Over the weekend I was working on a car in my driveway and I needed a large volume of air at the far end of the car to try and unplug a clogged sunroof drain line. Rather than trying to move the car while it was mostly taken apart, I just hooked up another air line extension and started to go to the drain. Even knowing what I know as an EXAIR Application Engineer about lengths of tubing, air restriction, and fitting restrictions, I went ahead with the quick and easy “fix”.
I grabbed another 30′ – 3/8″ i.d. air line with 1/4″ quick disconnects (see why this is wrong with this blog) on both end, rather than getting out the 50′ long 1/2″ i.d. air line that I have with proper fittings that then reduce down to a 1/4″NPT at the end to tie into most of my air tools. By doing so I ended up hooking up a Safety Air Gun which then gave a very light puff of air into the tube and the clog in the line went nowhere. As a matter of fact, it was almost like it laughed because the tubing vibrated as if the clog said, “Pfft I am going nowhere.”
I then, stepped back and evaluated what I had done in a rush to try and get a job done rather than taking the extra five minutes to get the proper air line to do the job. I then spent 10 minutes putting that hose up and getting out the correct hose. Then, with a whoosh and a thud the clog was launched into my yard from the clogged drain port and I finished the repairs.
If only I had watched Russ Bowman’s spectacular video on Proper Compressed Air Supply Plumbing the day before. Rather than wasting time with the quick “fix” that cost me more time and didn’t fix anything I should have taken a little more time up front to verify I had properly sized my lines for the job at hand.
If you would like to discuss compressed air plumbing, appropriate line sizes, or insufficient flow on your compressed air system, please contact an EXAIR Application Engineer.
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.
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.
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.
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.
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.
Quick Disconnects are a quick and easy solution to hook up devices to your compressed air system. These units can be found in quite a few factories and are more often than not being used incorrectly. I know that on the air compressor in my garage, the only way to hook anything up to it was to use 1/4″ quick disconnects. Chances are they are even a few of them within your facility, assuming you have compressed air available.
When you really look at a quick disconnect though you start to see why it shouldn’t be used to install every compressed air driven device there is. You can see in the pictures below that a 1/4″ quick disconnect that goes to a 3/8″ NPT adapter has a .192″ opening at the small end. A 3/8″ Schedule 40 iron pipe will actually carry a .493″ inner diameter. If you were to use this quick disconnect on something like a 2″ Heavy Duty Line Vac, you will starve it for air due to the limited ability of the small diameter to carry enough air volume. This, in turn, will limit the performance of the Line Vac. This is because the through hole on the quick disconnect cannot pass enough air to feed through to the Line Vac.
On the 1/4″ quick disconnect to a 3/8″ NPT this may not be as large as a problem as the next picture. Below you can see a 1/2″ quick disconnect that is going up to a 3/4″ NPT. a 3/4″NPT Schedule 40 iron pipe is actually a .824″ inner diameter. The quick disconnect at most has a .401″ inner diameter.
Even though you are providing the correct thread size for your connection (a 3/8 MNPT and a 3/4 FNPT respectively in our example) the quick disconnect’s small inside diameter could be too much of a restriction for the volume demanded by an end use product. Due to this restriction point you will see pressure drops in your system when using a device with a properly sized inlet for its demand of compressed air being fed with an improperly sized quick disconnect. This is one of the main reasons one of our first questions in troubleshooting an EXAIR products performance with a customer is whether or not they are using quick disconnects.
Every day I speak with engineers who are having trouble using compressed air products. A common problem they have is not providing an adequate air supply to their unit. I go through a basic troubleshooting technique to ensure that their pressure and flow rate is adequate. I ask them to install tee on the inlet to the compressed air product in order to install a pressure gauge right at the inlet to the pipe. This allows us to know exactly what pressure we are supplying to the product. Customers are always surprised how the gauge on the compressor or the regulator may read 120 PSIG, but the gage on the inlet to the compressed air product is significantly less.
Last year, my colleague, Russell Bowman, made an excellent video showing how the inlet pressure at the knife will have a significant impact on the performance of the Super Air Knife. In the video, he changes the length and ID of the compressed air supply to illustrate the difference a proper supply line will have on the performance of a compressed air products.
Not providing adequate air supply is commonly caused by these three mistakes, when plumbing compressed air systems.
1. Incorrectly Sized Piping – This can be the single biggest problem. A lack of planning before installing a compressed air product. Not all compressed air systems are created equal. Though a 1/4″ shop air hose may work for a number our products, some of our products require a larger air line because they require more volume of air to be effective. We often speak with customers an illustrate this problem by stating small air lines are like trying to feed a fire hose with a garden hose – there simply is not enough volume to create the pressure necessary to reach the fire, or solve the application in our scenarios. We publish the flow rates for all of our products and make inlet pipe size recommendation in the installation and maintenance guide furnish with the products so you may avoid this common problem. We also have air data tables in our Knowledge Base or you may consult an application engineer who will be happy to make the proper recommendation.
2. Quick Disconnects – These handy connectors are great when operating a brad nailer, or a small blow gun, but the small through diameter can severely limit the flow rate into a long air knife, large diameter air operated conveyor, or big vortex tubes. Due to this fact it is strongly advised to use threaded fittings or over-sized quick disconnects.
3. Adding extra hose or pipe – Extra hose is never a bad thing, right? No, an extra 30 feet of air hose can significantly drop the pressure of a compressed air system. 20 feet of ½ Pipe can flow 70 CFM with a 5 PSI pressure drop. 50 feet of ½” pipe will only flow 42 SCFM with the same 5 PSIG pressure drop. Keep your hose or pipe lengths to a minimum to improve the volume of air you can deliver to a compressed air product.
Last week I took a call from a customer stating their 54” Super Air Knife was, “Barely producing any output flow or increase in velocity”, thus they wanted to adjust the gap in the air knife by adding shims to try and increase their output. I explained that by adding more shims, they were only going to increase their air demand (which was already exceeding supply) and lessen the output velocity.
I decided to take another approach, so instead of just taking the sale for more shims, we began to troubleshoot the issues they were experiencing.
After a brief discussion with the customer, I asked if they could take a picture of the process application and send via email. Below is the image that was sent…
After reviewing the image it was determined there were a few issues with the installation of the Super Air Knife, with the main concern being the in-feed pipe size and connection. The customer was using ¼” O.D. tubing and a quick disconnect which was actually “starving” the Super Air Knife and causing severe pressure drops. You can also explain in this way, it’s like feeding a fire hose with a garden hose, the smaller hose just can’t provide enough volume of water for the larger hose to spray the water out at a high volume and velocity.
EXAIR provides a chart explaining what size we recommend for compressed air supply lines into our products within our installation and maintenance guides. Per the above chart, for our 54” Super Air Knife we recommend a 3/4” in-feed pipe size for a 10’ length of run, 1” pipe size for 50’ and 1-1/4” pipe size for 100’. Also, you should not use restrictive fittings, such as quick disconnects, which will cause excessive air volume lost, resulting in pressure loss through the Knife.
If you are having a similar issue or believe you are getting sub par performance from your EXAIR product, please do not hesitate to contact an Application Engineer at 1-800-903-9247 for assistance, we are confident that we can get it up and running to solve your application.
EXAIR uses our blog platform to communicate everything from new product announcements to personal interests to safe and efficient use of compressed air. We have recently passed our 5 year anniversary of posting blogs (hard for us to believe) and I thought it appropriate to share a few of the entries which explain some more of the technical aspects of compressed air.
Here is a good blog explaining EXAIR’s 6 steps to optimization, a useful process for improving your compressed air efficiency:
One of the Above 6 steps is to provide secondary storage, a receiver tank, to eliminate pressure drops from high use intermittent applications. This blog entry addresses how to size a receiver tank properly:
Thanks for supporting our blog over the past 5 years, we appreciate it. If you need any support with your sustainability or safety initiatives, or with your compressed air applications please contact us.