What is the Venturi Effect?

In 1797 a Italian physicist named Giovanni Battista Venturi wrote a dissertation on the “Venturi Effect”.  However, an actual device was never created or applied until 1888 where Clemens Herschel was awarded the patent for the first Venturi tube.

The Venturi effect is a decrease in fluid pressure when fluid flows through a constricted area of a pipe.  In other words, as the diameter becomes smaller, the fluid velocity becomes faster.  This increase in velocity will create a lower pressure just past the constricted area.  When designed correctly, you can create a strong vacuum or a large negative pressure.

The EXAIR E-Vac® Vacuum Generators use this phenomenon by using compressed air as the fluid.  This type of Venturi tube restricts the internal area to generate a fast velocity through the body creating a vacuum pressure for suction.

EXAIR offers three types of Venturi tubes; low vacuum, high vacuum and adjustable.  Low vacuum units are typically used with porous material because the trade off for low vacuum is higher vacuum flow. The high vacuum generators can create a vacuum level as high as 27” Hg (71 KPa).  The Adjustable E-Vacs can alter the internal air velocities by turning the body and getting different vacuum pressures.  Without any moving parts or electric motors to break, the EXAIR E-Vacs are a simple design that is very durable, effective and long-lasting.  A great product for applications like pick and place, clamping, lifting and vacuum forming.

In-Line E-Vac How It Works
EXAIR E-Vacs provide instantaneous vacuum response, and are engineered for high efficiency to minimize air consumption.

The Venturi effect was discovered in 1797, brought into existence in 1888, and is still used in vacuum applications to this very day.  If you have an application where a Venturi tube could help you, please contact an Application Engineer.  We will be happy to assist you.

Jordan Shouse
Application Engineer
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Porous and Non-Porous E-Vac Vacuum Generators

Getting a vacuum from compressed air seems a bit like magic, but it works and it works well. EXAIR’s E-Vac® Vacuum Generators are compressed air powered, single stage vacuum generators. They are a low cost way to create vacuum for pick and place, clamping, lifting, chucking, vacuum forming and other applications.

The Low Vacuum Generators are ideal for ‘porous’ types of applications.  When we say ‘porous’ we are describing those processes where a lighter vacuum level combined with higher vacuum flows are needed. A good example of this is lifting a cardboard box. The cardboard is not air tight, and when you place a vacuum on it, air is able to be pulled through the cardboard. To maintain the vacuum level, the air needs to be able to be pulled through the cardboard and exhausted as fast as it is being pulled through in order to maintain the vacuum level. This requires higher vacuum flow and the design of the Low Vacuum Generator allows for the development of a good vacuum level and a high rate of vacuum flow.

The High Vacuum Generator is ideal for ‘non-porous’ type of applications. ‘Non-porous’ are those processes where the material is air tight, and no or very little air can pass through. Material such as glass, ceramic, and steel are ‘non-porous’. Because little or no air passes through, the need for high vacuum flow is not as important, and the highest of vacuum level can be achieved. A perfect vacuum is 29.92 in-Hg, and the High Vacuum Generator is designed to reach vacuum levels of 27 in-Hg, or a 90% vacuum level.

 

E-Vac Video

 

Click above Image to View the Video

Both the Low Vacuum and High Vacuum Generators come in 7 different sizes, ranging from light to very strong vacuum capabilities, to match any application. Special Kits are  available as a way to experiment with an assortment of vacuum cups to determine the best configuration.

evac_nonporouskit
E-Vac Kit

And for maximum flexibility, EXAIR offers the Adjustable E-Vac Vacuum Generator. Engineered for high efficiency, compressed air can be minimized due to the ability to adjust and tune the vacuum flow and level to perfectly match the application requirements.

adjevac
Lifting a Concrete Block with the Adjustable E-Vac Vacuum Generator

If you have questions about vacuum generation and the E-Vac or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

 

Brian Bergmann
Application Engineer
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Vacuum Generator Accessories

In my last blog, I went over How to Choose/Build an E-Vac system, and you can read about that here–  The E-Vac’s are a compressed air powered, single stage vacuum generator, providing a low cost solution for creating a vacuum for many applications. Today, we will look at the many accessories that are available to complete a vacuum system best suited to your vacuum application.

For pick and place operations and hold down or clamping processes, we offer an array of Vacuum Cups. Available from stock are small and large Round, Oval, and Bellows styles. Round cups are best suited for smooth, flat surfaces.  Oval cups provide the most vacuum due to the larger surface area, making them ideal for lifting heavy loads. The Bellows style is best suited for textured or uneven surfaces, where the folds provide a collapsible area that allows the cup to compress and seal to the uneven surface.

vacupfam
Small and Large Round, Oval and Bellows Vacuum Cups

For vacuum processes where personnel are nearby, there are two (2) types of mufflers available to reduce the sound level to comply with the limits OSHA Standard 29 CFR – 1910.95(a) has established. The EXAIR E-Vac Mufflers are designed so that the E-Vac exhaust is not impeded, so that the highest and fastest vacuum response is achieved. The Standard Muffler (for use with In-Line E-Vacs only) has a closed end and is best suited for vacuum draws that are free from dust and debris.  The Straight Through Muffler is open all the way through and is recommended for those vacuum draws where there will be dirt and debris, since it will not plug up. The Straight Through style offers the best sound level reduction, up to 26 dBA.

E-Vac Mufflers
Standard and Straight Through Mufflers

The vacuum port of the E-Vacs has an NPT threaded connection and with a suitable connector, a vacuum cup can be closely installed, minimizing the system air volume. When vacuum cups are to be remotely mounted, Push-In Connector Type Fittings of assorted styles are available along with the polyurethane tubing to make the installation and vacuum plumbing a cinch.

E-Vac Fittings
Push-In , Swivel Elbow, Swivel Branch Tee, and Bulkhead Connectors

And finally, to get the best performance and maintenance free operation from your E-Vac, always use a source of clean, dry compressed air. We can help you do that with a wide array of Automatic Drain Filter Separators and Oil Removal Filters sized to pair up with the various E-Vac’s. Also available are Pressure Regulators, Vacuum Gauges, Manual Shut Off Valves, Solenoid Valves, and Compressed Air Hose.

If you have questions about E-Vacs and accessories or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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How to Choose A Vacuum Generator for Your Application

EXAIR’s compressed air powered E-Vac single stage vacuum generators are a low cost way create vacuum for many operations including- pick and place, clamping, chucking, alignment, lifting, and many others.

The E-Vac provide instantaneous response and are commonly used for pick and place operations.

EXAIR offers the In-Line and Adjustable style of E-Vacs. Both are compact and easy to mount at point of use. With 18 total models available, there is sure to be one that meets any application.

Industrial Robot
An E-Vac in Robotic Lift Operation

How to Build An E-Vac System:

Step 1 – Select E-Vac type:

A – Determine if the part to be lifted is porous (Example, cardboard) or non-porous (Example, plastic sheet)

  • Porous materials require a low vacuum generator which produces a lower vacuum in exchange for higher vacuum flow which is capable of maintaining a good vacuum level through material that aloows air to flow through itself.
  • Non-Porous materials are best suited to use the high vacuum generator which is capable of producing more powerful vacuum for the application.

B – Select a style of E-Vac – In-Line Low Vacuum, In-Line High Vacuum, or Adjustable

  • Porous – low vacuum generator, max vacuum = 21″ Hg (71 kPa)
  • Non-Porous – high vacuum generator, max vacuum = 27″ Hg (91 kPa)
  • Adjustable – max vacuum = 25″ Hg (85 kPa)

Step 2 – Find the weight of the part to be lifted:

Step 3 – Multiply the weight by a vacuum cup safety factor (2 for a horizontal vacuum cup position, and 4 for a sideways vacuum cup position)

Step 4 – Determine the number of cups needed, considering the following:

A – How many cups are needed to evenly distribute the weight for stable lifting and placement.

B – What is the weight that each vacuum cup can lift based on maximum vacuum available?

C – Select the appropriate vacuum cup from the different styles available.

Step 5 – Choose the E-Vac model, considering the entire vacuum system from the E-vac to the part:

A – Number of vacuum cups per E-Vac.

B – Length and size of the vacuum tubing.

C – Vacuum cup size and type.

  • The volume of air to evacuate from your vacuum system and the vacuum flow of the E-Vac selected will determine the time it takes to build the lifting vacuum level.
  • A lower volume of air in the system and/or higher capacity (SCFM/SLPM) E-Vac will result in faster pick-up times.
  • It is difficult to calculate an exact pick-up time.

Example – Sheet of material 3′ x 3′ (0.91m x 0.91 m) that weighs 25 lbs. (11.3 kg). Each sheet is in stack and will be placed on a conveyor.E-Vac Example

As you can see, there is a lot to consider when building an E-Vac system. Feel free to contact us and we can help go through the steps.

If you have questions about E-Vacs or any of the 15 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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Overview: Adjustable E-Vac Vacuum Generators and Vacuum Cups

Adjustable E-Vac

When it comes to vacuum systems, EXAIR manufactures a very compact and reliable product line called the E-Vac Vacuum Generators.  As a simple vacuum pump, you only need to connect to a compressed air source.  It uses a venturi design to generate high vacuum levels very efficiently.  Since they do not require motors, they are low cost with a wide range of vacuum flows and pressures.  EXAIR offers three different types, the High Vacuum Generators for non-porous objects, the Low Vacuum Generators for porous objects, and the Adjustable E-Vac Vacuum Generators.  In this blog, I will cover the Adjustable E-Vac Vacuum Generators and the variety of suction cups that we provide.

The Adjustable E-Vac gives flexibility to your vacuum system to change the vacuum levels.  The simplicity in the design makes it a great tool for lifting, clamping, chucking, and pick-and-place.  The design also allows for adjustability.  By loosening a lock nut, you can turn the body to reach different vacuum levels.  So, they can be used to move both porous and non-porous materials.  We offer four different sizes with vacuum flows ranging from 5.8 SCFM (164.2 SLPM) to 81 SCFM (2293.6 SLPM).  With the Adjustable E-Vac, you can change the vacuum pressure to go as high as 25” Hg (85 KPa).  Ideal for dialing in the correct vacuum for delicate materials or controlled clamping.

Adjustable E-Vac: How it works

The Adjustable E-Vacs can be packaged in a variety of ways.  The kits help to experiment with different vacuum cups to help determine the best fit for your application.  EXAIR offers two types of kits, the standard kit and the deluxe kit.  The Adjustable E-Vac Kit would include the E-Vac, an assortment of four vacuum cups that are matched to the performance of the Adjustable E-Vac, an assortment of vacuum fittings and 10 feet (3 meters) of vacuum tubing.  The Adjustable E-Vac Deluxe Kit has the items in the standard kit above plus an Automatic Drain Filter and Pressure Regulator with gage.  With both individual units and kits, you can add a muffler to help reduce the noise even more by adding an “M” to the end of the model number.

EXAIR also offers a variety of suction cups to attach to a variety of objects.  We have the small round, the large round, the oval, and the bellows suction cups.  With the different designs, you can pick up a wide range of materials, both porous and non-porous items.  The vinyl material resists wear and distortion for many repetitive cycles.  Here is a better description of each cup below:

Round Cups

Round:  EXAIR has a small and large round style.  This gives us a range of surface areas that we can target to help maximize lift.  They can come either with cleats for heavier lifting and stability or without cleats.  They work great with flat smooth surfaces for horizontal and vertical lifting.

Oval Cup

Oval:  The vacuum is defined by a skinny long area.  EXAIR offers four different sizes.  If you have tight spaces or selectable targets like opening a bag at the top, then the oval shape will work.  They can also handle flat rigid sheets like wood, glass, cardboard, and composites.

Bellows Cup

Bellows:  These suction cups are best suited for uneven or contoured surfaces.  The convolutions around the diameter allow for the cup to collapse and “wrap” around uneven surfaces.  The internal volume is larger than the other cups, so the release and attach times will be extended.  But, for odd surface formations, they can come in very handy.

To combine the Adjustable E-Vac with the Vacuum Cups, how can we determine which ones to use in your application?  Here is some information that we will have to know before getting started.  I like to use anagrams for memory recall, and here is a list that I like to call MOST:

  1. Material
  2. Orientation
  3. Size/weight
  4. Time

Material will tell us if the object is porous or non-porous.  Porous objects are items like cardboard, fabric, cement, etc.  The material can have a rough surface or pores that will allow air to pass through or around the cup.  The Adjustable E-Vac can have the vacuum pressure altered to pick up the material without damaging the surface.   Non-porous objects are items like glass, metal sheets, and plastic.  They have a smooth texture on the surface.  These materials should use the highest vacuum pressure of 25” Hg (85 KPa) to hold the most weight.

Orientation will help us to calculate a safety factor.  EXAIR’s motto has always been safety.  This is important because we want to make sure that the object is secure during movement.  We just need to know if the object is being picked up horizontally only, or if the object is being picked up vertically or rotated in a vertical position.  Then we can apply a safety factor to handle the weight in any orientation.

Size/Weight is simple.  The size is the area that we can pick up the object.  In some instances, we may only have a small target area while in other applications, we will have an entire sheet.  The type of Vacuum Cups is selected by this target area.  The weight will determine the number of Vacuum Cups and Adjustable E-Vacs required to pick up large objects safely.

Time is for applications with cycle rates.  If the job requires a set time to support and release in a known time frame, then we can determine the correct Adjustable E-Vac This can be used for leak checking, clamping, and automatic packaging.

The Adjustable E-Vac Generators are simple, flexible, and very reliable.  As a vacuum pump, they are very compact because they do not use any motors which can wear out.  If you contact an Application Engineer at EXAIR with MOST, we will be able to get the most from your vacuum system.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

E-Vacs: Shrinking Foam Packages

In-Line E-Vac Family

A foam manufacturer was looking for a way to reduce the size of their shipping packages.  The type of product was a polyurethane open-cell foam that they would place inside plastic bags to ship.  With shipping charges, the dimensional weight, not actual weight, is used, and it can be very costly.  Since it was open-cell foam, they wanted to evacuate the air from the plastic bags.  This would decrease the package volume and reduce shipping costs dramatically.

The company gave me some details on the product and their process.  The polyurethane foam had a density of 1.1 lb./ft3 (18 Kg/M3), and they were bagging pieces of the foam in plastic bags with the dimensions of 30” long by 10” diameter (0.75m long by 0.25m diameter).  They attempted to use a shop vac to reduce the volume; but, it was too loud and too cumbersome for their process.  They also noticed that the vacuum level was not enough to maximize the shrinkage.  They searched the internet for a better way, and they found the E-Vac™ Vacuum Generators.  They contacted EXAIR to get more information.

The EXAIR E-Vacs use compressed air to create a vacuum by a venturi method.  It can reach vacuum levels up to 27” Hg (91 kPa).  They are very compact and lightweight, and they do not have any moving parts to wear.  So, they are very durable and long lasting in systems with cycling or continuous operations.  In comparison, a typical electric vacuum has a vacuum pressure near 6” Hg (20 kPa).  With the EXAIR E-Vac having a vacuum level 27” Hg (91 kPa), we can draw out much more air to reduce the volume.

At EXAIR, we pride ourselves on customer service.  With this application, I was able to setup a representative sample for testing.  I shot a short video to show the power of our smallest E-Vac.  The video shows a representative sample with a smaller bag.  You can see the volume change with polyurethane foam.

In addition to the video, I was able to calculate the time to evacuate the package to 27” Hg (91 kPa).  EXAIR manufactures seven different sizes of High Vacuum E-Vac Generators with different flow ranges.  The above customer requested an evacuation time in about 30 second.  With Equation 1, I can determine the correct E-Vac size to meet the requirement.

Equation 1:  q = V * ln(p0 / p1)  / t
q = Vacuum flow rate (SCFM)

V = enclosed volume (ft^3)

p0 = atmospheric pressure (“Hg)

p1 = end vacuum pressure (“Hg)

t = evacuation time (min)

Details:
Volume of cylindrical plastic bag: V = 1.36 ft3

Atmospheric air pressure: p0 = 29.92” Hg

Final absolute air pressure: p1 = (29.92” Hg – 27” Hg) = 2.92” Hg

Time to evacuation: t = 0.5 min.

Thus,

q = V * ln(p0 / p1) / t

q = 1.36 ft3 * ln(29.92” Hg / 2.92” Hg) / 0.5 min

q = 6.3 ft3/min or 6.3 SCFM

From the specification on our E-Vac, I was able to recommend the model 810013M.  At 80 PSIG, this model has a vacuum flow rate of 6.85 SCFM; plenty enough to hit the target time.  After installing the E-Vac in their packaging process, they were able to reduce the size by almost 70%.  This was very helpful in reducing the dimensional weight for each shipment; saving the company and their customers much money.

If you would like to send samples in for vacuum test or need calculations for performance improvements, EXAIR Application Engineers will be happy to assist you.  EXAIR always likes to go that extra mile for our customers.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

The Case For The Adjustable E-Vac Vacuum Generator

Vacuum generation is vital to many industrial processes:

*Pick-and-place. Vacuum cup systems are used to move metal sheets onto laser & plasma cutting beds, precisely place parts for assembly using end-of-arm robotic tooling, or moving awkward objects, like plates of glass, by hand.

The same Adjustable E-Vac Vacuum Generator can be used for a range of products, from the cinder bloc (left) to small pavers (right.)

*Bag/package opening.  When plastic bags come off a roll and are fed through an automated filler, vacuum cups can make quick work of opening them up, immediately before the filling operation.

*Vacuum filling.  A closed container can be easily filled, without a pump, by simply drawing a vacuum on it.  Same mechanism (and simplicity) as when you drink a beverage through a straw.

These are just a few of the typical uses for an EXAIR E-Vac Vacuum Generator…I’ve written before about how this is our most versatile product line (by number of different applications) but these in particular are the ones I want to use to make the case for the Adjustable E-Vacs.

EXAIR Adjustable E-Vac Vacuum Generators are available in four distinct models, depending on the needs of your application.  Performance is variable not only by regulating the air supply pressure (like any compressed air product) but also by threading the plug into the body, which changes the size of the annular gap that feeds the Venturi, changing the vacuum and flow levels.  This can be used to overcome vacuum loss due to material porosity or vacuum cup leakage in a pick-and place application, to accommodate different bag sizes or types in an opening application, or to change the rate at which a liquid is moved in a vacuum filling operation.

With four to choose from, EXAIR has an Adjustable E-Vac that will fit your vacuum generating needs.

Because of their larger throat diameter, they’re also better suited for situations where particulates or moisture may be entrained…they won’t clog or ‘stall out’ as is common with other Venturi-type products.  This is especially useful in vacuum chucking/clamping, or when contaminants from dirty environments can make their way into the system.

EXAIR E-Vacs provide instantaneous vacuum response, and are engineered for high efficiency to minimize air consumption.

Like EXAIR In-Line Vacuum Generators, they instantly develop rated vacuum as soon as compressed air is supplied, so they’re well suited for fast moving operations.  With no moving parts, they’re durable, effective, and if you feed them with clean, dry air, they’ll operate a good long time, virtually maintenance free.

If you have a vacuum generating application you’d like to discuss, please give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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