Vacuum Pumps and Air Compression: What’s The Difference

Posted on: September 4, 2020


Here at Quincy, we are no strangers to the wide variety of industries that use compressed air. For many, it is an essential utility, vital for operation. Many corporations considered a part of the critical infrastructure industry such as hospitals, pharmaceutical companies, and food companies depend on our support by relying heavily on compressed air.

We incorporate a variety of technologies to produce and deliver compressed air. Every technology has advantages and disadvantages, creating homes for each in specific markets that call on a variety of applications. At this point, you may be asking, “What does this have to do with vacuums?” I’m glad you asked!

Vacuum vs Air Compression Technology “Same, but different…”


For the most part, the technology used to compress air is the exact same technology used in industrial vacuums. “Industrial” is a keyword here. We aren’t talking about your mom’s standard carpet vacuum. Quincy vacuums reside in a range higher than your typical household vacuum called the “Rough Vacuum Range”. Most industrial vacuums operate within this range. Medium, High, and Ultra-High ranges deal with a much different market involving more rigorous applications like simulating space vacuum levels, scientific research, producing semi-conductors, and so on. Whether it be our reciprocating, rotary screw, rotary vane, dry claw, or liquid ring assemblies, the technology can act as either an air compressor or a vacuum! Wherever air is being compressed, a vacuum is being created. Application and configuration are the only changes.

For instance, let’s take a moment to look at how a rotary screw air compressor generally operates. The basic process involves two large screws (one male, one female) rotating side by side. The screws pull air in at one end, rotate together to compress the air between each other, and finally push the compressed air out of the other end. Now, depending on how we plan to use this rotary screw pump, it could act either as an air compressor or a vacuum pump. Do we need to pull air in? Do we need to push air out? Well lucky us, this technology can do both! Our vacuum pumps are used in various industries for a wide range of applications. Let’s take a look at the rotary screw market. Just to name a few…


  • Composite forming(production of helicopter parts, airplane parts, cabin sheathing, boat and submarine parts)
  • Thermoforming(plastic parts)
  • Holding(parts being held in place during machining or assembly)
  • Altitude Simulation(evacuating air to test the performance of equipment at various altitudes)
  • Leak Detection(testing equipment seals for leaks that may occur in higher altitudes)



  • Evacuation of A/C Units
  • Composite Forming(car parts, special Kevlar parts, coachworks, refrigerated trucks)
  • Thermoforming(plastic car parts)
  • Holding(parts on assembly lines)

Chemical/Gas Petrochemical

  • Degassing Materials and Solvents(removing dissolved gasses from sensitive liquids)
  • Evacuation(removing air from and refilling gas bottles, removing air from pipes and tubes)
  • Mixing
  • Lab Testing

Food Processing

Food Processing

  • Vacuum Packaging(meat, cheese, coffee/tea, etc.)
  • Filing Packages(corn flakes, nuts, liquids)
  • Vacuum Cooling(vacuums cause warm liquids to evaporate, drawing heat away from hot foods)
  • Vacuum Forming Packages

…and so on. This is only the tip of the iceberg. Keep in mind, we just glossed over one of many technologies used in our vacuum pumps. Rotary screw vacuum pumps, along with the other mentioned vacuum technologies, are an integral part in many other industries: Electronics Manufacturing, Glass/Ceramic/Brick/Tile, Laboratories, Laser, Mechanical/Steel, Medical, Pharmaceutical/Cosmetics, Plastic/Rubber, Printing/Paper, and Wood.

With this information in mind, chances are there’s an application for a vacuum in whatever industry you work in!

So, you or your company needs a vacuum pump. What kind of pump do you need? What is the right size pump for your application? How are you supposed to know?

These important questions are being asked every day by people just like you, searching for the right vacuum pump. The truth is, you aren’t supposed to know. We are! But we can give you a general idea and make sure you’re asking the right questions when the time comes for you to select and purchase your vacuum pump.

Choosing the Right Pump for You

Choosing the Right Pump for You

As easy as it would make all of our lives, vacuum pumps are far from being “one size fits all”. Not only do you have the size to consider when choosing a vacuum pump, but more importantly type. I will briefly touch on some of the advantages and disadvantages associated with each vacuum technology we deal with. This should give you a better understanding of where to begin your search.


  • Advantages(traditional, large capacity ranges, easy to install, simple design, can handle vapors and some liquids)
  • Disadvantages (a large number of parts subject to wear, low efficiency, high maintenance, higher noise level, higher initial cost on larger units, oil carryover)

Rotary Screw

  • Advantages(long pump life, long maintenance life with lower maintenance costs over time, energy-efficient, vibration-free, virtually no oil exhaust, air or water-cooled, complete vacuum system)
  • Disadvantages(large size and weight, limited operating pressure range, particulate and liquid sensitive, high initial cost)

Rotary Vane

  • Advantages(low initial cost, direct drive-low vibration, wide operating pressure range, air-cooled, low noise level)
  • Disadvantages(high maintenance due to vane wear, rebuild every 2-3 years or sooner, particulate sensitive, can be vapor sensitive, discharges oil out of the exhaust, unable to handle water or liquid slugs, frequent oil changes)

Rotary Piston

  • Advantages(reliable, handles particulates well, long operation life, low rotational speed leading to less wear, large oil reservoirs for contamination dilution)
  • Disadvantages(overheats if operating at high pressures, high vibration levels, high noise levels, large footprint)

Liquid Ring

  • Advantages(low maintenance, high reliability, low vibration due to one moving part, handles contaminants very well, can use various sealing liquids, low noise levels)
  • Disadvantages(water consumption and disposal, low energy efficiency, discharge saturated with liquid, particles can clog inlet and discharge, low water pressure can cause vacuum loss, subject to performance fluctuations based on water temperature)

Many of these advantages and disadvantages may already help you eliminate some choices based solely on the environment your pump will be operating in. If water is a costly utility in your area or consistent water pressure is a concern, you may want to eliminate liquid ring pumps from your selection choices altogether. If water is not a concern, but noise and vibration levels are, we may actually lean towards the liquid ring as a good fit for your application.

Look at that! We’re already narrowing your search down by eliminating options simply based on the operating environment. Here are some other questions to keep in mind when searching for the right pump for you…

Questions to Keep in Mind


Is your process continuous or cyclic? Continuous processes like assembly lines, where vacuum is constantly being pulled, are much easier on pumps and less likely to pull in stray particulates that could contaminate your pump. A cyclic process (one that involves repeated pump downs of a closed system from normal atmospheric pressure to a lower desired pressure) can lead to excessive oil mist in the exhaust lines if too much time is spent operating in a very slight vacuum. Processes like thermoforming bathtubs, where hot plastic sheets are pulled into a mold one after the other, are examples of cyclic processes. It’s important to know which one applies to your process.

Are there heavy vapor loads or liquids coming off the process? Different process gases can condense in the pump oil affecting its ability to lubricate pump components. Liquids are not compressible. This can cause binding or cracked housing. When we introduce our vacuum pumps to other process vapors or liquids, we put our pump and operator’s safety in jeopardy if we aren’t prepared.

Is there possible particulate contamination in the operating environment around the pump? What size and quantity? Your pump needs different filtration for fine solid particulates like baby powder or sawdust compared to larger contaminants like wood chunks or metal shards. Improper filtration leads to damaged pump components. Damaged pump components cause failures. Failures can lead to injury. We need to minimize these scenarios at all costs.

What are the ambient operating conditions? Is this pump operating in a hot environment? What elevation? High ambient temperatures can overheat a vacuum pump. Higher elevations call for further adjustments to the pump’s gauge configuration due to varying atmospheric pressure.

These are some of the many questions we ask in the pump selection process. Knowing them ahead of time can help you and everyone else involved in this decision avoid a lot of headaches. With that being said, there are two more very important pieces of information that will need to be answered before we can accurately size your pump.

What level of pressure does this vacuum pump need to pull? This question is easier to answer if there is an existing pump currently operating that needs replacement. We simply look at the level of vacuum it is pulling right now. We ask ourselves, “Is this enough vacuum? Will it require more vacuum?” You may be satisfied with the current level of vacuum and simply need a new one. You may be growing your operation in the future which will require more suction.

What kind of pump speed/capacity is needed? When referencing pump speed/capacity we’re asking what volume of gas needs to be removed in a certain amount of time. Usually, we express this in CFM (cubic feet per minute). This question can be tricky, especially if your operation is expanding in the future. In a cyclic process like thermoforming bathtubs, it may be easier to answer. Each bathtub has a specific volume that needs to be pumped down in the same amount of time repeatedly. If you need continuous suction for a very large assembly line, it may not be as easy of a question to answer. That’s why we’re here for you.

Now that we have a good idea of the capacity and speed you require from your vacuum pump, we can start sizing it.

Pump Sizing


Let’s assume we’ve already narrowed your search down to one specific type of pump we believe is best suited for your application. We now need to identify the right size pump to use. Here at Quincy we have performance curves for all of our pumps. These curves tell us the capacity each pump can push at various levels of vacuum.

When considering our QSV line of rotary screw pumps, for example, our larger sized QSV 1100 can push nearly four times the capacity that our smallest size QSV 205 can push at the exact same level of vacuum. For this reason, and various others, we wouldn’t want to install a QSV 1100 where a 205 would get the job done. An oversized pump draws more power and isn’t as efficient. We would only want to oversize a pump if the operation is rapidly growing to match some demand.

It’s always a good idea to consult professionals when sizing a vacuum pump. Most of the variables that determine the size pump required are difficult to measure. It’s easy to assume you need a higher level of vacuum suction for your operation because the current level isn’t sufficient. But what if there is a leak somewhere in your operation you aren’t aware of? Well, you just oversized your vacuum pump to compensate for a leak. Now your pump is drawing more power, you’re paying more for energy, and your boss is mad that you didn’t consult professionals. Or, for instance, let’s say you’re pumping down a relatively small process chamber.

You determine one of our smaller pumps will get the job done. But hold on, you didn’t consider all of the pipes connecting your pump to the process chamber. You didn’t consider the pressure drop occurring across these pipes or within your filtration elements and liquid separators. Well, my friend, you just undersized your pump. Now you’re guaranteed to spend more money trying to fix a problem that wouldn’t exist had you consulted a vacuum professional. Never hesitate to call us. We will make sure mistakes like this don’t happen. Our job is to save you from these headaches.

Vacuum Pump Failures/Safety


Improper pump selection or sizing can not only cost you excess in cash, but it can also lead to pump failures. Avoiding failures is critical for the safe operation of vacuum pumps. Not only do you want to protect your investment, but you also want to protect your workers most of all. Any time equipment fails, safety is a concern. The safest way to operate any vacuum pump is by first having the right pump operating. Most safety concerns can be avoided ahead of time in the selection and sizing process. However, after your pump is installed and operating, it is very important to maintain it. Proper maintenance is a must to continue avoiding failures, keeping your operators safe.



Many failures during operation can be traced back to improper maintenance in some way or another. Have you been cleaning and changing your pump’s inlet filtration elements as advised by the pump’s provider? Some pumps require more upkeep than others. If your pump’s filtration isn’t being kept up according to our advised maintenance schedule, solid particulates can likely make their way inside your pump, damaging various sensitive components depending on your pump type.

Many companies put the responsibility on machine operators to clean and replace inlet filters without the assistance of qualified maintenance personnel. If this is not done correctly, a particulate bypass occurs and may degrade your pump. Inlet filtration elements that handle solid particulates are not rated to handle liquids or vapors introduced to the pump by your process.

Process liquids require a different type of separator to assure liquids don’t make their way into your pump. Minor liquid damage can cause couplings to break, contaminate the oil, and cause rust or corrosion of internal pump components. Moderate liquid damage can cause electrical drive motor failures due to excessive loading, broken vanes in rotary vane pumps, damage to exhaust valves, deformed internal pump components from hydraulic pressure, bearing failure from the contaminated lubricant, or sludge buildup. Severe water damage can permanently destroy the pumping module if it attempts to compress a liquid.

Process vapors or gasses are handled with condensers or cold traps. Different types of gasses or vapors require different precautionary measures. For example, corrosive process gasses may require filters containing materials such as polypropylene, fiberglass, or stainless-steel mesh to eliminate or reduce chemical attack. Water vapors may not be an issue if operating a water-sealed vacuum pump. If the vacuum pump is oil-sealed, we certainly need to consider the damages water vapor can cause.

Even with proper inlet filtration practices, filtration at the exhaust may also be a necessary safety measure to take depending on the process and environment. With work areas becoming cleaner and regulations becoming more stringent regarding airborne oil contamination, there is heightened awareness of contaminants in vacuum pump discharge air. This awareness has resulted in an effort to not only keep the air clean and free of oil smoke but also to keep production machinery, factory walls, ceilings and roofs all clear of oil contamination.

The bottom line is that oil sealed vacuum pumps can discharge oil even when supplied with quality OEM separation packages. Your pump likely already possesses a separation system, after the pump itself, responsible for removing oil from the exhaust air through various methods. If other equipment operating near your pump’s exhaust is sensitive to oil contamination, excess exhaust filtration may be necessary.

Other Safety Precautions

Other Safety Precautions

Always wear the proper personal protective equipment (PPE) when operating a vacuum pump. Your facility has rules and regulations in place for handling all types of mechanical and electrical equipment. Vacuum pumps possess electrical and moving mechanical components that can cause serious injury without the proper PPE. You and your operators should always consult your facility’s PPE regulations. Items likely required or prohibited by your facility to safely operate this equipment may include…

  • Steel Toe Boots
  • Protective Eyewear
  • Best 4500 Gloves
  • Hearing Protection
  • Exclusion of watches, rings, long hair, or other jewelry
  • Shock/Flash hazard protection

It’s important to remember these are only recommendations. Because safety regulations vary from facility to facility, consulting your own facility’s rules is of utmost importance.

With the information provided here, you are not only prepared to begin the vacuum pump selection and sizing process, you are equipped with the knowledge to begin practicing safe vacuum pump operation. Remember, no matter your level of vacuum pump awareness, do not forget to consult professionals. Here at Quincy, we want to solve these problems for you, providing guidance in selecting the proper pump for you.

At Quincy Compressor, we sell a range of reciprocating and rotary screw air compressors in addition to vacuum pumps. To learn more about our inventory, browse our site and check out our helpful air compressor resources.