Tag: PSIG

Venturi Effect in Use

Published on by jasonkirbyLeave a comment

The Venturi effect describes the phenomenon where a fluid, such as air or water, accelerates as it passes through a constricted section, resulting in a decrease in pressure. This occurs because the fluid is drawn into the narrower area, and the increase in velocity leads to a corresponding drop in pressure. The effect is named after Giovanni Battista Venturi, who first articulated this principle in 1797.

A perfect example of the Venturi Effect can be found in our Air Amplifiers. Compressed air enters through the air inlet and flows into an annular chamber, where it is accelerated through a small ring nozzle. This high-velocity primary airstream follows the Coanda effect, guiding it toward the outlet. As a result, a low-pressure zone forms at the center, drawing in a significant volume of surrounding air into the primary flow. The mixture of the primary airstream and the surrounding air is then expelled from the Air Amplifier at a high volume and velocity.

The Venturi Effect is represented in amplification ratios. A ratio represents the relationship between two quantities, indicating how many times one value is contained within another. In the case of the Super Air Knife, this ratio illustrates the volume of ambient air that is drawn in alongside the primary flow of compressed air. With an impressive amplification ratio of 40:1, the Super Air Knife incorporates 40 parts of ambient air for every single part of compressed air, making it one of the most efficient air-operated knives available. This addition of mass enhances the device’s ability to deliver a powerful force, enabling it to perform more effectively in various applications.

The Venturi effect is integral to various EXAIR products designed for cooling, drying, and cleaning, alongside our vacuum generators. If your facility has a process that could benefit from an Intelligent Compressed Air solution, please reach out to us. We would be pleased to discuss your specific application and develop a solution that not only lowers your compressed air expenses but also enhances worker safety.

Jason Kirby
Application Engineer
Email: jasonkirby@exair.com
Twitter: @EXAIR_jk

Intelligent Compressed Air: Two Different Products Called “Air Amplifiers”

Published on by Russ BowmanLeave a comment
A 2psi change in compressor discharge pressure equates to a 1% change in compressor power consumption.

They say that necessity is the mother of invention, so it’s no coincidence that mechanical means of compressing air came about in the early days of the Industrial Revolution, eventually becoming known as the “4th Utility” along with electricity, water, and gas. For most of the 20th Century, compressed air system pressure was commonly generated in the neighborhood of 100psig, although many modern industrial air compressors can be operated at 160 to 200psig. Operating an air compressor at higher discharge pressure increases the cost of operation, though, so it’s in EVERYONE ‘S best interests to run compressed air systems at the lowest pressure possible, that still gets the job done for all the air-operated gear in the facility.

So, what if most of your compressed air loads operate at 80-100psig, but one (or a handful) needs 120psig? Or 160psig? Or even higher? Increasing your compressor discharge pressure from 100psig to 160psig means you’re using 30% more power to run the compressor. That’s a LOT for one (or a handful) of operations.

Good news: the laws of physics say that pressure is the amount force applied to a specific area…as in pounds(force) per square inch, or psi. So, if we apply a certain pressure to a large diameter piston, and attach that with a shaft to another smaller diameter piston, the amount of force doesn’t change, but the area does, so the pressure on the other side of the smaller piston HAS to:

Let’s say the primary pressure (P1) is 100psi, and the primary piston (D1) is 4″ in diameter, with a surface area of 12.56 in2. That means the force applied to the primary piston (D1) is : 100 lbf/in2 x 12.56 in2 = 1,256 lbf.
This is the same force applied to the air on the other side of the secondary piston (D2), which has a diameter of 2″ and a surface area of 3.14 in2. Since pressure is force divided by area, that 1,256 lbf applied to 3.14 in2 results in a secondary pressure (P2) of 400psi.

This is the basic theory behind how air (pressure) amplifiers – also known as booster regulators – work. Essentially, you’re trading compressed air flow (into the larger cylinder) for pressure. Now, if EVERYTHING you operate needs higher pressure, the best way to do that is to increase the compressor discharge pressure. But if you only have one, or a few, loads that need higher pressure, the increase in air consumption for those loads is likely less costly than compressing the air to a higher pressure than is needed for the majority of your loads.

The other type of air amplifier is the one that EXAIR manufactures – it’s an air FLOW amplifier, and here’s how it works:

In this case, we’re trading pressure for flow, and getting a much higher total developed air flow rate than just the amount of compressed air it uses. Not only does the entrained air make them incredibly efficient, it also develops a low-velocity boundary layer that attenuates the sound level of the total air flow. They can be used for cooling, drying, cleaning, ventilation, fume exhaust, and even material conveying, especially if the material to be conveyed is very light, or already airborne.

With (16) models to choose from, EXAIR Air Amplifiers are a quick and easy way to provide a tremendous amount of cooling air flow from a compact, lightweight product.

EXAIR Air Amplifiers come in a range of sizes, from 3/4″ to 8″. Super Air Amplifiers are lightweight, durable aluminum, and Adjustable Air Amplifiers are available in aluminum or 303SS. If you’d like to find out more about them, give me a call.

Russ Bowman, CCASS

Application Engineer
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The Value Of A Pressure Regulator At Every Point Of Use

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regulator
EXAIR Pressure Regulator

To understand the value of a having a Pressure Regulator at every point of use we should start with identifying the two types of Pressure Regulators, Direct Acting & Pilot Operated.  Direct Acting are the least expensive and most common (as shown above), however they may provide less control over the outlet pressure, especially if they are not sized properly.  However when sized properly they do an outstanding job.  Pilot Operated Regulators incorporate a smaller auxiliary regulator to supply the required system pressure to a large diaphragm located on the main valve that in turn regulates the pressure.  The Pilot Operated Regulators are more accurate and more expensive making them less attractive to purchase.  The focus of this Blog will be on the Direct Acting Pressure Regulator.

The Direct Acting Pressure Regulator is designed to maintain a constant and steady air pressure downstream to ensure whatever device is attached to it is operated at the minimum pressure required to achieve efficient operation.  If the end use is operated without a regulator or at a higher pressure than required, it result’s in increased air demand and energy use. To clarify this point, if you operate your compressed air system at 102 PSI it will cost you 1% more in electric costs than if the system was set to run at 100 PSI! Also noteworthy is that unregulated air demands consume about 1% more flow for every PSI of additional pressure.  Higher pressure levels can also increase equipment wear which results in higher maintenance costs and shorter equipment life.

Sizing of the Air Regulator is crucial, if it is too small to deliver the air volume required by the point of use it can cause a pressure drop in that line which is called “droop”.  Droop is defined as “the drop in pressure at the outlet of a pressure regulator, when a demand for compressed air occurs”.  One commonly used practice is to slightly oversize the pressure regulator to minimize droop.  Fortunately we at EXAIR specify the correct sized Air Regulator required to operate our devices so you will not experience the dreaded “droop”!

Standard Air Knife Kit
EXAIR Standard Air Knife Kit Which Incudes Shims, Properly Sized Pressure Regulator & Filter Separator

Another advantage to having a Pressure Regulator at every point of use is the flexibilty of making pressure adjustments to quickly change to varying production requirements.  Not every application will require a strong blast sometimes a gentle breeze will accomplish the task.  As an example one user of the EXAIR Super Air Knife employs it as an air curtain to prevent product contamination (strong blast) and another to dry different size parts (gentle breeze) coming down their conveyor.

EXAIR products are highly engineered and are so efficient that they can be operated at lower pressures and still provide exceptional performance!  This save’s you money considering compressed air on the average cost’s .25 cents per 1000 SCFM.

Super Air Knife Performance
EXAIR Super Air Knife Performance Specifications At 5 Different Pressures.

If you would like to discuss Air Regulators or quiet and efficient compressed air devices, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer
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EXAIR Blogs This Week Are Almost As Cool As Shark Week

Published on by Russ BowmanLeave a comment

Yes, ALMOST. This week, the EXAIR Blog has featured some excellent explanations of the science behind the operation of compressed air products. On Tuesday, John Ball posted the best explanation of SCFM vs ACFM that I’ve come across, and I’ve been explaining this to callers for almost four years now. I’m using his blog to perfect my “elevator pitch” on this topic. It will still likely require a building with more than ten floors, but I think that’s OK.

Also on “Two Blog Tuesday,” (this week only; I’m not trying to start anything) Dave Woerner’s gem of a blog detailed the terminology associated with pressure measurement, and why we use “psig” (g = gauged) – in a nutshell, the compressed air inside the pipe doesn’t care what the pressure outside the pipe is. And, since he mentioned it, I might add that most of agree that we care even less about how a certain NFL team’s footballs were (or were not) properly inflated.

Brian Farno’s “One Blog Wednesday” entry was a quite useful (if not alphabetical…OK; now I AM trying to start something) list of some common terms and expressions we use on a regular basis while discussing the operation and performance of EXAIR compressed air products. If you liked his photo demonstration of the Coanda effect with the foam ball & Super Air Amplifier, I encourage you to experience the Coanda effect for yourself, if you have access to a leaf blower and a volleyball:

I mention these earlier blogs to get to the point of MY blog today…a bit of theory-to-practice, if you will. Once you’ve gotten a decent understanding of these principles (or have the above links bookmarked for quick reference,) we can apply it to what’s needed for the proper operation of a compressed air product itself.

With a working knowledge of air flow (SCFM) and compressed air supply pressure (psig,) we can more easily understand why certain pipe sizes are specified for use with particular products. For instance, the longer the Super Air Knife and/or the longer the run of piping to it, the larger the pipe that’s needed to supply it:

This table comes directly from the Installation & Operation Instructions for the Super Air Knife.
This table comes directly from the Installation & Operation Instructions for the Super Air Knife.

The reasons for this are two-fold: First, the pipe…longer runs of pipe will experience more line loss (a continuous reduction in pressure, due to friction with the pipe wall…and itself) – so, larger diameter pipe is needed for longer lengths. For another practical demonstration, consider how much faster you can drink a beverage through a normal drinking straw than you can through a coffee stirrer. Not as dramatic as the leaf blower & volleyball (you really want to try it now, don’t you?) but you get my point.

Second, the Air Knife…the longer the Air Knife, the more air it’s going to use. And, if it’s longer than 18”, you’ll want to feed it with air at both ends…line loss will occur in the plenum as well.

In closing, I want to leave with another video, shot right here at EXAIR, showing the actual reductions in pressure due to line loss through different lengths, and diameters, of compressed air supply line to a Super Air Knife.

If you ever have any questions about compressed air use, or how EXAIR products can help you use your compressed air more efficiently, safely, and quietly, please give us a call.

Russ Bowman
Application Engineer
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