Proper Supply Line Size And Fittings Provide Peak Performance

Many times when we provide the air consumption of an EXAIR product, we get a response like…. “I’ve got plenty of pressure, we run at around 100 PSIG”. While having the correct pressure available is important, it doesn’t make up for the volume requirement or SCFM (Standard Cubic Feet per Minute) needed to maintain that pressure. We commonly reference trying to supply water to a fire hose with a garden hose, it is the same principle, in regards to compressed air.

When looking to maintain an efficient compressed air system, it’s important that you use properly sized supply lines and fittings to  support the air demand (SCFM) of the point-of-use device. The smaller the ID and the longer the length of run, it becomes more difficult for the air to travel through the system. Undersized supply lines or piping can sometimes be the biggest culprit in a compressed air system as they can lead to severe pressure drops or the loss of pressure from the compressor to the end use product.

Take for example our 18″ Super Air Knife. A 18″ Super Air Knife will consume 52.2 SCFM at 80 PSIG. We recommend using 1/2″ Schedule 40 pipe up to 10′ or 3/4″ pipe up to 50′. The reason you need to increase the pipe size after 10′ of run is that 1/2″ pipe can flow close to 100 SCFM up to 10′ but for a 50′ length it can only flow 42 SCFM. On the other hand, 3/4″ pipe is able to flow 100 SCFM up to 50′ so this will allow you to carry the volume needed to the inlet of the knife, without losing pressure through the line.

Pipe size chart for the Super Air Knife

We also explain how performance can be negatively affected by improper plumbing in the following short video:

 

Another problem area is using restrictive fittings, like quick disconnects. While this may be useful with common everyday pneumatic tools, like an impact wrench or nail gun, they can severely limit the volumetric flow to a device requiring more air , like a longer length air knife.

1/4″ Quick Connect

For example, looking at the above 1/4″ quick disconnect, the ID of the fitting is much smaller than the NPT connection size. In this case, it is measuring close to .192″. If you were using a device like our Super Air Knife that features 1/4″ FNPT inlets, even though you are providing the correct thread size, the small inside diameter of the quick disconnect causes too much of a restriction for the volume (SCFM) required to properly support the knife, resulting in a pressure drop through the line, reducing the overall performance.

If you have any questions about compressed air applications or supply lines, please contact one of our application engineers for assistance.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

Proper Air Supply Is Key To Optimal Performance

I recently worked with a customer who was using our 36″ aluminum Super Air Knife to remove dust and light debris from a conveyor but wasn’t seeing good performance. They initially called because they read in their catalog that increasing the shim gap would increase their force and flow and wanted to know what kind of increase in performance they would see.

The Super Air Knives are shipped from EXAIR with a .002″ shim installed and the performance data shown in the catalog reflects this gap setting. The shim sets, for aluminum knives, include a .001″, .003″ and .004″ shim and by changing to the .003″ shim, the force and flow would be 1.5 times as great and using the .004″ shim would double these amounts. While some applications do require the additional force and flow, trying to blow off dust or light materials typically wouldn’t fall into this category.

sak-shims

Replaceable shims provide varying levels of force and flow.

Switching our focus to the supply side of things, it turns out they were using 1/4″ hose and only plumbing one end of the unit. This poses 2 concerns that relate directly to the mentioned poor performance. The first would be the 1/4″ hose is severely undersized for a 36″ Super Air Knife. We recommend 3/4″ Schedule 40 pipe if the length of supply from a main header is 10′ or less and a 1″ pipe up to 50′ of supply run. It is possible to use hose but that hose needs to be at least 1″ ID to be able to carry enough volume to support a 36″ unit. Secondly, for knives that are 24″ in length or longer, you need to plumb air to both ends to maintain an even, laminar flow across the length of the knife.

With the proper supply, the Super Air Knife is going to produce an exhaust air velocity of 11,800 feet per minute when operated at 80 PSIG, which is more than enough to eject lightweight material from a flat surface (in fact you could most likely clean dust and light debris at a lower pressure). If the customer did increase the shim gap dimension, the increase in  air demand would only worsen the problem of undersized supply lines.

Pipe sizes

Recommended supply line sizes per the IOM – Installation and Operation Manual.

This is just one example of how proper supply line size and installation is key to achieving optimal performance. If you are experiencing similar issues or need any assistance with a product or application, give me a call, I am glad to help.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

 

 

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