Stainless Steel Super Air Knife Solves Problem In Molding Application

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These stainless steel molds have residual material after forming which needs to be blown off

 

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The table of this machine spins, with identical mold setups in the front and rear

The images above show a molding machine process with a spinning table.  The “front” side of the setup is used to remove finished product, while the “back” side forms new product over the stainless steel mold.  Each side of the table uses an identical setup with application temperatures as high as 140°F.

The end user of this machine contacted EXAIR in search of a blowoff solution to be permanently installed and operated automatically.  Any solution offered needed to use minimal compressed air, meet OSHA safety standards for dead end pressure (OSHA CFR 1910.242(b)), and be suitable for installation in a 140°F workspace.

The purpose of the blowoff would be to remove any debris/residual material left on the stainless steel mold after the finished product is removed.  So, as the mold spins back into the machine, they wanted a way to remove any burrs or residual debris.  The current process is to stop the machine and have a machine operator blow off the molds by hand (shown below).  This reduces the efficiency of the machine and reduces the throughput of the process.

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The current process is to stop the machine and blow off the molds by hand

With the full scope of the application uncovered and discussed, we found the perfect solution for this application in a stainless steel Super Air Knife.  The stainless steel Super Air Knife can provide an efficient and repeatable blowoff solution, all while meeting OSHA safety standards and the temperature needs of the application.  Plus, the Super Air Knife can be configured alongside a PLC or Electronic Flow Controller to allow for a “trigger-on” installation in which blowoff is only provided when needed.  This setup saves compressed air, reducing operational cost and further increasing efficiency in the application.

The exact product used in this application was the model 110012SS, which provides a laminar blowoff 12” wide using a 303 grade stainless steel Super Air Knife.  But, we also have knives ranging from 3” to 108” with the ability to machine custom lengths upon request.  So, if you have an application in need of an efficient and laminar blowoff solution, reach out to us.  We’ll be happy to help.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

Quick Disconnects & Why Not To Use Them

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.

1/4" Quick Disconnect male and female.
1/4″ Quick Disconnect male and female.

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.

Inner Diameter of 1/4" quick disconnect.
Inner Diameter of 1/4″ quick disconnect.

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.

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1/2″ quick disconnects

 

Inner diameter of 1/2" quick disconnect.
Inner diameter of 1/2″ quick disconnect.

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.

If you would like to learn more about how to properly plumb your EXAIR Intelligent Compressed Air Product, feel free to contact us, or take a look around our Knowledge Base.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

 

 

Air Compressor Throughput Control

Throughput Control

At the end of my last blog, I mentioned the slide valve operation on a screw compressor.  A slide valve is the basis of throughput control for a screw compressor.  Throughput control is a term used to describe the process of controlling the energy input to the compressor in order to reach the control objective (output pressure and/or flow).  No matter the type of compressor, throughput control is achieved by using speed control, suction throttling, discharge throttling, or recycle control.  There are a few other methods of controlling throughput, but these four are the most common, and throughput control is a common practice used to dial in the needs of a compressed air system/application.

The first, speed control, is the most common and most efficient method.  Essentially, the output flow and pressure are regulated by adjusting the speed of the motor driving the compressor unit.  Increasing the speed of the motor driving the compressor will result in an increased output flow at a constant pressure, or an increased output pressure at a constant flow.  Speed control can also be coupled with other control methods to fine tune the throughput of the compressor.

Suction valve throttling is exactly what it sounds like.  The incoming air flow and pressure are restricted by installing a control valve immediately upstream of the compressor inlet, and the valve’s position is controlled as a function of the exhaust discharge pressure and/or flow.  When the valve is activated and the suction is “throttled” or restricted, the output flow will decrease (because there is less air taken in by the compressor), and the output pressure will subsequently increase.

Discharge valve throttling restricts the pressure from the compressor to match the process requirements at a constant flow.  As a result of this setup, the compressor must work harder than the process requires and this control scheme is extremely inefficient.

Recycle control uses a valve to return compressor discharge flow back to the suction port of the compressor.  As many people know, compressing a gas can generate a good amount of heat, and this heat is often transferred into the compressed air.  Because of this, a cooler is usually (and should be) installed in the line between the recycle control and the suction valves.  The recycle valve can modulate from fully open to fully closed, which gives a full range of control over the discharge flow and can help with loading/unloading of the compressor.

These control methods are all fairly straightforward and on their surface aren’t too intimidating.  They remind me of rudimentary PID controllers, which can be dialed in to a tee.   Think of the way an elevator car reaches the intended floor without slamming to a stop or jolting when it starts moving.  That’s achieved though PID control, and similar methodology is applied to compressor load and unload as well as operation.  But if I get under the surface of compressor control and see PID diagrams, I’m getting the professor!

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE