Advantages of Thermal Mass or Thermal Dispersion Flow Measurement

EXAIR’s Digital Flow Meter offers an easy way to measure, monitor and record compressed air consumption. The Digital display shows the current amount of compressed air flow, allowing for tracking to identify costly leaks and/or inefficient air users.

dfm

How exactly does the Digital Flow Meter work?  The unit falls under the category of Thermal Mass or Thermal Dispersion type flow meters.  Below shows the backside of a unit.

IMG_7387

Thermal mass flow meters have the advantage of using a simple method of measuring flow without causing a significant pressure drop. The EXAIR units have (2) probes that are inserted through the pipe wall and into the air flow.  Each of the probes has a resistance temperature detector (RTD.) One of the probes measures the temperature of the air flow.  The other probe is heated to maintain a preset temperature difference from the temperature measured by the first probe.  The faster the air flow, the more heat that is required to keep the second probe at the prescribed temperature.  From Heat Transfer principles, the heat energy input required to maintain the preset temperature is based on the mass velocity of the air.  Using basic physical properties for compressed air, the volumetric rate can be determined (SCFM), and displayed.

It is important to note that the compressed air should be filtered to remove oils, and dried to remove water, as these liquids have different physical properties from air, and will cause erroneous readings.

Advantages

  • Easy to install – No cutting or welding required
  • Summing Remote Display and Data Logger available
  • Sensitive at low flows
  • Rugged, reliable and no moving parts
  • No calibration or set-up required
  • Models from 1/2″ to 4″ schedule 40 iron pipe in stock
  • Short lead time for sizes up to 6″ Schedule 40 iron pipe
  • Available for size 3/4″ to 4″ copper pipe
  • New Wireless Capability

If you have any questions about the Digital Flow Meter 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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Air Amplifiers – What is an Amplification Ratio?

On Friday my colleague, Russ, blogged about the Super Air Amplifier (see that BLOG here, including a video demo)  In discussing the Air Amplifiers, the topic of amplification was mentioned. Today, I’d like to expand a bit further the amplification aspect of the Air Amplifier performance.

As the name of the device implies, the compressed air used by the Air Amplifier is added to, and thus ‘amplified’, the total output flow of the unit. Depending on the size and type of Air Amplifier, the amplification ratio starts at 12:1 and goes up to 25:1, with the ratio being the output flow to the compressed air usage.

AirAmplifiers.jpg
Super Air Amplifier and Adjustable Air Amplifier

EXAIR offers (2) types- the Super Air Amplifier and the Adjustable Air Amplifier.  The Super Air Amplifier uses a patented shim technology to maintain a precise gap, which controls the compressed air flow and expansion through the unit.  As the expanded air flows along the Coanda profile, a low pressure area is created at the center which induces a high volume flow of surrounding air into the primary air-stream.  The combined flow of primary and surrounding air exhausts from the Air Amplifier in a high volume, high velocity flow.  The larger diameter units have a greater cross sectional area with larger low pressure areas, resulting in greater amplification ratios.

The Below table shows the amplification ratios.

SuperAirAmplifierPerformance

The Adjustable Air Amplifier does not use a shim, but rather has an infinitely adjustable gap, allowing for fine adjustment of performance.  Force and flow is changed by turning the exhaust end to adjust the gap, and is then locked into place. The method of the amplification is the same as for the Super Air Amplifier, and the amplification ratios are similar and shown below.

AdjustableAirAmplifierPerformance

The Super Air Amplifiers and Adjustable Air Amplifiers are ideal for use in applications and processes that require cooling, drying and/or cleaning of parts, or the ventilation of confined areas or weld smoke or the exhausting of tank fumes.

If you have questions regarding the Air Amplifier, 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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Glass Filled PEEK Super Air Knife w/ Brass Hardware & PTFE Shim? No Problem!

That’s right folks, we’ve gone and done it again.  When a customer calls for custom product because their environment calls for it or due to dimensional requirements, EXAIR has the ability and flexibility to meet those needs!

This time around it was a customer with specific material requirements due to their environment. I had a customer contact me recently that was using an aluminum Super Air Knife near a high voltage operation and was getting ground interference due to the aluminum air knife.  They asked if it was possible to make them a custom knife out of PEEK plastic.  After some light discussions about the form of the knife and what other materials are safe for their environment we settled on a 30% glass filled PEEK plastic for the knife, brass bolts and pipe plugs, with a PTFE shim installed.   The form factor of the knife would follow the same shape as our PVDF Super Air Knives that are available from stock.   The customer could not use PVDF due to high temperature and potential off-gassing in the process.

The results are shown below.

IMG_6590
EXAIR 6″ Super Air Knife in 30% Glass Filled PEEK Plastic w/ Brass Hardware and PTFE Shim
End View – 6″ Super Air Knife in 30% Glass Filled PEEK Plastic w/ Brass Hardware & PTFE Shim

Whether you are looking for a one off product that is tailor made to your application or want to have a simple feature like hardware material changed in a stock EXAIR product that you are incorporating into thousands of machines, we have the solution for you.

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

 

 

 

 

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

Not All Quick Disconnects Are Equal

Quick disconnect pneumatic fittings have been a staple in any manufacturing facility I have ever visited in my 10+ years as part of the manufacturing world.   The fact is, they have been around for a lot longer than 10 years.   The style we see most often is the 1/4″ Quick Disconnect Fitting, and we are typically troubleshooting a lack of air volume problem because they are not sized properly for the application.  These can be found in any industrial supply companies catalog, your local hardware stores, and even auto parts stores.   Quick Disconnects are even sold with certain EXAIR Industrial Housekeeping products, the key being they are properly sized.

Properly sizing the quick disconnect is a critical step in the process of deciding how to lay out your piping system as well as how to ensure products operate at optimal performance.  As you can see in the picture above, the two quick disconnects on the left are both larger quick disconnects as well as larger NPT thread sizes.   The two on the right are smaller and probably a bit more common to see.  Also notice the thread sizes on each, these are also manufactured in many other NPT thread options.   The through hole on the quick disconnects is decided by the size of the QD, not the thread size on the other end.   The example I am illustrating is comparing the 3/8 NPT and 1/4 NPT quick disconnects: Even though you can have 3/8 NPT threads, your throat diameter of the QD is still restricted to .195″ I.D., the same as the 1/4 NPT.  This can be a large restriction on a product with a 3/8 NPT thread size.

The Inner Diameters of the Quick Disconnects

Also to be noted is that all QD’s of the same size are not made equally, tests have shown that you can lose as much as 20 psi through a quick disconnect and up to 40 psi when not properly matched with the female QD.   This leads to the next step which is to ensure that you are not purchasing a QD on appearance.  MAke sure to choose the QD designed to permit the amount of air you need to operate your point of use product without a volume or pressure loss.

These two points are reasons why quick disconnects can diminish your point of use compressed air product performance.  If you have questions on which size to use with your EXAIR product or need help determining why your point of use product is not performing how you would like, contact us.

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

 

Where Does 25 Cents For 1,000 Standard Cubic Feet Of Air Come From?

Wasting compressed air 2

Being an Application Engineer at EXAIR you tend to do a good amount of return on investment (ROI) calculations.   This is mainly to tell customers just how fast installing an EXAIR product on their system is going to pay its purchase price back and start saving them money.

In order to do these calculations there are several variables we must know.   The list is below.

  • Cost of EXAIR Product (This is an easy one for us to know.)
  • EXAIR Product Consumption (Another easy one!)
  • Current Product Consumption (If this is an unknown, we will test it for free!)
  • Cost of Compressed Air / 1,000 SCF (This is the most common unknown.)

With these four variables we can calculate the amount of air and the amount of money the EXAIR product will save over an existing non-engineered blowoff.   Let me address the two variables which have to come from you, the customer.

Current Product Consumption – If this value is not known please don’t guess at it.  We offer a free service which we refer to as our Efficiency Lab where you send us in your existing blowoff device and we will test it for force flow and noise level.   If you don’t know what pressure you are operating the piece at we will help you find out how to get that and then we will test our products at the same pressures.   This way you get a true apple to apples comparison.   Then, once we are done testing, you will get a recommendation from us in a formal report as to what EXAIR product will best replace your existing product.  Then we will pay for return shipping of your blowoff device back to you. So, if you don’t know how much air you are currently using then give us a call.  We will figure it out for you.

Efficiency Lab
The EXAIR Efficiency Lab is FREE!

Cost of Compressed Air/ 1,000 SCF – This is more often than not, the unknown variable in the equation.  The good news is there is a general standard assumption of twenty-five cents per 1,000 Standard Cubic Feet of compressed air.   This works out to be around 8 cents per kW/hr.  So even if you don’t know what you pay to compress the air, if you know what you are paying per kilowatt hour for your energy then we can calculate within reason what it costs for you to generate your compressed air. For reference, 8 cents per kilowatt-hour falls between the average US cost per kilowatt hour for commercial end-users (10.7/kWh) and industrial end-users (6.9/kWh).*

The best part of all is…EXAIR has a calculator available right on our website which provides air and dollar savings per minute, hour day and year as well as a payback in days for the EXAIR product purchase. On top of that, any step along the way that you aren’t sure of, we will help you out for free, even testing your product!

In case you would like to see the math, the formula used is below.

Basic Equation To Go From Cost Per kiloWatt Hour to Cost Per 1,000 Standard Cubic Feet of Compressed Air
Basic equation to go from Cost Per kiloWatt Hour to Cost Per 1,000 Standard Cubic Feet of Compressed Air

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

*latest U.S. EIA report here

 

 

 

Calculating Force and Pressure For Air Nozzles

I assisted with an application where logs were being shaved to make thin laminate.  Because the logs were non-concentric or entirely smooth, the beginning of the sheet was riddled with scrapes and defects until it was about 8 foot (2.4 meters) long.  This was a very quick process, and once good product was coming from a shaved log, the machine would divert the material from the scrap bin to the production feed line with a nip roll.  At the speeds that the material was traveling, they needed to kept pressure on the leading edge of the sheet so that it would not “curl” up before the nip roll closed and grabbed the sheet. The drive rolls were pushing the laminate product toward the nip roll and they needed to keep the curl pushed flat along a plate and wondered if we had a product that could accomplish this.

We suggested a series of 2” flat air nozzles, model 1122, to keep the product pressed down on the plate with the force from the airflow.  In their trial runs, they tried to find the correct amount of air pressure to keep the product flat.  Once they found the pressure required, they noticed that the thin and delicate laminate was getting damaged.  Of course, it was just at the beginning length when it was being held in place as it slid into the nip roll, approximately 3 feet (0.9 meters).  Like any company, they did not want to waste any more product and wondered if we had anything else that we could recommend.

Thus a question was presented, and a solution was needed.  In thinking about this, it took me to my Michigan days where snow was abundant.  When walking on snow, you would fall through, but if you had snow shoes, you could stay on top of the snow.  This brought me to the factors of Pressure and Force.  Like with the laminate, if a smaller area does damage to the product (boots through the snow), can we expand the area to keep it from being damaged (snow shoes on top of the snow).

Snow Shoes
Snow Shoes

With the application, we needed to apply the same force on the material.  The equation for force is F = P *A (Equation 1), where F – Force, P – Pressure, and A – Area.

We can do an equality statement from Equation 1 which shows F = P1 * A1 = P2 * A2 (Equation 2).  The amount of pressure required from other EXAIR products can be determined, i.e. if I can double the surface area, then I can reduce the pressure by ½.  For model 1122, we can determine the pressure that was generated from Equation 1 and from the catalog data:

Imperial Units of Model 1122                                                      S.I. Units of Model 1122

F = 1.4 lbf (catalog)                                                                       F = 0.624 Kg (catalog)

A1 = Length X Width                                                                    A1 = Length X Width

= 5 inches X 2 inches (catalog)                                                   = 12.7 cm X 5.1 cm (catalog)

= 10 in^2                                                                                         = 64.8 cm^2

P1 = F/A1 (Rearranging Equation 1)                                         P1 = F/A1 (Rearranging Equation 1)

= 1.4 lbf/10 in^2                                                                            = 0.624 Kg/64.8 cm^2

= 0.14 PSI (pounds per in^2)                                                     = 0.0096 Kg/cm^2

Super Air Amplifier
Super Air Amplifier

Now that we have all the information from model 1122, we can determine the pressure required for a different product to keep the force the same.  With the 2” Super Air Amplifier, model 120022, it has a much larger footprint than the 2” flat air nozzle, model 1122.  So, with Equation 2, we can determine the amount of pressure required.  We will use model 1122 for our P1 and A1, and we will use model 120022 for P2 and A2.  From the catalog data for model 120022, we get a target area as follows:

 

Imperial Units for Model 120022                                               S.I. Units for Model 120022

A2 = pi * (diameter/2)^2                                                              A2 = pi * (diameter/2)^2

= 3.14 * (5.15 in/2)^2                                                                    = 3.14 * (13.1 cm/2)^2

= 20.8 in^2                                                                                      = 134.7 cm^2

 

When we apply the information to Equation 2, we get the following information:

 

Imperial Units                                                                                  S.I. Units

P2 = P1 * A1 / A2                                                                              P2 = P1 * A1 / A2

=(0.14 PSI * 10 in^2) / 20.8 In^2                                               =(0.0096 Kg/cm^2 * 64.8cm^2) / 134.7 cm^2

= 0.067 PSI                                                                                       =0.0046 Kg/cm^2

 

Now that the area was increased like the snow shoes above, the pressure was reduced and no additional waste was incurred.  Sometimes you have to think outside the igloo.  As with any application or product, you can always contact us at EXAIR for help.

 

John Ball
Application Engineer
johnball@exair.com
twitter.com/exair_jb

 

Image courtesy of VasenkaPhotography. Creative Comment License