Issues and Problems with Pressure Drop

 

Super Air Knife Install Sheet

Pressure drop comes in different forms, and it causes inefficiencies within your pneumatic system.  EXAIR writes statements in the installation manuals to help find the correct pipe sizes to supply the different products.  (Reference Super Air Knife Installation Manual above).   But there are other areas that can affect the performance.  These can be fittings, tubing, valves, and accessories.  In this blog, I will cover some pitfalls that can minimize the potential of your EXAIR products.

Pressure drop by definition is a difference or loss in pressure.  A properly sized Filter Separator will typically have a pressure drop of 5 PSID (0.3 bar) at the rated conditions.  So, if you start with 100 PSIG (6.9 bar), the air pressure after the filter separator will be 95 PSIG (6.6 bar).  But what happens when a filter separator is undersized or too small?  The pressure drop will be much higher.  So, if the pressure drop is 30 PSID (2 bar), then the downstream air pressure will only be 70 PSIG (4.8 bar).  At that pressure, you may not be able to get the performance that is required to do the job.

The first thing in determining these potential issues is what I like to call forensics.  If you can install a pressure gage at the inlet of any EXAIR product, then you can deduce if a potential problem is within your setup.   For example, if the Pressure Regulator is at 100 PSIG (6.9 bar), and the pressure gauge at the inlet is reading only 60 PSIG (4.1 bar), then there is a pressure drop of 40 PSID (2.8 bar) between these two points.  You can look in this area for the problem or problems.  If the gauge on the Pressure Regulator goes down as well when you are operating, then the problem area is upstream of the Pressure Regulator.  This can be from the pipe size or the air compressor.

The most common issues are fittings and tubing.  With fittings, small openings may not allow enough air to pass through.  Above is a photo of some typical fittings.  You notice that the right side of the chart has large enough openings to decrease pressure drop.  In some instances, quick connect fittings are commonly used to easily connect or disconnect pneumatic devices; but if you use too small or too many of these fittings, they can cause a large pressure drop.

The other problem is with the inner diameter of tubing, hoses, or pipes that are not properly sized.  Russ Bowman, a colleague, created a video showing the issues with improperly sized plumbing.  It is a very interesting video that shows the effect on a Super Air Knife.

If you want to get the most from your EXAIR products, you will need to reduce the amount of pressure drop in your system.  Pressure drop is wasted energy and can affect your pneumatic system.  You can follow my recommendations above.  Or if you would like to discuss your setup with an Application Engineer, we will be happy to assist.

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

Typical Compressed Air Plumbing Mistakes

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).

Issue 1
Issue 1

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.

Issue 2
Issue 2

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

Answer 3: I don’t know.

Picture: We have multiple issues.

  1. The ¼” NPT compressed air line is too small (huge restriction).
  2. 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.
  3. 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)
  4. 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.

Issue 3
Issue 3

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