About Rotary Scroll Compressors

The Rotary Scroll compressor is a popular style compressor and is used primarily for air conditioning refrigerant systems.  Recently, since it is very efficient, quiet and reliable it has been adopted by industrial air compressor manufacturer’s to expand their product offering for their smaller, high-efficiency product line.

They operate on the principle of two intermeshing spirals or scrolls with one being stationary while the other rotates or orbits in relation to it.  They are mounted with 180° phase displacement between them which forms air pockets having different volumes.  Air enters through the inlet port located in the rotating/orbiting scroll which fills the chambers and as is moved along and compressed along the scroll surfaces.

scroll compressor finalSome of the key advantages of a Rotary Scroll Compressor are:

  • Pulsation free delivery due to the continuous flow from the suction port to the outlet port.
  • No metal to metal contact thereby eliminating the need for lubrication
  • Low noise levels
  • Fewer moving parts means less maintenance
  • Energy Efficient
  • Air cooled

The largest disadvantage is they are available in a limited range of sizes and the largest SCFM outputs are around 100 SCFM.

This is exactly where EXAIR shines, we offer 15 product lines of highly efficient & quiet point of use compressed air products and accessories to compliment their limited output volume of air.  All EXAIR products are designed to use compressed air efficiently and quietly, many of which reduce the demand on your air compressor which will help control utility costs and possibly delay the need to add additional compressed air capacity.

As an example, EXAIR’s Super Air Knives deliver exceptional efficiency by entraining ambient air at ratios of up to 40:1 and they are able to deliver an even laminar flow of air ranging from a gentle breeze to exceptionally hard-hitting force.

Super Air Knife
EXAIR’s Super Air Knife entrains ambient air at a 40:1 ratio!

EXAIR’s Super Air Amplifiers are able to entrain ambient air at ratio’s up to 25:1.  The model 120024 – 4″ Super Air Amplifier developes output volumes up to 2,190 SCFM while consuming only 29.2 SCFM of compressed air @ 80 PSI which can easily be operated on a 100 SCFM output compressor.

Super Air Amplifier
EXAIR Air Amplifiers use a small amount of compressed air to create a tremendous amount of air flow.

For your blow off needs EXAIR’s Super Air Nozzle lineup has an offering that will fit nearly any need or application you may have.  Nozzles are available in sizes from M4 x 0.5 to  1 1/4 NPT and forces that range from 2 ounces of force up to 23 Lbs at 12″ from the discharge.  We offer sixty two nozzles that could all be operated easily from the limited discharge or a rotary scroll compressor.

nozzlescascadeosha
Family of Nozzles

If you need to reduce your compressed air consumption or you are looking for expert advice on safe, quiet and efficient point of use compressed air products give us a call.  We would enjoy hearing from you!

Steve Harrison
Application Engineer
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Discharge of Air Through an Orifice

My Application Engineer colleagues and I frequently use a handy table, called Discharge of Air Through an Orifice. It is a useful tool to estimate the air flow through an orifice, a leak in a compressed air system, or through a drilled pipe (a series of orifices.) Various tables and online calculators are available. As an engineer, I always want to know the ‘science’ behind such tables, so I can best utilize the data in the manner it was intended.

DischargeThroughAnOrifice

The table is frequently found with values for pressures less than 20 PSI gauge pressure, and those values follow the standard adiabatic formula and will not be reviewed here.  The higher air pressures typically found in compressed air operations are of interest to us.

For air pressures above 15 PSI gauge the discharge is calculated using by the approximate formula as proposed by S.A. Moss. The earliest reference to the work of S.A. Moss goes back to a paper from 1906.  The equation for use in this table is-EquationWhere:
Equation Variables

For the numbers published in the table above, the values were set as follows-

                  C = 1.0,      p1 = gauge pressure + 14.7 lbs/sq. in,    and T1 = 530 °R (same as 70 °F)

The equation calculates the weight of air in lbs per second, and if we divide the result by 0.07494 lbs / cu ft (the density of dry air at 70°F and 14.7 lbs / sq. in. absolute atmospheric pressure) and then multiply by 60 seconds, we get the useful rate of Cubic Feet per Minute.

The table is based on 100% coefficient of flow (C = 1.0)  For well rounded orifices, the use of C = 0.97 is recommended, and for very sharp edges, a value of C = 0.61 can be used.

The table is a handy tool, and an example of how we use it would be to compare the compressed air consumption of a customer configured drilled pipe in comparison to that of the EXAIR Super Air Knife.  Please check out the blog written recently covering an example of this process.

If you would like to talk about the discharge of air through an orifice or any of the EXAIR Intelligent Compressed Air® Products, 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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Shocking Credit Cards Costs … In Manufacturing

Winter’s weather comes with a variety of problems. I hope that folks in the Northeast get a break from all this snow soon. In Cincinnati we have not had to deal with much precipitation this year, but it has been cold and gloomy for too long. Personally, I am ready for spring to come and to the see the flowers pop up. I’m also tired of the getting shocked every time I pet my dog. Also, his hair that generally falls everywhere is now stuck to the side of couch.

On a more serious note, the dry air of winter can have a significant impact on manufacturing processes. The same static that attracts dog hair to a couch will also attract dust on to a non-conductive substrate like plastic or glass. I was working with a customer this week who manufactures credit cards and gift cards with custom logos. They fell prey to the dry, statically charged air of winter which caused a quality issue during these winter months. To create the promotional cards, the company would first digitally print the logo on a PVC substrate. This substrate is then stacked to await lamination. As they pulled each sheet from the stack, a charge would build up on the surface which would attract any dust in the area. The dust needed to be removed before the last clear layer was applied or it showed up as ugly bumps on the card surface. This dust was nearly impossible to clean off and still maintain a good finish on the PVC substrate. They tried to wipe the material off with soft fabric, but the rubbing only increased the static while moving the dust around, not off the laminate.

1559 before
Laminating station two stacks of PVC substrate in the plastic bins
1559-photo
Laminating Station with the 110036″ Super Ion Air Knife installed

Using an EXAIR Static Meter, part number 7905, the customer measured 19.5 kV/inch on the PVC sheets before lamination. Because of this charge the customer installed a 36″ Super Ion Air Knife, part number 111036, above the lamination station. The operator would pull a sheet from the stack and pass it under the Super Ion Air Knife. After passing under the Super Ion Air Knife the charge on the sheet read 1.3 kV/Inch, and the dust was removed by the air blowing from the Super Air Knife. This dust removal drastically reduced their scrap levels. In the 3 months of winter, it was accepted that they would loss approximately 15% of all the cards they created do to blemishes on the cards. After installing the Air Knives, they only scrapped 3% of the cards they created. This scrap rate was even better than there summer production. The air knives will now be used year round.  The Super Ion Air Knife reduced scrap by 80%! Also, operators no longer tried to clean the dust with cloth, which allowed them to increase their production.

Dave Woerner
Application Engineer
@EXAIR_DW
DaveWoerner@EXAIR.com