Tag: pressure drop

Six Steps To Optimizing Your Compressed Air System — Step 5: Intermediate Storage

Published on by Russ BowmanLeave a comment

If you use compressed air for ANYTHING, odds are EVERYTHING you use it for has a minimum supply pressure for proper operation. And if the supply pressure drops below that:

  • Blowoff devices won’t develop enough flow & force to effectively clean or dry the object(s) you use them for.
  • Air-operated chucks on CNC machines won’t hold the piece steady enough for proper cutting, and tool changers will operate slowly/sluggishly. This is a bad combination…increasing the time it takes to make something, AND making it poorly.
  • Pneumatic cylinders will actuate slowly…if at all. This can cause a big problem if, for instance, they’re used to lift a lid on a mixing tank for an automated chemical add, which ends up pouring all over the partially closed lid of the tank instead of going inside it.

These are just a few of the problems that inadequate supply pressure can lead to, and I list them specifically because I experienced them all during my storied (and strange) career path before EXAIR made me the compressed air know-it-all expert I am today. It wasn’t my job to fix those problems (I was on site doing field service on a scale, a hydraulic motor, and a chemical pump, respectively), so I had no idea HOW to fix the compressed air-related problems…but I do now.

One quick & easy fix would have been to increase the compressor discharge pressure. That’d work just fine, but it comes with a cost. Every 2psi increase in discharge pressure increases the power consumption of the compressor’s motor by 1%. Let’s say you increased the discharge pressure from 100psig to 120psig – that’s a 10% increase in power consumption…and operating cost. To add insult to injury, that also increases the magnitude of any leaks in your system, making them more costly as well.

EXAIR Model 9500-60 60 Gallon Receiver Tank.

Actually, that probably IS what I’d have done as a scale, hydraulics, or industrial pump technician. The RIGHT answer, though, is intermediate storage. A properly sized Receiver Tank, located close enough to those operations, would have prevented those problems without increasing operating costs. In fact, it could have even brought them down, if the compressed air header pressure was already set to overcome any pressure drops on the way to those air guns, CNC machine, or mixing tank lid cylinders. Every 2% DECREASE in discharge pressure will also decrease the compressor motor’s power consumption by 1%. Which is actually Step 6 in our Six Steps To Optimizing Your Compressed Air System.

You electrical-types out there could also think of it as a capacitor – absorbing demand spikes & helping the circuit run more evenly.

Sizing a Receiver Tank is fairly straightforward, and we’ve written about it here, here, and here. You can, of course, always contact an Application Engineer to do (or check) the math…give me a call.

Russ Bowman, CCASS

Application Engineer
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Pressure Drop vs Differential Pressure

Published on by John BallLeave a comment

I find myself interchanging these terms; pressure drop and differential pressure.  This is very common as both are determined by the change in pressure between two points.  In this blog, I will cover the difference between these two terms in my view.

Pressure drop only occurs when the air is flowing.  The higher the velocity, the higher the pressure drop.  Velocity is created when the pressure changes.  So, the higher pressure will go toward the lower pressure.  But we wish that pressure difference to be as low as possible.  Pressure drops are always a loss, and you cannot regain that energy.  Forms of pressure drop that can be found are small diameter pipes or tubing; restrictive fittings like quick disconnects, and undersized conditioning equipment like after coolers and air dryers.  If a pressure drop is too large, the pneumatic equipment will not have enough power to operate effectively and efficiently.  I have another blog with a video that helps demonstrate this, “Pressure Drop and its Relationship to Compressed Air”. 

Differential pressure can be static or flowing.  It is very similar to pressure drop except that the energy is stored.  The most common device that does this is the pressure regulator.  You can reduce the pressure downstream to the point-of-use.  This type of pressure reduction will save you money, instead of wasting money.  For every 10 PSI reduction in pressure, it will save you 5% in energy.  With blow-off devices, you want to use the least amount of pressure to “do the job”.  Over-driving compressed air pressure is a common and wasteful condition found in facilities.

Here is a graph of a typical compressed air system.  As you can see, the typical pressure drop from the air compressor to the point-of-use.  So, if you can reduce the pressure drop through the system and optimize the differential pressure from the regulator to your point-of-use, you can enhance your compressed air system.

Pressure Drop Chart

In a simple statement, pressure drop loses energy while differential pressure stores energy for later use.  EXAIR offers a variety of efficient, safe, and effective compressed air products to fit within the demand side and which can help to reduce pressure drops within a system.  This will include the EXAIR Super Air Knives, Super Air Nozzles, and Safety Air Guns.  If you wish to go further in optimizing your system, an Application Engineer at EXAIR will be happy to help you.

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

How To Prevent Pressure Drops

Published on by jasonkirbyLeave a comment
Issue 1

Compressed air serves as the essential utility for operation, and its performance limitations are determined by the supply available. To effectively utilize EXAIR products and pneumatic equipment, it is crucial to establish a method for transferring compressed air from the source to the point of use. This can be accomplished through three primary means: pipes, hoses, and tubes.

As compressed air travels through the distribution system, it experiences friction against the inner surfaces of pipes, tubes, and hoses. Factors such as the diameter of the pipe, its length, the number of bends, and the smoothness of the inner wall contribute to this friction. Consequently, a reduction in air pressure occurs due to this resistance. Additionally, pressure drops can also happen at the point of use, particularly if the line is inadequately sized, which can significantly affect the performance of the equipment being powered.

When designing and maintaining a compressed air system, it is essential to take pressure measurements at various locations to detect and resolve potential issues before they escalate. The Compressed Air Challenge recommends specific points for regular pressure assessments to accurately gauge the operating pressure of your system.

  • 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.

After taking the necessary measurements, you should sum the recorded pressure drops and subtract this total from your compressor’s operating range. The resulting value represents the actual operating pressure at the point of use.

If your distribution system is correctly sized and the pressure drops across your equipment are within acceptable limits, any pressure drop observed at the point of use suggests a lack of sufficient air volume. This issue may stem from restrictive fittings or inadequately sized air lines, hoses, or tubes. It is essential to ensure that the point of use product is installed in accordance with the manufacturer’s specifications for compressed air.

If you have questions about pressure drops, or anything regarding EXAIR and our products, please do not hesitate to reach out.

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

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