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Subject: Re: construction of thermal vacuum chamber

Date: 11/14/01 at 3:42 AM
Posted by: Vladimir Tchoutko
E-mail: chutko@earthlink.net
Message Posted:

In Reply to: Re: construction of thermal vacuum chamber posted by manar tantawie on 11/14/01 at 12:20 AM:

Dear Manar,

The theory of vacuum systems design is described in books, for instance, Armand Berman "Vacuum Engineering Calculations, Formulas, and Solved Exercises", Academic Press, Inc. You can find general rules in some catalogs, for instance, all practically necessary information contents in Kurt J.Lesker Catalog. But in a real life your choise is usually very limited. First, it is your chamber dimensions that define the maximum possible diameter of input flange. Second, the cost of pump that strongly increases with its power. Third, design of high vac valve, presence of buffle, etc. As a result very often you can spend two times more money and reach just 20% of REAL pumping speed increasing. Besides a lot depends on your goal. What do you need? Imagine, you pump down yor chamber during 15 min. Using an other pump two times more powerful (and expensive!) you will be able to pump dowm yuor chamber during 7 - 10 min... Is it important for you? So the pump selection is usually the choise among not a lot of opportunities. Experienced guy never will calculate (if it is not some very special case - very big chambers, chambers with complicated shape, special vacuum requirements) - he just tell you: "This pump should be optimal (not a best!) for your goal; better by it in that company, they offer more cheap and weii working pumps." And do not forget that vacuum system performance depend on all vacuum elements - mechanical pump, valves, pipes. If you have never designed it before better ask experts at first time, than you'll see that it is not very complicated....


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