Every once in a while I will receive an inquiry that concerns the comparison of our Air Nozzles to that of an open blowing pipe for an application.

The person making the inquiry usually makes the assumption that we market our air nozzles to have an equivalent force to an open blowing pipe. Nothing could be further from the truth and I would like to dedicate this blog to explaining why.

First, there is not any good way to measure and show such data about open pipes that is reasonable and applicable to all situations. Second, we are not interested in promoting the use of open pipes for a variety of reasons including safety, noise and general wastefulness. You may then reply by asking, “Aren’t you comparing your performance to an open pipe?”  I have to say no, we are generally not trying to compare our nozzle performance to an open pipe in terms of force generated on a target. This is simply what we will see in applications where a pipe or copper tube with a squashed end might be used as a “nozzle”. 
We are not trying to duplicate the force values of open pipe with our air nozzles. It is physically impossible to do. The extreme difference in the amount of compressed air volume used when comparing our nozzles to open blowing pipe is so large, it really is not a true apples to apples comparison. For example, if you compare the air consumption of an open ¼ steel pipe to our model 1100 (1/4 NPT nozzle), the nozzle uses only 10% of the air volume of the open pipe; two, totally different values all together. If the customer needs all of the force generated by the open pipe, simply move up to the next larger air nozzle in the range to get desired force.

Generally, it is our experience that the customer does not need all the force generated by the wasteful open pipe anyway. We find that this practice is usually started by someone who is a novice in compressed air systems and are in the habit of over-compensating when it comes to blowing applications.

To further clarify, the premise on which we are working when discussing air nozzles with customers is that our nozzles allow the air to be used much more effectively. There are a couple of reasons.
First, the biggest difference is going to be that our nozzles to not allow a significant pressure drop to occur across the supply pipe as is the case with an open pipe. Because we are restricting the flow all the way out to the very end of the pipe, the full system pressure is available at the nozzle tip. This is not the case with an open pipe. The diameter of an open blowing pipe is too large for it it to maintain working pressure all along its length and so a pressure drop occurs which makes the open pipe blowing even less efficient.

Take the following example with a simple garden hose. The hose running without a nozzle uses a lot of water but is actually ineffective at most cleaning operations (example, when you wash your car or the side walk). See following photo. The water comes out in great volumes but has no real energy to do the necessary work.

 
When you put a nozzle on the end of the pipe / hose, you restrict the flow and have higher velocity fluid flow much like the following photo.

  
You can achieve the high velocity power simply by adding the nozzle to the end of the open pipe. This allows the full, system pressure to be available at the point of use (for greater power to do more work in the application) and reduces the fluid flow.   

Getting back to the open pipe comparison, again I want to stress we are not trying to make our nozzles comparable to the kind of force you get from an open pipe but then again, that open pipe is hugely inefficient anyway in terms of compressed air waste. In fact, we challenge the customer who thinks they need all of that wasted power generated by an open pipe. It is our experience that they mostly do not need as much force as is being generated. Precision blowing that is well matched to the application is the name of the game. Using engineered air nozzles made for the express purpose of generating force in an application with a regulated air supply at the point of use is the recommended method of addressing such a need.

If the customer does have a rather challenging application in which a lot of force is truly needed, we have  larger Super Air Nozzles which can provide the necessary force. Models are available up to 1-1/4 pipe size and flow rates up to 460 SCFM @ 80 PSIG to develop up to 23 lbs (10.4 kgs.) of force.  95% of people do not need that much force, but if they do, we have the solution. Simply up-size to the nozzle that gives the force wanted / needed for the application. You can still save  air volume with the more efficient, safe and low sound operation of the nozzle vs. open pipe. 

Neal Raker
International Sales
nealraker@exair.com