Digital Flowmeters: Converting Them to Serial Communication

Model 9090-DAT

An international customer purchased three Digital Flowmeters, model 9090-DAT in yr2018.  This model number refers to the EXAIR Rev3 Digital Flowmeter with a Datalogger (photo above) for ½” Schedule 40 black pipe.  They used the Datalogger to log flowrates for their blow-molding machines.  A new engineering manager joined their team and was looking for a more “real time” reading of the flowrates.  They could compare flow data results from prior setups to monitor the program for their current blow-molded products with certain materials and sizes.  It was important for quality control to measure and compare the results to verify the proper machine set points.  They contacted EXAIR to see what we could offer.

EXAIR offers a variety of Digital Flowmeters for black pipe, aluminum tubes, and copper pipes.  They can accurately measure compressed air and nitrogen flow by measuring the temperature difference between the two probes.  The display is large for easy reading, and it can be programed for different units like SCFM, M3/hr, and M3/min.  For software data collection, we have the Wireless communication, USB Datalogger, and wire communication.  We also have Hot Tap versions, Pressure measuring, and Remote Display. 

In describing their current programming system, they were using a Modbus RS485 network.  This type of network system uses a “master” device to communicate with multiple “slave” devices.  In this instance, they were going to use a computer as the “master” device to communicate with the Digital Flowmeters.  With this type of serial communication, each Digital Flowmeter would have a particular and exclusive node address.  The master device can “open” the serial communication with that particular Digital Flowmeter and transfer data points of flow measurements.  The serial boards that EXAIR uses can connect to over 100 meters with a total length of 4,000 feet (1,212 meters).

Now, for our customer above, they did not need to purchase different Digital Flowmeters.  EXAIR offers a model 901785 serial communication board to convert the standard Rev3 Digital Flowmeter to connect to Modbus RS485.  They purchased three of them and converted each unit that they had without removing them from the compressed air system.  Since they were using the serial communication to connect to a computer, they requested an Ethernet connection.  EXAIR is able to convert serial communication to either Ethernet or USB connection with a converter.  With the Ethernet converter, they were able to connect directly to their computer.  They downloaded a software program at no charge to start monitoring and collecting flow information from all the digital flowmeters.  This improved the setup times for each machine.  As an extra bonus, they could also determine if they had some pneumatic issues with valves, cylinders, or leaks with the readings from the Digital Flowmeters. 

EXAIR Digital Flowmeters for large pipe

When you need to analyze your pneumatic components, flow is an important point.  The EXAIR Digital Flowmeter can give you that important data point.  You can cut energy consumption, improve pneumatic efficiencies, reduce setup times, and save yourself money.  If you are missing that detail with your pneumatic system, an Application Engineer at EXAIR can help you select the best Digital Flowmeter.  And if in the future you wish to upgrade, we may have a simple solution for you as seen with our international customer above. 

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

NEMA/UL and IP ratings

From right to left: Small NEMA 12, Large NEMA 12, Large NEMA 4X

EXAIR manufactures Cabinet Coolers to keep your electrical components inside cool.  This will help to stop any costly shutdowns or premature electrical failures due to overheating.  The EXAIR Cabinet Cooler System is a simple device that generates cold air with no moving parts, condensers, or freon.  They are maintenance-free with a long-life cycle; and installation is quick and easy.  But when mounting the system to your electrical panel, you want to make sure that the Cabinet Cooler meets or exceeds the integrity standard for that environment.  There are standards that categorize electrical panels to protect workers, shield the environment, and contain the electrical components. 

Electrical panels come in all shapes, sizes and colors; and can be used in a variety of environments; indoor, outdoor, and even hazardous locations.  Depending on the place and setting, you will need to determine the minimum requirements for the integrity of your electrical panel.  For example, you do not want to use an “indoor only” electrical enclosure for outside areas.  Also, you would not want a standard enclosure to be used in a hazardous area, as it can be very dangerous.  The major organizations that create these electrical standards are NEMA, UL, and IP.  In this blog, I will cover these organizations and how they rate them.

NEMA, or National Electrical Manufacturer Association, and UL, or Underwriters Laboratory, are generally used in North America.  The difference between these two organizations is that the NEMA ratings are self-certifying while the UL requires testing by qualified inspectors, independent of the manufacturer, for compliance.  They use numbers and in some instances letters to indicate the type of environment that the enclosure can operate. EXAIR Cabinet Cooler Systems are UL listed; so, they have been tested and verified.  Currently, there are over 20 different NEMA/UL classifications.  Here is a description by WIKA that shows the different categories for both NEMA and IP.

IP, or Ingress Protection, is an international standard commonly used in Europe and is established by the International Electrotechnical Commission, or IEC.  This organization also allows for self-certification.  They use two digits to define levels of integrity for electrical enclosures against intrusion from foreign bodies and moisture. The first digit ranges from 1 to 6 which specifies the protection rating from solids.  The second digit, which ranges from 1 to 8, specifies the protection rating for ingress of water.  The higher the number, the better the protection.  The combination of these two numbers will give the protection level of the enclosure against dust and water.  There is an equivalence with the NEMA ratings to the IP ratings, but it is up to the preference of the user to verify the protection requirement. 

EXAIR offers three main NEMA types for our Cabinet Cooler Systems which are the most commonly found within facilities. We also offer an additional two types that are designated strictly for Hazardous Locations and are separately certified by UL to meet those standards.

NEMA 12

NEMA 12 (IP54) Cabinet Coolers are rated for dust tight and oil tight. NEMA 12 cabinet coolers are ideal for general industrial environments where no liquids or corrosives are present and are located inside.

NEMA 4

NEMA 4 (IP66) Cabinet Coolers are rated for dust tight, oil tight, splash resistant and indoor/outdoor service. These Cabinet Coolers incorporate a low-pressure relief valve to allow the internal hot air to escape as well as to close and seal when the cooler is not in operation.  This allows for this Cabinet Cooler to maintain the integrity of a NEMA 4 enclosure.

NEMA 4X

NEMA 4X (IP66) Cabinet Coolers offer the same protection as the NEMA 4 but are constructed of stainless steel for food service and corrosive environments.

HazLoc Cabinet Cooler Systems

HazLoc Cabinet Coolers are designed for hazardous locations and are mounted to NEMA 7, 8, and 9 enclosures.  EXAIR catalogs these Cabinet Coolers as NEMA 4 (IP66) or NEMA 4X (IP66) as mentioned above.  But their registration by UL classified is for Class I, Class II, and Class III hazardous areas.  The reason that they do not match the NEMA rating of the hazardous panels is because they require an X-type or Z-type purge system.  In combination, they will not sacrifice the integrity of hazardous electrical panels. 

EXAIR has Cabinet Coolers in stock with a variety of cooling capacities from 275 BTU/hr to 5,600 BTU/hr (69 Kcal/hr to 1,411 Kcal/hr).  We also offer them in 316SS, high temperature versions, and non-hazardous purge.  We do have a Cabinet Cooler System Calculator to help determine the best product for your application.  If you have any additional questions, an Application Engineer at EXAIR can assist you.   

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Compressor Intake – Air Flows 

Flow rate is the quantity of material that is moved per unit of time.  Generally, the quantity of material can be expressed as a mass or a volume.  For example, mass flow rates are in units of pounds per minute or kilograms per hour.  Volumetric flow rates are stated in cubic feet per minute, CFM, or liters per hour, LPH.  The trick begins when volumetric flow rates are used with compressible gases.  In this blog, I will go over the various acronyms and the reasons behind them.

What acronyms will be covered?

CFM – Cubic Feet per Minute

SCFM – Standard Cubic Feet per Minute

ACFM – Actual Cubic Feet per Minute

ICFM – Inlet Cubic Feet per Minute

The volumetric component of the flow rate is CFM or Cubic Feet per Minute.  This term is commonly used for rating air compressors.  From the history of air compressors, they could calculate the volume of air being drawn into the air compressor by the size of the cylinder.  With the volume of the compression chamber and the rotations per minute of the motor, RPM, they could calculate the volumetric air flows.  As conditions change like altitude, temperature, and relative humidity, the volumetric value of CFM changes.  To better clarify these conditions, compressor manufacturers have decided to add terms with a definition.  (For your information, air compressors still use CFM as a unit of air flow, but now this is defined at standard temperature and pressure).

The first letter in front of CFM above now defines the conditions in which volumetric air flow is being measured.  This is important for comparing pneumatic components or for properly sizing pneumatic systems.  Volume is measured within three areas; temperature, pressure, and relative humidity.  We can see this in the Ideal Gas Law, reference Equation 1.

Equation 1:

P * V = n * R * T

Where:

P – Absolute Pressure

V – Volume

n – Number of molecules of gas

R – Universal Gas Constant

T – Absolute Temperature

The volume of air can change in reference to pressure, temperature, and the number of molecules.  You may ask where the relative humidity is?  This would be referenced in the “n” term.  The more water vapor, or higher RH values, the less molecules of air are in a given volume.

SCFM is the most commonly used term, and it can be the most confusing.  The idea behind this volumetric air flow is to set a reference point for comparisons.  So, no matter the pressure, temperature, or relative humidity; the volumetric air flows can be compared to each other at that reference point.  There have been many debates about an appropriate standard temperature and pressure, or STP.  But as long as you use the same reference point, then you can still compare the results.  In this blog, I will be using the Compressed Air and Gas Institute, CAGI, reference where the “Standard” condition is at 14.5 PSIA, 68 o F, and 0% RH.  Since we have a reference point, we still need to know the actual conditions for comparison.  It is like having the location of a restaurant as a reference, but if you do not know your current location, you cannot move toward it.   Similarly, we are “moving” the air from its actual condition to a reference or “Standard” condition.  If we do not know the actual state where the air began, then we cannot “move” toward that reference point.  We will talk more about this later in this blog.

ACFM is the volumetric air flow under actual conditions.  This is actually the “true” flow rate.  Even though this term is hardly used, there are reasons why we will need to know this value.  We can size an air compressor that is not at “Standard” conditions, and we can use this value to calculate velocity and pressure drop in a pneumatic system.  We can correlate between SCFM and ACFM with Equation 2.

Equation 2:

ACFM = SCFM * [Pstd / (Pact – Psat * Φ)] * (Tact / Tstd)

Where:

ACFM – Actual Cubic Feet per Minute

SCFM – Standard Cubic Feet per Minute

Pstd – standard absolute air pressure (PSIA)

Pact – absolute pressure at the actual level (PSIA)

Psat – saturation pressure at the actual temperature (PSI)

Φ – Actual relative humidity (%)

Tact – Actual ambient air temperature (oR)

Tstd – Standard temperature (oR)

ICFM is one of the newest terms in the history of air compressors.  This is where devices are added to the inlet of an air compressor, affecting flow conditions.  If you have a blower on the inlet of an air compressor, the volumetric flow rate changes as the pressure and temperature rises at the “Inlet”.  If a filter is used, then the pressure drop will decrease the incoming pressure at the “Inlet”.  These devices that affect the volumetric flow rate for an air compressor should be considered.  The equation to relate ACFM to ICFM is Equation 3.

Equation 3:

ICFM = ACFM * (Pact / Pf) * (Tf / Tact)

Where:

ICFM – Inlet Cubic Feet Per Minute

ACFM – Actual Cubic Feet per Minute

Pact – absolute pressure at the actual level (PSIA)

Pf – Pressure after filter or inlet equipment (PSIA)

Tact – Actual ambient air temperature (oR)

Tf – Temperature after filter or inlet equipment (°R)

To expand on my explanation above about SCFM and ACFM, a technical question is asked often about the pressure when using SCFM.  The reference point of 14.5 PSIA is in the definition of the term for SCFM.  Remember, this is only a reference point.  The starting location is also needed as it gives us the ACFM value where the air values are true and actual.  Then we can make a comparison of actual air usage. 

As an example, let’s look at two air nozzles that are rated at the same air flow; 60 SCFM.  The EXAIR Super Air Nozzle, model 1106, is cataloged at 60 SCFM at 80 PSIG, and a competitor is cataloged at 60 SCFM at 72 PSIG.  By comparison, they look like they use the same amount of compressed air, but actually they do not.  To simplify Equation 2, we can compare the two nozzles at the same temperature and RH at 68 oF and 0% RH respectively.  This equation can be reduced to form Equation 4.

Equation 4:

ACFM = SCFM * 14.5 / (P + 14.5)

@72 PSIG Competitor:

ACFM = 60 SCFM * 14.5 PSIA/ (72 PSIG + 14.5 PSIA)

= 10.1 ACFM

@80 PSIG EXAIR Super Air Nozzle:

ACFM = 60 SCFM * 14.5 PSIA / (80 PSIG + 14.5PSIA)

= 9.2 ACFM

Even though the SCFM is the same amount, you are actually using 10% more air with the competitive nozzle that was reported at 60 PSIG.  So, when it comes to rating pneumatic products, improving efficiency, and saving money; always determine the pressure that you are at.  The more you know about volumetric flow rates, the better decision that you can make.  If you need more information, you can always contact our Application Engineers at EXAIR.  We will be happy to assist.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Photo: Compressor equipment by terimakasih0Pixabay license

Super Air Wipes can Help to Protect a Camera Lens

2403SS

An oil and gas company was using a camera to watch a drilling rig.  During the operation, water and mud could be slung toward the camera lens, and create spots.  An operator would have to leave their position to clean the lens.  Since they were looking for a way to force the water and mud away from the lens, but it had to be clear.  Since air is transparent, they contacted EXAIR for our expertise. 

As an air barrier, customers have used the Super Air Knives to separate material/heat/gases from different areas in similar applications.   But, for this customer, they were interested in the Super Air Wipe; and at EXAIR, we state that there is more than one way to solve a riddle.  With the speed of the water and mud, I was not keen on the ability of how well the Super Air Wipe could work.  So, I decided to test it. 

At EXAIR, we offer customers the option for us to test our products in different applications.  This could also include testing your items with our products.  EXAIR offers an Application Assistance form to help get this started.  If we have the capabilities, we can setup a “mock” system to test and verify, and we can shoot a short video to present the information to you.  This can include conveyance testing, product comparisons, cleaning, cooling; and, for the customer above, air barrier testing. 

Their current operation was using a wiper to clean the glass.  Like with any wiper, material can get wedged under the wiper and cause streaks, and it could scratch the glass lens.  To stop replacing the wiper blade or in some instances, the glass lens; they were looking for a non-contact way to keep the water, sand, mud from the camera lens.  Since it was difficult for them to determine the velocity of the material that would be heading toward the camera, they requested that I use water for my test.  With a 1/4” (6 mm) O.D. tubing, they believed that it could represent a good velocity with a pressure of 20 PSIG (1.4 Bar) and a flow of 30 GPH (113.6 LPH).  This would create a velocity of 9.3 mph (15 kph).  Since the lens had a diameter of 2” (51mm), I recommended the model 2403SS, 3” Stainless Steel Super Air Wipe.  Here is a video of the results with the inlet air pressure at 80 PSIG (5.5 Bar).

Water Test

To expand a bit more on the Super Air Wipe, it is designed to blow compressed air in a 360-degree flow pattern.  This air pattern is directed at a 30-degree angle toward the center to blow the debris back away from the camera lens, just like a cone.  The Coanda effect maximizes the entrainment of ambient air into the compressed air.  This makes the unit very efficient and very powerful.  The model 2403SS Super Air Wipe has an I.D. of 3” (76 mm) which gives it enough clearance away from the view of the camera.  It is constructed of 303 stainless steel construction for corrosion resistance with a stainless-steel braided hose that connects the two halves together.  The design is very rugged for outdoor use. 

At EXAIR, we offer a 30-day unconditional guarantee on our stock products for US and Canadian customers to try things out.  But sometimes this may not be enough.  For the customer above, we were able to try something different to verify the effectiveness in keeping the camera lens clean.  And at EXAIR, we will take that extra step to help our customers.  If you have a pneumatic application that requires some additional service, you can fill out the Application Assistance form or contact an Application Engineer.  We will be happy to help you, and perhaps we can put some “focus” on a solution. 

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb