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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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
Send me an email
Find us on the Web 
Like us on Facebook
Twitter: @EXAIR_BB

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