Tag: electronic control valve

Compressed Air and Pressure Drop: Explained

Published on by Tyler DanielLeave a comment

A critical component to optimal performance of any compressed air operated product is ensuring sufficient compressed air flow. Simply put, inadequate air flow won’t allow you to get the job done.

 As compressed air moves through the distribution system, it encounters friction inside the walls of the pipe, tube, hose, etc. The diameter of the pipe, length, number of direction changes, and finished surface of the inner wall all play a part in this. A drop in air pressure will occur as a result of this friction. In addition to pressure drops experienced due to the distribution system, they can also occur at the point of use. If the line is undersized, this pressure drop will be great enough to impact the performance of the product. 

When designing and maintaining your compressed air system, pressure measurements should be taken at varying points to identify (and fix) any issues before they create a greater problem down the road. According to the Compressed Air Challenge, these are the places you should take regular pressure measurements to determine your system operating pressure:

  • Inlet to compressor (to monitor inlet air filter) vs. atmospheric pressure
  • Differential across air/lubricant separator
  • Inter-stage on multistage compressors
  • After-cooler
  • At treatment equipment (dryers, filters, etc.)
  • Various points across the distribution system
  • Check pressure differentials against manufacturers’ specifications. If high pressure drops are noticed, this indicates a need for service.

*More recent compressors will measure pressure at the package discharge, which will include the separator and after-cooler.

Once you’ve taken these measurements, simply add the pressure drops measured and subtract that value from the operating range of your compressor. That figure is your true operating pressure at the point of use.

If your distribution system is properly sized and the pressure drops measured across your various equipment are within specifications, any pressure drop noticed at the point of use is indicative of an inadequate volume of air. This could be due to restrictive fittings or undersized air lines, hose, or tube. Check that the point of use product is properly plumbed to compressed air per the manufacturer’s specifications.

EXAIR Products are designed to minimize this pressure drop by restricting the flow of compressed air. The more energy (pressure) that we’re able to bring to the point of use, the more efficient and effective that energy will be. The photo below shows two common examples of inefficient compressed air usage. With an open-ended blow off, a pressure drop occurs upstream inside the supply line. If you were to measure the pressure directly at the point of use, while in operation, you’d find that the pressure is significantly lower than it is at the compressor or further up the line. In the other photo with a modular style hose, some pressure is able to build up but if it gets too high the hose will blow apart. These types of modular style hose are not designed to be used with compressed gases.

EXAIR’s Super Air Nozzles, on the other hand, keep the compressed air right up to the point of discharge and minimize the pressure drop. This, in addition to the air entrainment, allows for a high force while maximizing efficiency. If you’d like to talk about how an EXAIR Intelligent Compressed Air Product could help to minimize pressure drop in your processes, give us a call.

Tyler Daniel, CCASS

Application Engineer

E-mail: TylerDaniel@EXAIR.com

X: @EXAIR_TD

Measure Your Facility’s Compressed Air Consumption w/ EXAIR’s Digital Flowmeters

Published on by Tyler DanielLeave a comment

If you’re a follower of the EXAIR Blog, you’re probably well aware that compressed air is the most expensive utility in an industrial environment. The average cost to generate 1000 Standard Cubic Feet of compressed air is $0.25. If you’re familiar with how much air you use on a daily basis, you’ll understand just how quickly that adds up. To make matters worse, many compressed air systems waste significant amounts of compressed air just through leaks. According to the Compressed Air Challenge, a typical plant that has not been well maintained will likely have a leak rate of approximately 20%!! Good luck explaining to your finance department that you’re carelessly wasting 20% of the most expensive utility.
Step 1 of EXAIR’s 6 steps to optimizing your compressed air system, is to measure the air consumption at various points within the facility to find the applications that consume a lot of air.

In order to have an understanding of your compressed air use across various processes and in your entire facility, you have to measure. Without a measurement of usage, there’s no way to determine your actual costs or evaluate opportunities for savings. To do so, EXAIR offers a range of Digital Flowmeters in sizes from as small as ½” Schedule 40 iron pipe and up to 4” Schedule 40 pipe from stock. Larger sizes and pipes calibrated for use on copper or metric pipe are also available.

The Digital Flowmeter provides a digital readout of the exact amount of compressed air being used. Many companies will install the DFM on each major leg of their air distribution system to allow for constant monitoring and provide a benchmark of compressed air usage.

Each Digital Flow Meter has a built-in LED display that provides the volume of air moving through the pipe in SCFM, m3/hr, or m3/min. Customizing the display is simple, using the button on the side of the meter. (3) different display modes are available: Current Rate, Daily Usage, and Cumulative Usage. The 4th option available allows you to change the unit of measure. The process is quite simple and easy:

Two small probes are inserted into holes in the pipe (drill guide kit w/ drill bit included) to detect the airflow. The unit seals to the pipe once the clamps are tightened. (If the DFM ever needs to be removed, EXAIR also offers blocking rings to seal off the holes) No cutting, welding, adjustments or calibrations are ever required.

If you need to export the data to your PC, EXAIR offers a USB Data Logger. Both of these options will allow you to track usage over time and upload that data to an Excel spreadsheet. The meter is offered from stock with 4-20 mA outputs you can use to export into any existing software you may be using, or we offer an optional RS-484 Modbus output as a special (contact EXAIR for more information).

If you’re “flying blind” when it comes to understanding the cost of compressed air in your facility, this is the first step. Contact an EXAIR Application Engineer today to get started. We’ll be happy to help you identify areas where you could take advantage of simple savings.

Tyler Daniel, CCASS

Application Engineer

E-mail: TylerDaniel@EXAIR.com

X: @EXAIR_TD

CAN YOU HEAR ME NOW??? The Digital Sound Level Meter

Published on by jasonkirbyLeave a comment

When it comes to manufacturing, there are plenty of hazards that companies and employees face on a daily basis. Of those hazards, one that may be overlooked is the danger associated with high decibel machinery and instrumentation. The Digital Sound Level Meter by EXAIR is an easy-to-use instrument that can measure and monitor the sound pressure level in a wide variety of industrial environments.

Sound levels are most commonly measured in decibels (dB), which range from barely audible to loud enough to cause physical pain. The risk of hearing loss starts at around 70 dB. Exposure to sounds at 85-decibel level and above has the potential to damage hearing. A normal conversation registers at around 60 decibels. That’s where The Digital Sounds Level Meter comes in handy. Prolonged exposures to everyday items such as a hairdryer, vacuum cleaner, or even a blender can cause hearing damage. Now imagine the dangers of the machinery and equipment used in industrial manufacturing.

Accurate and responsive, The Digital Sound Level Meter from EXAIR measures the decibels of the sound and displays the reading on the large LCD screen. The Liquid Crystal Display has a backlight button for easy viewing. Another helpful feature of the Digital Sound Level Meter is the F/S response time button. This button gives you the choice between slow response measurements for comparatively stable noise measurement, or fast for varying noise. The “Max Hold” setting gives you the freedom to set your desired decibel level, and will notify you if that level is exceeded. The Digital Sound Level Meter carries a certificate from the NIST (National Institute of Standards and Technology) for initial calibration to guarantee precision and accuracy.

If you have any questions about The Digital Sound Level Meter by EXAIR, or any EXAIR product or application, please feel free to reach out to our team of Application Engineers for assistance.

Jason Kirby
Application Engineer
Email: jasonkirby@exair.com
Twitter: @EXAIR_jk

Understanding Pressure Requirements For Your Compressed Air System

Published on by Russ BowmanLeave a comment

One of the advantages to compressed air operated equipment is the ability to precisely “dial in” the performance by regulating the supply pressure. Consider an EXAIR Super Air Knife, for example. The flow & force can be adjusted from a “breeze to a blast” and any point in between, via a point-of-use Pressure Regulator. I know of users who operate them with a supply pressure as low as 5psig (that’s the “breeze”) and as high as 120psig (that’s the “blast”), depending on the requirements of the application.

EXAIR Stainless Steel Super Air Knives are popular in food processing applications (left to right): removing excess moisture prior to flash freezing of fish fillets, preventing clumping while packaging shredded cheese, and (my personal favorite) ensuring a consistent and even glazing of fresh, delicious doughnuts.

For a wide variety of typical industrial blowoff applications, a supply pressure of 80psig is a good place to start. So, it stands to reason that the compressed air header pressure will have to be at least 80psig. If the piping/distribution system is sized properly to carry the total amount of air flow you need to the points of use, though, it doesn’t need to be an awful lot higher than 80psig…and that’s a good thing. Here’s why:

Any fluid encounters friction as it flows through a pipe (or hose or tube) which causes a drop in pressure along every bit of the length of flow. The larger the pipe (or hose or tube) the lower the friction and hence, the lower the pressure drop. Now, that’s only important if you care about how much you’re spending on running your air compressor(s). Consider this:

We’ve got a customer that puts our Model 110042 42″ Aluminum Super Air Knives on machinery they make & sell to their customers. This Air Knife will use 121.8 SCFM when supplied at 80psig with the stock 0.002″ thick shim installed, and does the job quite well, most of the time. Some specific applications, however, need higher flow & force from the Air Knife, so our customer offers, as an option, the Super Air Knife with a 0.004″ thick shim installed. Since this doubles the air gap, it also doubles the air consumption. They’d plumbed the supply line to the Air Knife per the recommended in-feed pipe sizes from the Installation & Maintenance Guide:

Super Air Knife Kits include a Shim Set, Filter Separator, and Pressure Regulator.

Since the drop was less than 10ft long, they used a 3/4″ pipe, which was fine…until they installed the 0.004″ thick shim, which meant the air consumption doubled, to 243.6 SCFM. To get that much flow, at 80psig to the Air Knife, they had to increase their header pressure to 110psig, from the 90psig level at which they had been running. This was well within the operating parameters of their air compressor, but it made the compressor work harder, so it used more energy…and cost more to run. In fact, every 2psi increase in compressor discharge pressure results in a 1% increase in operating horsepower (source: Compressed Air & Gas Institute Compressed Air Handbook, chapter 4, page 8).

So, by increasing the discharge pressure by 20psi, the compressor’s power draw (and hence, operating cost) went up 10%. Now, I never found out what size their customer’s compressor was, but I DID look up prices for SCH40 black iron pipe, and for an 8ft length, the 1″ pipe was only $10-15 more than the 3/4″ pipe they were using. Since 243.6 SCFM is roughly 60HP worth of a typical industrial air compressor load (industry thumb rule says they use about 1HP to make 4 SCFM), we can assume that it’s at least a 75HP compressor. Using the following formula to calculate the operating cost while it’s drawing 80% of full load (while making a few reasonable assumptions):

Cost ($) = bhp x 0.746 x # of operating hours x $/kWh x % time x % full load bhp
motor efficiency

bhp = motor full load horsepower (frequently higher than nameplate HP but we’ll use nameplate 75HP to be conservative)
0.746 = conversion from hp to kW
# of operating hours (assume a month’s worth, 8 hours/day, 5 days/week, 4 weeks/month=800 hours)
$/kWh (assume $0.08/kWh)
% time = percentage of run time at this operating level (assume 85% of the time)
% full load bhp = brake horsepower as percentage of full load bhp at this operating level (assume 60HP load, 85%)
Motor efficiency = motor efficiency at this operating level (assume 95% fully loaded)

75HP x 0.746 x 800 x $0.08 x 0.85 x 0.85 = $2,723.29
.95

An additional 10% power draw changes the % full load bhp to 95%, and the cost for monthly operation is:

75HP x 0.746 x 800 x $0.08 x 0.95 x 0.85 = $3043.68
.95

That’s an extra $320.00 spent on running the compressor (per month) at 110psig discharge pressure, instead of an extra $15.00 spent on a larger pipe (one time cost) to run it at 90psig.

This is just one example of the effect of “artificial demand”, which is, essentially, wasted energy due to running your system at a higher pressure to compensate for undersized lines, leaks, intermittent high loads, etc. In addition to helping you specify the right supply line size for your compressed air operated products, we can assist with leak detection, intermediate storage, regulating supply pressures for differing loads, and replacing inefficient devices with engineered products. If you’d like to talk about any, or all, of that, give me a call.

Russ Bowman, CCASS

Application Engineer
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