7.1.2. Compressed air requirement of cylinders


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Fig. 7.3: Clamping device with pneumatic cylinder
Compressed air cylinders are especially used in the area of automation. A distinction is made between two types of cylinder when determining the consumption of compressed air:
    • The single-action cylinders use compressed air to generate the movement of the working stroke only. The return stroke is performed by spring power or from the outside.
    • Double-action cylinders use compressed air to generate movement in both stroke directions. Force is used for both strokes. Accordingly, the consumption of compressed air is twice as high.
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The compressed air consumption q of pressure cylinders is determined by using the following formula:


    q = Air consumption(1 bar abs and 20° C ) [l/min]
    d = Piston diameter [dm]
    S = Length of piston path (Stroke) [dm]
    p = Operating pressure [barabs]
    a = Work cycles per minute [1/min]
    b = 1 with single-action cylinders, 2 with double-action cylinders
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d = 100 mm = 1,0 dm
S = 130 mm = 1,3 dm
p = 7 barabs
a = 47
b = 1
Example

A singe-action cylinder with a piston diameter of 100 mm is required to work at an operating pressure of 7bar abs . Its working stroke is 120 mm at 47 work cycles per minute.

This cylinder consumes approx. 336 Litres of compressed air per minute.