Do I Have To Install A Compressed Air Filter?

2″ Heavy Duty Line Vac Kit – Model 152200

Recently I took a call from an existing customer that is questioning their Heavy Duty Line Vac Kit setup. They are experiencing around a 38 psig pressure drop from before the filter in the system to the inlet of the Line Vac.  At first glance, they assumed this was due to the filter restricting the flow. They then posed the question, “Do I have to run this filter or can I take it out?  I mean I already have a filter at my compressor.” The answer is yes, install the filter. It will keep dirt, scale and condensate from entering the Line Vac or other components downstream. In the case of a Line Vac, a filter will also prevent this unwanted debris from getting into the material being conveyed.

Example of an Improper Filter Setup

However, this is a great question, especially when assuming the filter is causing the pressure drop – but that was not the case for this application.  So more questions were asked to our customer to determine what the root cause of the pressure drop could be. Seeing a pressure drop across a filter can be caused by several factors.

One would be an inappropriately sized filter. This can restrict the volumetric flow of air through to the point of use causing a pressure drop.  All of the filters supplied with our product kits are auto-drain, have 5 micron filter elements and appropriately sized to operate the product at 80 psig inlet pressure so this was not the problem.

The next issue could be that the filter is clogged, this brought on another question.  If you see more than a 5 psig pressure drop across a filter from EXAIR then we suggest changing out the filter element as it could be clogged and not permitting the full volumetric flow through.  This installation was fairly new and a quick test without a filter element installed proved it was not the filter element that was clogged.

That brought us to the last variable, the length, size, and number/type of fittings between the filter and the Heavy Duty Line Vac. This length of pipe was more than 30′ in length and was only appropriately sized for a 10′ length or shorter run.  The customer was using a 1/2″ Schedule 40 black iron pipe to feed a 2″ Heavy Duty Line Vac at 80 psig inlet pressure. The 2″ Heavy Duty Line Vac Kit will utilize 75 SCFM at 80 psig inlet pressure.  That will need a 1/2″ Sched. 40 pipe that is 10′ long or less in order to not have friction loss within the feed pipe.  Armed with this information the customer is researching whether or not the line needs to stay that long.  If it does, they will have to re-plumb the system with a minimum of a 3/4″ Sched. 40 black iron pipe.

Luckily this was all able to be discussed within a few hours of time and the customer is on their way to an optimal supply system for their in-line conveyor.  One brief phone call took this customer from lackluster performance and thinking a product was not going to work for what they need, to performing beyond their expectations, and being able to keep up with their production needs.

If you have a product or any part of your compressed air system that you question why it may be performing or not performing a certain way, please do not hesitate to reach out to our knowledgeable team of Application Engineers. We are always interested in finding a solution to your needs.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Importance Of Proper Pneumatic Tube, Pipe, And Fittings

When it comes to engineered compressed products, the number one cause of less-than-optimal performance is improper supply line sizing.  This can mean one of two things:

  • The hose, pipe, or tubing running to the device is too small in diameter.
  • The hose, pipe or tubing is big enough in diameter, but too long.

The problem with either of these is line loss (follow that link if you want to do the math.)  Put simply, the air wants to move faster than it’s physically permitted to.  Any time fluid flows through a conduit of any sort, friction acts on it via contact with the inside surface of said conduit.

With smaller diameters, a larger percentage of the air flow is affected…no matter what diameter the line is, the air closest to the inner wall is affected by the friction generated.  When diameter increases, the thickness of this affected zone doesn’t increase proportionally, so larger diameters mean less of the air is affected by friction.  It also means there’s a lot more room (by a factor of the square of the radius, times pi…thanks, Archimedes!) for the air to flow through.

Likewise, with longer lengths, there’s more contact, which equals more friction.  Length, however, is often a non-negotiable.  You can’t just up and move a 100HP air compressor from one part of the plant to another.  So, when we’re talking about selecting proper supply lines, we’re going to start with the distance from the compressed air header to our device, and pick the diameter that will give us the flow we need through that length.  In fact, that’s exactly how to use the Recommended Infeed Pipe Size table in EXAIR’s Super Air Knife Installation & Maintenance Guide:

This table comes directly from the Installation & Operation Instructions for the Super Air Knife.

Once we have the correct line size (diameter,) let’s consider the fittings:

  • Tapered pipe threads (NPT or BSPT) are the best.  They offer no restriction in flow, and are readily commercially available.  If you’re using pipe, these are the standard threads for fittings.  If you want to use hose, a local hydraulic/pneumatic shop can usually make hoses with the fittings you need, at the service counter, while you wait.
  • If you need to frequently break and make the connection (e.g., a Chip Vac System that’s used throughout your facility,) quick connects are convenient and inexpensive.  Push-to-connect types are by far the most common, but a word of warning: they’re notoriously restrictive, as the inside diameter of the male end is markedly smaller than the line size.  If you use them, go up a size or two…a quick connect made for 1/2 NPT connections will work just fine for a 1/4″ line:
  • The nice thing about these quick connects is that you don’t have to depressurize the line to make or break the connection.  If you have the ability to depressurize the line, though, claw-type fittings (like the one shown on the right) provide the convenience of a quick connect, without the restriction in flow.

Proper air supply is key to performance of any compressed air product.  If you want to know, at a glance, if you’re supplying it properly, install a pressure gauge right at (or as close as practical) to the inlet.  Any difference in its reading and your header pressure indicates a restriction.  Here’s a video that clearly shows how this all works:

I want to make sure you get the most out of your compressed air system.  If you want that to, give me a call with any questions you might have.

Russ Bowman
Application Engineer
EXAIR Corporation
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Proper Compressed Air Supply Plumbing Equals Success

EXAIR manufactures and stocks Super Air Knives in lengths ranging from 3”-108”. They’re designed to dramatically reduce compressed air usage when compared to similar blowoffs while still maximizing both force and flow. With an air entrainment ratio of 40:1, it’s the ideal solution for a variety of applications that necessitate a wide, laminar sheet of high velocity airflow.

I recently worked with a customer who makes wooden pallets. They were using a Model 110048 48” Super Air Knife to remove sawdust from the pallets prior to stacking them. When the grooves are cut into the pallet to accommodate the forks from a forklift or pallet-jack, there’s a good amount of sawdust that remains on the pallet. They would prefer to not have sawdust all over the finished pallets that they send to customers, so they looked towards a Super Air Knife to provide a curtain of air capable of removing that sawdust just prior to stacking them.

They purchased the Model 110048, but after installing it they didn’t get the level of force they had been hoping for. After some initial discussions, we identified that the issue lied with the plumbing of the air supplied to the knife. A 48” Super Air Knife will need to be fed with compressed air to (3) of the ¼ NPT air inlets. This ensures that an adequate volume of air is fed to the full length of the knife, keeping a consistent airflow.

Not only had they been plumbing compressed air to just (1) air inlet, but they were also using a restrictive quick-disconnect fitting. The I.D. of a quick connect fitting restricts the overall volume of air that can be passed through it. Length of the pipe or hose is also critical as the diameter of the pipe will need to be larger for longer runs or greater volumes. Accompanying any Super Air Knife is our Installation & Maintenance Guide which outlines the necessary requirements for each available length that we have available as well as how many air inlets need to be supplied with compressed air.

SAK pipe sizing

To confirm that air supply was the issue, they installed a pressure gauge directly at the air inlet to the knife. Line pressure was around 90 PSIG, but when they opened the valve and supplied air to the knife the pressure gauge dropped all the way to 35 PSIG. We’ve talked about pressure drop before here on the EXAIR Blog, the only way to confirm this is to take a pressure reading directly at the air inlet.

They removed the quick disconnect fitting, increased to a 1/2″ supply hose in place of 1/4″, and plumbed compressed air to each end and the center air inlet. On all Super Air Knives, compressed air inlets are available on either end as well as on the bottom. After fixing their plumbing, they noticed a dramatic increase in both force and flow and the pressure directly at the air inlet increased to 85 PSIG. The sawdust was easily blown off of the pallets and the customer was pleased that their pallets were free of sawdust.

sak pallet

At EXAIR, we stand by our products with the Unconditional 30 Day Guarantee. If you’ve just purchased a new product and aren’t seeing the results that you were hoping for give us a call. Our highly-trained team of Application Engineers is ready and standing by to investigate the application and provide support to help make sure you’re getting the most out of our products. Most of the times the solution is simple, but we won’t be satisfied until we find a resolution!

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

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.

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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.