When designing the hydraulic system, it is necessary to optimize the design to achieve the minimum pressure drop. Hydraulic system designers have found that using a combination of valves and blocks with the correct cartridge is an effective way to optimize the system. When using this method, it is important to choose the correct size of the hydraulic valve, drill hole and runner.
It is also important to choose the right hydraulic hose or hard hose to connect to the hydraulic block. Hoses and rigid tubes need to be of appropriate diameter, length, smoothness, and shape to accommodate hydraulic flow. Hoses or rigid tubes that are too small can cause turbulence and overheating. Too large a hose or hard pipe can increase the cost, size, and weight of the system.
 
To understand the "right size" of hydraulic hoses and pipes, you need to first understand the nature of the fluid and friction. When a fluid flows, it loses mechanical energy to overcome the viscous forces in the fluid. In hydraulic systems, this loss is considered a pressure drop in the flow direction
Every component of a hydraulic system causes a pressure drop,  valve, hose,hydraulic fitting,  a filter, etc. This lost energy is transferred to the hydraulic fluid to raise the temperature of the oil.
The friction coefficient in the hydraulic pipeline largely depends on the smoothness of the inner wall of the pipeline, and the friction coefficient has a great influence on the pressure loss. It is generally believed that the inner wall of the hydraulic pipeline is relatively smooth. Based on years of experience, designers have summarized the recommended value of the appropriate flow rate of the hydraulic fluid in the oil pipeline:
The flow in the hydraulic oil line can be estimated according to the flow required by the actuator, and the recommended value is adopted for the flow rate. In this way, the inner diameter of the pipeline can be determined. The calculation formula of the inner diameter of the pipeline is as follows: