The ratio of the maximum selected valve capacity to the valve capacity demanded by the compressor surge curve (worst case scenario) should fall between 1.8 and 2.2. A small change in controller output will have a large flow from the oversized valve. Oversized valve will deliver excess flow to the compressor which leads to the compressor running in the choked flow region. Depending upon actuator type, volume tank and related accessories may be required.Īnti-surge valve must be neither undersized nor oversized so as to keep compressor operation within the desired operating region/envelope.Īn undersized valve will fail to provide enough recycle flow/ minimum flow which leads to the compressor frequently running on the surge limit line. The anti-surge control valve typically comprises a valve, actuator, positioner, and other accessories, like volume booster, solenoid, and position transmitter. Anti-surge valve Design, Sizing, and Selection Anti-surge controller logic, control parameters for tuning.Anti-surge valve design, sizing, and selection.Two important design aspects should be looked into as overall compressor operation is impacted by the controller parameter as well as a control valve. Whenever the process upsets the role of this valve starts. The operating limits for the compressor are the surge line and the choke flow line, beyond which compressor operation can cause severe mechanical damage over and above process upsets.ĭuring the normal operation of the compressor, this anti-surge valve remains in closed condition. If you correlate the compressor head (Pressure) vs flow curve, you will notice that minimum flow corresponds to higher head, and maximum flow corresponds to minimum head pressure, for a given one speed. Measurement of compressor suction pressure, suction temperature, suction flow, discharge pressure, and discharge temperature is important to calculate proximity to surge line. The basic function of the anti-surge controller and control valve is to maintain minimum flow through compressor and handle the surges. During the extreme condition, the compressor has to run in minimum flow condition (keep running without any trip) There is a change in the compressor operating point (which is moving towards surge line). To prevent the compressor from surges, a reversal of flow, process instability, and compressor damage, the compressor discharge flow is diverted to compressor suction via an anti-surge / recycle control valve.
![the surge 2 map the surge 2 map](https://www.overclockers.ua/news/games/124852-The-Surge2-settings-3.png)
Generally, surge cycles are at a rate of 0.3s to 3s per Surge cycles, during surges compressor vibrates, the temperature rises, and causes noise. This situation arises when there is an emergency shutdown or downstream consumers are not available. Since compressor keeps running additional build up pressure has to transfer to atmosphere or suction side of compressor. It is an operating point where downstream pressure of compressor discharge rapidly increases due to a decrease in flow demand from the compressor outlet. “Surge” phenomenon is common in Centrifugal compressors.