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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Adjustable Air Amplifier Keeps Sensor Cool

Our distributor in China has a customer who visited the United States, while their customer was in the US they saw an EXAIR product installed and wanted to replicate the setup in China. He saw the EXAIR label and reached out to our distributor for help in identifying the part. Taking a quick measurement of the inlet side of the Adjustable Air Amplifier led us to discern it was a Model 6041 1-1/4” Adjustable Air Amplifier.

adjustable air amplifier sensor cooling
EXAIR Model 6041

The product was installed on a baghouse monitoring system. The sensor is used to detect minor leaks within the dust collection system before the leaks create a major problem. The environment in which the sensor was installed results in temperatures that are just above the normal operating temperatures during warmer months and can result in erroneous readings. When this occurs, production is shutdown to prevent a failure of the dust collection system while the filters can be inspected. By installing the Adjustable Air Amplifier to provide a large volume of air and a low level of compressed air consumption, the temperature is able to be maintained within typical operating range for the sensor. This alleviates the need for unnecessary shutdowns (or unnecessary filter replacement), while ensuring that the working environment remains dust-free.

EXAIR’s Adjustable Air Amplifiers are available in both Stainless Steel and Aluminum from sizes ranging from ¾”-4” on the air outlet. The outlet can be ducted as seen in this application, or it can be used as-is. The air gap of the Adjustable Air Amplifier is infinitely adjustable, allowing you to regulate both the air consumption and outlet flow from a “breeze” to a “blast”. In addition to the standard Adjustable Air Amplifiers, we also have a Model 121021 High Temperature Air Amplifier available that is capable of withstanding temperatures as high as 700°F.

Air Amplifiers can be used in a variety of different applications. Not only can they be used in applications requiring cooling, but the air entrainment properties of the amplifier can be used to exhaust smoke as discussed in this application at a foundry. An Adjustable Amplifier can also be used for drying or cleaning parts as well as for conveying light materials.

Regardless of the application, EXAIR has a suitably sized Air Amplifier to fit your needs. If you need an efficient and reliable way to vent, cool, clean, or dry parts give us a call. An Application Engineer would be happy to take a look at your application and provide the best recommendation.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

Two Types of Air Amplifiers – Volume and Pressure

When the topic of Air Amplifiers comes up, there are two avenues to consider –  is it the air pressure or the air volume that you wish to amplify?  There exists technologies to amplify either parameter, and we will examine them both.

There may be equipment or processes within a facility that operate best at air pressures higher than can be delivered, due to air compressor limitations or the supply system. An Air Pressure Amplifier can take the existing compressed air supply, and boost the pressure allowing for the higher needed air pressure without requiring a dedicated compressor capable of operating at the higher pressure.

An Air Pressure Amplifier is basically an air pump, driven by a portion of the compressed air supply.  The pump cycles and compresses the remaining amount of compressed air to a higher outlet pressure. This higher output pressure can be used to operate the equipment or process that required the pressure levels that the base system could not supply. The drawback is that the pump system consumes a good amount of the compressed air volume, to power the pump which reduces the amount of air available for other equipment or processes.  This drives up the compressed air consumption for the system, and requires the extra capacity to operate.

The other type of Air Amplifier is the kind that amplifies the air flow volume. EXAIR manufactures this type of amplifier.

AirAmplifiers

The air flow amplification works by taking compressed air (1) and directing into an annular chamber (2). It is then throttled through a small ring nozzle (3) at high velocity. This primary stream of air adheres to the Coanda profile (4) and is directed through the outlet. A low pressure area is created at the center, inducing a high volume flow (5) of surrounding air to be drawn in and added to the main air stream. The combined flow of primary and surrounding air exits as a high volume, high velocity flow.

salworksani

EXAIR manufactures (2) types of Air Amplifiers, the Super Air Amplifier and the Adjustable Air Amplifier.  In addition, a special model for High Temperature applications is available.  Sizes range from 3/4″ (19mm) to 8″ (203mm) to meet most air flow requirements.  Air amplification ratios start at 12:1 for the 3/4″ model and increase to 25:1 for the 4″ and 8″ models.

Charts and tables are available to help determine the right Air Amplifier for the job.

If you have questions about the Air Amplifiers, or would like to talk about 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 Amplifiers – Adjustability for Blowoff, Drying, Cooling, Circulation and Ventilation

The Super Air Amplifier is a powerful, efficient, and quiet air mover. Applications currently in place include blowoff, drying, cooling, circulation and ventilation. Sizes from 3/4″ to 8″ are available to best match the air volume that is necessary to achieve the process goals. There are a couple of ways to change the performance of the Super Air Amplifier if either a small or large change to the output flow is required.AirAmplifiers

The chart below shows the Total Output Flow for each of the 6 models. As an example, the Model 120021 or 121021, when operated at 60 PSIG of compressed air supply, will have a total output flow of 120 SCFM. These same devices when operated at 80 PSIG will have a total flow of 146 SCFM. By simply using a pressure regulation device on the compressed air supply, the output performance can be tuned to match the desired outcome.

Capture

For those applications where much greater flow and/or force is needed, the option of installing a thicker shim is available.  The Super Air Amplifiers are supplied with a 0.003″ shim installed (the 8″ model 120028, has a 0.009″ shim as standard) and can be fitted with shims of thicknesses of 0.006″ or 0.009″ (the 8″ model has an optional 0.015″ shim.) Installation of a thicker shim increases the slotted air gap, allowing for a greater amount of controlled air flow.  As a general rule, doubling the shim thickness will double the air flow rates.

Super Air Amplifier Shims
Patented* Shim Design for Super Air Amplifiers

The Super Air Amplifier design provides for a constant, high velocity outlet flow across the entire cross sectional area,.  The balanced outlet flow minimizes wind shear to produce sound levels that are typically three times quieter than other air movers. By regulating the compressed air supply pressure and use of the optional shims, adjustability and flexibility of the unit is wide ranging and sure to meet your process needs.

If you have questions regarding the Super 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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*Patent #5402938

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

Calculating Air Volume for Cooling

Motores_en_el_robot
Robot motor in need of cooling

 

dims
Accompanying information about motor in need of cooling

Usually, when discussing application solutions we can make recommendations for proper product based on experience, empirical test data, and application parameters.  Sometimes, though, we need to take things just a little further and aim to dial in the recommended solution before any testing ever occurs.

I recently had an exercise in this, involving the need to cool the robot motor shown in the photo above.  This motor, existing in two forms (one weighing 23kg and the other weighing 25kg) is currently operating, creating heat, and registering a temperature of 90°C.  The desired operating temperature is 60°C, and we can safely assume an ambient temp. no higher than 35-40°C.

The questions posed to me were:  “Which product should be used to cool this motor?  And, how do you know?”  So, I took a certain degree of liberty (though not much) in considering the motor in question is comprised of copper windings, and these windings comprise the total weight of the motor.

Considering this, our knowns for this application were:

Weight:                              23kg and 25kg

Material:                            Copper

Starting temp:                   90°C

Ending temp:                    60°C

 

What we didn’t know was:

Specific heat of copper:                  (determined to be 0.385 Joules/g°C)

Amount of airflow to cool this motor by 30°C:                     XXX cubic feet per minute

 

This airflow was determined using the process shown below, and the resulting calculations shown below.

heat load calc process
Process to calculate the required airflow in a cooling application

 

heatcalcs
The calculations used to determine the required airflow in this application

 

Super Air Amplifier Performance Specs
Performance specifications of our Super Air Amplifiers

The end result was confirmation that EXAIR model 120022, our 2” Super Air Amplifier, can use just 15.5 SCFM of compressed air at 80 PSIG to produce an airflow to cool this motor.  And, thanks to the skills of the team here at EXAIR we have the numbers to back up that claim.

If you have an application with a similar need and think we may be able to help, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

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