The main classification of pipeline fittings determines its functional purpose, namely:
- Shut-off valve. It has only two working positions "open" and "closed". Provides complete shutoff of the operating medium flow. The most common version is a gate valve.
- Control valves allow you to adjust the parameters of the medium by changing the flow rate. This type includes throttling devices and some types of valves.
- Distribution and mixing valves are used to distribute the substance in separate directions or to mix them.
- Safety or protective valves provide pipeline protection against inadmissible pressure, unpermitted change of flow direction. This type of fittings also includes dampers for air and gas ducts in different modifications, which are described below.
The main difference between these devices is determined by their geometrical configuration, which determines their application in return.
Round butterfly damper
It is set in a pipeline with suitable diameter and provides unobstructed passing of operating medium at a given pressure. If the pressure drops, the flap of the device moves down and blocks the duct.
Rectangular louver damper
It is set in water mains of appropriate geometry. It can be either rectangular or square. It performs the same functions as the previous device. Considering that mains with such a cross-section are used, as a rule, for supplying air or gas mixtures, tightness requirements to this equipment are increased.
Explosion relief valve
These fittings are installed in process pipelines exposed to risk of spur pressure increase due to an explosion or pressure jump of the medium. This type of valve can be of different shapes. Diaphragm, which is destroyed in emergency, is an attribute of this device. Thus, the operating medium is released into the atmosphere, preventing the destruction of the pipeline and process equipment damage.
The corrosion resistance and strength characteristics of different cast iron and steel grades are values to choose for valves manufacture.