Hydraulic valves are used to control the flow of oil in a hydraulic system or regulate its flow and pressure.

Directional control valve is a kind of hydraulic valve, which controls the flow direction of oil by replacing the flow passage.


One-way directional control valves are directional control valves that allow air flow only in one direction, such as check valves, shuttle valves, dual pressure valves, etc.



Directional control valve is a directional control valve that can change the flow direction of the air flow.


According to the control method can also be divided into electromagnetic valve, mechanical valve, air control valve, and human control valve.

Pipeline expression
1. Pipes of water and gas transmission steel pipes (galvanized or non-galvanized), cast iron pipes and plastic pipes shall be marked with the nominal diameter “DN” (eg DN15, DN50).

Second, seamless steel pipe, welded steel pipe (straight seam or spiral joint), copper pipe, stainless steel pipe and other pipe, pipe diameter should be expressed in diameter × wall thickness (such as De108 × 4, De159 × 4.5, etc.); Non-ferrous metal pipes, should be marked "outer diameter × wall thickness." For example, Φ108×4, ф can be omitted.

Third, reinforced concrete (or concrete) pipes, clay pipes, acid-resistant ceramic tubes, cylinder tiles and other pipe, pipe diameter should be represented by the inner diameter d (such as d230, d380, etc.).

Fourth, plastic pipe, pipe diameter should be expressed according to product standards.

5. When the design uses the nominal diameter DN to indicate the pipe diameter, there shall be a comparison table of the nominal diameter DN and the corresponding product specifications.

other instructions
Nominal diameter, also known as mean outside diameter. In order to make the pipe and pipe fittings uniform in size, the nominal diameter (also called nominal diameter, nominal diameter) is expressed by DN.

Because the unit has a distinction between metric (mm) and inch (inch), the following methods are called.

1. Measure DN (metric unit) on the basis of metric (mm)

II. In inches (inch)

Three. DN (nominal diameter) NB (nominal bore) OD (outside diameter)

IV. [Examples] Galvanized steel pipe DN50, sch 20 Galvanized steel pipe NB2”, sch 20

Note: The pipe table number (Sch.) is not a wall thickness but a wall thickness series. The actual wall thickness, the same diameter, and its thickness in different tube numbers.

In 1938 the American National Institute of Standards and Regulations ANSIB36.10 (Welding and Seamless Steel Pipe) standards stipulated that the pipe number (Sch.) is the ratio of the design pressure to the allowable stress of the material at the design temperature multiplied by 1000, and is rounded. The value after.

ISO metric dimension denotes the outer diameter of the PVC tube and ABS tube in Da. De represents the outside diameter of the PP pipe and the PE pipe.

For example, the metric diameter of a plastic pipe with an outer diameter of 63mm is Da63, which is for PVC pipes and ABS pipes.

New materials and plastic pipes use de, note that it is lowercase.

Dn is mainly used in cast iron pipe, galvanized steel pipe and steel-plastic composite pipe. In addition, Dn100 is equivalent to de110, and Dn150 is equal to the diameter of de160.