What are the shutdown steps for a back-pressure steam turbine? What tasks are there after shutting down?

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Parking steps: a. Maintain clear communication with the control post. Pay attention to the pressure in the steam pipeline network. b. When loading, follow the principle of reducing pressure first and then reducing speed to prevent the unit from entering the surge zone. c. When the unit drops to the lowest control speed of the 505 governor, external air supply for the dry gas seal is activated on-site. d. Reduce the unit to no-load speed using the 505 governor or the on-site no-load/loaded rating switch. e. Press the unit shutdown button, and the unit’s speed gradually decreases to 0 rpm. Precautions after parking: a. When the unit’s rotational speed is zero, activate the cranker on site and confirm that the unit rotates properly. b. Open the turbine cylinder drain, steam drain, and vent. c. Adjust the cooling water flow of the oil cooler to maintain the oil temperature in the tank at around 35 degrees. If there is anything missing, please fill it in.

Normal shutdown: 1. Departments should be notified in advance to make preparations before reducing the load； 2. Test each auxiliary oil pump ； 3. Check whether there is any sticking in the main valve stem and the control valve stem ； 4. Check the temperature and pressure reduction bypasses ； 5. Gradually reduce the speed and load; the rate of such reduction can be determined by referring to the process of increasing speed and load. Constantly monitor the expansion and vibration conditions of the unit ； 6. Make sure to check whether the regulating valve is stuck. If the regulating valve gets stuck and cannot be resolved during operation, the main air valve or electric isolation valve should be gradually closed to reduce the load and shut down the system. 7. When the load is reduced to zero, upon receiving the signal, shut off the main steam valve by closing it; turn the handwheel of the main steam valve control mechanism all the way down, and check to ensure that the main steam valve is properly closed ； 8. Close the electric isolation valve on the backpressure exhaust line, open the vent to atmosphere valve, and shut down the steam seal heater. 9. During the shutdown and speed reduction process, it is necessary to check whether the electric oil pump starts operating automatically; if not, the oil pump must be started manually to maintain the lubricating oil pressure at least at 0.055 MPa (gauge pressure) ； 10. After the rotor has come to a complete stop, perform manual turning of the rotor: turn it every 10 minutes within 2 hours of shutdown, and every 15 minutes after 2 hours of shutdown, until the turbine is fully cooled (the metal temperature of the cylinders is below 150 degrees) ； 11. When the oil temperature at the cold oil cooler outlet drops below 35 degrees, close the water side valve of the cold oil cooler ； 12. Close all valves on the soda pipeline, open the direct drain valve, and close the drain valve leading to the cylinder body to prevent air leakage into the cylinder.