Pfeiffer Vacuum

7.1 General

This section will discuss simple dimensioning questions:

All of these questions can naturally not be discussed exhaustively in this chapter. Simple examples will be used and the anticipated results estimated. The technical data of the pumps and components that are used must be taken into consideration for the concrete application in question. And special literature can also be useful for dimensioning


Every physical technical parameter consists of a numeric value and a unit. The SI system has been adopted worldwide and standards have been defined for the basic values of length (m), mass (kg), time (s), temperature (T), substance volume (mol), electric current (A) and luminous intensity (cd); these values are used for calibration purposes in the individual countries. All other values are derived from these basic values. With few exceptions, the formulas that are used in this discussion contain only the physical technical values and no conversion factors whatever, such as Pa to mbar. This means that after employing the values in SI units, the results will also be in SI units. Examples of SI units are 1 Pa = 1 N/m2 = 0.01 mbar for pressure and 1 m3/s = 3,600 m3/h. Used largely throughout the following sections are popular non-SI units; however SI units will be used wherever it would appear to be appropriate due to the required conversion.

Exclusive use of SI units would avoid many errors and much conversion effort. Unfortunately, this advantage is only very slowly gaining acceptance throughout the world.

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