On 28 August 2019, Vacuum Science World contributor Dr Saim Memon hosted an international, one-day conference on Renewable Energy and Vacuum Insulation for Nearly Zero Energy Buildings (NZEBs) at London South Bank University.
In terms of engineering and science, it is hard to over emphasise the importance of measurements. They are the very essence of these two disciplines, which we use to explain the otherwise unexplainable with equations, tables, graphs and figures. In turn, this allows us to compare, contrast, repeat and define the apparent chaos which defines our world.
A residual gas analyser (RGA) is a small and usually rugged quadrupole mass spectrometer, typically designed for environment analysis, process control and contamination monitoring in vacuum systems. RGAs can monitor the quality of the vacuum by detecting (and measuring) minute traces of impurities in a low-pressure gaseous environment. RGAs can also be used as sensitive in-situ leak detectors, usually using helium.
The presence of gaseous molecules, whether slow or fast moving, is what gives rise to pressure. A vacuum is created by reducing the number of molecules that exist within, for example, a chamber or a flask. However, by reducing the number of molecules that exert a pressure on the internal surface of such a chamber, one reduces the pressure. Unfortunately, this causes “additional” molecules to enter into play.
When atmospheric air (or a gas) is used as a source for a vacuum system, it will however “pure” it may appear to be invariably contain some vapour. As the pressure drops this vapour will condense out and unless vented from the system form a contaminant which will prevent the pump from achieving its optimum vacuum pressure. In addition, this condensate can enter the pump’s oil-seal where as a contaminant, it can have a further detrimental effect.
In simple terms, a gas ballast valve incorporated into the system will allow a small portion of the compressed gas (containing this detrimental condensate) to be expelled without impacting upon the overall performance of the pump.
There are several types of pumps that can deliver high and ultra-high vacuum pressures; diffusion pumps, cryo pumps; ion getter pumps (IGP); titanium sublimation pumps (TSP); non-evaporable getter (NEG) pumps; and turbomolecular pumps (TMP).
The methods whereby these pumps are capable of producing high and ultra-high vacuum pressures (between 10-3 and 10-11 mbar) are either by momentum transfer of gas molecules or by capturing them (either physically or chemically).
Multistage roots pumps are dry vacuum pumps used in low, medium, high and ultra-high vacuum systems to produce “dry” conditions.
The simple (single-stage) roots pump is most commonly employed as a booster pump for several types of fore-pumps (such as rotary vane pumps, screw and liquid ring pumps) to improve ultimate pressure and pumping speeds. When multistage roots pumps are employed, no fore pump is required and they can operate from atmospheric pressure. Roots pumps are suitable where a dry and clean atmosphere is important or more likely essential. Consequently, they are frequently used in the manufacture of semiconductors and solar panels, as well as for coatings and other industrial applications.
In the world of vacuum systems, scroll pumps hold a valuable place as one of the few pumps that are traditionally employed in low (i.e. 1000 mbar to 1 mbar) and medium (i.e. 1 mbar to 10-3 mbar) systems, and yet are now also frequently being employed as fore (or backing) pumps in high and ultra-high (i.e. 10-3 to 10-12 mbar) vacuum systems.
Vacuum simulation (or modelling) is an essential part of vacuum system design. It is now a well-established practice and is primarily concerned with the prediction and calculation of how vacuum pumps and systems will perform in specific scenarios.
These simulations enable engineers to identify anomalies in the design stage and acquire the right components, rather than building a vacuum system that later needs to be redesigned.
Sharing knowledge and expertise on all things vacuum science and technology is our foundation. We are delighted to share this opportunity to learn from international researchers and innovators in the Renewable Energy and Vacuum Insulation community at the International Conference on Renewable Energy and Vacuum Insulation for Nearly Zero Energy Buildings.
