Test your knowledge with these statements about vacuum. Are they fact or are they fiction?
1. A vacuum cleaner works like a vacuum pump.
False. Actually it's not even close.
A vacuum cleaner is designed for flow at a very minimal pressure differential while a vacuum pump causes a very high-pressure differential at a modest flow.
A vacuum cleaner motor is a fan that spins very fast and has vanes on it. The vanes spin the air and the air is thrown to the outside by centrifugal force. This creates a large flow of air but the pressure is limited. Since the centrifugal action requires air to be flowing through the fan, this type of pump will stall if the airflow drop below a certain critical amount. That's why if you put your hand over the end of the hose of your vacuum, it revs really high and doesn't suck your hand into the hose. The fan stalls and presres are typically limited to 1-5 psi less than atmospheric pressure.
Vacuum pumps, on the other hand, use different designs but a piston design is pretty common. It uses a piston that moves up and down and valves that only allow air to flow in one direction. The total airflow is much less with this type of pump, but because of the valves, it won't stall at low airflow rates. As a result, vacuum pumps can reach extremely low pressures.
2. There is more than one type of vacuum pump.
True. There are 3 main types.
A) Positive Displacement Vacuum Pumps (piston pumps, diaphragm pumps): A positive displacement pump moves air by repeatedly surrounding a volume of fixed mass and moving the air ‘mechanically’ through a system.
B) High Vacuum Vacuum Pumps (turbopumps, diffusion pump): A high vacuum vacuum pump is a type of pump which works alongside a positive displacement pump. This type of pump needs a positive displacement pump to work. Gas molecules are taken from the ‘vacuum’ side to the ‘exhaust’ side. In order for that to happen, a positive displacement pump maintains the pressure and reduces it to a rate that is plausible to work with.
C) Entrapment Vacuum Pumps (Cryopumps, sorption pump): An entrapment pump, which is most commonly a cryopump, uses cold temperatures to turn the gases into a solid or absorbed state. A ‘chemical’ pump then reacts with these gases to make a residue and then ionizes the gases to solid substances.
3. A vacuum pump was the first type of pump.
False. The predecessor to the vacuum pump was the suction pump. Dual-action suction pumps were found in the city of Pompeii. Later Arabic engineer Al-Jazari described dual-action suction pumps as part of water-raising machines developed in the 13th century. The suction pump later appeared in medieval Europe from the 15th century.
4. The vacuum pump was invented in 1650.
True! Check out our post on The Fascinating History of the Vacuum Pump for more details.
5. A sealed potato chip bag will explode in a vacuum.
Watch this experiment done by The Action Lab for proof. When vacuum is applied to an air filled potato chip bag, it will expand until it explodes. Better still, if you poke a hole in the bag and suck all the air out, then remove the vacuum, it will condense to the real size of the bag (vacuum packed & quite small). But be careful! The vacuum will crush the chips into crumbs!
6: A perfect vacuum can be achieved in a pump.
In practical terms, it is impossible to make a perfect vacuum in a vacuum pump. A perfect vacuum is defined as a region in space without any particles. The problem is that to maintain a vacuum in a region you have to shield it from the environment. Although you can get very close to perfect, there would still be a few atoms in the pump.
Even space isn't a perfect vacuum, although it is close. Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum. But no vacuum is truly perfect, not even in interstellar space, where there are still a few hydrogen atoms per cubic meter.
7. Vacuum quality comes in various levels.
True. Vacuum quality is subdivided into ranges according to the technology required to achieve it or to measure it.
Atmospheric Pressure– is variable but is standardized at 760 Torr or 101.325 kPa.
Low Vacuum– also called rough vacuum, is a vacuum that can be achieved or measured by basic equipment. For example a vacuum cleaner.
Medium Vacuum– is a vacuum that is typically achieved by a single pump, but the pressure is too low to measure with a mechanical manometer. It can be measured with a McLeod gauge, thermal gauge, or a capacitance gauge.
High Vacuum– The distance between molecules is a function of pressure and is knows as the mean free path. (MFP). As the chamber is pumped down into vacuum and molecules are removed, the MFP becomes greater and greater.
As pressure decreased in a chamber, fewer molecules are present, and the mean free path increases. Similarly, as the gas density reduces, there are fewer chances of molecular collision. Air molecules are usually removed from the chamber through a type of positive displacement put such as an oil-sealed rotary pump.
High vacuum usually requires multistage pumping and ion gauge measurement. For example, according to NASA, the vacuum level recorded on the moon was 1×10-9 Torr.
Ultra-High vacuum– requires baking the chamber to remove trace gasses and other special procedures. Most standards define ultra-high vacuum as pressures below 10-8 Torr.
Deep Space– is generally much emptier than any artificial vacuum.
Perfect Vacuum – is an ideal state of no particles at all. It cannot be achieved in a laboratory, although there may be small volumes which, for a brief period, happen to have no particles of matter in them.
8. At AVAC, we've been expertly rebuilding vacuum pumps for over 50 years.
Absolutely True, of course! AVAC will repair your equipment to meet or exceed OEM specifications, covered with a One-Year Warranty.
- Your pump will be inspected by our factory-trained technicians, covering all aspects of the pump operation, including, tolerances, seals, gaskets, vanes, rotors, shafts, bearings, pulleys, electric motors, etc. for optimum vacuum levels and safety.
- Your comprehensive quotation will include the highest quality parts and will utilize our superior technical procedures, developed over 50 years.
- Our prices are always competitive, with your bottom line in mind.
- Our comprehensive 24- hour test and rigorous quality control process is how we can warrant our repairs for One Year.
- Our turnaround is fast. Expedite and exchange service is also available in most cases if you need it even quicker.
- You will receive a detailed Final Inspection Report documenting results in Microns or Millitorr, Safety Checklist and accessories, along with your Warranty.
- Learn more about our amazing vacuum pump service and support!