In the production process automation system, the control valve is an essential and indispensable link, called the “hands and feet” of the production process automation, is one of the terminal control elements of the automatic control system.

The simple flow path and low resistance of the control valve make it suitable for general forwarding use (installation). However, in the case of a high-pressure drop, the valve is used in reverse to improve the unbalance force, reduce the damage to the spool, facilitate the medium’s flow, and avoid coking and blockage of the valve. When using the control valve in reverse, it is essential to avoid long periods of small openings to prevent strong oscillations and damage to the spool. Especially in the trial production phase of chemical plants, due to the low load during trial production, the design process conditions are unlikely to meet the requirements soon, the reverse use of the control valve should be avoided as far as possible to avoid a long period of small opening conditions to prevent damage to the control valve.

The control valve is composed of two parts: the actuator and the valve. From a hydrodynamic point of view, the regulating valve is a throttling element whose local resistance can be varied. Therefore, the regulating valve is designed to change the resistance coefficient by changing the stroke by the input signal, thus regulating the flow.

Pressure instrument is a critical process instrument in industrial production. For example, if the pressure exceeds the rated value in high-pressure vessels, it is unsafe and must be measured and controlled. In some industrial production processes, stress directly affects the quality of the product and production efficiencies, such as ammonia, nitrogen, and hydrogen being synthesized under a certain pressure, and the size of the stress directly affects the yield level. In addition, under certain conditions, the pressure measurement can also indirectly lead to parameters such as temperature, flow, and level.

As the most crucial process instrument in industrial production, level measurement, together with temperature, pressure, and flow rate, is one of the industry’s four most critical working parameters. Technology development has resulted in multiple level measurement methods, from the old scale to the modern ultrasonic and radar measuring instruments. Level process instrument technology has also undergone a quantum leap.

Temperature measurement instruments are industrial process instruments that measure the degree of heat and cold of an object. It uses thermocouples and RTD as the temperature measuring element. The output signal from the temperature measuring element is sent to the transmitter module, which is converted into a 4~20mA current signal 0-5V/0-10V voltage signal with a linear relationship with the temperature after the circuit processing of voltage stabilization and filtering, operational amplification, non-linear correction, V/I conversion, constant current and reverse protection, etc., and RS485 digital signal output. A temperature transmitter is widely used in petroleum, chemical, chemical fiber, textile, rubber, building materials, electric power, metallurgy, medicine, food, and other industrial fields on-site temperature measurement process control.