Keys to an Efficient Compressed Air System

How do I make our compressed air system efficient?

This is a critical question which plagues facilities maintenance, engineering, and operational personnel.  There are concerns over what is most important, how to approach efficiency implementation, and available products/services to assist in implementation.  In order to address these concerns (and others), we must first look at what a compressed air system is designed to do and the common disruptions which lead to inefficiency.

The primary object of a compressed air system is to transport the compressed air from its point of production (the compressors) to its point of use (applications) in sufficient quantity and quality, and at adequate pressure for proper operation of air-driven devices.[1]  In order for a compressed air system to do so, the compressed air must be able to reach its intended destination in proper volume and pressure.  And, in order to do this, pressure drops due to improper plumbing must be eliminated, and compressed air leakage must be eliminated/kept to a minimum.

But, before these can be properly addressed, we must create a pressure profile to determine baseline operating pressures and system needs.  After developing a pressure profile and creating a target system operating pressure, we can move on to the items mentioned above – plumbing and leaks.

Proper plumbing and leakage elimination

The transportation of the compressed air happens primarily via piping, fittings, valves, and hoses – each of which must be properly sized for the compressed air-driven device at the point of use.  If the compressed air piping/plumbing is undersized, increased system (main line) pressures will be needed, which in-turn create an unnecessary increase in energy costs.

In addition to the increased energy costs mentioned above, operating the system at a higher pressure will cause all end use devices to consume more air and leakage rates to increase.  This increase is referred to as artificial demand, and can consume as much as 30% of the compressed air in an inefficient compressed air system.[2]

But, artificial demand isn’t limited to increased consumption due to higher system pressures.  Leaks in the compressed air system place a tremendous strain on maintaining proper pressures and end-use performance.  The more leaks in the system, the higher the main line pressure must be to provide proper pressure and flow to end use devices.  So, if we can reduce leakage in the system, we can reduce the overall system pressure, significantly reducing energy cost.

 

How to implement solutions

Understanding the impact of an efficient compressed air system is only half of the equation.  The other half comes down to implementation of the solutions mentioned above.  In order to maintain the desired system pressure we must have proper plumbing in place, reduce leaks, and perhaps most importantly, take advantage of engineered solutions for point-of-use compressed air demand.

The EXAIR Ultrasonic Leak Detector being used to check for leaks

Once proper plumbing is confirmed and no artificial demands are occurring due to elevated system pressures, leaks in the system should be addressed.  Compressed air leaks are common at connection points and can be found using an ultrasonic noise sensing device such as our Ultrasonic Leak Detector (ULD).  The ULD will reduce the ultrasonic sound to an audible level, allowing you to tag leaks and repair them.  We have a video showing the function and use of the ULD here, and an excellent writeup about the financial impact of finding and fixing leaks here.

The EXAIR catalog – full of engineered solutions for point-of-use compressed air products.

With proper plumbing in place and leaks fixed, we can now turn our attention to the biggest use of compressed air within the system – the intended point of use.  This is the end point in the compressed air system where the air is designed to be used.  This can be for blow off purposes, cleaning, conveying, cooling, or even static elimination.

These points of use are what we at EXAIR have spent the last 34 years engineering and perfecting.  We’ve developed designs which maximize the use of compressed air, reduce consumption to absolute minimums, and add safety for effected personnel.  All of our products meet OSHA dead end pressure requirements and are manufactured to RoHS, CE, UL, and REACH compliance.

If you’re interested in maximizing the efficiency of your compressed air system, contact one of our Application Engineers.  We’ll help walk you through the pressure profile, leak detection, and point-of-use engineered solutions.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

 

[1] Compressed Air Handbook, Compressed Air & Gas Institute, pg. 204

[2] Energy Tips – Compressed Air, U.S. Department of Energy

Proper Supply Lines are Key to Air Knife Performance

A few weeks back I chatted with a customer on an Air Knife application where they were using our 48″ aluminum Super Air Knife to remove leftover dough from a baking pan. The knife was working somewhat, but they were seeing some residual dough being left in certain areas on the pans due to what they perceived as “weak” airflow. After reading through our catalog and installation guide, they noticed that there were available shim sets that would allow them to increase the gap setting to get more force and flow out of the knife.

Available in lengths from 3″ to 108″ in aluminum, 303ss or 316ss construction

Our aluminum Super Air Knives are shipped from stock with a .002″ shim installed. The optional shim set includes a .001″, .003″ and .004″ shim that would allow you to decrease or increase the performance. By operating the Super Air Knife with the .003″ shim installed, this would increase the force and flow by 1.5 times and using the .004″ shim would double the performance. Sometimes achieving greater force and flow may be required but with the customer saying they were seeing weak airflow, it seemed there may be a restriction on the supply side.

Super Air Knife with Shim Set

I asked the customer how the knife was plumbed and what size supply lines he was using. He advised that they were plumbing air to all 3 inlets on the bottom of the knife but they were using 3/4″ hose with a run of about 30′. I advised the customer that plumbing air to all 3 inlets is required for a 48″ Super Air Knife but we actually recommend 3/4″ Schedule 40 Pipe up to 10′ or 1″ pipe up to 50′. If using hose, he would need to go up a size to maintain a large enough ID to carry the volume required for the unit. In his case, since the length of the supply is close to 30′, he would need to use 1-1/4″ ID hose.

Improper plumbing line size is a common issue we deal with here at EXAIR. Using undersized supply lines can cause excessive pressure drops because they aren’t able to carry the volume of air necessary to properly supply the compressed air device. In this particular application, if the customer were to install either the .003″ or .004″ shim, while keeping his current plumbing size, the performance would actually be worse as now the lines are even more undersized due to the increased air volume requirement from the larger Super Air Knife gap.

If you are looking to change the performance with one of our Air Knives or if you would like to discuss a particular application or product, please contact one of our application engineers for assistance at 800-903-9247.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

Consider these Variables When Choosing Compressed Air Pipe Size

Here on the EXAIR blog we discuss pressure drops, correct plumbing, pipe sizing, and friction losses within your piping system from time to time.   We will generally even give recommendations on what size piping to use.  These are the variables that you will want to consider when selecting a piping size that will suit your need and give the ability to expand if needed.

The variables to know for a new piping run are as follows.

  • Flow Rate (SCFM) of demand side (products needing the supplied compressed air)
  • System Pressure (psig) – Safe operating pressure that will account for pressure drops.
  • Minimum Operating Pressure Allowed (psig) – Lowest pressure permitted by any demand side point of use product.
  • Total Length of Piping System (feet)
  • Piping Cost ($)
  • Installation Cost ($)
  • Operational Hours ( hr.)
  • Electical Costs ($/kwh)
  • Project Life (years) – Is there a planned expansion?

An equation can be used to calculate the diameter of pipe required for a known flow rate and allowable pressure drop.   The equation is shown below.

A = (144 x Q x Pa) / (V x 60 x (Pd + Pa)
Where:
A = Cross-Sectional are of the pipe bore. (sq. in.).
Q = Flow rate (cubic ft. / min of free air)
Pa = Prevailing atmospheric absolute pressure (psia)
Pd  = Compressor discharge gauge pressure (psig)
V = Design pipe velocity ( ft/sec)

If all of these variables are not known, there are also reference charts which will eliminate the variables needed to total flow rate required for the system, as well as the total length of the piping. The chart shown below was taken from EXAIR’s Knowledge Base.

Piping

Airflow Through 1/4″ Shed. 40 Pipe

Once the piping size is selected to meet the needs of the system the future potential of expansion should be taken into account and anticipated for.   If no expansion is planned, simply take your length of pipe and start looking at your cost per foot and installation costs.    If expansions are planned and known, consider supplying the equipment now and accounting for it if the additional capital expenditure is acceptable at this point.

The benefits to having properly sized compressed air lines for the entire facility and for the long term expansion goals makes life easier.   When production is increased, or when new machinery is added there is not a need to re-engineer the entire system in order to get enough capacity to that last machine.   If the main compressed air system is undersized then optimal performance for the facility will never be achieved.   By not taking the above variables into consideration or just using what is cheapest is simply setting the system up for failure and inefficiencies.   All of these considerations lead to an optimized compressed air system which leads to a sustainable utility.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

Undersized Plumbing Creates a Performance Problem

Sometimes we get calls or emails from our customers experiencing a problem with their application already using EXAIR products.  These calls can range from difficulties associated with installation angle, installation, or, in many cases, the compressed air plumbing to the product itself.

That was the case in the application of the photos above.  The end user had been using our model 6084 Line Vac to move plastic pellets from the floor to the top of a machine hopper, and they needed to increase the flow.  The problem, was that they weren’t getting the performance from the 6084 that they thought they should.

Chip Vacuum 1

                                                                 EXAIR model 6084 Line Vac used for conveying plastic pellets

 

Chip Vacuum 2

Model 6084 Line Vac used to convey plastic pellets from the floor to the top of a machine hopper

 

Given the bulk density of the plastic pellets in this application, the end user should’ve been able to move more than enough material in the time they desired for the application needs.  But, instead, the Line Vac was moving little-to-no material and even “stalling” – a condition in which the conveyed material could enter into the Line Vac and then cease to convey.

What we found, after exchanging contact information and discussing the photos above, is that the compressed air line feeding the Line Vac is too small, creating a pressure drop and leading to an inadequate compressed air flow.  This, in turn, leads to lower air velocity at the exhaust of the Line Vac, which simultaneously means lower vacuum and material flow at the inlet.

The end result is the condition described by the end user – a low flow, or no-flow, of the material being conveyed.

After our discussion the end user set out to make the required change to the supply line, providing proper flow to the Line Vac at the proper pressure, and moving the material as required.

It’s always rewarding to help an end user solve their problems.  If you have an application problem and think EXAIR might be able to help, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Proper Plumbing Makes Full Flow Air Knives Operational

Full Flow Air Knives for plate drying

These EXAIR Full Flow Air Knives were in need of an EXAIR Application Engineer’s expertise

Sometimes we get calls or emails from our customers that need help.  Help can be in the form of product selection, heat load calculation, or proper installation.  I had one such interaction with an end user of our Full Flow Air Knives, using them in the manner shown above.

The problem they were having was poor flow and low force from the blow off.  We originally discussed the application over the phone, and after suspecting a plumbing issue may be at play, I asked for a photo.  I received a quick photo of their setup and immediately saw the two knives were poorly plumbed.  The clear/light blue hose, and the dark blue hoses in the photo just aren’t big enough for two knives of this size.

When installing any compressed air driven product, pressure and flow are the name of the game.  Sometimes, as in this case, there was good pressure at the gauge (which, if checked at the inlet of the knife would have shown a significant pressure drop), but there just wasn’t enough flow.  The root cause was diameter of the piping used to deliver the air from the main line to the point of use.

Once the compressed air line sizes were increased, the knives worked flawlessly and the end user could use them as intended – which was blowing debris off of a plate fed through the middle of the two knives.

If you have an application that you think may have a plumbing concern, or any other need for EXAIR products, contact an EXAIR Application Engineer.  We’ll be happy to help.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Quick Disconnects & Why Not To Use Them

Quick Disconnects are a quick and easy solution to hook up devices to your compressed air system.  These units can be found in quite a few factories and are more often than not being used incorrectly.  I know that on the air compressor in my garage, the only way to hook anything up to it was to use 1/4″ quick disconnects.  Chances are they are even a few of them within your facility, assuming you have compressed air available.

1/4" Quick Disconnect male and female.

1/4″ Quick Disconnect male and female.

When you really look at a quick disconnect though you start to see why it shouldn’t be used to install every compressed air driven device there is.   You can see in the pictures below that a 1/4″ quick disconnect that goes to a 3/8″ NPT adapter has a .192″ opening at the small end.  A 3/8″ Schedule 40 iron pipe will actually carry a .493″ inner diameter.   If you were to use this quick disconnect on something like a 2″ Heavy Duty Line Vac, you will starve it for air due to the limited ability of the small diameter to carry enough air volume. This, in turn, will limit the performance of the Line Vac.  This is because the through hole on the quick disconnect cannot pass enough air to feed through to the Line Vac.

Inner Diameter of 1/4" quick disconnect.

Inner Diameter of 1/4″ quick disconnect.

On the 1/4″ quick disconnect to a 3/8″ NPT this may not be as large as a problem as the next picture.  Below you can see a 1/2″ quick disconnect that is going up to a 3/4″ NPT.  a 3/4″NPT Schedule 40 iron pipe is actually a .824″ inner diameter.  The quick disconnect at most has a .401″ inner diameter.

IMG_4614

1/2″ quick disconnects

 

Inner diameter of 1/2" quick disconnect.

Inner diameter of 1/2″ quick disconnect.

Even though you are providing the correct thread size for your connection (a 3/8 MNPT and a 3/4 FNPT respectively in our example) the quick disconnect’s small inside diameter could be too much of a restriction for the volume demanded by an end use product. Due to this restriction point you will see pressure drops in your system when using a device with a properly sized inlet for its demand of compressed air being fed with an improperly sized quick disconnect.  This is one of the main reasons one of our first questions in troubleshooting an EXAIR products performance with a customer is whether or not they are using quick disconnects.

If you would like to learn more about how to properly plumb your EXAIR Intelligent Compressed Air Product, feel free to contact us, or take a look around our Knowledge Base.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

 

 

3 Common Mistakes in Your Compressed Air System

Every day I speak with engineers who are having trouble using compressed air products. A common problem they have is not providing an adequate air supply to their unit. I go through a basic troubleshooting technique to ensure that their pressure and flow rate is adequate. I ask them to install tee on the inlet to the compressed air product in order to install a pressure gauge right at the inlet to the pipe. This allows us to know exactly what pressure we are supplying to the product. Customers are always surprised how the gauge on the compressor or the regulator may read 120 PSIG, but the gage on the inlet to the compressed air product is significantly less.

Last year, my colleague, Russell Bowman, made an excellent video showing how the inlet pressure at the knife will have a significant impact on the performance of the Super Air Knife.  In the video, he changes the length and ID of the compressed air supply to illustrate the difference a proper supply line will have on the performance of a compressed air products.

Not providing adequate air supply is commonly caused by these three mistakes, when plumbing compressed air systems.

1. Incorrectly Sized Piping – This can be the single biggest problem. A lack of planning before installing a compressed air product. Not all compressed air systems are created equal. Though a 1/4″ shop air hose may work for a number our products, some of our products require a larger air line because they require more volume of air to be effective. We often speak with customers an illustrate this problem by stating small air lines are like trying to feed a fire hose with a garden hose – there simply is not enough volume to create the pressure necessary to reach the fire, or solve the application in our scenarios. We publish the flow rates for all of our products and make inlet pipe size recommendation in the installation and maintenance guide furnish with the products so you may avoid this common problem. We also have air data tables in our Knowledge Base or  you may consult an application engineer who will be happy to make the proper recommendation.

2. Quick Disconnects – These handy connectors are great when operating a brad nailer, or a small blow gun, but the small through diameter can severely limit the flow rate into a long air knife, large diameter air operated conveyor, or big vortex tubes.  Due to this fact it is strongly advised to use threaded fittings or over-sized quick disconnects.

3. Adding extra hose or pipe – Extra hose is never a bad thing, right? No, an extra 30 feet of air hose can significantly drop the pressure of a compressed air system. 20 feet of ½ Pipe can flow 70 CFM with a 5 PSI pressure drop.  50 feet of ½” pipe will only flow 42 SCFM with the same 5 PSIG pressure drop. Keep your hose or pipe lengths to a minimum to improve the volume of air you can deliver to a compressed air product.

Dave Woerner
Application Engineer
DaveWoerner@EXAIR.com
@EXAIR_DW

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