Tag: compressed air flow

Undersized Plumbing Creates a Performance Problem

Published on by Lee EvansLeave a comment

Sometimes we get calls or emails from our customers experiencing a problem with their application already using EXAIR products.  These calls can range from difficulties associated with installation angle, installation, or, in many cases, the compressed air plumbing to the product itself.

That was the case in the application of the photos above.  The end user had been using our model 6084 Line Vac to move plastic pellets from the floor to the top of a machine hopper, and they needed to increase the flow.  The problem, was that they weren’t getting the performance from the 6084 that they thought they should.

Chip Vacuum 1
                                                                 EXAIR model 6084 Line Vac used for conveying plastic pellets

 

Chip Vacuum 2
Model 6084 Line Vac used to convey plastic pellets from the floor to the top of a machine hopper

 

Given the bulk density of the plastic pellets in this application, the end user should’ve been able to move more than enough material in the time they desired for the application needs.  But, instead, the Line Vac was moving little-to-no material and even “stalling” – a condition in which the conveyed material could enter into the Line Vac and then cease to convey.

What we found, after exchanging contact information and discussing the photos above, is that the compressed air line feeding the Line Vac is too small, creating a pressure drop and leading to an inadequate compressed air flow.  This, in turn, leads to lower air velocity at the exhaust of the Line Vac, which simultaneously means lower vacuum and material flow at the inlet.

The end result is the condition described by the end user – a low flow, or no-flow, of the material being conveyed.

After our discussion the end user set out to make the required change to the supply line, providing proper flow to the Line Vac at the proper pressure, and moving the material as required.

It’s always rewarding to help an end user solve their problems.  If you have an application problem and think EXAIR might be able to help, contact an EXAIR Application Engineer.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

EXAIR Blogs This Week Are Almost As Cool As Shark Week

Published on by Russ BowmanLeave a comment

Yes, ALMOST. This week, the EXAIR Blog has featured some excellent explanations of the science behind the operation of compressed air products. On Tuesday, John Ball posted the best explanation of SCFM vs ACFM that I’ve come across, and I’ve been explaining this to callers for almost four years now. I’m using his blog to perfect my “elevator pitch” on this topic. It will still likely require a building with more than ten floors, but I think that’s OK.

Also on “Two Blog Tuesday,” (this week only; I’m not trying to start anything) Dave Woerner’s gem of a blog detailed the terminology associated with pressure measurement, and why we use “psig” (g = gauged) – in a nutshell, the compressed air inside the pipe doesn’t care what the pressure outside the pipe is. And, since he mentioned it, I might add that most of agree that we care even less about how a certain NFL team’s footballs were (or were not) properly inflated.

Brian Farno’s “One Blog Wednesday” entry was a quite useful (if not alphabetical…OK; now I AM trying to start something) list of some common terms and expressions we use on a regular basis while discussing the operation and performance of EXAIR compressed air products. If you liked his photo demonstration of the Coanda effect with the foam ball & Super Air Amplifier, I encourage you to experience the Coanda effect for yourself, if you have access to a leaf blower and a volleyball:

I mention these earlier blogs to get to the point of MY blog today…a bit of theory-to-practice, if you will. Once you’ve gotten a decent understanding of these principles (or have the above links bookmarked for quick reference,) we can apply it to what’s needed for the proper operation of a compressed air product itself.

With a working knowledge of air flow (SCFM) and compressed air supply pressure (psig,) we can more easily understand why certain pipe sizes are specified for use with particular products. For instance, the longer the Super Air Knife and/or the longer the run of piping to it, the larger the pipe that’s needed to supply it:

This table comes directly from the Installation & Operation Instructions for the Super Air Knife.
This table comes directly from the Installation & Operation Instructions for the Super Air Knife.

The reasons for this are two-fold: First, the pipe…longer runs of pipe will experience more line loss (a continuous reduction in pressure, due to friction with the pipe wall…and itself) – so, larger diameter pipe is needed for longer lengths. For another practical demonstration, consider how much faster you can drink a beverage through a normal drinking straw than you can through a coffee stirrer. Not as dramatic as the leaf blower & volleyball (you really want to try it now, don’t you?) but you get my point.

Second, the Air Knife…the longer the Air Knife, the more air it’s going to use. And, if it’s longer than 18”, you’ll want to feed it with air at both ends…line loss will occur in the plenum as well.

In closing, I want to leave with another video, shot right here at EXAIR, showing the actual reductions in pressure due to line loss through different lengths, and diameters, of compressed air supply line to a Super Air Knife.

If you ever have any questions about compressed air use, or how EXAIR products can help you use your compressed air more efficiently, safely, and quietly, please give us a call.

Russ Bowman
Application Engineer
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