The shut-off and control valve is a type of piping fitting intended to regulate the values of the working medium. The regulation of parameters involves the adjustment of flow rate of the environment, maintaining the pressure of the medium within specified limits, blending various media in the required proportions, maintenance of the specified liquid level in the vessels and some others. The control valve accomplishes its own functions by changing the flow rate of the medium through its inside diameter.
Various types of the control valve depend on the particular operating conditions, most often using external energy sources and controlled by command from sensors fixing the environment in the pipeline. Automatic control specifically for the working environment is also used. In modern industry, it is rare, but still occurs, the main way to control the regulators in the past - manual control (see figure on the right).
Depending on the parameters of the working medium (pressure, temperature, chemical composition, etc.), different requirements apply to each type of regulation, which has led to the emergence of many design types of control valves.
From the point of view of the automation of industrial enterprises, each of them is regarded as an element of the automatic process control system, which takes place with the participation of liquid and gaseous working media and is regulated by the command information obtained.
Control valves include: pressure controller, temperature regulators, flow regulators (pressure differential), governor and balancing valves.
Pressure controllers are a type of control valve that automatically maintains the specified pressure of the working medium in the pipeline. Pressure controllers are after themselves (normally open) and up for themselves (normally closed).
Pressure differential regulators (flow rate) are a type of control valve, which automatically due to the pressure of the medium ensures the maintenance of a given pressure difference between the straight and back pipeline.
Temperature controllers are a type of control valves that automatically maintain the specified temperature of the working medium in the pipeline by changing its flow rate.
Governor valves are a type of control valves that ensure the maintenance of a specified flow rate in the pipeline and are controlled from an extraneous energy source (manual, electric drive, pneumatic drive).
Balancing valve is a type of control valve designed to limit the heat transfer rate in heating and hot water installations.