Self-Induced Fault of a Hydraulic Servo Valve by Taehun Seung

Author:Taehun Seung
Language: eng
Format: epub
ISBN: 9783030035235
Publisher: Springer International Publishing

Fig. 2.24Full water hammer effect at the switching-off: GRB No. 1; normal/no fault

Fig. 2.25Reduced water hammer effect at the switching-off: GRB No. 3; abnormal

Fig. 2.26Full water hammer effect at the switching-off: PPT No. 2; normal/no fault

Fig. 2.27Reduced water hammer effect at the switching-off: PPT No. 6; abnormal/fault

2.1.2.5 Fluid Dumping Behaviour at the Control Circuit

In normal cases, whenever the solenoid is switched off and accordingly the flapper closes the inlet nozzle due to the spring preload, then the control circuit dumps the fluid trapped in the spool’s control chamber via the outlet nozzle as the coil spring resets the spool back to the start position (cf. Fig. 1.​2).

Such dumping processes are traceable in the record of the return pressure. For better understanding, the following description refers to the Figs. 2.28 and 2.29, of which time frames are from 19.0 to 24.0 s, from 139.0 to 143.3 s, respectively. It must be said that the system behaviour is generally quite reproducible, regardless of the ramp profile of the commands (cf. Fig. 2.30 and 2.31).

Fig. 2.28Return pressure development after PPT No. 1; normal/no fault

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