Compressed Air Regulators: The Design and Function

Regulator

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
Email: johnball@exair.com
Twitter: @EXAIR_jb

Spring Cleaning All Around

Now that Spring is officially here, my “honey-do” list has grown quite substantially as of late. Besides all the work we’ve done inside the house, moving our first son to his new room and putting the nursery back together for our second’s arrival, we now need to focus on the outside of the house (of course this is what my wife thinks is the #1 priority and hey, she is 9 months pregnant so I am going to agree!).

Spring Cleaning
They way I felt over the weekend!

First on the list is pressure washing the siding and since we were expecting temperatures near 65° this past Saturday, I wasn’t going to mind being outside. One problem though, the pressure washer was buried in the garage behind plastic tubs of old baby clothes (thank goodness we held on to these), bicycles, bags of old toys/clothes for donation and every other thing we’ve “needed to hang on to”, which meant that I was going to need to clean the garage before I could clean the house. Adding another item to the already lengthy, spring-cleaning list.

Are you looking to do some clean up around your facility? If so, EXAIR has you covered with our Industrial Housekeeping Products. ALL of these units are compressed air operated and require no electricity to operate so there are no motors to wear out or moving parts, making them virtually maintenance free!

For liquid only clean up, we offer 3 different products:

Reversible Drum Vac – attaches to any standard 30, 55 or 110 gallon closed head drum. Capable of empty or filling a 55 gallon drum in less than 2 minutes.

High Lift Reversible Drum Vac – Up to 15’ of vacuum lift and able to empty or fill the same 55 gallon drum in 85 seconds

Chip Trapper – incorporates the Reversible Drum Vac to filter solids from liquid and traps them in a reusable filter bag. The unit can they be turned into a pump to empty the filtered, clean liquid back to a tank or reservoir.

For dry materials, we offer 3 different products as well:

Chip Vac – Used for vacuuming wet or dry chips and deposits them into a steel drum.

Heavy Duty Dry Vac – Similar to the Chip Vac but made of hardened alloy construction for abrasion resistance and a higher vacuum rate.

Heavy Duty HEPA Vac – Used in dusty environments to filter contaminants to HEPA standards while providing the same high vacuum rate.

For help selecting the right product for your application, give us a call at 1-800-903-9247.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

 

Comet Cleaner image courtesy of garlandcannon. Creative Commons License 

Can We Help Identify Your Existing EXAIR Product? – Yes.

From time to time we have customers call in and say “We have one of your products and need another. But we installed it so long ago that we no longer have the paperwork to know which model we bought.” That’s a great thing to hear in a way. Our products have outlasted their filing system, and not only that, but now we have potential to solve another problem for the same customer.

When this happens, we can sift through our files to find out which model was purchased, or if the original purchase was made through a third party, we can determine the model number in other ways. We can use the dimensions, material of construction, description over the phone, or a photo emailed to an Application Engineer such as the one below.

Cabinet Cooler

But, the needs of the application don’t end there. We may be able to pinpoint the model number of the device currently in use, but we also need to confirm that this model will be suitable for the new application. For the end user that sent in the photo above, this meant the completion of a Cabinet Cooler Sizing Guide for new heat load calculation.

What we determine in many cases is that the new application has specific needs which dictate the use of a product with different attributes (in this case a different Btu/Hr rating on a Cabinet Cooler). Whether it is because of heat load, ambient temperature concerns, required material, or any other variable, we are sure to provide the most suitable solution.

As spring gains momentum and warmer months are to come, it may be time to consider an EXAIR Cabinet Cooler solution for an overheating electrical panel in your facility. Contact an EXAIR Application Engineer for help calculating heat load and choosing the right system.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Prepping For The Heat. (Not Solar Flares)

Well, the first day of Spring is right around the corner.  It’s hard to believe that the Summer heat isn’t that far out for us here in Cincinnati.  Of course the first thing on my mind is hanging out outside with my daughters, and track days.  What isn’t on my mind is the heat that most production environments feel.  It most likely isn’t on your mind either, and won’t be until the heat is here and the machine is shutting down.

High Temp Cabinet Cooler

Why not be proactive and fill out a Cabinet Cooler Sizing Guide so that we can help to prevent that down time in the Summer months?  Even though the temperatures aren’t as hot as they will be in a few months, the temperature differential will still allow us to calculate the heat load that is generated within the enclosure.

Sizing Guide

There’s no better time than now to start preventative measures to keeping your machines running.  Whether that is by installing a thermostat controlled Cabinet Cooler System, using a Chip Trapper to filter coolants or a Cold Gun Aircoolant System to keep a cutting tool cool.  All methods will help you to keep production up and lessen the down time and the costly replacements of your equipment.

If you have any questions on how we can help, feel free to contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

The Wrath and Glory of Warm Weather

Last week we had a taste of warm weather with a couple of days in the mid seventies. After a cold winter it actually took some getting used to. Summer is on its way and with it come the inquiries for cabinet coolers. Last years hot summer generated a ton of cabinet cooler sizing guides for me to calculate. So, I am sitting here exercising my writing fingers in preparation for the upcoming season.

The introduction of electronics for industrial and commercial applications has been a definite advantage. The downside though is heat. Electronics do not do well in hot environments. Most all are situated in some sort of enclosure which prevents heat from dissipating away. Installing vents only allows the entrance of contaminants.

I had a customer in the confectionery business that was having trouble with sugar dust getting into his panels. I jokingly commented that he had sugar-coated circuit boards. He promptly corrected me claiming that he had candy coated circuit boards! The sugar melts and crystallizes destroying the board. It was costing him $1500 each time a board had to be replaced. Installing an EXAIR Cabinet Cooler System, not only was he able to cool his panel but the cooler imparted a slight positive pressure which kept out the contaminants.

If you would like to size up a cooler for one of your panels, collect the temperature values and enter them into this FORM and send it to me and I will do the calculations for you.

Joe Panfalone
Application Engineer
Phone (513) 671-3322
Fax   (513) 671-3363
Web: http://www.exair.com
Twitter: http://www.twitter.com/exair_jp
Facebook: http://www.facebook.com/exair