How should the compressed air system of a power plant be designed? Instrument air, maintenance air, and reliability requirements.

The Core Role of Compressed Air Systems in Power Plants

In the daily operation and maintenance of power plants, compressed air systems play an indispensable role. They not only supply power to pneumatic control valves but also provide an air source for equipment maintenance, purging, and cleaning. A well‑designed compressed air system is the foundation for ensuring the safe, stable, and efficient operation of generator sets.

Design Requirements for the Instrument Air System

Instrument air is primarily used to power pneumatic actuators and control instruments, placing extremely high demands on air quality and supply continuity.

• Temperament standardsInstrument air must undergo rigorous drying and filtration to ensure it is free of oil, water, and particulates. The dew point temperature must be lower than the local historical minimum temperature to prevent condensation or freezing inside the piping.
• Continuous gas supplyThe control system is highly sensitive to interruptions in the air supply. The design must incorporate a dual‑circuit air supply or a backup air source to ensure an uninterrupted supply of instrument air in the event of a failure of the main air compressor.
• Pressure stable: The end of the pipeline network must maintain a stable operating pressure to prevent pressure fluctuations from causing control valves to malfunction or respond sluggishly.

Design Features of the Gas System for Maintenance and Overhaul

Maintenance air is primarily used for equipment purging, powering pneumatic tools, and on-site cleaning, and its design priorities differ from those of instrument air.

• Flow and Pressure Requirements: Maintenance air consumption typically features intermittent, high‑flow demand. During design, the peak air demand must be accurately calculated to ensure that, when multiple pneumatic tools are operating simultaneously, the pipeline pressure does not experience a significant drop.
• Independent pipeline networkTo prevent fluctuations in the maintenance air supply from affecting the quality and pressure of the instrument air, it is generally recommended to separate the maintenance air piping network from the instrument air piping network downstream of the air receiver tank, or to install a dedicated pressure-reducing valve assembly.
• Safety and ConvenienceThe arrangement of maintenance access points shall cover the main equipment areas and be equipped with the necessary pressure-reducing and filtration devices to ensure the safety of operating personnel.

Key Measures to Enhance System Reliability

Reliability is a core consideration in the design of compressed air systems for power plants and must be optimized from both equipment configuration and system architecture perspectives.

• Redundant configuration: Air compressors and dryers shall be configured in a redundant mode. When either unit requires maintenance or experiences a failure, the standby unit shall automatically come online, ensuring that the system’s total output remains unchanged.
• Gas storage tank design: Properly sizing the gas storage tank not only helps mitigate pressure fluctuations during peak demand but also provides a critical emergency air supply during compressor switching or brief shutdowns.
• Piping Layout and MaterialsPipeline network design should minimize bends and dead ends, adopting a looped or dual‑mainline configuration to enhance gas supply reliability. Pipe materials should be selected for their excellent corrosion resistance to prevent internal rust from contaminating the gas supply.

System Maintenance and Monitoring Design

Good design must also be supported by robust monitoring capabilities. The system should integrate real-time monitoring of critical parameters such as pressure, temperature, and dew point, and incorporate comprehensive alarm and interlock protection mechanisms. By leveraging an automated control system, intelligent scheduling and energy‑efficiency management of compressor units can be achieved, ensuring high reliability and cost‑effectiveness throughout the equipment’s entire lifecycle.