Calibration – Keep Your Meters True

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EXAIR offers meters to measure the level of physical parameters such as sound and static. Each meter has sensitive electrical circuitry and a periodic calibration is recommended to ensure the meter readings are tried and true.

The model 9104 Digital Sound Level Meter is an easy to use instrument that measures and monitors the sound level pressure in a wide variety of industrial environments. The source of loud noises can be quickly identified so that corrective measures can be taken to keep sound levels at or below OSHA maximum allowable exposure limits.

The sound meter comes from the factory with an NIST (National Institute of Standards and Technology) certificate of accuracy and calibration.  As a good practice, EXAIR recommends a yearly calibration of the instrument, and we offer a service that calibrates the unit to the same NIST standards and provide a written report of the calibration.

The model 7905 Static Meter allows easy one-hand static measurements.  It is useful in both locating sources of high static charge and checking the reduction of static after treatment with an EXAIR Static Elimination product.  The unit is sensitive and responsive, and indicates the the surface polarity of objects up to +/- 20 kV when measured from 1″ away.

It is also recommended that the Static Meter be calibrated on a yearly basis.  EXAIR offers (3) levels of calibration service.  The first two provide calibration in accordance with MIL Standards using accepted procedures and standards traceable to NIST.  The third calibration service conforms to the same Mil Standard, as well as ISO/IEC standards.

Annual calibration service of your EXAIR Digital Sound and Static Meter, along with proper care and storage, will keep your meter performing tried and true for many years, providing accurate and useful measurements.

To initiate a calibration service, give us a call and an Application Engineer will issue an Returned Good number, and provide instructions on how to ship the meter to EXAIR.

If you have questions regarding calibration services for your meters or would like to talk about any EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Intelligent Compressed Air: How do Vortex Tubes Work

Published on by John BallLeave a comment

A vortex tube is an interesting device that has been looked upon with great fascination over the last 89 years since its discovery by George Ranque in 1928. What I’d like to do in this article is to give some insight into some of the physics of what is happening on the inside.

With a Vortex Tube, we apply a high pressure, compressed air stream to a plenum chamber that contains a turbine-looking part that we call a generator to regulate flow and spin the air to create two separate streams. One hot and one cold.

Below is an animation of how a Vortex Tube works:

Function of a Vortex Tube

 

The generator is a critical feature within a vortex tube that not only regulates flow and creates the vortex spinning action, it also aligns the inner vortex to allow its escape from the hot end of the vortex tube. Note the center hole on the photo below. This is where the cooled “inner vortex” passes through the generator to escape on the cold air outlet.

Vortex generator

Once the compressed air has processed through the generator, we have two spinning streams, the outer vortex and the inner vortex as mentioned above.  As the spinning air reaches the end of the hot tube a portion of the air escapes past the control valve; and the remaining air is forced back through the center of the outer vortex.  This is what we call a “forced” vortex.

If we look at the inner vortex, this is where it gets interesting.  As the air turns back into the center, two things occur.  The two vortices are spinning at the same angular velocity and in the same rotational direction.  So, they are locked together.  But we have energy change as the air processes from the outer vortex to the inner vortex.

If we look at a particle that is spinning in the outer vortex and another particle spinning in the inner vortex, they will be rotating at the same speed.  But, because we lost some mass of air through the control valve on the hot end exhaust and the radius is decreased, the inner vortex loses angular momentum.

Angular momentum is expressed in Equation 1 as:

L = I * ω

L – angular momentum
I – inertia
ω – angular velocity

Where the inertia is calculated by Equation 2:

I = m * r2

m – mass
r – radius

So, if we estimate the inner vortex to have a radius that is 1/3 the size of the outer vortex,  the calculated change in inertia will be 1/9 of its original value.  With less mass and  a smaller radius, the Inertia is much smaller.  The energy that is lost for this change in momentum is given off as heat to the outside vortex.

Adjustments in output temperatures for a Vortex Tube are made by changing the cold fraction and the input pressure.  The cold fraction is a term that we use to show the percentage of air that will come out the cold end.  The remaining amount will be exhausted through the hot end. You can call this the “hot fraction”, but since it is usually the smaller of the two flows and is rarely used, we tend to focus on the cold end flow with the “cold fraction”.  The “Cold Fraction”  is determined by the control valve on the hot end of the Vortex Tube. The “Cold Fraction” chart below can be used to predict the difference in temperature drop in the cold air flow as well as the temperature rise in the hot air flow.

Vortex Tube Cold Fraction

By combining the temperature drops expressed above with the various flow rates in which Vortex Tubes are available, we can vary the amount of cooling power produced for an application. The above cold fraction chart was developed through much testing of the above described theory of operation. The cold fraction chart is a very useful tool that allows us to perform calculations to predict vortex tube performance under various conditions of input pressure and cold fraction settings.

The most interesting and useful part about vortex tube theory is that we have been able to harness this physical energy exchange inside a tube that can fit in the palm of your hand and which has a multitude of industrial uses from spot cooling sewing needles to freezing large pipes in marine applications to enable maintenance operations on valves to be performed.

We would love to entertain any questions you might have about vortex tubes, their uses and how EXAIR can help you.

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

Non-Hazardous Purge Cabinet Coolesr Solve 2 Problems At Once

Published on by Lee EvansLeave a comment
Electrical control panel above belt press machine

The image above shows an electrical panel located over a belt press machine.  Belt press machines can be used in a variety of mechanical separation applications, from juice manufacturing to de-watering of grains, and even algae extraction.  The use in this application, however, was to assist in the removal of liquid from styrene via multiple “wedge zones” which force the styrene between an upper and lower belt, applying increasing pressure and forcing the liquid from the styrene roll.

The Plant Manager of the facility which uses this cabinet contacted EXAIR in search of a solution to provide cooling for this enclosure, and wanted to know if we could also provide some means to provide a constant ventilation as well.  We discussed the merits of the Cabinet Cooler in terms of cooling power, and also discussed our Non-Hazardous Purge Cabinet Cooler systems which provide a constant feed of 1 SCFM of compressed air into an enclosure.  This slight airflow into the cabinet provides a slight positive pressure which further helps to prevent any dust from entering the cabinet.  For older cabinets with potentially weakened seals, these systems can provide an added level of protection against harmful dust in the ambient environment.

After sending a Cabinet Cooler Sizing Guide and determining the proper model number (NHP4825), the customer asked about lead time.  They said that the machine was intermittently shutting down and they needed something FAST.  I informed them that EXAIR Cabinet Coolers ship from stock and we can even ship UPS Next Day Air if need be.

Knowledgeable engineering support coupled with a shoe-in solution and on-the-shelf availability got this application under control quickly.  If you’re having a similar experience with your electrical control panels, contact EXAIR’s Application Engineering department for a similar solution experience.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

EXAIR’s Heavy Duty Line Vac Resists Abrasion and Outperforms the Competition!

Published on by Tyler DanielLeave a comment
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Family of Heavy Duty Threaded Line Vacs

EXAIR’s line of Heavy Duty Line Vacs are our most powerful of our pneumatic conveyors. It is very similar to our standard Lind Vacs, but the generator holes have been drilled out to boost the performance. You can also modify a standard Line Vac to match the performance of a Heavy Duty. We have a great video here that shows you exactly how. In addition to an increased performance, the Heavy Duty Line Vac is constructed of a hardened alloy steel that helps to prevent premature wear that can occur when conveying abrasive media.

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Heavy Duty Threaded Line Vac conveying steel shot

I recently worked with a customer that had a Clean Sweep vacuum that they had purchased and were experiencing premature wear on the conveyor that was installed on the system. They were using it to reclaim blasting media that they use for several of their processes in the facility. The conveyor that was installed in the Clean Sweep vacuum system was constructed of aluminum and was quickly wearing out. By the time they found EXAIR, they had already replaced this unit twice and were getting close to needing a third replacement. A quick search of the internet brought him to our blog page where he saw this blog post about the Heavy Duty Line Vac. A quick review of the drawing for the vacuum system and we were able to identify that a 2” Model 151200 Heavy Duty Threaded Line Vac would match up perfectly and allow for a quick and easy installation. They have a total of (3) of these systems in their warehouse and wanted to try one out first. Once the warehouse manager returned from vacation he intended to purchase another two to replace the other units before they too wore out. The operators were pretty pleased at the boosted performance that the Heavy Duty Line Vac offered, and management was pleased that they no longer have to worry about one of their vacuum systems wearing out. Another satisfied customer!

If you have a vacuum application with abrasive or harsh media, give EXAIR a call. Our team of Application Engineers is standing by ready to recommend the best solution for your application.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD