Have you ever heard of the Puffing Billy?
The first vacuum cleaner was called the Puffing Billy and was invented in 1901. The suction from the cleaner was a result of creating a pressure difference between inside and outside the machine.
Are you surprised to know that man and scientist have had a love affair with vacuums that go way back beyond 100 years? The first vacuum pump goes back as far as 1654. From there, many famous scientists such as Boyle and Hooke were able to use this technology to study the physical properties of fluids and gases.
There is no doubt the use of a vacuum unit has been at the heart of science and engineering for a long time. This technology has continued to improve and is now an essential process within a broad base of industries.
Learn the fundamentals and let that information lead you to the right vacuum generator for your needs.
What is a Vacuum Generator?
A vacuum is a space with an absence of anything else in that space. An absolute vacuum is almost impossible as there will always be a tiny amount of air particles in that space. However, the quantity will be so small they will not have any demonstrable effect on anything else.
A vacuum generator creates the vacuum by forcing the evacuation of particles from the desired space. The more particles forced or evacuated from the space the greater the pressure difference between the vacuum and atmospheric pressure.
Starting Point – Atmospheric Pressure
Atmospheric pressure is measured by a Barometer. A standard Barometer measures atmospheric pressure in inches of Mercury (in Hg). A Barometer is in itself a demonstration of the value of creating a vacuum. This is because the mercury is sealed within an evacuated tube. The bottom of the tube containing the mercury is exposed to the atmosphere
2 Fundamental Reference Points
The Barometer is calibrated so that atmospheric pressure is 0 on the barometer measuring scale. An increase in atmospheric pressure leads to a positive number on the scale and a decrease in atmospheric pressure leads to a negative number on the scale.
The second reference point is that of a perfect vacuum. However, it is important to understand that a vacuum is always relative to atmospheric pressure.
Therefore the simplest measurements of a vacuum involve a U-shape tube partially filled with mercury in the middle and the end of the tubes exposed to either the atmosphere or the vacuum space. As the vacuum increases the mercury will move away from the atmosphere end towards the vacuum end.
The relative height difference of the mercury in both legs of the tube can be taken as the measurement of the vacuum. This device is called a manometer.
Vacuum Unit – 3 Levels
The type of vacuum unit you choose will depend on how accurate you need to create and measure the vacuum you wish to use. There are 3 categories as follows:
These systems can create vacuums of 12 to 18 inHg. The application is normally lifting and holding. There is greater benefit in increasing the surface area between 2 surfaces and applying the vacuum at this level than increasing the pull of the vacuum itself.
Process Applications (Middle)
The vacuum can be measured up to 1 micron. The typical applications are freeze drying and coating type processes. Also removing unwanted gases so that processes can take place in a pure environment.
The vacuum can be measured in levels less than 1 micron. This type of vacuum is used in laboratory processes that require an absence of unwanted particles even at a molecular level. They are used for particle accelerators and electron microscopes etc.
How to Choose the Right Vacuum Unit
You may think it is as simple as comparing specifications between pumps. A little bit like choosing your new mobile phone and comparing the screen size, memory and, operating systems.
Unfortunately, it may not be that simple. Here’s why…
Compare Flow Rates
Manufacturers will present flow rates in the specification as a means of making comparisons between pumps. The flow rate is the volume of whatever you are displacing when the pump is operating at maximum speed.
That may sound like a reasonable starting point. However, as the vacuum is created, it has an effect on the system itself. When the system reaches a perfect vacuum then the laws of physics will not allow the pump to displace anymore volume.
That means maximum displacement occurs with minimum vacuum and minimum displacement (if any) occurs with the maximum vacuum.
Compare Operational Flow Rates
What you really want to know, is how does the vacuum unit perform when operating at the working vacuum level? What is the displacement when the system has created the desired vacuum?
This is a much better means of comparison. You can plot the performance of 2 pumps at their operational vacuum level for better comparison. Of course one of the best ways to choose the right vacuum unit is to speak to an expert, someone with a great deal of experience in matching the right vacuum unit to the right application. Check out our catalog here.
Positive Peer Pressure
Now you know some of the basics of what vacuum generators are, you will have a far better idea of what you may be looking for. First, make sure you choose the vacuum unit in the right level category. That will help narrow down your search. Then make smarter comparisons between pumps by comparing the operation flow rates.
Get in touch with us here to learn more about how we can help you. We have over 60 years of experience helping clients just like you.