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

Do I Have To Install A Compressed Air Filter?

2″ Heavy Duty Line Vac Kit – Model 152200

Recently I took a call from an existing customer that is questioning their Heavy Duty Line Vac Kit setup. They are experiencing around a 38 psig pressure drop from before the filter in the system to the inlet of the Line Vac.  At first glance, they assumed this was due to the filter restricting the flow. They then posed the question, “Do I have to run this filter or can I take it out?  I mean I already have a filter at my compressor.” The answer is yes, install the filter. It will keep dirt, scale and condensate from entering the Line Vac or other components downstream. In the case of a Line Vac, a filter will also prevent this unwanted debris from getting into the material being conveyed.

Example of an Improper Filter Setup

However, this is a great question, especially when assuming the filter is causing the pressure drop – but that was not the case for this application.  So more questions were asked to our customer to determine what the root cause of the pressure drop could be. Seeing a pressure drop across a filter can be caused by several factors.

One would be an inappropriately sized filter. This can restrict the volumetric flow of air through to the point of use causing a pressure drop.  All of the filters supplied with our product kits are auto-drain, have 5 micron filter elements and appropriately sized to operate the product at 80 psig inlet pressure so this was not the problem.

The next issue could be that the filter is clogged, this brought on another question.  If you see more than a 5 psig pressure drop across a filter from EXAIR then we suggest changing out the filter element as it could be clogged and not permitting the full volumetric flow through.  This installation was fairly new and a quick test without a filter element installed proved it was not the filter element that was clogged.

That brought us to the last variable, the length, size, and number/type of fittings between the filter and the Heavy Duty Line Vac. This length of pipe was more than 30′ in length and was only appropriately sized for a 10′ length or shorter run.  The customer was using a 1/2″ Schedule 40 black iron pipe to feed a 2″ Heavy Duty Line Vac at 80 psig inlet pressure. The 2″ Heavy Duty Line Vac Kit will utilize 75 SCFM at 80 psig inlet pressure.  That will need a 1/2″ Sched. 40 pipe that is 10′ long or less in order to not have friction loss within the feed pipe.  Armed with this information the customer is researching whether or not the line needs to stay that long.  If it does, they will have to re-plumb the system with a minimum of a 3/4″ Sched. 40 black iron pipe.

Luckily this was all able to be discussed within a few hours of time and the customer is on their way to an optimal supply system for their in-line conveyor.  One brief phone call took this customer from lackluster performance and thinking a product was not going to work for what they need, to performing beyond their expectations, and being able to keep up with their production needs.

If you have a product or any part of your compressed air system that you question why it may be performing or not performing a certain way, please do not hesitate to reach out to our knowledgeable team of Application Engineers. We are always interested in finding a solution to your needs.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF