Viscosity – Why it Matters

EXAIR has been manufacturing Intelligent Compressed Air Products since 1983.  We work every day with air properties, such as compressed air pressures and flow rates, when evaluating product performance to provide a solution to a customer problem. We also need to be versed on a certain liquid property, viscosity, as it relates to the operation of (2) of the EXAIR product families, the Atomizing Spray Nozzles and the Industrial Housekeeping liquid vacuums (Reversible Drum Vac and Chip Trapper).

Viscosity is often referred to the thickness of a fluid.  A common example would be water and honey.  Water is a low viscosity fluid, while honey is a high viscosity material.

Dynamic, Shear, or Absolute Viscosity is a measure of the resistance to shearing flow.  If you think of 2 plates (see below) with the bottom one stationary and the top one moving horizontally, and with a fluid between them – this illustrates Absolute Viscosity. When the top plate moves to the right, there will be induced multiple horizontal layers of the fluid, each moving at different speeds (the fluid will be at rest at the bottom, and the top layer will move with the top plate.) The friction generated between the layers will give rise to a force resisting this motion.  The force is proportional to the speed and area of the plate and inversely proportional to the distance between the plates.Capture

In simplest terms, viscosity is the ratio of the shear stress, τ,  to the velocity gradient du/dy.  Of concern to us, it takes more force to cause a very viscous (thick like honey) fluid flow.

Centipoise, cP,  is the common unit of measure for viscosity, and 1 cP is equal to 0.01 g/cm/s.

Water has a viscosity of 1 cP at room temperature and honey ranges from 2,000-10,000 cP.

How does all this relate to EXAIR? It relates to EXAIR because we engineer products to specifically move and use liquids. There are limitations to the viscosity each of these products can handle and still perform well.

The EXAIR Atomizing Spray Nozzles can be used with liquids up to 800 cP. The Internal Mix type nozzles can be used on liquids up to 300 cP. The External Mix nozzles can be used with liquids over 300 cP and up to 800 cP.  Lastly, the Siphon Fed models are good to 200 cP, and do not require a pressure source for the liquid. Each nozzle type will atomize the fluid and provide a very small droplet size, which is ideal for washing,  rinsing, coating, cooling and other applications. Exceeding the cP each of these nozzles are designed to use will result in larger droplet sizes and a more inconsistent fluid flow, which may impact your process.

atomizing nozzle
Atomizing Spray Nozzle

The other EXAIR product family where viscosity is important, is the Industrial Housekeeping Products, especially the High Lift Reversible Drum Vac and High Lift Chip Trapper.  They are capable of moving liquids with viscosities of up to 1400 cP through 20′ of hose.  Simply provide compressed air and turn any closed head drum into a high powered liquid vacuum. Great for coolant, hydraulic oils, waster water, and many other fluids. For these products, as the cP increases, so does the time it will take to move the liquids into or out of the drum.

HLRDVpr_openpit_3mbcmyk (2)
High Lift Reversible Drum Vac

To discuss your fluid viscosity and how an EXAIR Intelligent Compressed Air Product can make your process better, feel free to contact EXAIR and myself or one of our other Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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A Lot Can Happen In Five Years

Five years ago, I wrote a blog about my (then) 11 year old son’s first-ever week away from home at Boy Scout Summer Camp. He’s departing again this weekend, but his troop has decided to venture “out of Council” this year, to Camp Howard W. Wall…it’s on the south coast of the island of St. Croix, in the US Virgin Islands.

They met last week to cover the final (and finer) details of international travel, flight schedules, logistics, etc., and activities…Camp Friedlander has a “blob:”

But Camp Wall has an OCEAN:

Just to put the distance into perspective...
Just to put the distance into perspective…

I’ve been thinking a LOT about the changes I’ve seen in the wide-eyed kid I dropped off at a camp that I drive past twice a day, and the smirking teenager that I’m driving to the airport on Sunday morning. And those changes are providing perspective on not only how fast those five years have passed, but how much can happen in that span.

In 2011, I was a wide-eyed “Dread Newbie” at EXAIR.  One of my very first meetings with the rest of the gang was to be trained on our brand new Atomizing Spray Nozzles…we only had three styles to choose from, but two of them came in four distinct models, and one came in FIVE. They were ALL Internal Mix, because hey, who doesn’t like the maximum range of adjustability that comes with being able to vary your flow rate and spray pattern size by adjusting liquid AND air supply pressures?

OK; it turns out that was just the beginning…within the year, our Engineering Department had developed:

External Mix – three styles, thirteen distinct models, to allow for independent adjustment of flow rate (by liquid pressure) and spray pattern (by air pressure.)

Siphon Fed – two styles, seven distinct models, that could be siphon OR gravity fed, for situations where it’s not practical to pressurize the liquid supply.

And, four years after that, looking back, it seems like THAT was just the beginning…we now have:

*Two sizes – the original 1/4 NPT and the new(er) 1/2 NPT.
*Sixteen styles – each available with our No-Drip option (so technically I guess we have thirty-two)
*Forty-five distinct models – we’ve got a flow rate/spray pattern combination for just about any application

And, like the rest of our catalog products, they’re all in stock, ready to ship today, on time, like we do 99.97% of the time…that’s actually one thing that HASN’T changed in the 17 years that we’ve been keeping track.

If you’d like to talk about Spray Nozzles…or any EXAIR products (old or new,) give me a call.

Russ Bowman
Application Engineer
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No Drip External Mix Atomizing Nozzle Wins Gold!

It is a very sad day for me at EXAIR… No, I’m not retiring or leaving the company, but today is my last day to write about Plant Engineering Product of the Year Awards …for this year. It has been quite an honor to write about four of our best innovations from the last year over the past weeks.  In case you missed the entries, you can click on the these links to read more about our other 2013 award winners: 316 Stainless Steel Dual Cabinet Coolers, 1 Inch Flat Super Air Nozzle or the Heavy Duty HEPA Vac. nodrip_EF Today’s post is about the No Drip External Mix Atomizing Nozzle, which the readers of the Plant Engineering magazine bestowed the gold award for fluid handling products.  EXAIR’s Liquid Atomizing Nozzles combine the liquid of your choice with compressed air to create a mist of atomized liquid.  The external mix nozzles have the highest liquid flow rate of any of EXAIR’s Liquid Atomizing Nozzles with flow rates up to 60 GPH.  They are a great solution for applications where independent air and liquid control is required.  Additionally, more viscous fluids can be used with the external mixing of the nozzle than either the internal mixing or siphon fed nozzles.  External Mixing Nozzles can be used to atomize liquids up to 800 centipoise. IMG_4031   In addition to the benefits of the external mix atomizing nozzle, this spray nozzle features a valve to positively stop liquid flow, when the compressed air drops below 30 psig. Any time you need to maintain a smooth finish or are spraying an expensive liquid, the no drip function can be invaluable to preventing rework, and ensuring a quality finish on each and every product.  The EXAIR no drip function is patent pending and does not require an additional air line to control the no drip mechanism, simplifying installation and functionality.

Dave Woerner
Application Engineer
Davewoerner@EXAIR.com
@EXAIR_DW