21. What are the inspection and startup steps before starting the deaerator?
Answer: (1) Check and verify that the system valve positions are correct, and test that all interlocks and alarms function normally. (2) Check that manhole covers are closed and that equipment piping and insulation are intact and in good condition. (3) Coordinate with thermal and electrical personnel to energize monitoring instruments, and ensure the electric and adjustable doors are powered up, their travel and test switch operations are normal. (4) Coordinate with the chemistry team to prepare an adequate supply of demineralized water. (5) Ensure that the standby steam source is fully drained for pipeline preheating, and appropriately open the deaerator vent valve. (6) Start the demineralized water pump or condensate pump to supply water to the deaerator. (7) When the water level rises to 1000 mm, gradually open the steam supply to begin heating the deaerator. (8) Heating begins as water is added to the deaerator; when the water level reaches 1450 mm, gradually increase the deaerator feedwater temperature and supply water according to boiler requirements. (9) During unit startup, when the third extraction pressure reaches 0.3 MPa, open the third extraction motorized valve, and gradually throttle and close the standby steam source valve. (10) After unit condensate recovery, open the valves directing condensate to the deaerator as appropriate, adjust the condenser water level, and close the drain valve before the #2 low-pressure feedwater outlet. (11) When switching high-pressure feedwater drainage to the deaerator, pay attention to its pressure and water level.
22. How to normally start a feedwater pump?
Answer: Pre-start checks:
1.1 Open the recirculation gate.
1.2 Remove any debris on the pump casing and clean up the site; check whether the foundation bolts are loose.
1.3 Inject lubricating oil into the bearings to the specified level: above the center and between 1/2–2/3.
1.4 Manually rotate the rotor to ensure it moves freely and observe whether the lubrication oil ring inside the bearing rotates.
1.5 Open the valves on the cooling water pipelines, ensuring the cooling water pressure is 0.1–0.2 MPa, and check for water leakage in each cooling chamber; also verify the seal water supply is normal.
1.6 Check and confirm that the motor rotation direction is correct.
1.7 Pay attention to the inlet water pressure and temperature; when t ≤ 105°C, the pressure at the inlet gauge should not be less than 0.09 MPa.
1.8 Ensure the feedwater pump is fully filled with water.
1.9 Open the feedwater pump recirculation manual gate (after normal operation, determine the valve position as needed) and close the outlet motorized gate.
2.0 Start the feed water pump motor. (Check that the motor insulation is normal and power supply is functioning properly)
2.1 Check whether the pressure and temperature of the feed water pump are normal. After a 50-second delay, open the outlet valve (adjustable) and open the water outlet gate, while observing whether the feed water pump is operating normally.
2.2 Check whether the oil ring in the sliding bearing is working properly, and adjust the recirculation according to boiler requirements to meet the needs of the boiler.
23. Steps for starting and stopping AC and DC lubricating oil pumps:
Starting:
(1) Check that the lubricating oil system has completed its operation, that the work permit has been retrieved, and that all safety measures have been restored.
(2) Check that the pump rotor rotates freely, verify with electrical measurements that the insulation of each motor is good, and supply power to the pump motor.
(3) Start the pump and check that pump current, sound, vibration, and bearing temperature are all normal.
(4) Ensure that the main oil tank temperature, oil pressure, and oil level meet the starting conditions.
(5) Engage the pump interlocks as required.
Stopping:
(1) Turn off the pump interlock switch.
(2) Stop the pump operation.
(3) If a backup is needed, engage the interlock switch.
24. How to operate when half of the condenser is out of service?
Answer:
(1) Contact the shift supervisor, reduce the unit load to below 25 MW, and start the standby circulating water pump as needed, but the water-side pressure must not exceed the specified value. Ensure that the vacuum is not below 87 KPa; otherwise, reduce the unit load until it returns to normal. (2) Close the inlet and outlet gates of the condenser on the cleaning side, as well as the cooling water gates. Monitor the circulating water pressure on the cleaning side to prevent the inlet connection gate from being improperly sealed and causing pressure buildup.
(3) Close the outlet gate of the cleaning side rubber ball chamber and the inlet gate of the rubber ball pump.
(4) Open the water drainage gate, air release gate, and inlet and outlet pipeline drainage gates on the cleaning side of the condenser.
(5) When the circulating water pressure on the cleaning side has dropped to zero and safety measures are confirmed in place, and the power to the circulating water pump and inlet/outlet gates is off, work may commence.
Recovery after half-side condenser maintenance:
(1) Check that the maintenance work is completed, retrieve the work ticket, and restore measures.
(2) Ensure no debris remains inside the condenser, close the water-side manhole and drainage gates, and open the air release gate on the cleaning side.
(3) Slowly open the circulating water outlet gate on the cleaning side to pressurize the water side, and check that the water-side pressure of the operating side condenser shows no significant change.
(4) Close the air release gate once water starts flowing out.
(5) Open the condenser inlet gate and cooling water gates. After checking that everything is normal, contact the shift supervisor, gradually restore the load to normal, and make the necessary adjustments.
25. What are the common causes of changes in the main engine oil tank level?
Answer: The reasons for the increase in the main engine oil tank level are as follows:
(1) Excessive pressure in the equalizing tank or too much steam at the end shaft seal.
(2) Malfunction of the shaft air extractor, causing the shaft seal steam to vent poorly, leading to water in the oil.
(3) Leakage in the copper tube of the cooler, with water pressure higher than oil pressure.
(4) Oil level gauge sticking, resulting in a false oil level.
(5) When starting, high-pressure oil pump and lubricating oil pump shaft cooling water leaks into the oil.
(6) When the oil temperature at the cooler outlet rises and viscosity decreases, the oil level also rises.
(7) The purifier filter oil pump cannot automatically stop when reaching the low oil level limit and continues to pump oil into the tank.
The reasons for the decrease in the main engine oil tank level are as follows:
(1) Accidental discharge from the tank or leakage/mistaken opening of other oil system components.
(2) Oil run-off from the purifier's automatic water ejector.
(3) The purifier filter oil pump cannot automatically start at the high oil level limit, causing oil to be pumped into the main tank.
(4) Leakage in the cooler copper tube when oil pressure is greater than water pressure.
(5) Low oil temperature at the cooler outlet, causing the oil level to drop.
(6) Bearing oil seals leaking.
(7) The tank was recently drained of water.
(8) Oil level gauge sticking.
26. What causes water to enter the oil system? What measures are taken during operation to prevent water from entering the oil system?
Answer: Water generally enters the oil system due to excessive steam leakage pressure in the high-pressure shaft sealing section of the turbine, improper adjustment of the shaft seal steam supply pressure, or malfunction of the shaft seal exhauster, causing steam to enter the oil system through the bearings. It may also be caused by setting the cooling water pressure of the oil cooler too high (higher than the oil pressure), so that if the copper pipes rupture, cooling water leaks into the oil system.
Measures to prevent water from entering the oil system:
① Always keep the oil cooler water pressure lower than the oil pressure, so that even if the copper pipe cracks, water will not enter the oil.
② Properly adjust the shaft seal steam supply pressure to ensure it is not too high, and keep the shaft seal exhauster functioning normally.
③ Regularly drain water from the main oil tank and have the oil quality chemically tested on a regular basis. If water is found in the oil, the oil should be filtered immediately using an oil purifier.
27. What are the signs of blade damage or breakage during operation and how should it be handled?
Answer: Signs (one or more of the following may occur):
(1) There are knocking sounds inside the cylinder, and vibrations suddenly increase.
(2) At the same load, the steam extraction pressure at the first stage or several stages rises.
(3) Condensate water hardness and conductivity may increase.
(4) Axial displacement increases, and the temperature of radial bearings and tungsten components rises abnormally.
Handling:
(1) Conduct a comprehensive inspection of the unit and measure unit vibrations.
(2) If unit vibrations are within acceptable limits but condensate water hardness has increased significantly, decide whether to reclaim it according to chemical requirements, while also considering a leak check on one side of the condenser. If knocking or friction sounds are clearly heard inside the cylinder and the unit experiences strong vibrations, perform an emergency shutdown by breaking the vacuum.
