Tools Of The Trade: The Rotameter

EXAIR’s Free Efficiency Lab

One of the free services we offer to customers here at EXAIR is our Efficiency Lab. In case you are not familiar here is a brief synopsis. Speak with an Application Engineer about your existing compressed air blowoff/point of use product and that you would like to know how much air it consumes. Fill out the brief survey and send the product you use in to our facility. Let us perform tests on calibrated test equipment to determine the force, flow, and noise level. We will then issue you a report that states what the EXAIR model would best be suited (if applicable) as well as how much compressed air you will be able to save. Order the recommendation and start saving money.

To do these evaluations, we have to have calibrated equipment that is reliable and capable of handling vast range of products we may receive in. For this, we could use a Digital Flowmeter, in some cases that is what has to be done due to large flow rates. For the majority of these though we go old school. We utilize a piece of equipment called a rotameter.

A rotameter pairs nicely with a calibrated pressure gauge as well.
The float can be seen with graduated marks for readings. The taper of the chamber is not easily seen with the naked eye.

This is a device that is designed to measure the flow rate of a fluid within a closed tube. The inside diameter of the tube is varied which causes the float within the meter to raise or lower.  They are calibrated for a specific gas at a given pressure and temperature, most are calibrated for atmospheric conditions, 14.7 psi (1.014 Bar). The meter must be mounted vertically and this is not always best suited for industrial environments.

When testing products the compressed air within the meter is pressurized which means we have to correct the reading for the given pressure, if the temperature is outside of the calibration temp then we must also perform that correction. We do this using a table provided by the manufacturer of the meter or by using the calculations shown to get exact values that may be in between the pressures in the table.

Pressure Correction Table


This will allow us to then multiply the Correction Factor by the meter reading and calculate our corrected flow for the point of use device at a given operating pressure and temperature.

Temperature correction table

Knowing where the values that are measured and calculated come from add validity to the reports and understanding all of the variables that go into reading like this helps to better validate the cost savings that can be seen.

In a pinch, for a field estimation, we can also use these Correction Factors and determine an approximate consumption rate of a device that has been measured at a pressure such as our cataloged 80 psig (5.5 Bar). This can often be done on the fly to help determine the flowrates currently on a system. This can be helpful when troubleshooting, giving estimated simple ROIs, and help justify results and reasons for future purchases of engineered solutions.

If you want to discuss the Efficiency Lab or any of the math behind our calculations, contact any Application Engineer, we can all help out.

Brian Farno
Application Engineer

Back To The Basics: Process Improvement Basics

We understand that it is more important than ever to realize savings within manufacturing processes. EXAIR can reduce compressed air consumption and provide simple ROI in a matter of weeks in MANY cases.

In the hustle and bustle of the daily grind wherever you are, there are certain processes that become muscle memory for you and certain processes that just work and don’t need any attention. Whether it be a login process for your computer network, the number of steps it takes to fill your coffee cup, or the compressed air applications in your facility.

You know what I am talking about, these items begin to get glanced over and often become overlooked. When going through process improvements or troubleshooting, it is easy to overlook processes which are not causing trouble or that have become “acceptable” because they are producing. EXAIR firmly believes compressed air applications are ripe for improvement, and our product lines are built to replace inefficient compressed air products with engineered and efficient solutions.

When evaluating a process for improvement creating a baseline is the necessary start. With this, we can then start to draw a realistic target of where the process needs to be in order to be optimized and document the changes from our starting baseline.

Much like the 6 Steps to Compressed Air Optimization, which starts with measuring compressed air consumption to provide a baseline.  Sometimes, this may require the installation of a Digital Flowmeter, others it may include taking advantage of our Efficiency Lab service for us to get a baseline of what air consumption and other key performance indicators are for your application.

Looking to “go green?” We can help.

Once we have the baseline and a target, we can then begin to design an improvement process. Whether this is implementing better controls for the air, such as pressure regulators, or implementing controllers such as the Electronic Flow Control, it may even be simply installing an engineered solution.  Once an improvement has been implemented we can then go on to the next testing phase to again gather data to see how much air was saved from the baseline.

EXAIR’s Free Efficiency Lab

Once the performance of the new process is determined then we can take the new cost of ownership numbers and give a simple return on investment back to determine what the actual savings by implementing these process improvements have amounted to.

The below example is from a customer who had already improved their static elimination application by using our Super Ion Air Knife instead of a homemade pipe with drilled holes. They further optimized the application with our Electronic Flow Control.

If you would like to talk through methods for process improvement or how we can help you determine these costs, please reach out.

Brian Farno
Application Engineer


Georges J. Ranque and the Vortex Tube

The Vortex Tube was invented by accident in 1928, by George Ranque, a French physics student. He was performing experiments on a vortex-type pump that he had developed for vacuuming iron filings and noticed that warm air exhausted from one end and cold air from the other when he inserted a cone at one end of the tube! Ranque quickly stopped work on the pump, and started a company to take advantage of the commercial possibilities for this odd little device that produced both hot and cold air, using only compressed air, with no moving parts. The company was not successful, and the vortex tube was forgotten until 1945 when Rudolph Hilsch, a German physicist, published a widely read paper on the device.

How A Vortex Tube Works

A vortex tube uses compressed air as a power source, has no moving parts, and produces hot air from one end and cold air from the other. The volume and temperature of the two air streams is adjustable with a valve built into the hot air exhaust.  Temperatures as low as -50°F (-46°C) and as high as 260°F (127°C) are possible.

During the second world war Georges J. Ranque started developing steels that would be used in military aviation efforts. After the war he took a job at  Aubert et Duval steelworks as director of metallurgical laboratory where he continued developing alloys for use in the aviation industry.

In 1972 he published a book on the search for the Philosophers stone, a legendary chemical substance capable of turning base metals such as mercury into gold. And in 1973 he passed away in his home just outside of Paris.

If you have any questions of want more information on how we use our vortex tubes to better processes all over industry. Give us a call, we have a team of application engineers  ready to answer your questions and recommend a solution for your applications.

Jordan Shouse
Application Engineer
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Video Blog: How To Calculate Air Consumption At A Pressure Other Than Published Values

The below video shows how to calculate the air consumption when operating at any pressure.

If you want to discuss efficient compressed air use or any of EXAIR’s engineered compressed air products, give us a call or email.  We would enjoy hearing from you!

Steve Harrison
Application Engineer
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