This is the seventh in a series of articles in our Vacuum Heat-Treatment Series. Here we talk about vapor pressure and how it is influenced by the various materials of construction used in a typical vacuum furnace as well as the materials we process.

All solids and liquids have a tendency to evaporate into gaseous form, and all gases have a tendency to condense back into their liquid or solid form. In other words, all materials have a characteristic vapor pressure that varies with temperature. Formally, vapor pressure is the pressure of a vapor in (thermodynamic) equilibrium with its condensed phase(s) in a closed container or vessel. READ MORE by Dan Herring

Next time, we will begin a discussion of the interior construction of vacuum furnaces by considering hot-zone designs.

This is the sixth in a series of articles in our Vacuum Heat Treatment series. Here we continue our discussion of the types and characteristics of vacuum gauges and offers insights into which gauge should be used when working in a specific vacuum range.

Counting molecules is a job for vacuum gauges and it’s now time to understand the differences between these devices and when to use them. Recall first that the vacuum level in a vessel is determined by the pressure differential between the evacuated volume and the surrounding atmosphere (Table 1). The two basic reference points in all these measurements are standard atmospheric pressure (760 torr) and perfect vacuum (0 torr), so calculating changes in volume in vacuum systems requires conversions to negative pressure (psig) or absolute pressure (psia). READ MORE by Dan Herring

Next time: Part seven of this series talks about vapor pressure and how it is influenced by the various materials of construction used in a typical vacuum furnace.

This is the fifth in a series of articles in our Vacuum Heat-Treatment Series. Here we begin a discussion of the types and characteristics of vacuum gauges and offer insights into which gauge should be used when working in a specific vacuum range.

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Counting molecules is a job for vacuum gauges. Depending on the type of vacuum systems and the required operating vacuum level, different vacuum gauges are required – often in combination with one another – to accurately determine and/or control the vacuum level of the chamber at any given moment in time. The criteria for selecting a vacuum gauge are dependent on various conditions, such as: READ MORE by Dan Herring

This is the fourth in a series of articles in our Vacuum Heat-Treatment Series. Here we conclude our discussion of vacuum pumping systems by reviewing the operation of diffusion pumps as well as offering troubleshooting tips for all types of vacuum pumping systems.

Vacuum pumps are the heart of a vacuum system. While mechanical pumps have the ability to work against atmospheric back pressure and booster pumps improve the speed and level to which we pump down, these pumps have the disadvantage of losing efficiency as the system pressure continues to lower. In order to reach extremely low vacuum levels, the use of diffusion pumps is required. READ MORE by Dan Herring

This is the third in a series of articles in our Vacuum Heat-Treatment Series. Here we will begin to discuss vacuum pumping systems, explore the operating characteristics of mechanical pumps and blowers, and consider what we can do to make the pumps we choose work better.

In order to create a vacuum within a closed container, or vessel, we need to remove the molecules of air and other gases that reside inside by means of a pump. The vacuum vessel and pumps (mechanical, booster, diffusion, holding) together with the associated piping manifolds, valves (mechanical pump, high vacuum isolation, vacuum (brake) release, backing), vacuum measurement equipment (molecule counters) and traps comprise a typical vacuum system (Fig. 1). READ MORE by Dan Herring

This is the second of a series of articles in our Vacuum Heat-Treatment Series. This part is intended to teach us all about how gases behave in a vacuum environment, look at the equations needed to explain their behavior and explore what happens when we pump down a vacuum vessel. It is important to understand something about the Theory of Gases since a vacuum environment is hardly a space containing” nothing at all.” What remains inside the vacuum vessel will definitely affect the component parts we process.

In vacuum heat, we are always dealing with the movement of gases. So, everyone needs to understand something about the nature (theory) of gases and how they behave, especially in vacuum. The main difficulty, however, is that too much theory tends to become a distraction. Our mission is to learn how these equations help us understand what goes on inside a vacuum vessel. READ MORE by Dan Herring

This is the first of a series of articles in our Vacuum Heat-Treatment Series. It is designed to explore the nature of vacuum, how it is used throughout the thermal-processing industry and the processes and applications that benefit most from its use.

Design features, operational issues and maintenance practices will be covered, all of which are necessary to produce quality component parts in captive and commercial heat-treat shops servicing the aerospace, automotive and industrial markets. A vacuum system (Fig. 1) provides a space in which the pressure can be maintained below atmospheric pressure at all times. The primary advantage of vacuum heat treatment is its versatility. READ MORE by Dan Herring