In the process of steam production at our company, a critical component is the temperature and pressure reducing system. This system is responsible for reducing the steam generated by the boiler (without power generation via a steam turbine) from 2.48 MPa and 430°C down to 0.35 MPa and 170°C, in order to meet the requirements of other steam-consuming units within the facility.
The system includes a pressure-reducing valve and a temperature-reducing water distribution valve, both of which are double-seat valves with model numbers Y45/Y100-Dg150. These have been in operation for over four years and have generally met the production needs. However, during this time, several issues have emerged that affect efficiency and control:
- **Leakage**: The double-seat valve experiences significant steam leakage when fully closed, especially under conditions where steam passes through the turbine. This leads to energy loss and increased operational costs.
- **Limited Adjustment Range**: The valve’s adjustment range is narrow. Under low load conditions (steam flow below 10 T/h), the pressure cannot be properly regulated.
- **Poor Control Accuracy and Stability**: The existing system uses an outdated electric actuator with a lever mechanism, resulting in unstable performance and low control accuracy, making manual operation necessary.
- **High Maintenance Requirements**: Frequent maintenance (2–3 times per week) and lack of automation increase the workload on operators.
To address these challenges and improve process safety and efficiency, we decided to upgrade the pressure-reducing and temperature-reducing valves along with their control systems. Based on current process conditions, the new valves must meet the following specifications:
**Steam Pressure Reducing Valve:**
- Diameter: DN150, PN10
- Medium: Steam
- Temperature: Max 430°C
- Flow: Qmin 4 T/h, Qnor 15 T/h, Qmax 20 T/h
- Inlet Pressure: 2.45 MPa
- Outlet Pressure: 0.35 MPa
- Electric Actuator: 220VAC/50Hz, 4–20mA signal, with manual override
**Water Reducing Valve:**
- Diameter: DN32, PN10
- Medium: Water
- Temperature: 108°C
- Flow: Qmax 2500 kg/h
- Inlet Pressure: 0 MPa
- Outlet Pressure: 0.4 MPa
- Electric Actuator: 220VAC/50Hz, 4–20mA signal, with manual override
After evaluating various options, we selected the German manufacturer Auma for the electric actuators due to its superior performance in high-temperature environments, sufficient torque output, and proven reliability in similar applications. For the control valves, we considered manufacturers such as Fisher (USA), Neles (Finland), and Samson (Germany). Each provided detailed calculations and proposals based on our specific requirements, including integration with the Auma actuator.
Ultimately, we chose the Neles control valve model QXA-T5D13061DE4.3 and FCO1DWSXKLGTDH3, which offer excellent performance, reliable service, and competitive pricing. The delivery lead time is approximately 16–20 weeks, including 4 weeks for sea freight.
This upgrade is expected to significantly improve the efficiency, stability, and safety of the steam reduction process, while reducing maintenance and operational burden.
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