In a hydrostatic transmission circuit should be used only clean fluid.
Hydrostatic transmissions are hydraulic systems designed to have a pump drive a hydraulic motor.
Hydrostatics deals with the potential energy available when a liquid is enclosed and under pressure. This potential energy is called hydrostatic energy. Hydrostatic energy is applied in most of the hydraulic systems. Hydraulics field is controlled by Pascal's law.
Hydrostatic law states that the rate of increase of pressure in a vertically downward direction must be equal to the specific weight of the fluid at that point.
The vertical height of the free surface above any point in a liquid at rest is known as the pressure head. This implies that the pressure (called head pressure) at any point in a liquid is given by the equation:
• p is the density of the liquid
• h is the free height of the liquid above the point
• g is the acceleration due to gravity.
Thus, the pressure at any point in a liquid is dependent on three factors:
1. Depth of the point from the free surface
2. Density of the liquid
3. Acceleration due to gravity.
Example: Calculate the hydrostatic pressure at the bottom of hydraulic oil container filled with oil ρ=0.6kg/dm³ up to a height of 600 mm.
Solution: p=h x l x g = 600 mm x 0.6 kg/dm³ x 9.81 m/s²
= 6 d x 0.6 kg/dm³ x 9.81 m/s² = 6 x 0.6 kg/dm² x 9.81 m/s²
= 6 x0.6 x 9.81 N/dm² = 6 x0.6 x 9.81(N x 100)/(dm² x 100)
= 6 x0.6 x 9.81(100 N)/m² = 3531 N/m² = 0.035 bar
A hydraulic transmission system simply transforms mechanical power into fluid power and then reconverts the fluid power into shaft power.
A hydrostatic machine is any hydraulic drive that can transmits its pressure energy into a mechanical output. This mean that a hydraulic pump is a hydrostatic device as oil is under pressure is supplied to the system for mechanical work. A simple hydraulic press is an example of a hydrostatic device.
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