to pay more for connectors but that does not mean someone else would not. I can see the benefit of better made connectors as to less wearing them out if they are used a lot. I don't think at 10 CFM you will have any issues unless you drop to small hose sizes. Worrying about the CFM is overkill in my opinion.

 

[Qualitytools]

I have switched to Prevost couplers and plugs and discovered-later that I can use the Milton euro plugs and I am very happy with them and the high flow rate. No regrets

 

[GeoBruin]

BTW, amazon has a box of 10 Milton v style 1/4" mnpt plugs for $3.69.

Milton Industries 760 1/4" MNPT HIGHFLOWPRO™ V-Style/European Interchange Brass Air Plug Fitting (High Volume Low Pressure Application) -Box of 10 https://www.amazon.com/dp/B003V5RPNQ/?tag=atomicindus08-20

 

[spectre6000]

I actually have that exact page open in another tab. The Stedlin/Prevost are about the same cost as well. The cost difference to go one way vs the other is pretty negligible at this point. Switching later will not be as cheap/easy.

Prevost male:

https://www.amazon.com/dp/B009I3FCB2/?tag=atomicindus08-20

Prevost female:

https://www.amazon.com/dp/B01AKEITRQ/?tag=atomicindus08-20

 

[GeoBruin]

I actually have that exact page open in another tab. The Stedlin/Prevost are about the same cost as well. The cost difference to go one way vs the other is pretty negligible at this point. Switching later will not be as cheap/easy.

Prevost male:

https://www.amazon.com/dp/B009I3FCB2/?tag=atomicindus08-20

Prevost female:

https://www.amazon.com/dp/B01AKEITRQ/?tag=atomicindus08-20

Well I received my Prevost coupler and plugs. Only problem is I didn't order any fnpt plugs, which would eliminate some fittings in the test rig. I just ordered those and they should be here tomorrow.

 

[johninct]

Get High Flow ones. Then all of your air tools really wake up.

 

[u2slow]

Thought I'd mention I upgraded to a full 1/2" pipe outlet on my compressor and G-type coupler into 1/2" 50' hose. Already had v-style on the working end... my 1/2" gun gets stuff done it couldn't do before.

Nice that M ******* fit the V couplers, for the less hungry tools.

 

[spectre6000]

@GeoBruin I'm guessing Memorial Day caught you off guard re: delivery dates as well. Did the fittings show up today?

 

[GeoBruin]

I've got all the fittings in hand. I did realize however that I don't have two gauges good/similar enough to perform the experiment. I picked up a couple cheap inflators locally with digital gauges but when I got home and broke the glue/threadlocker free, they have a wacky metric thread where the gauge meets the inflator body.

Anyway, down the rabbit hole I went and now I've got a couple of nice digital gauges on the way.

Sorry for the delay, but it will probably be a couple more days yet. I'll try to get the test rig setup in the meantime and see if I can cobble together some initial tests with what I have.

By the way, this Prevost Coupler is really nice but man is it heavy. It going to be like welding a mace with that thing on the end of a hose.

 

[Wiz02]

@spectre6000 , you are a bit ahead of me on the air line journey, while I am still in analysis paralysis over the cooling manifold design, the topic of couplers and fittings was my next hurdle and here I find that you are trying to make the same decisions as me. Great thread.

@GeoBruin, thanks for doing this experiment as I am anxious to see the results. I do agree that once the system is up to pressure, the compressor flow rate is not relevant until the tank pressure drops below the turn on threshold.

 

[GeoBruin]

Okay folks, I'm still waiting on the nicer gauges to arrive but in the meantime I mocked up the test rig and even did a little "control" test using a Harbor Freight industrial coupler and plug. As I suspected, the drop at 10 CFM was hard to detect/measure on the small, analog gauges but it was a good proof of the test rig.

I put everything together with fittings I had lying around so it's not the most efficient use of fittings, but it simulates a real scenario which would require reducing down from a 1/2" hose or hard line.

Anyhow, here's a link to a quick video of the baseline test.

 

[thesilverone]

Prevost here too. My spray guys really like the High Flow Safety Couplers

 

[spectre6000]

That is excellent! With that test rig set up, it might be worth trying out a few other things if you have them on hand. The thing that most immediately comes to mind (and the only thing at the moment) is swivels. Specifically block swivels vs. Stedlin. I KNOW the Stedlin is going to flow better, but the question is how much better, and do the high flow fittings help. I am super stoked! I have everything purchased for my air system except the fittings and likely some short lines to go between tank/filter/reel. I'm holding off because this is solid gold!

 

[GeoBruin]

Updates: (I'll just edit this post as the additional videos become available)

Test Rig Explanation + Baseline Test: Merlin Industrial coupler/plug, 90 PSI static pressure, 10CFM.
Test 2: Merlin Industrial coupler/plug, 90 PSI dynamic pressure, 10CFM.
Test 3: Merlin Industrial coupler/plug, 90 PSI dynamic pressure, 20CFM.
Test 4: Prevost High Flow safety coupler, Milton V-Style plug, 90 PSI dynamic pressure, 10CFM.
Test 5: Prevost High Flow safety coupler, Milton V-Style plug, 90 PSI dynamic pressure, 20CFM.
Test 6: Stedlin Quick Connect Coupler, Stedlin Full Flow plug, 90 PSI dynamic pressure, 10 CFM.
Test 7: Stedlin Quick Connect Coupler, Stedlin Full Flow plug, 90 PSI dynamic pressure, 20 CFM.
Test 8: Stedlin Quick Connect Coupler, Merlin Industrial plug, 90 PSI dynamic pressure, 10CFM.
Test 9: Stedlin Quick Connect Coupler, Merlin Industrial plug, 90 PSI dynamic pressure, 20 CFM.
"Highly technical" modification to Merlin industrial plug.
Test 10: Stedlin Quick Connect Coupler, modified Merlin Industrial plug, 90 PSI dynamic pressure, 10 CFM.
Test 11: Stedlin Quick Connect Coupler, modified Merlin Industrial plug, 90 PSI dynamic pressure, 20 CFM.
Test 12: Stedlin Quick Connect Coupler, Stedlin Full Flow plug, Merlin swivel connector, 90 PSI dynamic pressure, 10 CFM.
Test 13: Stedlin Quick Connect Coupler, Stedlin Full Flow plug, Merlin swivel connector, 90 PSI dynamic pressure, 20 CFM.
Test 14: Stedlin Quick Connect Coupler, Stedlin Full Flow plug, Stedlin Orbital, 90 PSI dynamic pressure, 10 CFM.
Test 15: Stedlin Quick Connect Coupler, Stedlin Full Flow plug, Stedlin Orbital, 90 PSI dynamic pressure, 20 CFM.
Air Tool Instantaneous Consumption (Sampler): Die Grinders, Needle Scaler, Band File, Approx 90 PSI dynamic pressure.

 

[spectre6000]

Post summarizing the results from the above. /|\

Love it!

Given the relative dearth of information available for home gamer level use cases, what is more common: 90psi static, or 90psi dynamic? I doubt people are adjusting their regulators for each individual tool, but my air tool use is limited/mostly a decade ago and I know I'm pretty ignorant on the subject still.

Once all the bits and pieces are in hand, the value is going to be in having enough datapoints to make some curves at these lower pressures/flow rates.

Halfway unrelated: my hose reel arrived today... destroyed. Combination of FedEx's coked up gorillas and what was clearly a very bad return situation... So, while I get that sorted, more time means more appetite for data!

 

[Wiz02]

Nice setup ! And the outcome matched expectations. After trying a higher pressure with no discernably change, I an interested in seeing the pressure drop at a higher flow.

 

[GeoBruin]

Love it!

Given the relative dearth of information available for home gamer level use cases, what is more common: 90psi static, or 90psi dynamic? I doubt people are adjusting their regulators for each individual tool, but my air tool use is limited/mostly a decade ago and I know I'm pretty ignorant on the subject still.

Once all the bits and pieces are in hand, the value is going to be in having enough datapoints to make some curves at these lower pressures/flow rates.

Halfway unrelated: my hose reel arrived today... destroyed. Combination of FedEx's coked up gorillas and what was clearly a very bad return situation... So, while I get that sorted, more time means more appetite for data!

I think it's fairly common to adjust the regulated pressure to see higher pressure at the tool. Remember most people are running through a hose, if not a distribution system and a hose, so they're seeing significant pressure drop at the tool. Speaking of significant pressure drop, I just posted the Merlin coupler/plug combo at 20 CFM. Now things are getting interesting...

 

[GeoBruin]

Nice setup ! And the outcome matched expectations. After trying a higher pressure with no discernably change, I an interested in seeing the pressure drop at a higher flow.

I just posted a version at 20 CFM. Test 3 linked in the post # 32.

 

[spectre6000]

I'm actually more interested in LOWER flow rates. Home gamer style. If we can get a handful of datapoints, we can fit a curve and know quite a bit.

Simulpost. I went back and watched the other video. That is pretty much EXACTLY the sort of relationship I was expecting. At high flow rates, the effects of the plug coupler are more pronounced. I noticed a lot of the tools at HD quote 4cfm. Money says no discernible losses there with that instrumentation setup. What's even more exciting is that this is just testing the setup, not the actual tests!

 

[GeoBruin]

I'm actually more interested in LOWER flow rates. Home gamer style. If we can get a handful of datapoints, we can fit a curve and know quite a bit.

You keep saying that, but a "home gamer" with a small compressor can still flow 100+ CFM as long as they have air in the tank, and no one is trying to run a 1/2" impact or an air hammer on an empty tank, so I'm interested in why you are so interested in unrealistically low flow rates?

Also, we're seeing a less than 1 PSI pressure drop at 10 CFM using the worst possible coupler/plug combo. The pressure drop will only decrease at lower flow rates, so what are you expecting to see?

 

[spectre6000]

I don't imagine a home gamer is going to be running more than a single tool at a time. I noticed that most, if not all, of the air tools at Home Depot want in the neighborhood of (if not exactly) 4 cfm. Seems like it must be some sort of benchmark they're trying to hit. Maybe that's a bad assumption. My guess was that it was correlated to what home gamer compressors were able to produce based on the labels on that side of the same aisle. Yes, home gamers CAN have massive rigs, but most have pancakes.

Regardless, if we get at least 3 flow rates (i.e. 5, 10, 20) we can try to fit a curve. More data points means a more accurate curve, and then we have ALL the flow rates below where the above chart leaves off at the bottom of the range.

My hypothesis (and I typed this out previously, but never posted... I've been sick... which might help explain other lapses should there be any) is that below 10 cfm, with high quality couplers (i.e. Stedlin and Prevost), the ****** style (industrial/high flow) won't make a difference. If the Merlin coupler (which Stedlin demonstrated creates a greater pressure differential than the Stedlin coupler using the same ****** profile) only drops 1 psi, I'll bet there's zero difference between industrial and high flow below some higher-than-most-home-gamers-will-ever-practically-use flow rate thresh hold.

 

[CallumRD1]

The 4 cfm numbers are normally a weighted average over a very low duty cycle. A die grinder, 1/2" impact wrench, or air hammer can easily use 30+ cfm while running.