Читать книгу Hydraulic Fluid Power - Andrea Vacca - Страница 88

Consider the hydraulic system in the figure below. The system is used to lift and lower a vertical load. The system requirement is that no leakage should occur while the system is in rest or standby (directional control valve (DCV) in neutral position). However, the cylinder seal is damaged so that leakages can occur between its piston chamber and its rod chamber. Assuming that the DCV can perfectly block the cylinder work ports, what happens to the piston when the valve is in rest position? Does it fall? Or it remains stand still? Also, provide the value of the reading of the two pressure gages A and B in such condition.

The following data are given: equivalent orifice resistance of the internal cylinder leakage = 50 (bar · min)/l; mass = 1000 kg; piston diameter 100 mm; rod diameter 40 mm.

Given:

The hydraulic schematic of a hydraulic lifting system, the piston diameter of the cylinder D = 100 mm and the rod diameter d = 40 mm. The gravitational load is known M = 10 000 kg. The internal leakage of the cylinder expressed as equivalent orifice resistance (Δp_{O, LAM} = R_LAMQ_LEAK) R_LAM = 50 [(bar · min)/l].

Find:

1 The motion of the cylinder in rest condition (vertical velocity)

2 The reading of the pressure gages A and B