邮箱: info@baird-valve.com
电话: +86 13512908623
地址: Baixin Industrial Park, Ninghe District, Tianjin
This system typically consists of three basic components, forming a complete control loop:
temperature sensor
Role: The 'eyes' of the system.
Function: Real time measurement of the actual temperature of the controlled medium (such as pipeline water temperature, room temperature, tank liquid temperature, reactor material temperature), and conversion into electrical signals (such as resistance, voltage, current, or digital signals) that are transmitted to the temperature controller.
Common types: PT100 platinum RTD (high precision), thermocouple (high temperature resistance), NTC thermistor (low cost).
Temperature Controller
Role: The 'brain' of the system.
Function:
Input: Receive electrical signals from temperature sensors and convert them into actual temperature values.
Comparison: Compare the measured actual temperature with the user-defined target temperature (set point).
Calculation: Based on the preset control algorithm (such as on/off, PID), calculate according to the generated error.
Output: Send control signals (commands) to the actuator (electric valve).
Electric actuator+valve
Role: The 'hands and feet' of the system.
Function: Receive commands from the temperature controller (usually on/off signals or modulation signals), drive the motor to manipulate the valve opening, thereby accurately adjusting the flow of steam, cold water, hot water or other media through the valve, and ultimately achieving temperature control.
Common types:
Electric 2-way/3-way valve: the most commonly used type of valve.
Electric butterfly valve/ball valve: used for large diameter pipelines.
2、 Advantages and characteristics
The entire system operates as a continuous closed-loop feedback control process. Compared with pure mechanical constant temperature valves, this electronic control system has significant advantages:
High control accuracy: The temperature controller using PID algorithm can significantly reduce temperature fluctuations and achieve precise constant temperature (accuracy can reach ± 0.5 ° C or even higher), far exceeding the typical ± 1-2 ° C of mechanical valves.
Remote and centralized control: The temperature controller can be installed in the control cabinet or wall to achieve remote setting and monitoring, eliminating the need for access near potential high temperature or hazardous valve locations.
Powerful and flexible features:
Capable of multi-stage program control, automatically changing temperature settings based on time curves (for heat treatment, fermentation, and other processes).
It has alarm output function (such as high/low temperature alarm, sensor fault alarm).
Support communication functions (such as MODBUS, PROFIBUS, Ethernet), allowing integration into DCS/SCADA or other upper level management systems for intelligent factory management.
Extremely wide applicability: By selecting appropriate sensors, valves, and actuators, the system can adapt to extreme temperatures ranging from -200 ° C to over 2000 ° C, as well as various pressure conditions and corrosive media environments.
High adjustability: PID parameters can be adjusted and optimized according to actual site conditions to achieve optimal control performance.
III、 Main application scenarios
This system is used for almost all industrial processes and high-end civilian applications that require precise temperature control.
Application field
Specific scene description
Central air conditioning system
Control the outlet temperature of air handling units/fan coil units by adjusting the flow rate of cold/hot water (or steam) entering the coil. This is a classic application.
industrial process control
Temperature control of reactors, fermentation tanks, ovens, boilers, etc. The control accuracy is directly related to product quality and production safety.
heating system
By adjusting the mixing of high-temperature water supply and low-temperature return water at the mixing station, the mixed water temperature of the district heating/underfloor heating system is controlled to provide a constant and appropriate temperature for underfloor heating.
laboratory equipment
Constant temperature water bath, incubator, environmental testing chamber, etc. have extremely high requirements for temperature accuracy and stability.
Food and pharmaceutical industry
Applications with strict hygiene and temperature requirements, such as pasteurization production lines, in-situ cleaning (CIP) systems, and drug storage.
IV、 Selection and key considerations
Control algorithm selection:
On/off control: Low cost, suitable for applications with low requirements, but with poor control accuracy and frequent valve start-up.
PID control (proportional integral derivative): the choice for the vast majority of industrial scenarios. Provide smooth, high-precision, and stable control. Need to adjust PID parameters.
Valve selection:
Bidirectional valve: used to control single flow (e.g. only for hot water or only for cold water).
Three way mixing/diversion valve: used to mix two fluids (such as hot and cold water) or divert one fluid into two paths. Very suitable for hybrid control applications.
Selection of actuator type:
ON/OFF type: The valve can only be fully opened or fully closed (applicable to ON/OFF control).
Modulation type (analog control): It can receive signals such as 4-20mA or 0-10V, and position the valve at any opening (0%, 25%, 50%, 100%). This is necessary for precise PID control.
System compatibility:
Ensure that the signal types of sensors, temperature controllers, and actuators/valves are compatible (e.g. PT100 input, 4-20mA output).
The flow coefficient (Kv/Cv value) of the valve must be correctly sized according to the pipeline size and flow requirements. Valves that are too large or too small can cause control failures.
summary
In short, the "electric valve with temperature control system" is a powerful and highly customizable automation solution. It effectively connects the three links of sensing, decision-making, and execution through electrical signals, making it suitable for complex applications that require high control accuracy, remote monitoring, and integration.