Centrifuge surge, how to adjust it

1. Open the anti-surge valve, mainly to keep the operating point away from the surge point. At a specific speed (inlet guide vane angle) and at a certain pressure, there is a minimum flow point. If the actual flow rate at the operating point is less than this flow rate, the compressor becomes unstable and we think the compressor surges (I personally believe that the essence of actual surge is that when the flow rate becomes smaller, the forward angle of the impeller flow channel inlet changes, resulting in unstable flow conditions in the impeller blade channel, leading to rotational stall, and further deterioration leading to surge). Therefore, the anti-surge control system (regulator) calculates based on the data measured by on-site instruments (temperature, pressure, flow) to obtain the actual operating point, and then compares it with the surge point (anti-surge line) to control the opening of the surge relief valve. 2. Because for process gas compressors, the anti-surge line returns to the inlet, so opening the anti-surge valve increases both the flow rate and the inlet pressure, and the outlet pressure decreases. For the air compressor, it is vented directly, only increasing the flow rate and reducing the outlet pressure. 3. You can understand it from two aspects. On the one hand, when the surge valve is opened, the flow rate increases and the outlet pressure increases. Then, in the performance curve of the compressor, the operating point moves downward and to the right (the anti-surge line is on the left, and the two extreme operating conditions of the compressor are surge on the left and blockage on the right), away from the surge point. On the other hand, as the flow rate of the compressor increases, the positive angle of attack of the gas into the impeller flow path becomes smaller, essentially eliminating surge. 4. Personal opinions, I hope industry experts can correct me.

“During the operation of the centrifuge, when the distance between the working point and the set point gradually becomes smaller, should the speed be increased or reduced?" Regarding the surge of this type of compressor, there are two types of surges based on the input capacity of a certain speed. One is caused by too low suction pressure, and the other is caused by excessive outlet pressure. Everything is based on the design pressure as the reference point, exceeding it is not advisable. If a problem arises, immediate measures should be taken to eliminate the surge. Then find the cause of the surge, eliminate it, and then resume production. Usually the equipment is equipped with matching equipment and can be adjusted within a certain range. The anti-surge valve is only an emergency adjustment and is usually fully closed. For reference.

I am a novice. When the working point is close to the anti-surge curve, I first increase the speed. Generally, when the distance is reduced, the inlet pressure of a section is also high. If the pressure is suppressed, the hydrogen gas is also high. I will first increase the speed to let the pressure drop. Once the pressure drops, its operating point will be far away from the surge curve. Then stabilize it for a period of time, check the inlet pressure, and then slowly reduce the speed. The poster said to reduce the speed, \ud83d\ude05\ud83d\ude05\ud83d\ude05 I panic when I encounter a point that is close to the surge curve. If I reduce the speed, I am afraid that it will get closer to the curve and cause a tripping incident, which will be a big deal. I'm a newbie, so I don't know if it's right or not. Can someone please correct me?

This post was last edited by lupg on 2022-4-13 10:37. The attachment is a schematic diagram of a randomly selected surge control line, which is used as an example to illustrate.: 1. The surge limit line is a line from the lower left to the upper right. The surge characteristics can be easily explained as: A low pressure ratio means a small flow, and a large pressure ratio means a large flow. 2. Generally, a control line is set on the right side of the limit line according to a certain ratio in the control system. When the working point reaches the control line, the anti-surge valve will be opened to move the working point to the right and away from the limit line. 3. Based on this principle, it depends on the characteristics of the compressor. Since the flow and pressure rise at the same time when the speed is increased, whether the working point approaches the limit line or leaves the limit line depends on the actual situation. 4. According to the principle shown in the diagram, increasing the flow rate is an effective measure to make the working point move away from the limit line. Therefore, opening the anti-surge valve is also a common and effective main measure. As for speed increase or decrease, it depends on the characteristics of the compressor.

Then why don't you open the surge valve?

I usually open the surge valve at 30