Expert Assistance Results in the Best Product for the Job

I’ve written before on the Principles of Operation of EXAIR products, and about how there may be more than one option to consider when choosing an engineered Compressed Air Product…here, here, and here.  This may, in fact, be the most valuable service that an Application Engineer can offer a caller: providing the BEST solution, regardless of what the initial idea was. Case in point:

A caller who was familiar with our Reversible Drum Vacs’ (RDV) two-way pumping action wanted to see if he could use one for a similar purpose: they were putting a thin plastic bag liner in an open top drum, and used an electric shop vacuum to suck the air out from between the drum and liner, essentially “form fitting” the liner to the drum. Then, when they fill that liner with their product, they reverse the shop vacuum, blowing air INTO the space between the drum & liner, to assist in removing the bag. This works, but the electric vacuum is loud, and they have to move the hose from one connection to the other every time they want to put a bag in or take it out of the drum.

Like I said, the caller was familiar with our Reversible Drum Vac, so he was picturing it pulling a vacuum on the drum to pull the bag in place (when the RDV is in the “fill” position) and porting air into the drum to expel the bag (when it’s in the “empty” position.)

With a simple turn of the knob, the Reversible Drum Vac can fill or empty a 55 gallon drum in 90 seconds!
With a simple turn of the knob, the Reversible Drum Vac can fill or empty a 55 gallon drum in 90 seconds!

Thing is, the RDV needs to be installed on a drum lid, and there wouldn’t be a very effective way to port it to the space between the drum & the bag. Here’s where our attention turned to another product: the E-Vac Vacuum Generator. Same principle of operation, but easily adaptable to their specific need, because it’s, quite simply, built for adaptability.

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

By plumbing the vacuum port (#4 above) to a tube inserted into the drum (same as their shop vac’s hose) they can quickly pull a vacuum, which pulls the bag into place. With a valve installed on the exhaust port (#5 above,) they can close the valve to port the compressed air supply back through the vacuum line, expelling the bag. No noisy electric motor, no constantly changing the hose, just a small (Model 800005M In-Line E-Vac Low Vacuum Generator w/Muffler, in this case) compressed air operated device, with no moving parts.

With (14) Models to choose from (seven sizes, all available in "High Vacuum" for non-porous products and "Low Vacuum" for lifting objects with a porous surface,) we've got the solution to your pick-and-place application.
With (14) Models to choose from (seven sizes, all available in “High Vacuum” for non-porous products and “Low Vacuum” for lifting objects with a porous surface,) we’ve got the solution to your pick-and-place application.

If you have a need for air flow, vacuum generation, cooling, static elimination, industrial housekeeping, atomized fluid spraying, bulk material conveyance, or just questions about improving your use of your compressed air, give us a call. We’re eager to help.

Russ Bowman
Application Engineer
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Principles of Operation

Last week, I wrote about frequently-asked-questions.  I really enjoy opportunities to engage in technical discussions with folks who want to know how a certain EXAIR product works, and, more importantly, how it will work for them.

Occasionally, we’ll get asked questions about the principle of operation, and, especially with our vacuum products, people will assume they operate on the Venturi principle (a constriction to fluid flow within a tube causes the velocity to increase and the pressure to fall), which is a very popular, tried-and-true method to create a vacuum.

Another way to do it, though, is to rely on the Coanda effect, which is the tendency of a stream of fluid flowing near a surface to follow the line of that surface, rather than its original course.  This is how our Air Knives turn a relatively small amount of compressed air into a tremendous amount of flow.  It’s also the way our Air Amplifiers work – when the compressed air leaves the internal nozzle and follows the internal surface (the Coanda profile) towards the outlet, it entrains a bunch of the existing air inside the product and takes it along, and a low pressure area (aka “vacuum”) is created.

Yet another way to do it is simply direct a high velocity of air towards the outlet.  The forceful exit of the air then entrains the air inside the item, creating a vacuum.  That’s how the Line Vacs, Chip Vacs, Heavy Duty Dry Vacs, and Vac-u-Guns work.  Fancy scientific principles aside, never underestimate the value of simple brute force!

That said, all of these products are quite similar in their basic construction.  The Air Amplifiers’ low pressure area allows it to pull an enormous amount of air through (albeit at a lower vacuum level), which is good for moving large quantities of air and airborne particulate.  The Line Vacs, Chip Vacs and Heavy Duty Dry Vacs don’t have as much vacuum flow, but are capable of pulling a pretty strong vacuum – as much as 144” H2O (-36 kPa), which is great if you’re vacuuming up, or conveying, solid materials.

For the record, our E-Vac Vacuum Generators use the Venturi principle to pull a strong vacuum of up to 27”Hg.  They’re ideally suited for a wide variety of applications such as: pick-and-place lifting, vacuum forming, mold evacuation, clamping/chucking, “hands-off” liquid sampling, and vacuum filling, just to name a few.

Strictly speaking, the Reversible Drum Vac operates on the Venturi principle as well, although the air path isn’t as straight forward as your plain old run-of-the-mill eductor type product.  That’s how it generates the vacuum to fill a drum with liquid.  Of course, to pump it out, with a simple turn of the knob, we’re back to good old brute force.

Regardless of the scientific principle behind the operation, if you have an application that requires pulling a vacuum, we can help…give us a call!

Russ Bowman
Application Engineer
EXAIR Corporation
(513)671-3322 local
(800)923-9247 toll free
(513)671-3363 fax