Excuse me.

At this point, the vibration of the expander and the shaft temperature are likely to rise significantly; the expander is probably going to shut down due to interlocks, so operations need to be restarted~~

This post was last edited by mnmxj on 2016-12-29 at 18:11. 1. Is it due to a problem with the check valve itself? Signal error or air supply issue. 2. Fully opening the backflow valve at the expansion machine’s inlet is one of the sequential actions that occur in case of an expansion machine failure; check whether all the parameters of the expansion machine are normal

The backflow valve is controlled by the expander’s logic interlock; if there is no fault with the valve, then it must be that a parameter of one of the expanders has exceeded the set interlock value

Turn the reflux valve fully open to determine what is causing the issue. In some units, the reflux valve opens once a speed alarm is triggered; in such cases, close the reflux valve of the expander, but do not close it completely – just ensure that the speed remains normal. Then adjust the process parameters to restore normal temperatures and pressures ahead of the expander, and gradually close the reflux valve thereafter. Sometimes having the backflow fully open can cause high vibration in the expander, which triggers an interlock; in such cases, the expander must be shut down, rather than dealing with the situation by keeping the backflow fully open. 2. Fully opening the backflow valve of the expander inevitably reduces the air extraction volume of the booster, resulting in an increase in exhaust pressure. The backflow valve will play a role in regulation; it is also possible for the operating point of the booster to enter the surge zone, which in turn causes the backflow valve to open fully. In such a case, the pressure of the high-pressure air is significantly affected as well. For the air separation unit as a whole, an increase in the exhaust pressure of the air compressors leads to a slight reduction in the total amount of air entering the tower. The amount of air in the high-pressure channel decreases significantly, while the increase in the amount of air flowing in the low-pressure channel is relatively small. This results in a temporary disruption of the material balance between the inlet and outlet of the tower, affecting the temperatures of oxygen, nitrogen, and other gases at the plate stages; therefore, adjustments need to be made to the amount of gas exiting the tower.

Just take a look at the alarm and interlock information to understand