What if the turbine emergency shutdown valve fails? (Participation rewards available)
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This post was last edited by yxmqh on 2010-11-9 at 11:29. Large steam turbines generally require long continuous operation periods. If prolonged operation leads to mechanical problems with the trip modules or quick-shut valves, resulting in those valves failing to close promptly or even becoming ineffective, what should be done in such situations? How to maintain daily care to prevent such things from happening! (No manual valve)
1. The quick-close valve should be subjected to regular short-stroke operation tests (see the instructions) to check whether the valve stem is covered in salt deposits or stuck. 2. The speed control valve should also be able to serve as a shut-off mechanism. 3. There should be a shut-off valve for the main steam as well
For routine maintenance, there is a test valve that allows for testing while the system is in operation; frequent use of it helps to prevent sticking. Some quick-close valves also have electric or manual actuators to close them. If neither of those is available, in the event of sticking, it is still possible to stop the machine by using the speed control valve; however, speed control valves generally do not have good sealing properties, so the only alternative is to use the shut-off manual valve.
The quick-shut valve failed, so the only option was to reduce the speed using the governor and close the main steam inlet valve. For the maintenance of quick-close valves, applying molybdenum disulfide to the sliding parts can help prevent sticking.
Conducting regular tests that move the valve stem over short distances can prevent jamming of the valve stem and packing. The inlet valve on the main steam pipeline can be closed to shut down the turbine
As the friends mentioned above, under normal circumstances it is possible to use a testing facility to check whether the quick-shut component is stuck, but if it fails, I think the only option is to close the main steam inlet valve and carry out subsequent repairs; there’s no other solution. I hope someone with more experience can suggest a good solution! ~
What the brothers upstairs said makes a lot of sense; daily maintenance indeed works that way, and there aren’t any other good solutions. Additionally, options such as reducing the speed through control valves or closing the steam valves are rather desperate measures; doing so is certainly not ideal. But if those measures aren’t taken, the unit still won’t stop running. I wonder if there are any other solutions? Did the unit quickly reduce its speed to come to a complete stop?
Tests on the quick-close valves in our facility are rarely carried out online, as people are not confident about them, and no one touches them while the equipment is in operation. I’m not sure if doing this is a good thing or a bad thing
Reply to 8# sean816: We didn’t dare to try it either, but after the major maintenance, by examining its structure, it’s clear that the test oil won’t cause it to close; the valve stem can only move about 1 cm. It’s still better to conduct tests regularly
I think that when it comes to rapid shutdown, after coordinating and reaching agreements in terms of production processes and the personnel on duty, etc., several emergency shutdown or interlock shutdown methods can also be used on-site. However, in doing things this way, preliminary contact and preparation are essential and cannot be overlooked.
It’s the same in our unit as well; if improper operation causes the quick-shut valve to close, there is a high risk of plant shutdown along with serious consequences in terms of accountability. Therefore, even though the manual states that it is possible to test the quick-shut device regularly while it is in operation, we don’t dare to do so.