What is an industrial air blower?

When blowers are mentioned, a layperson may think of a leaf blower or a snow blower.  So what is a blower and why are they so critical across so many industries?

To put it very simply, a blower is a machine that is used for blowing or sucking air and gas.  Moving air/gas is a critical mechanism that enables healthcare treatment, large-scale food production, operation of power plants, treatment of sewage and wastewater, production of plastics, sawmill operations, recycling of landfill gases, remediating pollution, manufacturing construction materials, and many other applications.

Blower vs Fan vs Compressor

So a blower moves air from one place to another, but so do fans and compressors. What’s the difference?

  • Fan – Moves air at low pressure. Generally the pressure upstream and downstream of the fan is ambient so there is very little pressure the fan must overcome to move the air.
  • Blower – Moves a large volume of air at a moderate pressure. Blowers are needed when there is resistance in the system that must be overcome, like pushing air through a piping system.
  • Compressor – Reduces the volume of gas by creating a high pressure. A compressor compresses!

 

Basically it all comes down to the ratio of the discharge pressure over the suction pressure, also known as the pressure rise. The ASME (American Society of Mechanical Engineers) defines these machines by a specific pressure ratio:

 

Pressure ratio Household examples Industrial examples
Fan Less than 1.1 – Ceiling fan
– Kitchen exhaust fan		 – Dust collection systems
– Rotary dryers to remove moisture during production processes
– Process cooling to remove heat between burners and boilers
Blower 1.11 to 1.20 – Leaf blower
– Furnace		 – Pneumatic conveying of materials through piping systems
– Aeration at wastewater treatment facilities
– Mechanical vapor recompression to remove contaminents
Compressor More than 1.2 – Refrigerator
– Air conditioner		 – Operating pneumatic tools for manufacturing production lines
– Brakes and suspension for trains and automotives
– Extracting, processing and refining oil and gas

Blowers vs Vacuum Pumps

You may have noticed that blowers are also sometimes referred to as vacuum pumps.

As a general term, pumps are compared with compressors. A pump is defined as a machine that moves a fluid (liquid or gas) from one place to another, while a compressor is a machine that squeezes a gas into a smaller volume and often pumps it somewhere else at the same time. So both fans and blowers can be considered types of pumps.

Industrial blowers are generally called blowers when they are pushing air or gas in a pressure system, and they are called vacuum pumps when they are pulling air or gas in a vacuum system.

Types of Industrial Blowers

The two most common types are positive displacement blowers and centrifugal blowers.

Positive Displacement
Constant flow, regardless of changes in pressure

Centrifugal Blowers
Constant pressure, at varying flow rates

The type of blower that is most appropriate for any given application will depend on a number of different factors.  More than one type may work for your situation, and the best choice may require trade-offs of energy efficiency or maintenance needs. Each type of blower has different advantages and disadvantages and they all have their own sweet spot for performance.

four PD blower packages
Roots positive displacement blower packages
CAGI guidelines on pressure ranges for PD blowers
General CAGI pressure range for PD blowers
CAGI guidelines on vacuum ranges for PD blowers
General CAGI vacuum range for PD blowers

Positive Displacement Blowers

Positive displacement blowers move air or gas by repeatedly trapping a set amount of air and pushing it out the other side of the blower into a piping system.  The volume of air does not change within the blower, it is simply displaced from the inlet to the outlet.

Positive displacement blowers have been in use since the 1850s and are found across a wide range of industries thanks to the constant and reliable flow of air they provide. Common applications include pneumatic conveying of bulk materials, wastewater treatment, chemical processing, and environmental remediation.

There are many different types of blower that operate with the positive displacement model.  The most common is the rotary lobe or Roots style blower:

Rotary Lobe / Roots – A pair of 2 or 3-lobed impellers rotate in opposite directions, sucking gas into the blower and moving it around the outer edge of the cavity inside the blower cylinder before pushing it out the other side. Rotary lobe blowers are equally suited for pressure and vacuum applications, producing a high volume of air and requiring little maintenance. However they can be very loud due to the pulses made by the lobes.

Helical screw – Inside this type of blower one impeller is lobed and fits into the flute of the second rotor; as they turn in a helical pattern they decrease the available volume causing the air to compress. These units can produce higher pressures than rotary lobe blowers with less noise and more energy efficiency, however this comes at a higher price tag.

Rotary vane / Sliding vane – As the rotor spins on this type of blower, sliding vanes move in and out of slots trapping air. The rotor is off center so the air pockets get smaller and compress the air as it moves toward the discharge. Sliding vane blowers may not be as efficient as other types, but they are quiet and are good for continuous duty applications.

Liquid Ring – This type of blower uses water or another compatible liquid as a sealant as the impeller spins, creating small chambers for gas to be trapped and compressed. The heat created is dissipated into the sealing liquid. Some of the liquid is discharged with the compressed gas where it is separated and cooled before returning to the pump. Liquid Ring blowers are often used as a safe choice for handling dangerous gases or achieving higher vacuum levels.

 

Claw – These units use claw shaped rotors to pull in air and compress it before pushing it out the discharge. They are limited in flow, but are able to go up to 25 psig. Claw pumps can be a more expensive option, but definitely have a sweet spot of flow, power, and vacuum where they are the best choice.

multistage centrifugal blowers installation
Multistage centrifugal blowers from Robuschi
single stage centrifugal blower
A single stage centrifugal blower from Atlantic Blowers
CAGI guidelines on pressure ranges for centrifugal blowers
General CAGI pressure range for centrifugal blowers
CAGI guidelines on vacuum ranges for centrifugal blowers
General CAGI vacuum range for centrifugal blowers

Centrifugal Blowers

Centrifugal blowers (also commonly called Centrifugal fans) use a bladed rotating impeller to increase the speed of the air that passes through. As the ambient air is pulled into the wheel, centrifugal force increases the speed of the air causing it to gain kinetic energy and decrease in volume; the air is rotated 90 degrees before it is discharged at a higher speed than it entered.  

A common type is the multistage centrifugal blower, which contains a progression of impellers down the rotating shaft so the pressure is increased gradually as the air passes through each of the impeller groups. A single-stage centrifugal blower must achieve all of the air compression in a single pass of the impeller, so it has to operate at a much higher speed than a multi-stage centrifugal blower.  Multi-stage units are ideal for creating high pressure from small volumes of air. These units are frequently used for applications that require constant pressure and a pulse-free flow, like aeration during wastewater treatment.

Regenerative Blower operating principle
Illustration of the regenerative blower operating principle, from FTZ. The vortex path of the airflow is shown in blue.
CAGI guidelines on pressure ranges for regenerative blowers
General CAGI pressure range for regenerative blowers
CAGI guidelines on vacuum ranges for regenerative blowers
General CAGI vacuum range for regenerative blowers

Regenerative Blowers

A third category is the Regenerative blower, also known as a side channel blower or ring compressor.  A regenerative blower has an impeller that is mounted directly onto an electrical motor.  As the impeller turns, intake air is pulled into the pockets between the blades of the impeller, accelerating both axially and radially. The airflow cycle creates a vortex as it spirals along the side channel, regenerating the velocity energy and building pressure as it passes from pocket to pocket until it is released through the discharge.

Regenerative blowers are a good choice to move a moderate volume of air at very low pressure or vacuum.  They are extremely easy to maintain as they are self-lubricated and contain no oil. Common applications include healthcare and scientific applications, vacuum hold down for packaging, agitation for plating, and low pressure pneumatic conveying.

How to Select an Industrial Blower

To select the best blower for a specific application, first gather information about your application’s specifications and requirements.

  • How much airflow is needed?
  • What pressure or vacuum level is needed?
  • What is the type of application?
  • Are there specific industry or regulatory requirements? (e.g. healthcare applications may require oil-free equipment)
  • Are there noise restrictions?
  • Will the blower be mobile (i.e. mounted in a truck or trailer) or will it have a permanent installation site?
  • What type of drive will power the blower (motor, engine, steam turbine)?
  • What is the elevation of the installation site?
  • What is the temperature range where the blower will be operating?
  • Are there specifications for existing systems the blower will be integrated into?
  • Who will be maintaining the equipment?

There are blower selection tools available that can help narrow down what type of equipment may work for your application based on basic flow and pressure/vacuum needs—here’s a blower guide from the CAGI industry association— but eventually you will want to speak with an experienced blower professional who has years of experience with similar applications and their challenges.

Speak with a blower engineer about your applicationContact us

For over 30 years, pdblowers has specialized in blower and vacuum pump technologies. From system integration to ground-up fabrication, we provide blower and vacuum pump solutions across a wide range of industries. At our 50,000 square foot production facility and headquarters in Gainesville, Georgia we build specialty equipment enclosures, positive displacement blower packages, multi-stage vacuum systems, soil remediation equipment, MET-certified UL control panels, and more.

We are the largest distributor of Roots blowers and we provide sales and service for positive displacement blowers and all the related equipment needed for your pressure or vacuum system. In addition to our primary location in Gainesville, Georgia we also have distribution locations in Ohio, Nevada, and North Carolina.

At pdblowers, Inc. we pride ourselves on providing excellent customer service, backed by decades of experience and specialized product knowledge.

pdblowers facility
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