When the piston rod is moving, the required medium, e.g. hydraulic oil, flows into the hydraulic cylinder or out of it on the other working side.
The medium's flow rate depends on the travel speed and the cross-sectional areas of the supply lines, especially in the ports and fittings. A high flow rate increases the power loss at the drive and thus reduces the hydraulic efficiency. So the flow rate should be kept as low as possible.
The admissible oil speeds depend on the medium's properties. The following table shows recommendations for mineral oils.
|Nominal pressure||> 3 bar||< 25 bar||> 63 bar||> 160 bar||> 250 bar|
|Adm. oil speed||< 3 m/s||< 5 m/s||< 6 m/s||< 8 m/s||< 10 m/s|
|Adm. oil speed||< 3 m/s|