Compressor anti-surge control

Compressor anti-surge control is a vital aspect of ensuring the safe and efficient operation of centrifugal and axial compressors. In this blog post, we will explain what compressor surge is, why it is harmful, and how to prevent it using anti-surge control systems.

Compressor surge is a phenomenon that occurs when the flow rate of the gas through the compressor drops below a certain value, causing the pressure ratio across the compressor to increase rapidly. This results in a reversal of flow direction, which creates pressure pulses and vibrations that can damage the compressor blades, bearings, seals, and other components. Compressor surge can also reduce the performance and efficiency of the compressor, leading to increased energy consumption and emissions.

To avoid compressor surges, anti-surge control systems are used to monitor the flow and pressure conditions of the compressor and adjust the inlet or discharge valves accordingly. Anti-surge control systems can be classified into two types: active and passive. Active anti-surge control systems use sensors and actuators to regulate the flow and pressure of the gas, while passive anti-surge control systems use mechanical devices such as orifices or bypass valves to create a resistance or a bypass path for the gas.

The main components of an anti-surge control system are:

- A flow transmitter that measures the actual flow rate of the gas through the compressor

- A pressure transmitter that measures the discharge pressure of the compressor

- A controller that calculates the surge line based on the flow and pressure data and compares it with the actual operating point of the compressor

- A valve actuator that controls the opening or closing of the inlet or discharge valve based on the controller's signal

The anti-surge control system works by keeping the operating point of the compressor above the surge line, which is a curve that represents the minimum flow rate required for stable operation at a given pressure ratio. If the operating point approaches or crosses the surge line, the controller sends a signal to the valve actuator to open or close the valve, depending on whether an active or passive system is used. This changes the flow and pressure conditions of the compressor, moving it away from the surge line and restoring stable operation.

Anti surge control systems are essential for protecting compressors from surge damage and ensuring their optimal performance. By understanding how they work and how to implement them, you can improve your compressor's reliability, efficiency, and safety.