Anti-surge control for centrifugal compressors

The default margin, simply put, is the distance between the operating point and the surge line; it is determined during the design of the unit. The various parameters involved in its calculation are numerous and complex. During actual operation, due to changes in operating conditions or deviations from the designed conditions, it is necessary to adjust the margin as appropriate – that is, to increase it. By doing so, the unit is less likely to experience surge. Surge count, which is the number of times surge occurs after the unit starts up. The surge PID is a variable-parameter control of the surge line; by adjusting the three parameters of the proportional coefficient K, integral time TI, and derivative time TD, it is possible to control the response speed and amplitude of the surge valve. As the operating point moves from right to left, gradually approaching or even crossing the control line, both the K value and TI value increase, thereby speeding up the response of the surge valve and preventing the operating point from crossing the surge line and causing surge. However, there are limits on these values, which can be found in the ITCC. However, in certain extreme situations, the PID control may not be able to open the surge valve in time; in such cases, the override mechanism in the system is activated. Simply put, it involves setting a certain flow rate, and when the actual flow rate falls below this value, the override takes over. Manually specified refers to the opening degree of the surge valve set by the current operator; valve position can be entered only in partial manual (semi-automatic) or fully manual mode. The one among these three that produces the larger output value is the one that takes effect. It’s just my simple understanding; I hope it’s useful. Please point out any mistakes if there are any!