Jan 26, 2022

How to identify the number of positions of the hydraulic valve?

The hydraulic valve is an important control component in the hydraulic system. According to the function of hydraulic valve, it can be divided into flow valves, such as throttle valve, speed control valve, diverter and collector valve; pressure valve, such as relief valve, pressure reducing valve, Sequence valve, unloading valve; directional valve, such as electromagnetic reversing valve, manual reversing valve, check valve, hydraulic control check valve.


Hydraulic reversing valve

The directional control valve is the reversing valve, which prevents and guides the oil to flow in and out of the passage according to the specified direction in the hydraulic system, that is, it plays the role of controlling the flow direction of the oil in the oil circuit. There are two important concepts in the reversing valve, namely position, and pass. Position means that the reversing valve spool has several working positions, which are indicated by squares in the schematic diagram; pass means that there are several oil inlet and outlet ports, and the oil inlet and outlet ports are indicated by arrows in the schematic diagram.


How to identify the positions and ports in the hydraulic reversing valve?

Then how to identify the positions and ports of the hydraulic valve?

Two-position (left, right) and three-position (left, right, and center) are more common in hydraulic reversing valves. The flow direction of oil is different in each working position. There are several oil pipes connected to the valve, and the common ones are two-way, three-way, four-way, and five-way. Several squares represent several valves, and several oil ports represent several valves, which together are called several valves. Such as a two-position two-way valve, three-position four-way valve. In the diagram, we can see that there are several "squares" separated by vertical lines in the symbol, and a few are just a few digits. Look at a certain square and there are several vertical lines that intersect with the border of the "square", and a few are the number of passes. The arrows indicate the passage (flow direction), one arrow indicates the two-way, namely oil inlet and oil outlet, and the two arrows are the four-way; the intersection of ┴ and ┬ with the box indicates that the passage is blocked by the valve core. If there are two arrows and a ┬ in a box in the picture, it means that the five links are blocked, and one link is blocked.



Graphical Symbol Meaning


  1. Bits—represented by square "□", and several bits are several squares.
  2. The number of intersections between the arrow ↑ head and tail and the truncation symbol ┴ and a square is the number of passes. ↑ indicates that the oil ports are connected, and the direction does not indicate the actual flow direction. ┴ Indicates that the oil port is blocked.
  3. P, A, B, T, O have a fixed orientation, P—the oil inlet; T, O—the oil return port; A, B—the working oil port connected to the actuator.
  4. Spring - W, drawn on both sides of the square.
  5. Normal position three-position valve, one grid in the middle; two-position valve, one grid by spring. (In the schematic diagram, the oil circuit should be connected in the normal position).


The hydraulic symbol schematic diagram is usually marked on the valve body of the solenoid valve. We can identify the reversing valve with several positions and several channels through the above schematic diagram. For example, REXROTH directional valves 4WE Series, customers can find the symbols on the nameplate:


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