Issues and Problems with Pressure Drop

 

Super Air Knife Install Sheet

Pressure drop comes in different forms, and it causes inefficiencies within your pneumatic system.  EXAIR writes statements in the installation manuals to help find the correct pipe sizes to supply the different products.  (Reference Super Air Knife Installation Manual above).   But there are other areas that can affect the performance.  These can be fittings, tubing, valves, and accessories.  In this blog, I will cover some pitfalls that can minimize the potential of your EXAIR products.

Pressure drop by definition is a difference or loss in pressure.  A properly sized Filter Separator will typically have a pressure drop of 5 PSID (0.3 bar) at the rated conditions.  So, if you start with 100 PSIG (6.9 bar), the air pressure after the filter separator will be 95 PSIG (6.6 bar).  But what happens when a filter separator is undersized or too small?  The pressure drop will be much higher.  So, if the pressure drop is 30 PSID (2 bar), then the downstream air pressure will only be 70 PSIG (4.8 bar).  At that pressure, you may not be able to get the performance that is required to do the job.

The first thing in determining these potential issues is what I like to call forensics.  If you can install a pressure gage at the inlet of any EXAIR product, then you can deduce if a potential problem is within your setup.   For example, if the Pressure Regulator is at 100 PSIG (6.9 bar), and the pressure gauge at the inlet is reading only 60 PSIG (4.1 bar), then there is a pressure drop of 40 PSID (2.8 bar) between these two points.  You can look in this area for the problem or problems.  If the gauge on the Pressure Regulator goes down as well when you are operating, then the problem area is upstream of the Pressure Regulator.  This can be from the pipe size or the air compressor.

The most common issues are fittings and tubing.  With fittings, small openings may not allow enough air to pass through.  Above is a photo of some typical fittings.  You notice that the right side of the chart has large enough openings to decrease pressure drop.  In some instances, quick connect fittings are commonly used to easily connect or disconnect pneumatic devices; but if you use too small or too many of these fittings, they can cause a large pressure drop.

The other problem is with the inner diameter of tubing, hoses, or pipes that are not properly sized.  Russ Bowman, a colleague, created a video showing the issues with improperly sized plumbing.  It is a very interesting video that shows the effect on a Super Air Knife.

If you want to get the most from your EXAIR products, you will need to reduce the amount of pressure drop in your system.  Pressure drop is wasted energy and can affect your pneumatic system.  You can follow my recommendations above.  Or if you would like to discuss your setup with an Application Engineer, we will be happy to assist.

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

Quick Disconnects & Why Not To Use Them

Quick Disconnects are a quick and easy solution to hook up devices to your compressed air system.  These units can be found in quite a few factories and are more often than not being used incorrectly.  I know that on the air compressor in my garage, the only way to hook anything up to it was to use 1/4″ quick disconnects.  Chances are they are even a few of them within your facility, assuming you have compressed air available.

1/4" Quick Disconnect male and female.
1/4″ Quick Disconnect male and female.

When you really look at a quick disconnect though you start to see why it shouldn’t be used to install every compressed air driven device there is.   You can see in the pictures below that a 1/4″ quick disconnect that goes to a 3/8″ NPT adapter has a .192″ opening at the small end.  A 3/8″ Schedule 40 iron pipe will actually carry a .493″ inner diameter.   If you were to use this quick disconnect on something like a 2″ Heavy Duty Line Vac, you will starve it for air due to the limited ability of the small diameter to carry enough air volume. This, in turn, will limit the performance of the Line Vac.  This is because the through hole on the quick disconnect cannot pass enough air to feed through to the Line Vac.

Inner Diameter of 1/4" quick disconnect.
Inner Diameter of 1/4″ quick disconnect.

On the 1/4″ quick disconnect to a 3/8″ NPT this may not be as large as a problem as the next picture.  Below you can see a 1/2″ quick disconnect that is going up to a 3/4″ NPT.  a 3/4″NPT Schedule 40 iron pipe is actually a .824″ inner diameter.  The quick disconnect at most has a .401″ inner diameter.

IMG_4614
1/2″ quick disconnects

 

Inner diameter of 1/2" quick disconnect.
Inner diameter of 1/2″ quick disconnect.

Even though you are providing the correct thread size for your connection (a 3/8 MNPT and a 3/4 FNPT respectively in our example) the quick disconnect’s small inside diameter could be too much of a restriction for the volume demanded by an end use product. Due to this restriction point you will see pressure drops in your system when using a device with a properly sized inlet for its demand of compressed air being fed with an improperly sized quick disconnect.  This is one of the main reasons one of our first questions in troubleshooting an EXAIR products performance with a customer is whether or not they are using quick disconnects.

If you would like to learn more about how to properly plumb your EXAIR Intelligent Compressed Air Product, feel free to contact us, or take a look around our Knowledge Base.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF