Compressed Air Regulators: The Design and Function


Compressed air regulators are a pressure reducing valve that are used to maintain a proper downstream pressure for pneumatic systems.  There are a variety of styles but the concept is very similar; “maintain a downstream pressure regardless of the variations in flow”.  Regulators are very important in protecting downstream pneumatic systems as well as a useful tool in saving compressed air in blow-off applications.

The basic design of a regulator includes a diaphragm, a stem, a poppet valve, an orifice, compression springs and an adjusting screw.  I will break down the function of each item as follows:

  1. Diaphragm – it separates the internal air pressure from the ambient pressure. They are typically made of a rubber material so that it can stretch and deflect.  They come in two different styles, relieving and non-relieving.  Relieving style has a small hole in the diaphragm to allow the downstream pressure to escape to atmosphere when you need to decrease the output pressure.  The non-relieving style does not allow this, and they are mainly used for gases that are expensive or dangerous.
  2. Stem – It connects the poppet valve to the diaphragm. This is the “linkage” to move the poppet valve to allow compressed air to pass.  As the diaphragm flexes up and down, the stem will close and open the poppet valve.
  3. Poppet valve – it is used to block the orifice inside the regulator. It has a sealing surface to stop the flowing of compressed air during zero-flow conditions.  The poppet valve is assisted by a spring to help “squeeze” the seal against the orifice face.
  4. Orifice – it is an opening that determines the maximum amount of air flow that can be supplied by the regulator. The bigger the orifice, the more air that can pass and be supplied to downstream equipment.
  5. Compression springs – they create the forces to balance between zero pressure to maximum downstream pressure. One spring is below the poppet valve to keep it closed and sealed. The other spring sits on top of the diaphragm and is called the adjusting spring.  This spring is much larger than the poppet valve spring, and it is the main component to determine the downstream pressure ranges.  The higher the spring force, the higher the downstream pressure.
  6. Adjusting screw – it is the mechanism that “squeezes” the adjusting spring. To increase downstream pressure, the adjusting screw decreases the overall length of the adjusting spring.  The compression force increases, allowing for the poppet valve to stay open for a higher pressure.  It works in the opposite direction to decrease the downstream pressure.

With the above items working together, the regulator is designed to keep the downstream pressure at a constant rate.  This constant rate is maintained during zero flow to max flow demands.  But, it does have some inefficiencies.  One of those issues is called “droop”.  Droop is the amount of loss in downstream pressure when air starts flowing through a regulator.  At steady state (the downstream system is not requiring any air flow), the regulator will produce the adjusted pressure (If you have a gage on the regulator, it will show you the downstream pressure).  Once the regulator starts flowing, the downstream pressure will fall.  The amount that it falls is dependent on the size of the orifice inside the regulator and the stem diameter.  Charts are created to show the amount of droop at different set pressures and flow ranges (reference chart below).  This is very important in sizing the correct regulator.  If the regulator is too small, it will affect the performance of the pneumatic system.

The basic ideology on how a regulator works can be explained by the forces created by the springs and the downstream air pressures.  The downstream air pressure is acting against the surface area of the diaphragm creating a force.  (Force is pressure times area).  The adjusting spring force is working against the diaphragm and the spring force under the poppet valve.  A simple balanced force equation can be written as:

Fa  ≡ Fp + (P2 * SA)

Fa – Adjusting Spring Force

Fp – Poppet Valve Spring Force

P2 – Downstream pressure

SA – Surface Area of diaphragm

If we look at the forces as a vector, the left side of the Equation 1 will indicate a positive force vector.  This indicates that the poppet valve is open and compressed air is allowed to pass through the regulator.  The right side of Equation 1 will show a negative vector.  With a negative force vector, the poppet valve is closed, and the compressed air is unable to pass through the regulator (zero flow).

Let’s start at an initial condition where the force of the adjusting spring is at zero (the adjusting screw is not compressing the spring), the downstream pressure will be zero.  Then the equation above will show a value of only Fp.  This is a negative force vector and the poppet valve is closed. To increase the downstream pressure, the adjusting screw is turned to compress the adjusting spring.  The additional spring force pushes down on the diaphragm.  The diaphragm will deflect to push the stem and open the poppet valve.  This will allow the compressed air to flow through the regulator.  The equation will show a positive force vector: Fa > Fp + (P2 * SA).  As the pressure downstream builds, the force under the diaphragm will build, counteracting the force of the adjusting spring.  The diaphragm will start to close the poppet valve.  When a pneumatic system calls for compressed air, the downstream pressure will begin to drop.  The adjusting spring force will become dominant, and it will push the diaphragm again into a positive force vector.  The poppet valve will open, allowing the air to flow to the pneumatic device.  If we want to decrease the downstream air pressure, the adjusting screw is turned to reduce the adjusting spring force.  This now becomes a negative force vector; Fa < Fp + (P2 * SA).  The diaphragm will deflect in the opposite direction.  This is important for relieving style diaphragms.  This deflection will open a small hole in the diaphragm to allow the downstream air pressure to escape until it reaches an equal force vector, Fa = Fp + (P2 * SA).  As the pneumatic system operates, the components of the regulator work together to open and close the poppet valve to supply pressurized air downstream.

Compressed air is expensive to make; and for a system that is unregulated, the inefficiencies are much greater, wasting money in your company.  For blow-off applications, you can over-use the amount of compressed air required to “do the job”.  EXAIR offers a line of regulators to control the amount of compressed air to our products.  EXAIR is a leader in manufacturing very efficient products for compressed air use, but in conjunction with a regulator, you will be able to save even more money.  Also, to make it easy for you to purchase, EXAIR offer kits with our products which will include a regulator.  The regulators are already properly sized to provide the correct amount of compressed air with very little droop.   If you need help in finding the correct kit for your blow-off application, an Application Engineer at EXAIR will be able to help you.

John Ball
Application Engineer
Twitter: @EXAIR_jb

Improving Auger Cleaning Process Using 2″ Flat Super Air Nozzles And Swivels

I recently worked with a customer who was looking to improve the cleaning process on the  inside of one of their screw augers. They were currently using a couple of 1/4″ pipes as air wands to clean the left over powder on the auger blades and direct it toward a chute at the bottom which fed into another auger used for recovery. While the setup worked somewhat, they were concerned with the amount of air they were using as well as the OSHA safety concerns associated to using open ended pipes and excessive noise levels.

The customer was able to send a sketch of their current setup and after some further conversations, I recommended our Model # 1122 2″ Flat Super Air Nozzle and our Model # 9053 1/4″ NPT Swivel Fitting. The 2″ Flat Super Air Nozzle produces a 2″ wide, high velocity laminar airflow and uses only 21.8 SCFM (80 PSIG) while maintaining a low sound level of only 77 dBA. The Swivel Fitting allows for 50 degrees of movement, so they can achieve the best angle to direct the air to the critical areas.

2″ Flat Super Air Nozzle
Swivel Fittings available from M4 up to 1″ NPT

All of our Air Nozzles are engineered to meet or exceed OSHA Standard 1910.24(b) for 30 PSIG dead end pressure, they cannot be dead-ended, there is always a path for the air to safely exit so the outlet pressure will never reach 30 PSIG. In addition, our products are going to meet the OSHA Standard CFR 29 – 1910.95(a) for allowable noise exposure levels as well.

If you are looking to reduce air consumption and noise while improving operator safety, give us a call at 800-903-9247 for assistance.

Justin Nicholl
Application Engineer

How To Make Compressed Air Get Cold…A Couple Of Different Ways

The Vortex Tube makes cold air for the same reason that a can of compressed air gets cold when I clean my computer keyboard, right?

That’s a common question, and since they both start with compress air and end up with cold(er) air, it’s not an unreasonable assumption.  But the answer is no; they’re not the same.   Both are curious physical phenomena, though:

Cans of compressed air get cold while they’re discharging because of a thermodynamic principle known as the adiabatic effect.  When you pressurize a gas by compressing it into a container, you’re putting all those molecules into a smaller volume of space…and you’re adding potential energy by the compression.  Then, when you release that gas back to atmospheric pressure, that energy has to go somewhere…so it’s given off in the form of heat – from the air inside the can, as the pressure inside the can decreases.  Now, the air that’s not under as much pressure as it was when you pushed the button on top of the can is going to start coming out of the can pretty soon.  I mean, there’s only so much air in there, right?  So, since it’s given off that energy immediately upon the drop in pressure, when it comes out of the can, it’s at a lower temperature than it was before you started spraying it out.

Vortex Tubes, on the other hand, generate a flow of cold air by a completely different phenomenon of physics called, maybe not so curiously, the Vortex Tube principle:

You can get a lot more cold air – and a much lower temperature – from a Vortex Tube than you can from a can of compressed air.

If you need a reliable and dependable flow of cold air, look no further than EXAIR’s comprehensive line of Vortex Tubes and Spot Cooling Equipment.  We’ve got 24 models of Vortex Tubes to choose from, as well as “out of the box” solutions for cooling applications like the Adjustable Spot Cooler, Mini CoolerCold Gun Aircoolant Systems. and, to protect your sensitive electrical and electronic enclosures from heat, Cabinet Cooler Systems.  If you’d like to find out more, give me a call.

Russ Bowman

Application Engineer
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EXAIR’s E-Vac Vacuum Generators & Accessories


EXAIR’s In-Line and Adjustable E-Vacs are powerful compressed air powered vacuum generators. They’re a low-cost way to create a vacuum for a variety of different applications: pick and place, clamping, chucking, lifting, surface mounting, and vacuum forming are just some of the possibilities. Both the In-Line and Adjustable E-Vacs are available in a variety of different sizes and flows and can accommodate a wide range of applications.

In addition to the vacuum generators themselves, EXAIR offers a variety of different accessories to help you build a complete system. To minimize the sound level and ensure you’re adhering to OSHA 29CFR 1910.95, we have Standard Mufflers as well as Straight Through Mufflers. The Straight Through Mufflers offer the best level of sound reduction, up to 26 dBA!!

Straight through mufflers are available from 1/4″-1″ MNPS

With no moving parts to wear out, EXAIR’s E-Vacs are virtually maintenance free when supplied with clean, dry compressed air. To maintain proper operation of your E-Vac, installation of an Automatic Drain Filter to remove any particulate and moisture from the air supply is necessary. In addition, oil removal filters are also available if your compressed air supply contains any oil as is common in many compressed air systems.

For pick and place or lifting applications, vacuum cups will be necessary. With a wide variety of different vacuum cups available: small round, large round, oval, and bellows, we can accommodate nearly any size or shape material. For heavier materials, round cups with cleats provide rigidity and ensure that the load remains stable. For applications on textured or uneven surfaces, bellows style cups have convolutions that allow for the cup to quickly decompress when it touches the surface of an uneven part or material.

EXAIR’s family of vacuum cups

The vacuum port of the E-Vac has an NPT thread, vacuum cups can be installed directly in this inlet. For applications where the vacuum cup(s) are remotely located, we offer polyurethane vacuum tubing as well as a variety of different fittings to connect them. Both 1/4” and 3/8” O.D. sizes are available in 10’ lengths up to 50’. Simply indicate the model number of the tubing and add the length with a “-“ at the suffix. For example, a 900795-30 would be 30′ of 1/4″ O.D. tubing. In addition to fittings and tubing, vacuum check valves are also available. These can be beneficial if there is potential for fluctuations in the compressed air pressure or supply. In the event that there is a significant drop in pressure or loss of compressed air supply, the check valve will ensure that the load remains held.

Push-in Swivel Tee Connector

With all of the different options making a selection can seem like a daunting task. A highly trained EXAIR Application Engineer is ready and available to help you!! With just a few quick details, we can help advise you about the proper size E-Vac generator for your application as well as recommend the most suitable cup and accessories. Give us a call, shoot us an e-mail, or reach out to us online via chat and we’ll make sure you have a complete vacuum solution ASAP with all parts ready to ship from stock!

Tyler Daniel
Application Engineer
Twitter: @EXAIR_TD

Threaded Line Vacs: Low Cost Conveyor Uses Ordinary Pipe!

EXAIR’s Threaded Line Vac air operated conveyor takes an ordinary pipe and converts it into a powerful conveying system.  A fast, low cost way to convey items such as pellets, scrap trim, bulk solids, chips, paper, small parts, sawdust, granules, and so much more. The Threaded Line Vac attached easily to plumbing pipe couplers, like PVC or iron, making it easy to build a complete system with parts readily available from your local supply house or hardware store.

The Threaded Line Vac are ideally suited for conveying large volumes of materials over long distances.  Like the standard, smooth bore ended Line Vacs, the unit works by ejecting a small amount of compressed air to produce a vacuum suction on the inlet side and a high output flow from the outlet side.  By using a pressure regulator to control the compressed air supply pressure, the rate of conveyance can be controlled to match the application needs, while minimizing the compressed air usage.


Models are available from 3/8 NPT to 3 NPT with materials of construction of aluminum and types 313 and 316 stainless steels (excellent corrosion resistance.)  High temperature versions of the stainless steel Threaded Line Vacs are available as well, for temperatures up to 900°F.

For those processes requiring the highest rates of conveyance over the longest distances and/or the most abrasive of materials, the Heavy Duty Threaded Line Vac is the right choice.  Designed with the most rugged industrial processes and applications in mind, the special hardened alloy construction helps prevent premature wear that could occur with standard aluminum or stainless steel models, under the harshest of conditions.  The performance has been boosted, to be able to convey more material, over longer distances and higher vertical rises.


To select the right model, information regarding these criteria is helpful-

  • Size of parts and bulk density of material being conveyed
  • What size hose, tube, or pipe is desired
  • Target conveyance rate
  • Distance of conveyance, both horizontal and vertical legs
  • Preferred material of construction

For another look, please see the video available that provides more details about the Line Vac family.

If you would like to talk about Line Vacs 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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Super Air Wipe Vs. Block Type Air Wipe

Air Wipes, which provide 360 degree blowoff, are typically used to remove heat, liquid, debris or static from wire, cable, pipe, tube, or extrusions.

We had a customer that was using a block type Air Wipe from a competitor to remove water from an extrusion.  These air wipes are built using a plastic material, typically with some additional ceramic insert to resist abrasion of the wire, the halves are hinged with air holes drilled into each half which carries air through the block and on to the wire. They were using these block air wipes on several lines. The interesting point of this blog is that it required 5 block type air wipes to equal the results of 1 EXAIR Super Air Wipe.

Since EXAIR’s Super Air Wipe equaled the performance of 5 of the competitors it consumed less air was less expensive and produced less noise.  Also in space sensitive applications the EXAIR Super Air Wipe is much thinner than the block type.  To highlight this the Super Air Wipe is 1.13″ thick on all 11 models that range from 3/8″ to 11″ throat diameter.   The performance of the block air wipe can only be changed by altering the inlet air pressure while the EXAIR Super Air Wipe can also be changed by adusting the inlet air pressure OR by adding an additional shim the force can be nearly doubled!

Many of these block type air wipes use a series of holes to direct the compressed air supply at an angle over the material that needs to be cleaned off.  EXAIR’s Super Air Wipe being an engineered compressed air product use’s fluid dynamic’s to create more force as demonstrated below. The air from EXAIR’s Super Air Wipes is a continuous 360 degrees, without the gaps a series of holes creates.

How The Air Wipe Works

Compressed air flows through the inlet (1) of the Air Wipe into the annular chamber (2).  It is then throttled through a small ring nozzle (3) at high velocity.  This primary airstream adheres to the Coanda profile (4), which directs down the angled surface of the Air Wipe.  A low pressure is created at the center (5) inducing a high volume flow of surrounding air into the primary airstream.  As the airflow leaves the wipe, it creates a conical 360° ring of air that attaches itself to the surface of the material running through it (6) uniformly wiping the entire surface with the high velocity airflow.

Block type air wipes are generally available in standard sizes up to 7″ in diameter while EXAIR’s Super Air Wipes are available in stock diameters up to 11″ and we also offer custom sizes to suit many other applications.

If you have any items that need to have a 360 degree blowing pattern, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer
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Sound Power Level and Sound Pressure

Energy…all day (and night) long, we humans are surrounded by – and bombarded by – all kinds of energy. Sometimes, the effects are pleasant; even beneficial: the warmth of the sun’s rays (solar energy) on a nice spring day is the sure-fire cure for Seasonal Affective Disorder, and is also the catalyst your body needs to produce vitamin D. Good things, both. And great reasons to get outside a little more often.

Sometimes, the effects aren’t so pleasant, and they can even be harmful. Lengthy, unprotected exposure to that same wonderful sun’s rays will give you a nasty sunburn. Which can lead to skin cancer. Not good things, either. And great reasons to regularly apply sunblock, and/or limit exposure if you can.

Sound is another constant source of energy that we’re exposed to, and one we can’t simply escape by going inside. Especially if “inside” is a factory, machine shop, or a concert arena. This brings me to the first point of today’s blog: sound power.

Strictly speaking, power is energy per unit time, and can be applied to energy generation (like how much HP an engine generates as it runs) or energy consumption (like how much HP a motor uses as it turns its shaft) For discussions of sound, though, sound power level is applied to the generation end. This is what we mean when we talk about how much sound is made by a punch press, a machine tool, or a rock band’s sound system.

Sound pressure, in contrast, is a measure of the sound power’s intensity at the target’s (e.g., your ear’s) distance from the source. The farther away you get from the sound’s generation, the lower the sound pressure will be. But the sound power didn’t change.

Just like the power made by an engine and used by a motor are both defined in the same units – usually horsepower or watts – sound power level (e.g. generation) and sound pressure (e.g. “use” by your ears) use the same unit of measure: the decibel.  The big difference, though, is that while power levels of machinery in motion are linear in scale, sound power level and pressure scales are logarithmic.  And that’s where the math can get kind of challenging.  But if you’re up for it, let’s look at how you calculate sound power level:

Sound Power Level Equation


Wis reference power (in Watts,) normally considered to be 10-12 W, which is the lowest sound perceptible to the human ear under ideal conditions, and

W is the published sound power of the device (in Watts.)

That’s going to give you the sound power level, in decibels, being generated by the sound source.  To calculate the sound pressure level:

Sound Power Level to Sound Pressure Equation


Lis the sound power level…see above, and

A is the surface area at a given distance.  If the sound is emitted equally in all directions, we can use the formula for hemispheric area, 2πrwhere r=distance from source to calculate the area.

These formulas ignore any effects from the acoustic qualities of the space in which the sound is occurring.  Many factors will affect this, such as how much sound energy the walls and ceiling will absorb or reflect.  This is determined by the material(s) of construction, the height of the ceiling, etc.

These formulas may help you get a “big picture” idea of the sound levels you might expect in applications where the input data is available.  Aside from that, they certainly put into perspective the importance of hearing protection when an analysis reveals higher levels.  OSHA puts the following limits on personnel exposure to certain noise levels:

Working in areas that exceed these levels will require hearing protection.

EXAIR’s line of Intelligent Compressed Air Products are engineered, designed, and manufactured with efficiency, safety, and noise reduction in mind.  If you’d like to talk about how we can help protect you and your folks’ hearing, call us.