Intermediate Storage Tanks & How To Size Them

When evaluating processes that utilize compressed air and adhering to the Six Steps to Compressed Air Optimization, intermediate storage proves to be a critical role coming in at step number five. Intermediate storage tanks may already be in place within your facility and often times can be implemented as modifications to aid existing lines that are struggling to maintain proper availability of compressed air to keep the line at peak performance.

EXAIR Receiver Tank in 60 Gallon Capacity

When determining whether or not a production line or point of use compressed air operation would benefit from a receiver tank/intermediate storage we would want to evaluate whether the demand for compressed air is intermittent.  Think of a receiver tank as a capacitor in an electrical circuit or a surge tank in a water piping system.  These both store up energy or water respectively to deliver to during a short high demand period then slowly charge back up from the main system and prepare for the next high demand.   If you look from the supply point it will see a very flattened demand curve, if you look from the application side it still shows a wave of peak use to no use.

Intermittent Applications are prime for rapid on/off of compressed air.

One of the key factors in intermediate storage of compressed air is to appropriately size the tank for the supply side of the system as well as the demand of the application.  The good news is there are equations for this.  To determine the capacity, use the equation shown below which is slightly different from sizing your main compressed air storage tank.  The formulate shown below is an example.

Where:

V – Volume of receiver tank (ft3 / cubic feet)

T – Time interval (minutes)

C – Air demand for system (cubic feet per minute)

Cap – Supply value of inlet pipe (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P1 – Header Pressure (PSIG)

P2 – Regulated Pressure (PSIG)

One of the main factors when sizing point of use intermediate storage is, they are being supplied air by smaller branch lines which cannot carry large capacities of air.  That limits your Cap value. The only way to decrease the V solution is to increase your Cap. The other key point is to ensure that all restrictions feeding into the tank and from the tank to your point of use are minimized in order to maintain peak performance.

If there are intermittent applications that are struggling to keep up with the production demands within your system, please reach out and speak with an Application Engineer.  We are always here to help and we may even be able to help you lower the demand needed by utilizing an engineered point of use compressed air solution.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

EXAIR Digital Flowmeters With Wireless Capability

“You can’t manage what you don’t measure” is a well-known axiom in engineering & process improvement circles.  We talk to callers every day who are keen on conserving compressed air use in their facilities by making a few tweaks, considering a complete overhaul, or more often, some point in between.  Bottom line (literally) is, compressed air isn’t cheap, so small gains in efficiency can add up.  And large gains can be complete game-changers…following our Six Steps To Optimizing Your Compressed Air System has resulted in users being able to shut down 50 and 100 HP air compressors, saving thousands of dollar A MONTH in operating costs.

Step #1 is measurement, and that’s where the EXAIR Digital Flowmeter comes in.  They’re easy to install, highly accurate, extremely reliable, and available for just about any size pipe used for compressed air distribution.  They can output a 4-20mA signal straight from their PCB board, or serial comms (RS485) through an optional control board.  USB Data Loggers and Summing Remote Displays have proven to be value-added accessories for data management as well.

Summing Remote Display (left) for remote indication and totalizing data. USB Data Logger takes data from the Digital Flowmeter to your computer and outputs to its own software (shown above) or Microsoft Excel.

If you want to go wireless, we can do that too: using ZigBee mesh network protocol, a radio module is installed in the Digital Flowmeter with wireless gateway to transmit data to an Ethernet connected gateway.  The transmitting range is 100 ft (30 meters,) and the data can be passed from one radio module to another, allowing for multiple Digital Flowmeter installations to extend the distance over which they can communicate with the computer you’re using for central monitoring.  Advantages include:

  • Wireless monitoring of EXAIR Digital Flowmeters throughout your plant.
  • Prevents unwanted joining upon the network.
  • Monitoring software is included at no extra charge.
  • Measures & transmits both current air usage, and cumulative air usage data.
  • 128 bit encryption for wireless transmissions.
  • Comes configured & programmed, out of the box, available for installation on 1/2″ to 4″ SCH40 iron pipe, or 3/4″ to 4″ Type L copper pipe.
Digital Flowmeter w/ Wireless Capability, Gateway, and Drill Guide Kit

If you’d like to find out more about how easy it is to measure, manage, and optimize your compressed air usage, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Supply Side Review: Deliquescent Type Dryers

As mentioned in my post last week.  The supply side of compressed air systems within a facility is critical to production.  The quality of air produced by your compressor and sent to the demand side of the system needs to be filtered for both moisture and particulate.  One method to dry the air, that is the topic for this blog, is deliquescent type dryers.

These dryers operate like an adsorbent dryer such as a desiccant medium dryer.  The main variance is that the drying medium (desiccant) actually undergoes a phase change from solids to liquids.  Because of this the material is used up and cannot be returned to its original state for reuse.   The liquids formed by the desiccant dissolving in the removed water vapor are then filtered out of the air stream before it is passed on to the demand side of the air system.

There are many compounds that are used to absorb the moisture in the wet compressed air.  A few options are potassium, calcium, or sodium salts and many that contain a urea base.  The desiccant compound must be maintained at a minimum level for the dryer to contain enough media to successfully dry the air.

These dryers are generally a single tank system that is fed with compressed air from a side port near the bottom of the tank.  The air then travels up past drip trays where the desiccant and water mixture fall and ultimately ends up in the bottom of the tank.  The air then goes through a material bed that must be kept at a given level in order to correctly absorb the moisture in the air.  The dry air is then pushed out the top of the tank.

As the desiccant material absorbs the liquid from the compressed air flowing through the tank it falls onto the drip trays and then into the bottom of the tank where it is drained out of the system.  This process can be seen in the image below.

 

Deliquescent type compressed air drying system
How a deliquescent air dryer works – 1(VMAC Air Innovated, 2017)

 

The dew point that this style dryer is able to achieve is dependent on several variables:

  • Compressed air temperature
  • Compressed air pressure / velocity
  • Size and configuration of the tank
  • Compression of the absorption media
  • Type of absorption media and age of media

These dryers are simplistic in their design because there are no moving parts as well as easy to install and carry a low startup cost.

Some disadvantages include:

  • Dewpoint range 20°F – 30°F (Again this is according to the media used.)
  • Dissolved absorption material can pose a disposal issue as it may not be able to be simply put down a drain
  • Replacement of the absorption material

Even with disadvantages the ability to supply the demand side of a compressed air system for a production facility is key to maintaining successful operations.  If you would like to discuss any type of compressed air dryer, please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

1 – Deliquescent Dryer Image: VMAC Air Innovated: The Deliquescent Dryer – https://www.vmacair.com/blog/the-deliquescent-dryer/

 

Understanding Compressed Air Supply Piping

An important component of your compressed air system is the supply piping. The piping will be the middle man that connects your entire facility to the compressor. Before installing pipe, it is important to consider how the compressed air will be consumed at the point of use.  You’ll also need to consider the types of fittings you’ll use, the size of the distribution piping, and whether you plan to add additional equipment in the next few years. If so, it is important that the system is designed to accommodate any potential expansion. This also helps to compensate for potential scale build-up (depending on the material of construction) that will restrict airflow through the pipe.

Air Compressor
Air Compressor and Storage Tanks

The first thing you’ll need to do is determine your air compressor’s maximum CFM and the necessary operating pressure for your point of use products. Keep in mind, operating at a lower pressure can dramatically reduce overall operating costs. Depending on a variety of factors (elevation, temperature, relative humidity) this can be different than what is listed on directly on the compressor. (For a discussion of how this impacts the capacity of your compressor, check out one of our previous blogs – Intelligent Compressed Air: SCFM, ACFM, ICFM, CFM – What do these terms mean?)

Once you’ve determined your compressor’s maximum CFM, draw a schematic of the necessary piping and list out the length of each straight pipe run. Determine the total length of pipe needed for the system. Using a graph or chart, such as this one from Engineering Toolbox. Locate your compressor’s capacity on the y-axis and the required operating pressure along the x-axis. The point at which these values meet will be the recommended MINIMUM pipe size. If you plan on future expansion, now is a good time to move up to the next pipe size to avoid any potential headache.

After determining the appropriate pipe size, you’ll need to consider how everything will begin to fit together. According to the Best Practices for Compressed Air Systems from the Compressed Air Challenge, the air should enter the compressed air header at a 45° angle, in the direction of flow and always through wide-radius elbows. A sharp angle anywhere in the piping system will result in an unnecessary pressure drop. When the air must make a sharp turn, it is forced to slow down. This causes turbulence within the pipe as the air slams into the insides of the pipe and wastes energy. A 90° bend can cause as much as 3-5 psi of pressure loss. Replacing 90° bends with 45° bends instead eliminates unnecessary pressure loss across the system.

Pressure drop through the pipe is caused by the friction of the air mass making contact with the inside walls of the pipe. This is a function of the volume of flow through the pipe. Larger diameter pipes will result in a lower pressure drop, and vice versa for smaller diameter pipes. The chart below from the Compressed Air and Gas Institute Handbook provides the pressure drop that can be expected at varying CFM for 2”, 3”, and 4” ID pipe.

ccfdfcfdddfcvgdsdfzxcv.png
Air Pressure Drop

To discuss your application and how an EXAIR Intelligent Compressed Air Product can help your process, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Jordan Shouse
Application Engineer
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Images Courtesy of  the Compressed Air Challenge and thomasjackson1345 Creative Commons.

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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Intelligent Compressed Air: How to Develop a Pressure Profile

An important part of operating and maintaining a compressed air system is taking accurate pressure measurements at various points in the compressed air distribution system, and establishing a baseline and monitoring with data logging.  A Pressure Profile is a useful tool to understand and analyze the compressed air system and how it is functioning.

Pressure Profile 1
Sample Pressure Profile

The profile is generated by taking pressure measurements at the various key locations in the system.  The graph begins with the compressor and its range of operating pressures, and continues through the system down to the regulated points of use, such as Air Knives or Safety Air Guns.  It is important to take the measurements simultaneously to get the most accurate data, and typically, the most valuable data is collected during peak usage periods.

By reviewing the Pressure Profile, the areas of greatest drop can be determined and the impact on any potential low pressure issues at the point of use.  As the above example shows, to get a reliable 75 PSIG supply pressure for a device or tool, 105-115 PSIG must be generated, (30-40 PSIG above the required point of use pressure.)  As a rule of thumb, for every 10 PSIG of compressed air generation increase the energy costs increase 5-7.5%

By developing a total understanding of the compressed air system, including the use of tools such as the Pressure Profile, steps to best maximize the performance while reducing costs can be performed.

If you have questions about getting the most from your compressed air system, 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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Finding Leaks and Saving Money with the Ultrasonic Leak Detector

Locate costly leaks in your compressed air system!  Sounds like the right thing to do.

The EXAIR Ultrasonic Leak Detector is a hand-held, high quality instrument that is used to locate costly leaks in a compressed air system.

Ultrasonic sound is the term applied to sound that is above the frequencies of normal human hearing capacity.  This typically begins at sounds over 20,000 Hz in frequency.  The Ultrasonic Leak Detector can detect sounds in this upper range and convert them to a range that is audible to people.

When a leak is present, the compressed air moves from the high pressure condition through the opening to the low pressure environment.  As the air passes through the opening, it speeds up and becomes turbulent in flow, and generates ultrasonic sound components. Because the audible sound of a small leak is very low and quiet, it typically gets drowned out by by surrounding plant noises, making leak detection by the human ear difficult if not impossible.

ULD_Pr
Detecting a Leak with the Ultrasonic Leak Detector

By using the Ultrasonic Leak Detector, the background noise can be filtered out and the ultrasonic noises can be detected, thus locating a leakage in the compressed air system. There are (3) sensitivity settings, x1, x10, and x100 along with an on/off thumb-wheel for fine sensitivity.  The unit comes with a parabola and tubular extension for added flexibility.

ULD_Kit
Model 9061 – Ultrasonic Leak Detector and Included Accessories

Finding just one small leak can pay for the unit-

A small leak equivalent to a 1/16″ diameter hole will leak approx 3.8 SCFM at 80 PSIG of line pressure.  Using a reasonable average cost of $0.25 per 1000 SCF of compressed air generation, we can calculate the cost of the leak as follows-

Capture

It is easy to see that utilizing the Ultrasonic Leak Detector, and identifying and fixing leaks is the right thing to do.  It is possible to find and fix enough leaks that a new compressor purchase can be avoided or an auxiliary back-up is not needed any more.

If you have questions regarding the Ultrasonic Leak Detector, 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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