Molecular Seive for making vacuum tubes

In summary, the conversation discusses the use of vacuum tubes in manufacturing image tubes and the processes involved in creating a vacuum. The main focus is on the use of vac-ion pumps and molecular sieves, specifically zeolites cooled with liquid nitrogen, to achieve a high level of vacuum. The purpose of the molecular sieve is to remove water and oil molecules from the air, and there is some uncertainty about whether it also removes other gas molecules. Overall, the conversation highlights the importance of maintaining a clean and efficient vacuum in the manufacturing process.
  • #1
Y2keddie
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im trying to jog my memory back 30years when I worked with vacuum tubes. I worked with manufacturing of image tubes. I remember the vacuum systems used vac-ion pumps to achieve -12 power torr. I alsoo remember first using a molecular seive for roughing,pumping to 10 microns.
The seive was a canister filled with a zeonolite which was cooled with liquid nitrogen.
I believe it worked as an adosorbtion process where water molecules would adhere to the zenolite surface thus removing water molecules from air in the beginning stages of vacuum.
What my memory is fuzzy about: is the seive used just for water,or other gas molecules?
 
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  • #3
My recall is not that good. I’m guessing the process sequence was:

Use Mechanical pump ( to 10 microns).
Isolate
Then molecular Seive (to ?? Torr) The decrease in pressure would indicate the oil molecules had decreased?
Isolate
Then Vac Ion pump to 10x-14 torr

That would make sense. The oil contaminants would destroy the tubes cathode properties.
 
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1. What is a molecular sieve and how does it work?

A molecular sieve is a material with very small pores that can selectively adsorb molecules based on their size and shape. In the context of making vacuum tubes, it is used to remove water and other impurities from the gas inside the tube, creating a higher vacuum. This is achieved through a process called adsorption, where the molecules of the impurities are trapped in the pores of the sieve, while the gas molecules pass through.

2. What are the benefits of using a molecular sieve in making vacuum tubes?

Using a molecular sieve in the production of vacuum tubes has several benefits. It helps to create a higher vacuum, which is essential for the proper functioning of the tube. It also removes impurities that can affect the performance and lifespan of the tube. Additionally, it allows for more precise control over the gas composition inside the tube, which can improve its overall efficiency.

3. How is a molecular sieve chosen for use in vacuum tube production?

The selection of a molecular sieve for use in vacuum tube production depends on several factors, such as the desired pore size, the type of impurities that need to be removed, and the gas composition inside the tube. Other considerations may include the cost and availability of the sieve, as well as its compatibility with the materials used in the tube.

4. Can a molecular sieve be reused in the production of vacuum tubes?

Yes, a molecular sieve can be reused in the production of vacuum tubes. However, it may need to be regenerated first to remove the impurities that have been adsorbed. This can be done by heating the sieve to a high temperature, causing the trapped molecules to be released. The sieve can then be cooled and reused multiple times.

5. Are there any potential drawbacks to using a molecular sieve in vacuum tube production?

One potential drawback of using a molecular sieve in vacuum tube production is that it can slow down the production process, as the gas must pass through the sieve to remove impurities. Additionally, if the sieve is not properly chosen or maintained, it can lead to decreased efficiency or even damage to the vacuum tube. However, these issues can be mitigated by carefully selecting and properly using the sieve.

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