Category: Hydraulic Physical Principles

Flow Resistance in Pipelines

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Flow Resistance in Pipelines

The friction between the flowing layers of liquid and the adhesion of the liquid to the pipe wall form a resistance which can be measured or calculated as a drop in pressure. Since the flow velocity has an influence on the resistance to the power of two, the standard values should not be exceeded.

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Friction, Heat, Pressure drop

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Friction, Heat, Pressure drop

Friction occurs in all devices and lines in a hydraulic system through which liquid passes. This friction is mainly at the line walls (external friction). There is also friction between the layers of liquid (internal friction). The friction causes the hydraulic fluid, and consequently also the components, to be heated. As a result of this […]

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Types of Flow

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Types of Flow

A distinction is made between laminar and turbulent flow. In the case of laminar flow, the hydraulic fluid moves through the pipe in ordered cylindrical layers. The inner layers of liquid move at higher speeds than the outer layers. If the flow velocity of the hydraulic fluid rises above a certain point (known as the […]

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Measurement of Flow Rate

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The simplest method of measuring flow rate is with a measuring container and a stop watch. However, turbine meters are recommended for continuous measurements. The speed indicated provides information about the value of the flow rate. Speed and flow rate behave proportionally. Another alternative is to use an orifice. The fall in pressure recorded at […]

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Temperature Measurement

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The temperature of hydraulic fluid in hydraulic installations can either be measured using simple measuring devices (thermometers) or else by means of a measuring device which sends signals to the control section. Temperature measurement is of special significance since high temperatures (> 60 degrees) lead to premature ageing of the hydraulic fluid. In addition, the […]

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Pressure Measurement

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Pressure Measurement

To measure pressures in the lines or at the inputs and outputs of components, a pressure gauge is installed in the line at the appropriate point. A distinction is made between absolute pressure measurement where the zero point on the scale corresponds to absolute vacuum and relative pressure measurement where the zero point on the […]

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Flow rate

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Flow rate

Flow rate is the term used to describe the volume of liquid flowing through a pipe in a specific period of time. For example, approximately one minute is required to fill a 10 litre bucket from a tap. Thus, the flow rate amounts to 10 l/min. In hydraulics, the flow rate is designated as Q. […]

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Pressure transfer

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Pressure transfer

The hydrostatic pressure p1 exerts a force F1 on the area A1 which is transferred via the piston rod onto the small piston. Thus, the force F1 acts on the area A2 and produces the hydrostatic pressure p2. Since piston area A2 is smaller than piston area A1, the pressure p2 is greater than the […]

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Displacement transmission

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Displacement transmission

If a load F2 is to be lifted a distance S2 in line with the principle described above, the piston P1 must displace a specific quantity of liquid which lifts the piston P2 by a distance S2 The necessary displacement volume is calculated as follows: V1 = S1 · A1 and V2 = S2 · […]

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