Proper Plumbing Prevents Poor Performance

There’s nothing quite like an ice-cold Coke from McDonald’s. While there’s many reasons for this, one of the reasons for the unique experience of a McDonald’s Coke lies in the straw itself. In their drinks, they provide wider straws that are designed to help enhance the taste of Coca-Cola, or so they claim. Another impact of this is it allows you to drink significantly faster. The wider the opening for liquid to pass through, the more volume you’re able to drink. Imagine trying to drink your Coke, or any other beverage, through a coffee stirrer. I imagine you’re going to have a difficult time and a dry mouth as you try and force what little amount of liquid you can through the small I.D. of a coffee stirrer. Try that with a milkshake and the problems compound…..

The same is true when it comes to plumbing of your point-of-use compressed air products. I recently assisted a customer that was experiencing lackluster performance from the Super Air Knife they purchased. The application was fairly straightforward, they were hoping to reduce the rate of rejected material on their production line of plastic sheets. The sheet goes through a washing process to remove any residual contaminants, then would air dry as it made its way down the line. As the material dried, there were water spots left on the material that would have to then be cleaned off. In the hopes of speeding up the drying process, they purchased a Model 110060 60” Super Air Knife to provide a wide laminar sheet of air to dry the material.

WhatsApp Image 2018-12-13 at 15.49.45 (2)

When they hooked everything up, the flow from the knife seemed far less than they were expecting. They were supplying full line pressure (just over 90 PSIG), so in theory they should feel a strong blast of air from the knife. When they installed a pipe tee and pressure gauge directly at the inlet, they noticed the pressure was dropping to 35 PSIG while the knife was in operation. When this occurs, it’s indicative of a lack of volume of air. This can be caused by undersized compressor,  or improper plumbing. In their case, they were only plumbing compressed air to one center inlet of the knife. For a 60” knife, EXAIR recommends a minimum of (4) air inlets to ensure adequate volume.

SAK plumbingh

The size of these lines is also critical. You can’t force greater volumes of air through a smaller hose or pipe, just like you can hardly drink through a coffee stirrer with any great success. A 60” knife requires a supply pipe size of 1-1/2” for up to a 50’ run, if you’re trying to supply a knife of this length with a 100’long, ¼” ID hose, you’re not going to get the performance you expect. If you’re experiencing less than optimal performance from any of your EXAIR Intelligent Compressed Air Products, there’s a good chance air supply is the culprit. The first step is determining what the actual inlet pressure is, install a pipe tee and pressure gauge right at the inlet. Then, give us a call and we’ll help work through the proper line sizes and ensure that you’re getting the most out of our products.

I hope I didn’t make you hungry or thirsty… But I think I know where and what I’m having for lunch 😊!

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

How to Calculate and Avoid Compressed Air Pressure Drop in Systems

EXAIR has been manufacturing Intelligent Compressed Air Products since 1983.  They are engineered with the highest of quality, efficiency, safety, and effectiveness in mind.  Since compressed air is the source for operation, the limitations can be defined by its supply.  With EXAIR products and pneumatic equipment, you will need a way to transfer the compressed air from the air compressor.  There are three main ways; pipes, hoses and tubes.  In this blog, I will compare the difference between compressed air hoses and compressed air tubes.

The basic difference between a compressed air hose and a compressed air tube is the way the diameter is defined.    A hose is measured by the inner diameter while a tube is measured by the outer diameter.  As an example, a 3/8” compressed air hose has an inner diameter of 3/8”.  While a 3/8” compressed air tube has an outer diameter that measures 3/8”.  Thus, for the same dimensional reference, the inner diameter for the tube will be smaller than the hose.

Why do I bring this up?  Pressure drop…  Pressure Drop is a waste of energy, and it reduces the ability of your compressed air system to do work.  To reduce waste, we need to reduce pressure drop.  If we look at the equation for pressure drop, DP, we can find the factors that play an important role.  Equation 1 shows a reference equation for pressure drop.

Equation 1:

DP = Sx * f * Q1.85 * L / (ID5 * P)

DP – Pressure Drop

Sx – Scalar value

f – friction factor

Q – Flow at standard conditions

L – Length of pipe

ID – Inside Diameter

P – Absolute Pressure

 

From Equation 1, differential pressure is controlled by the friction of the wall surface, the flow of compressed air, the length of the pipe, the diameter of the pipe, and the inlet pressure.  As you can see, the pressure drop, DP, is inversely affected by the inner diameter to the fifth power.  So, if the inner diameter of the pipe is twice as small, the pressure drop will increase by 25, or 32 times.

Let’s revisit the 3/8” hose and 3/8” tube.  The 3/8” hose has an inner diameter of 0.375”, and the 3/8” tube has an inner diameter of 0.25”.  In keeping the same variables except for the diameter, we can make a pressure drop comparison.  In Equation 2, I will use DPt and DPh for the pressure drop within the tube and hose respectively.

Equation 2:

DPt / DPh = (Dh)5 / (Dt)5

DPt – Pressure drop of tube

DPh – Pressure Drop of hose

Dh – Inner Diameter of hose

Dt – Inner Diameter of tube

Thus, DPt / DPh = (0.375”)5 / (0.25”)5 = 7.6

As you can see, by using a 3/8” tube in the process instead of the 3/8” hose, the pressure drop will be 7.6 times higher.

Diameters: 3/8″ Pipe vs. 3/8″ tube

At EXAIR, we want to make sure that our customers are able to get the most from our products.  To do this, we need to properly size the compressed air lines.  Within our installation sheets for our Super Air Knives, we recommend the infeed pipe sizes for each air knife at different lengths.

There is also an excerpt about replacing schedule 40 pipe with a compressed air hose.  We state; “If compressed air hose is used, always go one size larger than the recommended pipe size due to the smaller I.D. of hose”.  Here is the reason.  The 1/4” NPT Schedule 40 pipe has an inner diameter of 0.364” (9.2mm).  Since the 3/8” compressed air hose has an inner diameter of 0.375” (9.5mm), the diameter will not create any additional pressure drop.  Some industrial facilities like to use compressed air tubing instead of hoses.  This is fine as long as the inner diameters match appropriately with the recommended pipe in the installation sheets.  Then you can reduce any waste from pressure drop and get the most from the EXAIR products.

With the diameter being such a significant role in creating pressure drop, it is very important to understand the type of connections to your pneumatic devices; i.e. hoses, pipes, or tubes.  In most cases, this is the reason for pneumatic products to underperform, as well as wasting energy within your compressed air system.  If you would like to discuss further the ways to save energy and reduce pressure drop, an Application Engineer at EXAIR will be happy to assist you.

 

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

Is PVC Pipe Alright to Use with Compressed Air?

A question arises every now and then on whether or not PVC pipe, yes the stuff from your local hardware store that says it is rated for 200 psi, is safe to use as compressed air supply line.   The answer is always the same,  NO! OSHA agrees – see their statement here.

Schedule 40 PVC pipe is not designed nor rated for use with compressed air or other gases.  PVC pipe will explode under pressure, it is impacted significantly by temperature and can be difficult to get airtight.

PVC pipe was originally designed and tested for conveyance of liquids or products that cannot be compressed, rather they can be pressurized.   The largest concern is the failure method of the piping itself.   When being used with a liquid that cannot be compressed, if there is a failure (crack or hole) then the piping will spring a leak and not shatter.   When introducing a compressed gas, such as compressed air, if there is a failure the method ends up being shrapnel.  This YouTube video does a good job of illustrating how the pipe shatters.

While it may seem that it takes a good amount of pressure to cause a failure in the pipe, that is often not the case.  I have chatted with some local shop owners who decided to run PVC as a quick and cheap alternative to get their machines up and running.

They each experienced the same failures at different points in time as well.  The worst one was a section of PVC pipe installed over a workbench failed where an operator would normally be standing. Luckily the failure happened at night when no one was there.  Even though no one got injured this still caused a considerable expense to the company because the compressor ran overnight trying to pressurize a ruptured line.

Temperature will impact the PVC as well. Schedule 40 PVC is generally rated for use between 70°F and 140°F (21°-60°C). Pipes that are installed outside or in non temperature controlled buildings can freeze the pipes and make them brittle.

If you haven’t worked with PVC before or do not let the sealant set, it can be hard to get a good seal, leading to leaks and a weak spot in the system.

The point of this is the cheapest, quick, and easy solutions are more often , the ones that will cost the most in the long run.

If you would like to discuss proper compressed air piping and how to save compressed air on your systems, please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

Image courtesy of: Dennis Hill, Creative Commons License

Sanitary Flange Line Vacs for Bulk Conveying

Piping systems have been a hallmark of human civilization for almost as long as people have been living in community with each other. Evidence of complex earthen pipe systems, with flanged fittings & asphalt sealants, date to 2700 BC. These were used for crop irrigation, potable water distribution, and wastewater removal in ancient civilizations from the Mediterranean to the Far East.

Over the centuries, new ways to use pipe led to new ways to make pipe.  Scientists and engineers figured out ways to make pipe stronger, lighter, cheaper, and in a variety of materials.  One of the more recent milestones is the development of sanitary piping and fittings.  The stringent cleanliness controls in certain industries (food and pharmaceutical, I’m looking at you) require highly corrosion resistant materials of construction.  The inside & outside surfaces of the pipe have to be finely finished so that they can be thoroughly and positively cleaned, with no crevices, “nooks & crannies,” etc., for material to gather or cling.  And since regular cleaning & sterilization is performed, the fittings must be able to be made & unmade in a manner that still provides for positive sealing when the system is restored to operation.

EXAIR Line Vac Air Operated Conveyors have always been well suited for applications like this.  With their open, unobstructed throats and smooth bores, they’re intuitively easy to clean, by design.  And we’ve made them, for years, in Type 316 Stainless Steel – the preferred material of construction for many food and pharmaceutical applications.  Many users in these industries were able to install them in sanitary piping systems by welding the flanges on our Stainless Steel Line Vacs, or by installing adapters on our Threaded Stainless Steel Line Vacs.

In the spring of 2017, EXAIR released the Sanitary Flange Line Vac with those same users in mind – eliminating the need to weld or thread flanges onto existing products.  They feature the same conveyance power as our Stainless Steel Line Vacs, and can even be modified to meet Heavy Duty Line Vac performance, if needed.  There are four sizes: 1-1/2″, 2″, 2-1/2″, and 3″…which covers the most popular size range of sanitary pipe systems.

While the sanitary piping systems are certainly most often found in those cleanliness-critical food & pharma type applications, other users incorporate them because of the smooth, continuous bore of the pipe and fittings, as opposed to a threaded pipe system, where the OD of the pipe threads into the ID of the fittings, causing a “step” in the throughput.  Because sanitary fittings mate via face-to-face flange seals, this eliminates that “step” which can make for a catch-point for certain items.  It’s for this very reason that a popular ammunition manufacturer uses sanitary pipe systems to convey shell casings…because they tumble with such turbulence in the air flow, they are especially prone to hanging up on any kind of catch-point.  So, they use sanitary piping & fittings, long radius elbows, and EXAIR Model 161150-316 1-1/2″ Sanitary Flange Line Vacs.

Air conveying of certain items, like these ammo shell casings, can be prone to clogging or jamming in systems where pipe, hose, and/or fittings are inserted into each other, creating catch-points.

EXAIR has a wide selection of engineered compressed air products that are “textbook” solutions for certain applications, but also make perfect sense for use in places you might not have thought of.  If you have a bulk material conveyance operation you’d like to discuss, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Shells photo courtesy of hydropeek  Creative Commons License