Tag: pressure gauge

Preventing Pressure Drop in a Compressed Air Distribution System

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 volume is available. Simply put, inadequate air flow won’t allow you to get the job done. When troubleshooting an application for EXAIR Products, the vast majority of problems occur due to pressure drops in the system not allowing the product to work optimally. Oftentimes, this can be something as simple as using an undersized air hose or supply line. Imagine trying to suck a thick milkshake through a coffee stirrer, compared to a wide-mouth straw. You’re not going to have much success with a coffee stirrer, but the increased cross-sectional area of the wide-mouth straw allows you to suck it up and enjoy it comfortably. The same concept is true for supplying air to your products. If there’s a restriction, it won’t work properly! Let’s talk about what you can do to ensure you’re operating effectively.

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 surface finish of the inner wall all play a part in the total amount of friction applied. 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 compressed air supply line is undersized, the pressure drop will manifest and be great enough to impact the performance of the product. 

When designing and maintaining your compressed air system, pressure measurements should be taken across varying points to identify (and fix) any issues before they create a greater pressure drop problem down the road. According to the Compressed Air Challenge, these are the places you should take regular pressure measurements to determine your system’s net 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
  • On treatment equipment (dryers, filters, etc.)
  • Various points across the distribution system
  • Check pressure differentials against a manufacturer’s specifications. If high pressure drops are noticed, this indicates a need for service on the affected equipment.

Newer compressors will measure pressure at the package discharge, which would 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 being transmitted across the distribution system. This could be due to restrictive fittings or undersized air lines, hose, or tubing. Check that the point of use product is properly plumbed into the compressed air supply per the manufacturer’s specifications.

EXAIR Products are designed to minimize this pressure drop by restricting the flow of compressed air at the point of use. The more energy (higher pressure) that we’re able to bring to the point of use, the more efficient and effective that energy will be at operating point of use equipment. 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 upstream in the compressed air distribution system. In the other photo, with a modular-style hose, some pressure is able to build up. But if it gets too high the hose connection can 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, restrict compressed air volume flow to a lower level to keep the compressed air pressure high, 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 by reducing the amount of air consumed. 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

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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Video Blog: What’s The Most Popular & Critical Accessory

Published on by Brian FarnoLeave a comment

Today’s video showcases and describes how one of the most important accessories functions and where to install it. Take a watch and let an Application Engineer know if you have any questions.

Brian Farno, MBA – CCASS Application Engineer

BrianFarno@EXAIR.com
@EXAIR_BF

Control Air Pressure at the Point of Use with EXAIR’s Pressure Regulators

Published on by Tyler DanielLeave a comment

In any application necessitating the use of compressed air, pressure should be controlled to minimize the air consumption at the point of use. Pressure regulators are available to control the air pressure within the system and throttle the appropriate supply of air to any pneumatic device. As the last of the six steps to optimizing your compressed air system, controlling air at the point of use can often be overlooked. To help you achieve this, EXAIR offers a line of point of use pressure regulators to make sure you’re operating at the optimal pressure for your application.

Pressure regulators utilize a control knob that is turned to either increase/decrease tension on a spring. The spring puts a load on the diaphragm which separates internal air pressure from the ambient pressure. Typically made of a flexible rubber material, these diaphragms react very quickly to changes in the air supply. By either increasing or decreasing the flow of air based on the load on the diaphragm, downstream pressure remains fairly constant.

Regulator Internal

While one advantage of a pressure regulator is certainly maintaining consistent pressure to your compressed air devices, using them to minimize your pressure can result in dramatic savings to your costs of compressed air.

As pressure and flow are directly related, lowering the pressure supplied results in less compressed air usage. EXAIR recommends operating your Intelligent Compressed Air Products at the minimum pressure necessary to achieve a successful application. If you notice a desirable result at a pressure of 60 PSIG, or even less, there’s no need to run full line pressure. In-line point of use pressure regulators are the simplest and most reliable way to allow you to dial down the pressure to any compressed air operated product. For example, a Model 110012 Super Air Knife will consume 42 SCFM when operated at 100 PSIG. When the pressure is reduced to 60 PSIG, this drops to just 27.6 SCFM. That’s a 34% reduction in compressed air usage, just by dialing down the pressure at the point of use!

When selecting a pressure regulator for your application, it’s critical that it is appropriately sized to supply adequate volume to the point of use devices downstream. Doing so, minimizes the risk of experiencing “droop”. Droop is a decrease in outlet pressure from the specified setting due to an increase in flow rate.  Droop occurs when the demand at the point of use exceeds the volume of air that the regulator can supply. By ensuring the pressure regulator is rated to deliver sufficient volume of air, you’ll reduce the chances of experiencing droop. EXAIR offers pressure regulators in kits along with many of our products, we’ve done the hard part for you and made sure they’re properly sized!

If you’re looking for ways to help lessen the demand on your compressor, EXAIR’s team of Application Engineers will be happy to help. Reach out to us via phone, chat, or e-mail and see for yourself just how easy it can be to start saving compressed air!

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