The air compressor vent valve is manually regulated; why is it fully open automatically? The low pressure is causing the air separation unit to shut down
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The air compressor vent valve is manually regulated, while the anti-surge valve is automatically regulated； Within one minute, the vent valve automatically opened fully for no apparent reason; then the anti-surge valve adjusted itself to close partially in order to maintain the pressure at the compressor outlet. However, due to the difference between the diameter of the vent pipe and that of the anti-surge pipe, the outlet pressure remained low, which caused a cascade shutdown of the subsequent systems
The surge prevention valve requires a relatively high coefficient, which enables it to effectively control flow and pressure and thus protect the equipment and pipelines. As for why the relief valve needs to be adjusted manually, I’m not quite sure; usually, such devices are supposed to be automatically regulated as well.
The manual adjustment of the vent valve is done via a controller, but for the sake of machine safety, there is a preferred option that is not under human control. This kind of issue tends to occur in systems with well-designed anti-surge control systems, especially during winter when the guide vane opening is small and the current is low.
“Did the relief valve automatically open fully within one minute for no reason? This claim is not valid; there must be some reason for it. Is the electrical wiring in good condition? ； Signal interference ； Human factors. Additionally, if it is a test run, there are also setup issues. (For reference)
No other causes have been found; it appears that no one was operating the system. The trend charts for the relief valve and the anti-surge valve showed activity at the same time, and then everything stopped working
Anti-surge control line? When the guide vane opening is small and the current is low in winter? Bro, could you explain it in more detail? Have you encountered such problems? I’ve only been working with air separation for half a year, and there are many things I don’t understand
Reply to 2#: The manufacturer at the Zhuhai liquefaction plant said that the vent valve and the anti-surge valve cannot both be set to automatic mode; only one of them can be controlled in automatic mode while the other is operated manually
1. First, you need to check the electrical wiring issues. 2. Next, examine the wiring of the vent valve’s instruments and adjust them as necessary. 3. Then, check whether there are any problems with the DCS wiring and settings. 4. Finally, verify if there are any interlock settings in place and whether those settings are correct.
This morning, one air compressor was shut down due to issues with the power grid; I think it’s related to the low load on that compressor.
Reply to 7# Snowy City: I’m not quite sure about this. Controlling the venting pressure manually? And on top of that, this pressure value also has a cascading effect? After all, it’s impossible to achieve such precision manually.
I don’t quite understand how manual control can lead to interlocking; it’s very rare. Is there a program set up for automatic venting? Here, the reflux at the booster end of the expander is controlled by such a program; when the reflux valve is manually closed to a certain position, the program takes control first, and manual control becomes ineffective at that point.