How To Select The Pipe Diameter for The Piping in A Custom Hydraulic System?

How to select the pipe diameter for the piping in a custom hydraulic system?

How should the pipe diameters be selected in a custom hydraulic system? The specific situation needs to be analyzed in detail because it depends on whether the distance between the pump station and the actuator is long or not. Does the speed of the actuator need to be strictly controlled? Also, some hydraulic systems operate continuously while others work for a short period and then rest for a long time. We can choose the size and thickness of the pipes based on the working pressure of the hydraulic system and the flow rate passing through it, and consider the material of the pipes. All these details can be found in the hydraulic system manual.

1. How to select the pipe diameter in the hydraulic system - How to choose the type of pipe?

First, consider the material. Should we choose a rubber hose or a steel pipe? For the steel pipe, we need to decide whether to use ordinary carbon steel or stainless steel. Secondly, based on the flow rate and pressure resistance requirements, select the inner diameter and form. The hose can be made of steel wire weaving or winding. Different layers correspond to different pressure resistance. For the steel pipe, the selection involves wall thickness and inner diameter. If it's a rigid pipe, the wall thickness should be chosen according to the inner diameter and pressure. If it's a flexible hose, only the inner diameter and pressure resistance value need to be determined, and the outer diameter does not need to be selected. Thirdly, choose the type of connector. Is it a direct connector or a 45-degree or 90-degree elbow?

2. How to select the pipe diameter in the hydraulic system - Refer to the formula

For the inner diameter of the hydraulic system pipes, we have a clear calculation formula: the specification of the oil pipe (inner diameter formula): D ≥ 4.61 × (Q/V)^1/2. Detailed explanation: D is the inner diameter of the oil pipe in MM; Q is the flow rate in the pipe in L/MIN; V is the flow velocity of the oil in the pipe in M/S. The suction pipe takes 0.5 - 1.5 M/S, the high-pressure pipe takes 2.5 - 5 M/S, and the return pipe takes 1.5 - 2.5 M/S.

In actual production, the selection of pipes usually does not require calculation because the pipe size is mainly determined by the diameter of the connecting fittings used in the system. This formula is mainly used for checking the flow velocity of the liquid in the pipeline to verify whether the selected pipe diameter is appropriate. The oil pipe is an externally purchased component, and its inner and outer diameters have standard specifications. The calculated inner diameter should be referred to the relevant manual and selected according to the standard.

3. How to select the pipe diameter in the hydraulic system - How to determine the wall thickness?

Formula - Wall thickness = Pressure (MPa) X Inner diameter of the pipe / (2 X Allowable stress). The value of allowable stress depends on the material of the pipeline. For ordinary equipment, a larger value can be chosen. Regardless of the material, it is set at 100 MPa. This value is already very conservative. For example, if the inner diameter of the oil pipe is 20 millimeters and the working pressure is 30 MPa, the wall thickness is: 20 X 30 / (2 X 100) = 3 millimeters.