Compressor surge control, or better stated, anti-surge control, is always a popular subject here on the blog. Posts written years ago still remain highly viewed. Preventing surge is critical for centrifugal and axial compressors. Wikipedia defines it:
Axi-symmetric stall, more commonly known as compressor surge; or pressure surge, is a complete breakdown in compression resulting in a reversal of flow and the violent expulsion of previously compressed air out through the engine intake, due to the compressor’s inability to continue working against the already-compressed air behind it. The compressor either experiences conditions which exceed the limit of its pressure rise capabilities or is highly loaded such that it does not have the capacity to absorb a momentary disturbance, creating a rotational stall which can propagate in less than a second to include the entire compressor.
The compressor will recover to normal flow once the engine pressure ratio reduces to a level at which the compressor is capable of sustaining stable airflow. If, however, the conditions that induced the stall remain, the return of stable airflow will reproduce the conditions at the time of surge and the process will repeat. Such a “locked-in” or self-reproducing stall is particularly dangerous, with very high levels of vibration causing accelerated engine wear and possible damage, even the total destruction of the engine.
Given the possibility of unplanned downtime all the way to equipment damage and risk to personal safety, it’s critical to recognize an impending surge condition and take immediate action to prevent it. The typical methods for accomplishing surge control are either a blow-off to atmosphere or recirculation from the outlet to the inlet of the compressor. The anti-surge control strategy is tightly integrated with the compressor load control strategy. The control strategy requires not only a fast acting controller, but a fast acting valve to release or recirculate the flow.I mention this as background because Emerson’s Fisher Valves & Instruments team has worked with Compressor Controls Corporation to establish to establish a new optimized anti-surge control simulation at the Emerson Innovation Center in Marshalltown, Iowa.
In this 2:50 YouTube video, Optimized Anti Surge Control Simulator, Emerson’s Tom Bass and CCC’s Rick Fausel describe the Innovation Center simulator setup. The purpose is to show the control strategies working with the control valve to meet the application requirements for surge protection.
Process manufacturers can actually see a process upset condition and how the CCC controller and Fisher antisurge control valve work together to avoid a surge condition. An analog output runs from the anti-surge controller to the valve, with valve position feedback running back as an analog input to the anti-surge controller. Trends show the response from when the valve position change command was made.
To see it in action for yourself, you can schedule a visit to the Innovation Center by working with your local Fisher valve sales office. You can also connect and interact with other valve specialists in the Valves track of the Emerson Exchange 365 community