Drive valves: types and features
Drive valves are a popular type of pipe fittings that are often used in the installation of medium and high pressure systems. The variety of sizes and designs of such units significantly reduces the complexity of installation work.
Device
Drive valves consist of three main components:
- Connecting elements;
- Enclosures;
- Drive.
Connection to the pipeline is carried out by means of flange, screw or welded joints through sealing elements - seals. The housing in which the moving parts of the valve are located is detachable: this ensures the possibility of periodic cleaning and maintenance of the valve. The moving parts of the valve include the stem, the gate, the wedge, and the seat rings.
Design features
They are determined by the execution of the wedge, which can be solid, hollow and multi-sectional (so-called split valves). A solid wedge is a solid monolithic structure. It does not compensate for changes in the alignment of the seat due to loads on the ends of the pipes, or due to thermal fluctuations.
Movable gate valves with a solid wedge are considered the most economical. They are usually used at moderate or reduced pressure. It is common practice to use solid wedge valves made of cast iron or ductile iron in cold water pipelines.
A hollow wedge is a version of a solid wedge, with an existing axial hole. The hollow wedge moves along the stem as a result of the mechanized movement of the threaded rod, opening or closing the valve opening.
The flexible wedge also has a solid construction, but differs in the presence of a cavity behind the seating surfaces, which increases the flexibility of the gate valves are hollowed out to ensure flexibility. This design compensates for changes in the alignment of the seats to improve the fit, while maintaining the strength of the solid wedge in its middle part. This design provides better tightness and improved performance.
Types of drives
Wedge gate valves with electric drive produce the following types:
- With a retractable spindle.
- With a swinging (rotary) spindle.
- With a split wedge.
In the first case, the rod receives a reciprocating displacement, and in the second - a rotational one, for which a special turbine engine is installed. This increases the technological capabilities of the valve, but complicates its maintenance.
The split wedge consists of two parts, which are installed between the conical seats in the valve body. The two parts of the split wedge seat are adjacent to the valve seats when the stem is moved down, and they move away from the valve seats when the stem is pulled up.
Multi-section drive valves most often consist of 2-3 sections.
They are located between the corresponding conical seats in the housing. The rods are connected with a screw spindle by means of a bar. This type of reinforcement is preferred when the housing seats may be distorted due to possible deformations of the pipeline.