1、 Process conditions and pre renovation process conditions
In the process production of steam for our company's own use, there is a key equipment called a temperature and pressure reducer. This equipment reduces the temperature and pressure of the steam produced by the boiler (without generating electricity through a steam turbine) from 2.48MPa430 ℃ to 0.35Mpa170 ℃ to meet the needs of other steam consuming units in the company; The pressure reducing valve and water distribution valve on this temperature and pressure reducer are matched with the factory, and the model is Y45/Y100-Dg150 double seat pressure reducing valve and equipment. Since their production by the company, they have been running continuously for more than 4 years and can basically meet the company's production requirements. However, during the more than 4 years of operation, we have also found some problems with the equipment, mainly manifested in the following aspects:
The leakage of the pressure reducing valve is large, especially when steam is generated through a steam turbine. Under such conditions, the pressure reducing valve should be closed tightly. However, due to the structure and product quality of the double seat valve itself, there is still a large amount of steam leakage when the valve is in the fully closed position, causing unnecessary energy loss and increasing production costs.
◆ Small adjustment range: From the adjustment characteristics of the double seat valve, it can be seen that the adjustment range of this valve is relatively small. According to the actual operation of the process, when the boiler is running at low load (steam production capacity is 10T/h), this pressure reducing valve cannot adjust the steam pressure, that is, when the steam flow rate is less than 10T/h, it cannot adjust the steam pressure.
Low control accuracy and poor stability: The control of the pressure reducing valve and the temperature reducing valve uses an angle stroke electric actuator with a servo amplifier, and the connection between the actuator and the valve stem uses a lever. The model of the servo amplifier is too outdated, and the adjustment of balance and stability is too complex. Due to the industrial processing of electronic components used in the servo amplifier and feedback board, the environmental requirements are also high, and the operation is unstable in high temperature and dust environments. The connection design between the actuator and the valve is unreasonable. Although the multi fulcrum lever connection method can amplify the output force of the angle stroke electric actuator, there are large mechanical gaps at each connection point of the lever, which cannot meet the requirements of the entire control system for control accuracy and stability, Therefore, the control accuracy and stability of these two valves are poor and cannot meet the requirements for automatic operation. Since production and operation, they have been in manual and on-site operation, with low control accuracy.
Large daily maintenance volume and difficult process operation: Due to certain defects in the equipment selection of the control system at that time, there are always some problems during actual operation, with 2-3 repairs per week. Moreover, the process has not been put into automatic mode since the beginning of production, which increases the difficulty of operation for process operators.
3、 How to solve equipment problems and carry out process transformation:
In order to solve the problems existing in the above equipment and better meet the requirements of process safety production, I have decided to modify the pressure reducing valve and temperature reducing water distribution valve and their control system on the temperature regulator. According to the requirements of the process and the current production situation of the company, these two valves should meet the following process production conditions:
a) Steam pressure reducing regulating valve:
Process pipe diameter: 150mm (DN150, PN1O) medium: steam temperature: Max430 ℃
Flow rate: Qmin4T/hQ5T/hQmax20T/h Inlet pressure: 2.45MPa
Export pressure: 0.35MPa with electric actuator: power supply is 220VAC/50Hz
The input signal is 4-20mA, and the valve position feedback signal is 4-20mA
The actuator is equipped with a manual on/off handle or handwheel
b) Cooling water valve:
Process pipe diameter: 32mm (DN32, PN10) medium: water temperature: lO8 ℃
Flow rate: Qmax2500kg/h Inlet pressure: 3.0MPa
Export pressure: 0.4MPa with electric actuator: power supply is 220VAC/50Hz
The input signal is 4-20mA, and the valve feedback signal is 4-20mA
The actuator is equipped with a manual on/off handle or handwheel
Based on the above process conditions, we will select the regulating valve and actuator separately. Firstly, we will determine the actuator, then select the regulating valve, and finally the supplier of the regulating valve will provide a complete set.
3、 Selection of electric actuators
Based on the needs of process operation and the requirements of process personnel, we have decided to choose an electric actuator for the actuator of this regulating valve. Based on the information we have, after multiple comparisons, we have selected the following three professional manufacturers of electric actuators that are among the best in the world.
(1) Japan KOSO (2) Germany Auma (3) UK Rotork

Main products:Medium pressure oxygen pressure reducer,High pressure oxygen regulator,Natural gas pressure regulator