Sequence for opening the quick shut-off valve and the medium-pressure steam manual valve
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After warming the pipes with medium-pressure steam up to the quick-close valve, we open the quick-close valve and then the medium-pressure steam manual valve, followed by starting the machine. I would appreciate it if experts could tell me what the effects would be if the order is reversed.
After the quick-shut valve is opened, another important step is the static test, whose purpose is to ensure that the control steam valve can adjust the speed accurately based on its opening degree; failing to conduct this static test can lead to overspeed. To conduct static tests, it is necessary to ensure that there is no steam pressure in front of the quick-shut valve and that the turbine is shut down. So, for safety reasons, these two steps cannot be reversed in order. :lol
I don’t understand – is there another manual valve behind the turbine emergency shutdown valve in your system? The pipes have been heated all the way to the quick-close valve – then why is it still necessary to open the medium-pressure steam manual valve? Was the medium-pressure steam manual valve closed again after the pipes were heated, or is it the bypass valve that was used for heating the pipes?
Well, just turn it up a bit while warming the pipes; the temperature rise takes some time. Twenty to thirty tons of steam is sufficient for warming them up, and you can then open the steam control valve fully before starting operation
What does it mean that warming up requires twenty to thirty tons of steam?
After the turbine is started for the first time, low-speed warming-up is required, with the speed maintained at around 800 revolutions per minute for no less than half an hour. 800 revolutions require basically twenty to thirty tons of steam
Although there is an intake control valve to regulate the amount of air intake, during operation the position of this valve still needs to be adjusted based on feedback from the turbine’s speed. If the valve is opened fully without consideration for this feedback, the amount of steam reaching the turbine will be at its maximum level. Generally, intake control valves are not airtight and can leak; when the quick-shut valve is opened, a large amount of steam enters the turbine suddenly, causing various negative effects. After all, the adjustment of the valve position relies on speed feedback, which takes some time to occur. This can lead to scraping between the rotor, the shaft seals, and the bearing shells. Additionally, such sudden forces can increase the axial force on the rotor, potentially even causing the shaft to bend :)
Also, if the back pressure on the quick-close valve is too high, it may fail to open, which might be why the quick-close valve should be opened first before fully opening the manual valve
Also, if the back pressure on the quick-close valve is too high, it may fail to open, which might be why the quick-close valve should be opened first before fully opening the manual valve