compressed air plumbing

As a manufacturer of Intelligent Compressed Air Products, we like to address one of the most common problems with installation, proper plumbing. A picture is worth a 1,000 words, and knowledge is power. I will show both to help eliminate any pitfalls when installing our products.

A customer purchased a model 110072 Super Air Knife. It is a powerful and efficient air knife that is 72 inches (1.8 meter) long. He mounted it across his sheet to blow debris off from the surface of his product. After installing the Super Air Knife, he was having issues in getting a strong even force along the entire knife. He would only get compressed air blowing on the ends of the Super Air Knife. The center did not have anything coming out. He needed our help to solve. In detailing my forensics, I asked him for pictures of his installation as I went over some basic questions. Here is what we found:

Question 1: What is the pressure at the entrance of the Super Air Knife?

Answer 1: 95 psig (6.5 bar)

Picture: The gage reading is at the regulator.

Solution: There should also be a pressure gage right at the entrance of the Super Air Knife. It helps to define any issues in the system by comparing line pressure at the regulator to inlet pressure at the Super Air Knife. This customer would see a very low air pressure at the Super Air Knife caused by all the restrictions (reference below).

Question 2: What size is your compressed air line that is supplying the Super Air Knife?

Answer 2: 1 ½” NPT pipe. (From the installation manual, this is the correct size pipe to supply the air required for the Super Air Knife when it is 150′ from the compressor.)

Picture: The compressed air line is reduced from 1 ½” NPT to ¼” NPT pipe. Yes, there is a 1-1/2″ pipe bringing air close to the Super Air Knife, but it is actually a 1/4″ NPT pipe fitting on a small coiled hose that is supplying the knife. Due to a lack of air vlume, the pressure drop is huge and it is performance of the Super Air Knife.

Solution: They will need to run 1 ½” NPT pipe to the Super Air Knife. Then uses Pipe Tees and/or Crosses to branch into the feed lines to the Super Air Knife.

Question 3: Do you have any restrictions in the compressed air line?

Answer 3: I don’t know.

Picture: We have multiple issues.

The ¼” NPT compressed air line is too small (huge restriction).
The red filter in photo above is too small (huge restriction). The black filter and black regulator are sized correctly to supply the Super Air Knife, but the red filter is too small causing a large pressure drop.
One of the biggest culprits in choking compressed air flow to a pneumatic product are Quick Disconnect fittings. The picture below is a quick disconnect on the inlet port to the Super Air Knife (huge restriction)
The yellow compressed air line is also way too small. I only bring this up because there is a difference in diameters from Schedule 40 pipe to air hose and tubing. Make sure that the inner diameters match or are larger than the recommended pipe size.

Solution: In order to have the Super Air Knife properly working, we have to make sure that it can get enough compressed air. I had the customer remove all the small fittings, yellow tubing, quick disconnects, and the small filter.

Question 4: How many ports on the Super Air Knife are you using to supply the compressed air?

Answer 4: 2 ports.

Picture: With this length of the Super Air Knife, it requires 4 ports to supply compressed air (reference the Installation Manual). They should be evenly spaced from one end of the Super Air Knife to the other. This is another reason that he only had compressed air coming out at the ends of the Super Air Knife.

Solution: EXAIR offers a Plumbing Kit to make sure the entire knife is supplied correctly. The plumbing kit contains all the proper size fittings and hose to plumb the correct number of Air Knife inlets. These kits prevent you from hunting for the right fittings and from using undersized parts, which will not be able to supply the knife with enough air.

Model 9078 PKI Kit — Model 9078 Plumbing Kit

With proper installation at the beginning, it will save you time and headaches, and you will be able to utilize the EXAIR products properly. If you have additional questions about your setup, you can contact an Application Engineer at EXAIR at 1-800-903-9247.

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

People have been using pipe to transport fluids for thousands of years. Archeologists have discovered evidence that the Chinese were using pipes made of reeds for irrigation as early as 2,000 B.C. Lead pipe began to supplement, and eventually replace, the Roman aqueducts in the first century A.D. In the early 1800’s, someone got the idea to use gas burning lamps to light city streets, and, over the next few years, men like James Russell and Cornelius Whitehouse came up with better and better methods of mass producing metal tubing and pipes.

Over the course of the 19th Century and the Industrial Revolution, iron pipe came to be manufactured in standard sizes, which were called out by the inside diameter of the pipe. ¼” pipe had a ¼” ID, ½” pipe had a ½” ID, ¾” pipe had a ¾” ID, etc. Iron pipe could be found in any facility that needed to move a gas or a liquid: factories, power generating stations, chemical plants…you name it.

As engineers and metallurgists came up with new ways to produce pipe, technological advances led to the ability to decrease the wall thickness and still maintain high structural integrity. This was a HUGE improvement: not only could piping manufacturers make more pipe with less material, bringing down the cost, it was also lighter in weight, making it easier to transport, handle, and install. Because of the massive amount of existing piping already in place, it made sense to keep the outside diameter the same, so that all the fittings would match when these facilities went to replace worn out or damaged pipe. So, the inside diameter was increased. That’s why, today, ¼” pipe has a 0.36” ID, ½” pipe has a 0.62” ID, ¾” pipe has a 0.82” ID, etc. Lower cost, lighter weight, more flow capacity…it’s all good, right?

Well, yes, but sometimes, it can lead to confusion, especially when we’re talking about properly sized compressed air lines. See, we know how much compressed air will flow through certain sized pipes of specific lengths. The Installation & Operation Instructions for all of our products contain recommended infeed pipe sizes to ensure sufficient air flow. Keep in mind, these are Schedule 40 pipe sizes, and should not be confused with hose or tubing sizes, which usually report the outside diameter but could also report the inside diameter, depending on the source.

Consider this example: you want to install an 6” Super Air Knife in a location 10 feet from the compressed air header. Following the “Infeed Pipe Size Length of Run” column (10’) down, we see that this will require a ¼” SCH40 pipe, which has an ID of 0.36”. If you want to use hose or tubing to supply it, that’s fine – it’ll have to have a 3/8” ID, though, or you’re going to risk “starving” the Air Knife for air. If you choose a 3/8″ tube remember that dimension is usually referring to the outside diameter of the tube and automatically means your inside diameter is smaller than we would recommend.

If you’d like to learn more, it’s actually been a pretty popular blog topic as well:

The Importance of Proper Compressed Air Supply Lines

Video Blog: Proper Supply Plumbing For Compressed Air Products

Top 6 Compressed Air Plumbing Mistakes and How to Avoid Them

…and that’s just to name a few. If you have specific questions about how to properly supply your EXAIR product(s), you can give us a call – we’re eager to help!

Russ Bowman
Application Engineer
EXAIR Corporation
(513)671-3322 local
(800)923-9247 toll free
(513)671-3363 fax
Web: www.exair.com
Twitter: twitter.com/exair_rb
Facebook: http://www.facebook.com/exair

Tag: compressed air plumbing

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