Vacaero

Manufacturers of heat treating and brazing vacuum furnaces and controls, complete hot zone and vacuum furnace retrofits, thermal spray coatings, plasma, HVOF and paint coating services.

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Archives for July 2018

Pumps for High and Ultra-High Vacuum

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Most of us are familiar with processing in the vacuum range up to around 1.33 x 10-3 Pa (1 x 10-5 torr) or slightly lower. There are also lessons to be learned from understanding the demands of ultra-high vacuum applications. What is an Ultra-High Vacuum? Practical high vacuum levels (Table 1) range down to approximately 1.33 x 10-4 Pa (1 x 10-6 torr) while ultra-high vacuum (UHV) levels are in the vacuum range characterized by pressures of about 10-7 Pa (7.5 x 10-10 torr) and greater. These vacuum levels demand the use of special materials of construction and processing techniques such as preheating (i.e. bake-out) of the entire system for several hours prior to processing to remove water and other trace gases, which adsorb on the surfaces of the chamber.

These vacuum levels demand the use of special materials of construction and processing techniques such as preheating (i.e. bake-out) of the entire system for several hours prior to processing to remove water and other trace gases, which adsorb on the surfaces of the chamber. At these low pressures, the mean free path of a gas molecule is approximately 40 km (24.8 miles), so gas molecules will collide with the chamber walls more frequently than they collide with each other. Thus, almost all gas interactions, therefore, take place on various surfaces in the chamber.

The Oil Sealed Rotary Vane Vacuum Pump – Background and Designs

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In this article we will only discuss one and two-stage “medium vacuum” oil sealed rotary vane vacuum pumps that can produce a catalog ultimate vacuum of about 1 x 10-2 Torr (0.01 Torr or 10 microns) for a one stage model and about 1 x 10-3 Torr (0.001 Torr or 1 micron) for a two-stage model. We will review the Vee Belt Drive design and the Direct Drive design.

Smaller vacuum pumps such as those used in the heating, ventilating and air conditioning industry (HVAC) are not included as they are often only for intermittent use and do not have the design features built into the laboratory sized continuous running vacuum pumps used in industry and science. Larger rotary vane vacuum pumps, ones that require ball or roller bearings to support the weight of the rotor are not included either. Although they have many similar features to the laboratory sized vacuum pumps, they also have a variety of options to suit different applications.

Tips for Selecting Vacuum Furnace Equipment

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Acquisition of a vacuum furnace represents a major capital equipment investment and one that creates a long-term relationship with your supplier partner. Thus the choice of what to buy and who to purchase it from requires careful planning and considerable up-front research. You need to know when and how to apply vacuum technology if it will be the most cost-effective solution for what you need to do, what questions to ask and what information to provide.

The process begins by understanding your specific needs and asking all the right questions. Is it more prudent to upgrade an older piece of equipment, purchase new or purchase used? Is it better to have one large furnace or two smaller ones? Is a batch solution best or is a continuous approach better?

Ask yourself what the equipment must do, what productivity must be achieved (now and in the future) and what type of specifications or compliance requirements (e.g. Nadcap, CQI-9) must be met. The type of material(s) being run, the skill of your workforce, the (internal and external) support available and the type of controls and/or quality records required are additional considerations. All of these will help define how much training and support will be needed from your supplier partner.