I have a Quincy QT 54 I have 50 ft of 3/8 hose. I am running a Aircat 1150. The regulator I have maxes out at about 140. I put a inline gauge at the end of the hose with the Aircat and stays steady about 80-85 psi. Do I need a regulator that goes higher or a 1/2 air hose?
Air Pressure
- Thread starter cquint
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Don1357
Well-known member
That's like expecting that if your speedometer maxes at 120 but the car can only get to 85 that maybe getting a speedometer that can do 150 will let you get a higher speed.
Bar something wrong with the regulator all it does is regulate. Put the gauge right after the regulator to see what it says.
Bar something wrong with the regulator all it does is regulate. Put the gauge right after the regulator to see what it says.
Stedlin
Well-known member
Is the Aircat free running when checking the pressure or is it working?
What kind of hose/tool connectors are you using?
vanapplebomb
Well-known member
Sounds typical. With 50 feet of hose, you will get quite a pressure drop. You might luck out and be about right with high flow couplers, or 3/8 body industrial/auto fittings.
Also, the less couplers, the better. You can eliminate a coupled between the hose and air source. That way you only have one coupler in the air line.
Also, what regulator? Certain regulators are unbelievably restrictive and lack the ability to flow the proper amount of air to keep line pressure from taking a dive.
Other thing you can do is run a 25 foot hose, if of course it will be long enough for your needs.
I run 25’ hoses. With one High flow quick coupler I need 120psi at the wall to make 90 at the gun. Two high flow and I need to knock it up to 130....but most the time I don’t bother, and just leave it at 120. Only time I really bump it up is with the 3/4 impacts and 4-1/2” angle grinder. Both eat air.
Stedlin
Well-known member
What counts is the pressure under load. You should check that.
Quick couplers vary tremendously in performance.
It would help if you stated what kind of couplers you are using.
Milton Shaw
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Regulator are designed to be close to the work, not on the whole system. I use them on the drops for items that need the pressure reduced from compressor/shop line pressure. If using several lengths of hose, I put the regulator on the last hose connection before the paint spray gun for example. With PVC piping you would use a regulator at compressor to reduce to 5 -10 PSI for safety. LOL
Stedlin
Well-known member
This video shows the pressure and pressure drop of a 25 foot 3/8 hose when using a 3/4" impact.
3/4" impact with 25 foot 3/8 hose
3/4" impact with 25 foot 3/8 hose
Manufactures ratings are based on the pressure being 90 psi at free speed.
Stedlin
Well-known member
Obviously.
Wouldn't be practical to set it any other way.
Hypothetical:
Let's say you connect your impact that consumes 40 CFM free running to a tank pressurized to 95 PSI with a 25 foot 1/2" hose that drops 5 PSI at 40 CFM.
You now operate the gun to apply torque which causes the air motor to slow down to the point where the pressure rises to close to the 95 PSI source pressure. In this case the highest torque you can apply is based on the 95 PSI source.
Hypothetical 2:
Same impact but this time you use a 25 foot 3/8" hose and couplers that drop 20 PSI @ 40 CFM.
You now operate the gun to apply torque and the pressure rises as the flow requirement decreases under load and now the pressure in the gun rises to more than 95 PSI.
Seems like you could potentially get higher performance from a more restrictive system.
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strutaeng
Well-known member
Based on this source, should only be 1.72 psi drop for the hose only:
https://www.gates.com/us/en/knowledge-center/calculators/air-flow-calculator.html
Hose diameter: 0.375"
Hose length: 50 ft
Gauge pressure: 90 psi
Flow : 8 cfm (per the manufacturer)
Pressure loss: 1.72 psi
I'd eliminate the regulator and check again...
Stedlin
Well-known member
My 3/8" hoses expand under pressure from a nominal OD of .625 to .66.
This would mean that the ID under pressure is no longer 3/8" but close to .43 or more depending on the compressibility of the hose material.
This will significantly reduce the hose pressure drop.
The manufacturer rating of 8 CFM is typically for a 25 percent duty cycle so it's about 32 CFM free running.
Depends. It's easy to measure either way and in most manufacturers labs both are recorded. Free-speed is easy because it it what it is. At load requires some judgement as to what load is applied. In my experience for impacts, a brake is used to load the tool down to 6-9 RPM.
Stedlin
Well-known member
I meant it wouldn't be practical for the end user to set the pressure under load.
You wouldn't happen to know at what pressure at the gun the torque rating is determined at would you?
You're right it would be pretty difficult for the user to set the pressure under load.
Typically air pressure is set at 90 psig while the tool is running at free speed. The gauge is connected with a T at the inlet after any type of coupling. That's one mistake that people make when checking air pressure at the tool is taking the gauge reading on the hose side of the QD.
Stedlin
Well-known member
I'm still wondering what the pressure drop across the impact is when it achieves the factory specification for torque. Obviously it must be greater than 90 since the air motor slows down.
Stedlin
Well-known member
As far as I'm concerned giving a torque rating for an air impact wrench without a corresponding dynamic pressure makes it meaningless.
Not quite sure what you are asking. Do you want to know if the pressure is set at 90 psig free speed, what pressure does that equate to when the tool is tightening a bolt? If that's the question then it is hard to say because the motor speed changes as the fastener tightens, so the pressure at the inlet is changing.
Stedlin
Well-known member
I will give an example of what I mean:
I connected my 3/4" impact to a tee with a pressure gauge to a short 1/2" hose to a regulated pressure source than pulled the trigger and ran it unloaded while adjusting the pressure regulator until the gauge at the tee read 90 PSI.
I then began tightening a bolt until maximum torque was reached and the gauge read 97 PSI maximum.
I then repeated the test only this time with a 25 foot long 3/8 hose and with a Stedlin coupler and plug on each end of the hose.
With the regulator now set to produce 90 PSI at the Tee I than began tightening the bolt again but this time the gauge read 110 PSI max.
So as you can plainly see the system with the couplers and longer smaller hose produces more torque than the low restriction setup.
This is the fallacy with setting the gun to 90 PSI unloaded.
This is why I wonder about the specification and how exactly it is determined.
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I get it. You are really just showing the difference between dynamic and static pressure. With the short hose, your source pressure required to hit 90 dynamic at f/s is lower than what is required with the long smaller hose. However, in both cases when flow hits zero, your pressure at the tool inlet equals your source pressure. When your impact is tightening a fastener motor speed starts out fast with flow high and slows as the bolt tightens and flow reduces causing your inlet reading to move toward the source pressure.
Stedlin
Well-known member
Right.
So in some cases as I have shown, a more flow restrictive setup actually produces more torque when setting the pressure at 90 PSI free speed.
Obviously with the source pressure constant the less restrictive system wins every time.