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Air compressor won't stay at configured level

guidoism

Member
I don't understand my air compressor's regulator ? When I set the output pressure to something lower, like 40, it will initially shoot out at 40, but within seconds the output pressure will fall to close to zero. If I modify the output pressure while continuously using it then when I stop using the air it will creep up to something like 100. Then when I use it again it will initially start out at 100 and then quickly drop down to the 40 which I initially wanted.

What's going on here? Is this how it's supposed to work?

I can make it work with my rivet gun if I'm careful, but it's certainly not ideal. Are there ways around this? I also have a brass inline regulator on my rivet gun but I don't understand it yet. Too many variables. Ugh.
 
Assuming the regulator is working correctly, it sounds like there is a restriction to the airflow------small diameter hose, too long of a hose, kink, or flap of the interior liner of hose blocking flow.

I would check the above, if all good then it could be a bad regulator.
 
Thanks Mike. I just checked and no kink and nothing that looks abnormal from the outside. I guess this is a good time to replace it one of those super lightweight hoses that I've seen and see how that works. Are there any inline regulators that work particularly well for riveting?
 
Regulator

I have several regulators from Harbor Freight. I use the small ones, and install a male fitting in one side and a female in the other. The regulator then plugs into the compressor and the hose.

https://www.harborfreight.com/14-in-mini-air-regulator-with-dial-gauge-68226.html

Each regulator is set for a specific tool, i.e. 3X gun, 2X gun, squeezer...once they are set, I never need to change the setting, only the regulator.

As for the pressures, the running pressure on the gauge will always be lower than the static pressure. Set the regulator for the running pressure...
 
Not sure it is a regulator problem . .

When reducing pressure from high to low with the regulator, it does not always bleed off the air in the hose/pipe. Try an air blower or tickling the trigger to discharge the air in the hose/pipe then turning the regulator up to the desired pressure.
 
When reducing pressure from high to low with the regulator, it does not always bleed off the air in the hose/pipe. Try an air blower or tickling the trigger to discharge the air in the hose/pipe then turning the regulator up to the desired pressure.

Alright, I just tried this with an air blower and it still does the same thing - After I stop using the tool the output pressure creeps up to a much higher setting.
 
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Alright, I just tried this with an air blower and it still does the same thing - After I stop using the tool the output pressure creeps up to a much higher setting.

A true pressure regulator should not do that. It should recover to the higher setting nearly immediately. It is normal for a little pressure drop during flow, but it should be less than 10 psi. The drop will be flow dependent, so a fully open hose or blower will drop more than a squeezer for example.

There are many small regulators available with various input/output size connections. HF, Grainger, Lowes, HD etc. If there is not a restriction somewhere, then it sounds like a bad regulator.

Lets just review for clarity though . . the input to the regulator is from a receiver tank at say 100, 125, 150, 175 psi. The output of the regulator has the pressure gage. The hose is connected directly, or with a quick coupler, to the output of the regulator. If all these are correct, then back to a bad regulator.

One last possibility, is that some debris has fouled the regulator passages. Some can be dissembled and access the diaphragm and valve. You might check that if it is possible.
 
Details needed.

You say "compressor's regulator". Is that what you literally mean? If so, and the tank pressure is going tens, or even a hundred psi above the set pressure, the regulator's bad (likely dangerously bad).

I suspect you're talking about a secondary, in-line regulator. If that's the case, You need to be specific about whether it's a true regulator, or a variable restrictor orifice, which is common on rivet guns.

If it's a true regulator, what is the gauge monitoring (pre or post regulator)?

Your symptom description almost sounds like you have a restrictor orifice, followed by a gauge. A restrictor orifice will allow downstream static pressure equal to source (tank or upstream regulator), and downstream pressure will drop proportional to size of orifice and flow through the tool.

Charlie
 
regulator

ALL of my downstream regulators read a higher static pressure.

Set the RUNNING pressure appropriate for the tool you are using and don't worry about the static pressure.

As in a previous post, set a low pressure, activate the tool, increase regulator pressure to what is appropriate for the tool, leave it there.

When I get to the shop today, I will take a photo and post it...(or try to)
 
This is what I have

Here's a video of what it is doing with an air blower: https://youtu.be/IyVJu_UIbKk

and this is what it looks like:

fCQqYvH.jpg
 
Here's a video of what it is doing with an air blower: https://youtu.be/IyVJu_UIbKk

and this is what it looks like:

fCQqYvH.jpg

Looks normal to me. That is what they do. As previous person mentioned, you set the pressure with the tool running/flowing and ignore the pressure shown when the tool is not running. The delta will be different for each tool, based upon it's flow rate.

Larry
 
Looks like a pretty small unit-------what is the PSI rating and what are the CFM ratings ??

You might need to get a better compressor............or possibly you could add an additional tank and get better performance.
 
changes

A bigger/better compressor isn't going to change what is being seen on the gauge...

I am using an 80 gallon, 14 CFM @ 175 PSI, two stage compressor plumbed with 3/4" lines and I see the same thing on my tool regulators...
 
5.30 CFM @ 90 PSI

Air drill needs about 12 CFM.

Rivet gun may eat that much also, but due to being used for short bursts it will not seem that hungry for air.

Paint gun and die grinders-----not sure, but probably pretty close to your unit's max output.

Does the compressor have a non-regulated output?? if so, you could try running that to a larger tank, then to regulate that output.

I am still of the opinion that your issue is one of airflow. It is also possible that the way your unit is plumbed, there may be restriction in the flow going to the regulator, and it is responsible for the pressure drop.
 
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I am using an 80 gallon, 14 CFM @ 175 PSI, two stage compressor plumbed with 3/4" lines and I see the same thing on my tool regulators...

Sounds like we have very similar compressors, I also see a pressure drop when using most any tool, but the drop is pretty small.

Guido is showing 35--40 PSI drop.......
 
Air drill needs about 12 CFM.

Rivet gun may eat that much also, but due to being used for short bursts it will not seem that hungry for air.

Paint gun and die grinders-----not sure, but probably pretty close to your unit's max output.

Mike,

This is a bit of thread drift, but I encourage you to rethink that post. While a drill might demand that much flow when actually running all out, the demands on the *compressor* by one guy in his garage building an a/c are nothing like that high. Through an entire -7 airframe build, the only time I had to wait on a little oil-less compressor with a 10 gal tank was while using a die grinder, which is *much* worse than a drill.

It does new builders a disservice when a 'veteran' builder tells them they can't build effectively without the most expensive tools, the biggest commercial shop size compressors, etc.

Charlie
 
It does new builders a disservice when a 'veteran' builder tells them they can't build effectively without the most expensive tools, the biggest commercial shop size compressors, etc.

Charlie

Charlie, sorry if that is how I came across---------I was not trying to tell him he "can't" build effectively, I was responding to his original question, and was trying to help him diagnose the reason his unit was acting the way it was in his video.
 
This is not that difficult.

S2GMH6nCp4dsQV4DSllcmFsoISpjJGMFRepewcZ1OpbOMaD7aZmrXIWT3qLrw0af1oxjedZ-r966qcCHD7ozYVj1viPR66zPKtiIH2XQz9kKIq7jCbpAUZ75ejPhZ9jsTWC37u0-DfF1_EG1mpvqaSEDp42ibrg2r4XrTI0HVh81AVIZPf-8gPwD_loYcq50yFmLtfleWLs4cFf6ASxqY9k4dHho-yX8zpM86AhWWFV2loA7L1bLDgcJGYpfVEPeFePFdXgjGB-H1hVty3CT7X6jxnkcvHbjALfWwENwBraBKAE5qK229oLVjKaKNLBQxFhiEr2568eHqz8qauKPHu4jMM9VquWoalg4un5c010PHqgdHJHVgutbDHFh4mk_2jmxyx8kqQ_YJDC8cXDSccPC538PuHyb2DMVNcmdbouSSfbc9K-ZYOn_qmIt55KXqCsmmETfwiQdHliQhs1PgqtOERxwIFJjMHb63wZwV5b8gRBy1z3FpzNyFWNPiWyROEDIQPOW9Sx-yNGNlSZnTm0xgyaqkW4duFrpuuzjyzl8Pt537bhXi17y_vwkRzN8JL0SiUugHRY-BNn5iKjJajy3RfhdWaLE2mit4ZF2uOep2g0abZl0MLRfJwciaYxdDaCmuAwOwp41Cei0GpfFUhbxKBgDnLN-4ETQbQtc6b6oBUP2143jpGvkF8SOHlRp1rYH5zJJ1GF-AKl-dQ=w476-h360-no


Looks normal to me. That is what they do. As previous person mentioned, you set the pressure with the tool running/flowing and ignore the pressure shown when the tool is not running. The delta will be different for each tool, based upon it's flow rate.

Larry

Yep, that's what it does.

Set the running pressure and don't worry about the static...

Looks like a pretty small unit-------what is the PSI rating and what are the CFM ratings ??

You might need to get a better compressor............or possibly you could add an additional tank and get better performance.

I just went and set mine to 60 psi and with an air blower it dropped way down to 55 psi. Tank size, compressor rated SCFM, has nothing to do with this regulator. I simply does not function properly 30psi drop is too much. It may be design, maybe an internal failure, but it is NOT NORMAL for a proper regulator. Back to Mike's first comment, it could be some internal restriction of the manifold.

More than 10psi drop is an issue for any regulator, they don't have to be expensive. If you have a hose connection to full tank pressure, put a regulator on a quick coupler at the end of your hose and try that. If it does not work properly then there is an internal restriction.
 
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Guido,

If your issue is actually affecting the tool (rather than being a gauge issue), something to consider is the 2ndary regulator *location*. If you have a really long run of small diameter hose, you could be seeing a further decrease in pressure *at the tool*, due to resistance in the hose itself, as Mike pointed out in his 1st post. The 'best' setup has the 2ndary regulator as close to the tool as is reasonable and convenient. I've seen guys using paint spray guns put the regulator on the gun itself, but that's hardly needed for any other type of tool.

But I'll bet there's nothing wrong. If you set up the system like Bob described, and adjust the 2ndary regulator with the tool running, does the gauge return to the same working pressure every time the tool is run?
 
Regulators

Guido,

If your issue is actually affecting the tool (rather than being a gauge issue), something to consider is the 2ndary regulator *location*. If you have a really long run of small diameter hose, you could be seeing a further decrease in pressure *at the tool*, due to resistance in the hose itself, as Mike pointed out in his 1st post. The 'best' setup has the 2ndary regulator as close to the tool as is reasonable and convenient. I've seen guys using paint spray guns put the regulator on the gun itself, but that's hardly needed for any other type of tool.

But I'll bet there's nothing wrong. If you set up the system like Bob described, and adjust the 2ndary regulator with the tool running, does the gauge return to the same working pressure every time the tool is run?

That's how my shop works. Full pressure from the tank is supplied to the end of the hose. Two pigtails with mini regulators control pressure at the tool. One pigtail is high (90 psi) one is low (20-30 psi). My DeVilbiss HVLP has a filter and regulator at the gun.
Better the regulator, more accurate the pressure. The high pigtail is an HF mini. The low pig tail and gun both have RTI mini 1/4" regulators. They never change from the set pressure. Every time I connect one and trigger the tool, it's exactly where I left it. Sounds OCD but it really improves riveting and paint work.
 
My set up is a lot like Larry's. 60 gallon compressor with 1/2" regulator at the tank https://www.harborfreight.com/12-in-air-line-filter-regulator-with-gauge-68281.html set at 130 psi and a 50' run of 3/8" HD hose https://www.harborfreight.com/12-in-x-50-ft-premium-rubber-air-hose-62882.html to my air supply manifold where I have two 3/8" regulators https://www.harborfreight.com/38-in-air-filter-with-regulator-68232.html for individual drops for high pressure set at 100 psi and low pressure around 30 psi depending on tool used . I usually only have around a 5 psi drop when using a tool. A 30 psi drop does not sound right.
 
Found the problem

To those who said it was the regulator: You were correct.

I bought a new hose and new regulator today at Harbor Freight. Swapping out just the hose didn't help. They were both 25' long, so length clearly shouldn't have been a problem. Next I added the regulator. Yup, that was it. With the new regulator I only got a 5 psi drop while using my tools. And my rivet gun doesn't smash through rivets anymore.

Thank you to everyone who helped me figure this out.

P.S., My 10 gal tank has actually been working out really well for me for my Sioux air drill.
 
...

I can make it work with my rivet gun if I'm careful, but it's certainly not ideal. Are there ways around this? I also have a brass inline regulator on my rivet gun but I don't understand it yet. Too many variables. Ugh.

Sounds like your ?brass inline regulator? is just an adjustable orifice, which only drops pressure under flow. With a rivet gun, the first few hits will be harder, as there is full pressure at the gun until flow starts.
The
For consistency in riveting, I use a compact regulator right at the gun. With a little practice you get a feel for where to set it depending on rivet diameter and length. Also, I just set the compressor regulator at 90 psi and just forget it; no need to set a ?running pressure?, which can vary depending on which tool and how much hose you have connected, and less likely to forget to reset the regulator when changing tools.

I use the 0-125psi version of this one from McMaster-Carr. This page from my build log shows it in use.
 
This! Regulator at the rivet gun

A thousand times this... I know that some folks just regulate at the compressor and in theory that is fine. But in reality you really need to be adjusting your gun a lot to do different types of rivets and even if you use different rivet sets. Longer rivet sets need higher pressures.

So for those who are newer at this do yourself a favor. Buy an inline regulator that attaches to the rivet gun. And you can run your compressor regulator high - I use about 90 psi and regulate it further at the gun with many of the widely available inline regulators. It allows you to finesse your gun pressure to whatever you are riveting at that particular moment. Otherwise you have to constantly move away from your work and go back and fiddle with the compressor regulator. Why not do it right at the gun itself...

Sounds like your ?brass inline regulator? is just an adjustable orifice, which only drops pressure under flow. With a rivet gun, the first few hits will be harder, as there is full pressure at the gun until flow starts.
The
For consistency in riveting, I use a compact regulator right at the gun. With a little practice you get a feel for where to set it depending on rivet diameter and length. Also, I just set the compressor regulator at 90 psi and just forget it; no need to set a ?running pressure?, which can vary depending on which tool and how much hose you have connected, and less likely to forget to reset the regulator when changing tools.

I use the 0-125psi version of this one from McMaster-Carr. This page from my build log shows it in use.
 
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