VACUUM SCIENCE BLOG

Cryopumps offer several advantages compared to other high-vacuum pumps. For instance, their pumping speed for water vapour is up to 4x higher than any other vacuum pump with the same inlet diameter. Furthermore, unlike gas transfer pumps, i.e. turbomolecular pumps or oil diffusion pumps, cryopumps condense all the gasses within them. The goal of this blog is to explain to you how they operate and where their capabilities are beneficial to the vacuum process. 

According to a report by the Food and Agriculture Organisation of the United Nations, at least one-third of food is lost or wasted between harvest and household. In North-America and Europe, this means more than 100 kg of food lost per capita – summing up to 1.3 billion tons annually worldwide! A reduction to this huge mass of food produced in vain would contribute greatly to reducing the greenhouse effect.

The 47th Conference on the Physics and Chemistry of Surfaces and Interfaces (PCSI-47) will be held from January 19-23, 2020 at Millennium Harvest House in Boulder, Colorado, USA. The annual PCSI conference is devoted to achieve a fundamental understanding of the physical, chemical, biological, structural, optical, magnetic and electrical properties of surfaces and interfaces.

Over the years, vacuum pumps have evolved to dry versions (no oil in the swept volume), robust, process specific, low power consumption and reduced footprint. With this shift in the industry, it was great to hear a range of discussions around this during the 10^th Vacuum Symposium UK.

Screw pumps belong to the family of dry compressing gas transfer pumps. They are positive-displacement pumps that use two screw shaped intermeshing rotors to move gas along the screw’s axis. They are frequently used in industrial vacuum applications, often in combination with roots blowers and as oil-free roughing pumps in high and ultrahigh vacuum systems.

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.

What is a residual gas analyser?

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.