NEWS
02
2022
-
05
Fluid viscosity and pressure loss in hydraulic system
Author：
During the use of the hydraulic system, the liquid has a certain viscosity, so friction will inevitably occur when the product flows in the pipeline, so the liquid in the hydraulic system will inevitably lose a part during the flow process, which is mainly manifested as pressure loss.
The pressure loss of the hydraulic system can be divided into the pressure loss along the hydraulic system and the pressure loss along the hydraulic system. The loss along the hydraulic system is the pressure loss due to friction when the liquid flows through a certain distance in a straight pipe of equal diameter.
The local loss of the hydraulic system is directly caused by the sudden change of the pipe section shape and the change of the liquid flow direction. Other forms of liquid flow resistance directly result in product pressure loss. The total pressure loss is equal to the sum of the loss along the way and the local loss.
Since the pressure loss in the hydraulic system is unavoidable, the rated pressure of the pump is greater than the maximum working pressure required for the system to operate. In general, the maximum working pressure required by the system can be estimated by multiplying the coefficient 1.3~1.5.
In the hydraulic system, each pressure-bearing element has a relatively moving surface, such as the inner surface of the hydraulic cylinder and the outer surface of the piston. Due to relative motion, there will be a certain gap between them. If one side of the gap is high pressure oil and the other side is low pressure oil, the high pressure oil will flow to the low pressure area through the gap, causing leakage.
The flow loss of the hydraulic system affects the movement speed, and leakage is inevitable, so the rated flow of the pump in the hydraulic system is slightly larger than the large flow required by the system.
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