Tag: air demand

Compressed air Storage: Do you need a Receiver Tank?

Published on by Jordan T ShouseLeave a comment

Maintaining a “supply and demand” balance in the design & operation of compressed air systems often includes receiver tanks.

Just like in economics, we have to consider both sides – supply AND demand – to best maintain this balance.  Also like in economics, there are numerous factors…on both sides…but the two most critical factors are:

  • Compressor capacity control (supply side)
  • System storage (demand side)

I wrote a blog on “Air Compressor Motors and Controls, Working Together”, outlining the ‘supply side’ variables, today lets look at the system storage. Distribution piping makes up a certain amount of this, and another great blog from my colleague, Tyler Daniel – “Intelligent Compressed Air: Distribution Piping and Pressure Drop” – gets me off the hook for THAT part of the discussion today.

We can consider the air capacity of system piping to be fixed for the purposes of this discussion, so our “variable” will be the capacity of storage tanks. Let’s start with the reasons for the need for system storage: Strategically placed point-of-use air receivers provide stored energy for intermittent demands.  This enables the compressed air system to handle fluctuating loads, efficiently & reliably.  It also minimizes impact (e.g., sudden and often detrimental drops) on the system pressure.

Next, we’ll look at location. There are a couple of common options to consider:

  • The intermittent demand. Installing a receiver here will provide enough air for short duration, high consumption events, protecting the rest of the system from pressure excursions. Dedicating the receiver to this application will mean isolating it from the rest of the system with a check valve (so it only supplies the load in question) and a needle valve (so recharging the receiver itself, between the intermittent uses, doesn’t adversely affect total system pressure).
  • The critical load(s). Instead of using stored air for the intermittent load, you can also use it for the important loads you’re trying to protect. All sorts of machinery with pneumatic components can “crash” if a nearby intermittent demand starts up & “steals” their air. You’ll use a check valve (same as above), but using a needle valve to throttle the air flow that recharges the receiver risks “starving” the critical load. Don’t do that unless there’s a really good (and likely really specific) reason for it.

Finally, we’re going to do some math, so we know how big this receiver has to be. Here’s the equation we use to do that:

Let’s calculate the receiver size needed to supply an intermittent load of 400 SCFM (C) @80psig (P2), that’ll run for one minute (T). You can use data specific to your system to come up with a value for (Cap) but here I’m going to assume we want the receiver to be able to handle the whole thing, so Cap = 0. I’m also going to assume we’re at sea level, so Pa = 14.7psia and that our compressor’s discharge pressure (the pressure at which the receiver can be charged to) is 120psig (P1):

That’s an awfully big tank. Now, let’s calculate the receiver size needed to protect a critical load that uses 55 SCFM @60psig, and that due to the system design, we can count on 25 SCFM @120psig from the compressor:

This is a much more manageable size, in fact, our 60 Gallon Receiver Tank (Model 9500-60) would be ideal. It’s 20″ in diameter and just over 50″ tall, so it doesn’t take up a lot of floor space. It comes with a drain valve and connections for compressed air flow in & out, pressure gauge, relief valve, etc.

Step Five of our Six Steps To Optimizing Your Compressed Air System: Use intermediate storage near the point of use.

Now, the above example is a completely hypothetical situation, and I purposely chose exaggerated values to show that there can indeed be a clear “winner” in the choice between the two installation points. If you have a situation like this, and would like help in finding the solution that makes the most sense, give us a call.

Jordan Shouse
Application Engineer

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How To Determine The Need For – And The Size Of – Compressed Air Receiver Tanks

Published on by Russ BowmanLeave a comment

Supply and Demand, in economics, defines the relationship between the volume of commodities that sellers want to exchange for a certain amount of currency, and the volume of said commodities that buyers are willing to exchange a certain (and sometimes different) amount of currency for.  The best chance for an ideal condition is when the volume produced is the same as the volume being consumed.  That typically means both sides are amenable to the same certain amount of currency, and everyone’s happy: the sellers are making a fair profit, and the buyers are paying a fair price.  Thing is, that’s a difficult balance to maintain.  The reasons for imbalances are often debated and usually contentious, and I have no intention of going in to them here.  I only brought up the subject to draw an analogy to the difficulties in maintaining a “supply and demand” balance in the design & operation of compressed air systems.

Just like in economics, we have to consider both sides – supply AND demand – to best maintain this balance.  Also like in economics, there are numerous factors…on both sides…but the two most critical factors are:

  • Compressor capacity control (supply side)
  • System storage (demand side)

My colleague Jordan Shouse wrote an excellent blog on “Air Compressor Motors and Controls, Working Together”, outlining the ‘supply side’ variables, allowing me to concentrate my efforts today on system storage. Distribution piping makes up a certain amount of this, and another great blog from another colleague, Tyler Daniel – “Intelligent Compressed Air: Distribution Piping and Pressure Drop” – gets me off the hook for THAT part of the discussion today.

We can consider the air capacity of system piping to be fixed for the purposes of this discussion, so our “variable” will be the capacity of storage tanks. Let’s start with the reasons for the need for system storage: Strategically placed point-of-use air receivers provide stored energy for intermittent demands.  This enables the compressed air system to handle fluctuating loads, efficiently & reliably.  It also minimizes impact (e.g., sudden and often detrimental drops) on the system pressure.

Next, we’ll look at location. There are a couple of common options to consider:

  • The intermittent demand. Installing a receiver here will provide enough air for short duration, high consumption events, protecting the rest of the system from pressure excursions. Dedicating the receiver to this application will mean isolating it from the rest of the system with a check valve (so it only supplies the load in question) and a needle valve (so recharging the receiver itself, between the intermittent uses, doesn’t adversely affect total system pressure).
  • The critical load(s). Instead of using stored air for the intermittent load, you can also use it for the important loads you’re trying to protect. All sorts of machinery with pneumatic components can “crash” if a nearby intermittent demand starts up & “steals” their air. You’ll use a check valve (same as above), but using a needle valve to throttle the air flow that recharges the receiver risks “starving” the critical load. Don’t do that unless there’s a really good (and likely really specific) reason for it.

Finally, we’re going to do some math, so we know how big this receiver has to be. Here’s the equation we use to do that:

Let’s calculate the receiver size needed to supply an intermittent load of 400 SCFM (C) @80psig (P2), that’ll run for one minute (T). You can use data specific to your system to come up with a value for (Cap) but here I’m going to assume we want the receiver to be able to handle the whole thing, so Cap = 0. I’m also going to assume we’re at sea level, so Pa = 14.7psia and that our compressor’s discharge pressure (the pressure at which the receiver can be charged to) is 120psig (P1):

That’s an awfully big tank. Now, let’s calculate the receiver size needed to protect a critical load that uses 55 SCFM @60psig, and that due to the system design, we can count on 25 SCFM @120psig from the compressor:

This is a much more manageable size, in fact, our 60 Gallon Receiver Tank (Model 9500-60) would be ideal. It’s 20″ in diameter and just over 50″ tall, so it doesn’t take up a lot of floor space. It comes with a drain valve and connections for compressed air flow in & out, pressure gauge, relief valve, etc.

Step Five of our Six Steps To Optimizing Your Compressed Air System: Use intermediate storage near the point of use.

Now, the above example is a completely hypothetical situation, and I purposely chose exaggerated values to show that there can indeed be a clear “winner” in the choice between the two installation points. “Your mileage may vary,” as the car folks say. If you have a situation like this, and would like help in finding the solution that makes the most sense, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Cover image courtesy of: Tennessee Valley Authority; SVG version by Tomia, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

EXAIR Wireless Digital Flow Meters Monitor Compressed Air Use

Published on by Jordan T ShouseLeave a comment

Would you like the ability to monitor your plants compressed air usage from one convenient location?  If the answer is yes, EXAIR has just the solution to fit your needs, EXAIR’s Digital Flow Meter with Wireless Capability.

Wireless capability is an option for EXAIR’s Digital Flowmeter’s.  It is the efficient way to monitor your compressed air consumption wirelessly utilizing the ZigBee® mesh network.  This is accomplished by a module located within the meter that transmits data to an ethernet connected gateway.  Each meter has a range up to 100 feet (30 meters), however the ZigBee mesh network protocol is very versatile as it allows data to also be transmitted from meter to meter, effectively extending the distance over which the system can operate.  So large facilities with great distances to cover are not a problem.

Digital Flowmeter w/ Wireless Capability, Gateway, and Drill Guide Kit

The Digital Flowmeter with Wireless Capability is offered in a kit with a wireless output flow meter, wireless to ethernet gateway, drill guide, power supplies for each component, and ethernet cable for gateway connectivity.  These kits are best suited for new installations.  They are also available without a gateway if you are simply adding an additional meter to a pre-existing Gateway in your plant.  EXAIR simplifies this process by configuring each gateway to communicate with the flowmeter to provide the necessary communication for monitoring your system.  Models from 1/2″ to 4″  iron pipe are in stock. 5″, 6″ iron pipe,  copper pipe ranging from 3/4″ to 4″ diameter and aluminum pipe from 25mm to 101mm diameter are available with short lead time as a special product offering.  Each digital flowmeter is calibrated for the pipe size to which it is mounted and the large digital display shows air use in either SCFM or Cubic Meters per Hour.

Setting up the EXAIR Digital Flow Meter with Wireless Capability is super easy.  After the meter is installed download the graphing software from our website and install on your computer.  There is also a video tutorial posted in the previous blog from Tyler Daniel, Video Blog: EXAIR’s New Wireless Digital Flowmeter Installation.

The Digital Flowmeter with Wireless Capability is designed for permanent or temporary mounting to the pipe.  It requires the user to drill two small holes through the pipe using the optional drill guide which includes the drill bit and locating fixture.  The two flow sensing probes of the flowmeter are inserted into these holes.  The unit seals to the pipe once the clamps are tightened.  No cutting, welding, adjustments or calibration are needed, ever!  If the unit needs to be removed, blocking rings are available for the 1/2″ to 4″  iron pipe sizes from stock with other sizes available on short lead time as special orders.

If you have questions on Digital Flowmeter’s, Digital Flowmeter’s with Wireless Capability or need expert advice on safe, quiet and efficient point of use compressed air products give us a call.   We would enjoy hearing from you!

Jordan Shouse
Application Engineer

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How to Calculate the Cost of Leaks

Published on by codybiehleLeave a comment

Leaks are a hidden nuisance in a compressed air system that can cause thousands of dollars in electricity per year. These leaks on average can account for up to 30% of the operation cost of a compressed air system. A leak will usually occur at connection joints, unions, valves, and fittings. This not only is a huge waste of energy but it can also cause a system to lose pressure along with lowering the life span of the compressor since it will have to run more often to make up for the loss of air from the leak.

There are two common ways to calculate how much compressed air a system is losing due to leaks. The first way is to turn off all of the point of use compressed air devices; once this has been complete turn on the air compressor and record the average time that it takes the compressor to cycle on and off. With the average cycle time you can calculate out the total percentage of leakage using the following formula.

The second method is to calculate out the percentage lost using a pressure gauge downstream from a receiver tank. This method requires one to know the total volume in the system to accurately estimate the leakage from the system. Once the compressor turns on wait until the system reaches the normal operating pressure for the process and record how long it takes to drop to a lower operating pressure of your choosing. Once this has been completed you can use the following formula to calculate out the total percentage of leakage.

The total percentage of the compressor that is lost should be under 10% if the system is properly maintained.

Once the total percentage of leakage has been calculated you can start to look at the cost of a single leak assuming that the leak is equivalent to a 1/16” diameter hole. This means that at 80 psig the leak is going to expel 3.8 SCFM. The average industrial air compressor can produce 4 SCFM using 1 horsepower of energy. Adding in the average energy cost of $0.25 per 1000 SCF generated one can calculate out the price per hour the leak is costing using the following calculation.

If you base the cost per year for a typical 8000 hr. of operating time per year you are looking at $480 per year for one 1/16” hole leak. As you can see the more leaks in the system the more costly it gets. If you know how much SCFM your system is consuming in leaks then that value can be plugged into the equitation instead of the assumed 3.8 SCFM.

If you’d like to discuss how EXAIR products can help identify and locate costly leaks in your compressed air system, please contact one of our application engineers at 800-903-9247.

Cody Biehle
Application Engineer
EXAIR Corporation
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