Please analyze the reasons for the automatic shutdown of a back-pressure steam turbine compressor
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First, let’s discuss the situation on site: there was significant air leakage from the turbine casing, and the vapor seal extractor was operating at near-positive pressure. The inlet valve of the vapor seal extractor was opened to adjust its negative pressure to a normal level. However, the air leakage from the turbine casing did not decrease significantly, and water began to appear in the discharge outlet of the vapor seal extractor; no water could be drained from any of the condensation drainage points. Before shutdown, due to issues with the utility systems, the steam inlet pressure of the turbine fluctuated and first dropped to 3.2 MPa. Then the steam inlet pressure began to rise rapidly (4 MPa at shutdown), the temperature dropped (260°C at shutdown), the vibration level of the turbine shaft increased (only 30 μm when the speed control valve was closed), and the temperature of the turbine shaft rose (up to 80°C). The speed control valve of the turbine was closed from 50 to 0 in 10 seconds; 10 seconds after the valve was fully closed, the compressor’s rotation speed started to decline. When the speed dropped to 3000, the vibration level of the turbine bearings reached 90 μm. The interlock for shutdown due to shaft temperature is 105°C, and the interlock for shutdown due to shaft vibration is 100 μm. No parameters have reached the interlock value; why does the speed control valve close automatically? Moreover, I saw that in the other workshops the steam temperature didn’t drop as quickly at that time
If any of the seniors need specific parameters, I can provide them
The trend of the speed control valve and rotational speed remained stable, staying linear until shutdown
The topic mentions something related to compressors, but that’s not mentioned in your description. Check whether it is caused by the interlock signal sent from the compressor side.
I’ve looked at the trend chart many times; there’s no issue with the compressor’s trend
Is there any expert who can help analyze this?
1. Is there a problem with the quick-shut oil pressure or other lubricating oil pressures? 2. Can rapid changes in steam pressure and temperature lead to the presence of water? It affects the turbine; in severe cases, it can cause damage to the impeller. Also, did the turbine’s speed increase due to overpressure, which led to the shutdown of the quick-shut valve and a decrease in the compressor’s speed, resulting in a stall and shutdown? It’s just my personal opinion; I haven’t been in this role for many years now, so I’ve lost a lot of familiarity with it. Please point out any mistakes
It seems that this might have been triggered as a form of self-protection; checking the trends at the engineer’s station should help clarify things. :lol
The trend was adjusted; no alarm was triggered before the speed control valve was closed. The first alarm occurred when the shaft vibration reached 90μm after the speed control valve was fully closed, with the interlock value set at 100μm
1. There is no trend in the oil pressure for rapid shutdown; the lubrication system was functioning normally before shutdown. 2. The rotation speed, the opening degree of the speed control valve, and the inlet differential pressure were also normal before shutdown, with straight-line trends in these values. I work at a small factory; we restarted the compressor immediately after shutdown. The reason for the shutdown is unknown. Additionally, the compressor monitoring system is damaged. I also want to ask: if steam contains water, is it necessary to disassemble the compressor for inspection?
1. There is no trend in the oil pressure for rapid shutdown; the lubrication system was functioning normally before shutdown. 2. The rotation speed, the opening degree of the speed control valve, and the inlet differential pressure were also normal before shutdown, with straight-line trends in these values. I work at a small factory; we restarted the compressor immediately after shutdown. The reason for the shutdown is unknown. Additionally, the compressor monitoring system is damaged. I also want to ask: if steam contains water, is it necessary to disassemble the compressor for inspection?