English (English)

5 Types of Industrial Vacuum Pumps and How They Work

08 March 2022 /

Learn from VFE, now a part of the Busch Vacuum Solutions group, about the various different types of industrial vacuum pumps available today and how they function.

A vacuum pump is a complex part but understanding it and how it works is important to the success of your operations. Many different types of vacuum pump are used across the advanced manufacturing process, with applications varying between operations and industries. Then there’s the matter of their routine servicing and maintenance.

All of this is to say that the more you know about your vacuum pumps, their operating principles and what makes them tick, the better you’ll be able to manage your operations. 

We hope this article helps provide you with some clarity on how each pump type operates and the ability to feel more confident about your own pumps powering your operations.

For expert support maintaining your vacuum pumps, get in touch today to find out what pump types we service and how our technical engineers can help.

An introduction to vacuum pumps

Before we dive into the different vacuum pumps themselves, know that there are two main types of vacuum pumps. Each is categorised according to the pumping principles — either gas transfer or entrapment

As we don’t currently service entrapment pumps, we’ll focus on gas transfer pumps in this article — specifically, positive displacement pumps and momentum transfer pumps.

How positive displacement vacuum pumps work

In a positive displacement vacuum pump, the vacuum is generated when a sealed chamber, which controls the flow of fluid using one-way valves, is expanded and contracted.

This vacuum draws the fluid into the chamber through an intake valve. On reaching the maximum expansion, the intake valve closes while the exhaust opens. The fluid is ejected out of the chamber as it compresses or contracts. The cycle repeats several times per second, creating a pulsating flow.

Like ordinary pumps, positive displacement vacuum pumps are classified according to the motion and the design of the chamber. You’ll find two main types: reciprocating and rotary.

Reciprocating vacuum pumps

In a reciprocating vacuum pump, the chambers expand and contract through the repetitive (or ‘reciprocating’) back-and-forth motion. The range of motion is called a stroke.

Reciprocating pumps have two one-way ports or valves, one for the inlet and the other for the exhaust. The alternate opening and closing of these valves allow the build-up of vacuum and ejection of the fluid.

Types of reciprocating vacuum pumps include:

  • Reciprocating piston vacuum pump
  • Plunger vacuum pump
  • Diaphragm vacuum pump

Rotary vacuum pumps

These types of vacuum pumps create low-pressure regions through the rotation of the moving components against the pump housing.

To prevent the fluid from leaking to the low-pressure side, the surfaces between the rotor and the housing have tiny clearances coated with self-lubricating or low friction materials such as graphite, PTFE (polytetrafluoroethylene), or PEEK (polyether ether ketone).

Rotary vacuum pumps have lower pulsating delivery compared to reciprocating types, making the flow more continuous. When inspecting a rotary pump, ensure that the fluids on which it runs don’t contain abrasive particles because these can erode the small clearances. 

Rotary vacuum pumps are also divided into several subcategories, this time according to the design of the rotor:

  • Rotary vane vacuum pump
  • Liquid ring vacuum pump
  • Rotary piston vacuum pump
  • Screw vacuum pump
  • Gear vacuum pump
  • Lobe (roots) vacuum pump
  • Scroll vacuum pump

Discover the single best reason to service your vacuum pumps.

What is a momentum transfer pump?

Momentum transfer pumps operate by inducing the movement of gas or liquid molecules through kinetic energy transfer.

The uniform velocity distribution (or ‘momentum’) of the molecules is altered to a preferred direction by the fast-moving surfaces hitting them. An example is a diffusion pump where high-speed jets of motive fluid impart momentum to the gases to be drawn from the inlet.

Momentum transfer pumps are suited for creating a high vacuum. However, to create a molecular flow, low pressure must exist throughout the system. The exhaust cannot be directly released to the atmosphere or at pressures where backstreaming (when fluid migrates back into the chamber, opposite to the direction of the desired flow) can occur.

To solve this problem, a backing pump is installed in tandem with the vacuum pump. The backing pump can be a positive displacement pump that operates at a lower vacuum level, capable of directly discharging to the atmosphere.

As well as diffusion pumps, turbomolecular pumps are another example of a momentum transfer pump, although we don’t service turbomolecular pump types at time of writing. 

Diffusion vacuum pumps

As referenced briefly above, a diffusion pump works by using a motive fluid to transfer momentum to the gas molecules. The motive fluid is usually oil or steam. 

The general design of an oil diffusion pump involves a heater to heat the oil, which is then ejected to nozzles on top of the boiler or vaporising chamber. The vaporised oil leaves the nozzles at supersonic speeds, collecting randomly flowing gases drawn from the low-pressure chamber as it does so.

Cooling coils then condense the vaporised oil, which returns to the boiler. But the collected gas molecules continue to flow towards the exhaust.

Steam or hydrocarbon gas ejectors work similarly, although these types don’t need a boiler since the steam or motive fluid is already vaporised and has sufficient speed.

Read more about extending the life of your vacuum pumps through maintenance and protection.

What types of vacuum pumps are your operations using?

The vacuum process is integral to production but getting your head around the different types of pumps involved takes experience, never mind confidently servicing and maintaining said pumps to the degrees of accuracy required by today’s manufacturing operations.

To help you build vacuum pump competencies across your team, we offer a variety of training courses specifically designed to deliver introductory knowledge and enhance in-house engineering teams responsible for maintaining heat treatment industry equipment.

You may have seen that in 2021, VFE was acquired by Busch UK, of the Busch Vacuum Solutions family. Busch’s experts have been delivering vacuum pump servicing since 1963, evidencing the technical skills and hands-on experience honed by their engineering teams. As part of the Busch group of vacuum specialists, our team has never been in a stronger position to advise you on best practice, deliver practical training, and improve your business. 

  • Courses can be delivered on-site or from our specialist training facility to suit your needs.
  • Each course covers functionality, safety, and applications.
  • Courses are fully compliant with the requirements of Nadcap, AMS2750 E, RPS 953 and ISO 9001:2008.

You can find out more about our training courses and how your team will benefit here

For sites requiring immediate support or ongoing maintenance, we can also arrange for technical engineers to visit at short notice to provide vacuum pump services and repairs.

In collaboration with Busch, we’ve also expanded our range of vacuum pump services to make your site maintenance easier. It’s never been simpler for new or existing customers to incorporate vacuum pump servicing into their ServiceCare agreements, providing the peace of mind that routine services are scheduled and your pumps are in safe hands.

In this free guide, learn how to simplify your heat treatment servicing plans and solve your maintenance challenges.

New call-to-action