2. Fitting and pneumatic installation
2−25
Festo P.BE−CPX−CMAX−SYS−EN en 0908NH
2.6.3 Air reservoir (optional)
If the positioning behaviour does not conform to your require
ments, and if you ascertain fluctuations in pressure of over
1 bar at the measuring point, then proceed as follows:
· Install an air reservoir (e.g. type VZS−...−B) between the
filter regulator and the proportional directional control
valve.
This way, you can reduce pressure fluctuations during posi
tioning. You can compensate for slight excesses in the per
missible pressure fluctuation by using supply tubing with a
larger cross section.
Reservoir volume The reservoir volume should be
at least four times as large
as the volume of the drive used.
V
P
= 4 * V
Z
V
P
= buffer volume
V
Z
= cylinder volume
(Linear drives: V
Z
= r
2
* ð* L
Z
)
L
Z
= cylinder stroke length
r = 1/2 * cylinder diameter
2.6.4 VPWP proportional directional control valve
Arrange the tubing between the valve (VPWP) and the drive
symmetrically.
Recommendation for linear drives and drives with piston rod:
tubing length = cylinder length
Fig.2/10 shows a schematic diagram of the tubing of a cylin
der (example) with the VPWP.
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