Detailed steps for starting a steam turbine

(1) Coordinate with the boiler to maintain stable steam parameters, gradually open the throttle valve to increase the load, and carry out warm-up at low load； (2) Gradually close the primary and secondary bypasses according to the boiler’s requirements ； (3) After the speed control valve is nearly fully open, instruct the boiler to increase temperature and pressure as well as load in accordance with the cold-start curve, and warm up the system at the specified load ； (4) Shut down the relevant steam traps, high-pressure heaters, steam heaters, switch the steam source for the deaerator, and carry out related adjustment tasks in accordance with the regulations ； (5) Ensure that parameters such as cylinder metal temperature, expansion difference, shaft misalignment, cylinder expansion, and vibration remain within normal ranges ； (6) When the main steam pressure approaches the rated value, keep the load constant and gradually close the throttle valve to operate at a constant pressure.

Once the pressure-raising heating process is complete, the vacuum system is operating properly, and the conditions for starting the turbine and compressor are met, the start oil switch and the quick-shut oil switch can be activated. This ensures that the levels of start oil, quick-shut oil, and secondary oil pressure are within normal ranges; after that, the start oil switch is turned off and the quick-shut valve is opened in preparation for starting up the equipment.

No-load test run of the steam turbine 1 Preparations before startup 1.1 The oil system is operated in circulation mode; the pressure at the outlet of the oil pump is 1.1 MPa (G), the pressure in the main oil lines is 0.25 MPa (G). The oil pressure in each feed line serving the bearings is 0.09–0.13 MPa (G), while the oil pressure for the thrust bearings is 0.025–0.13 MPa (G). The pressure of nitrogen in the accumulators is 0.6 MPa (G), and the oil pressure should be adjusted to 0.7–0.9 MPa (G). (1) Method of adjusting oil pressure: During the circulation of the oil system, the electric heater is turned on first to heat the oil in the tank. Once the oil temperature reaches 22°C, the auxiliary oil pump can be activated to enable self-circulation of the oil, ensuring even heating of the oil in the tank and accelerating the rise in temperature to 40–50°C. After that, the auxiliary oil pump is turned off, the switch is set to the automatic start position, and the main oil pump is activated. The oil pressure in the turbine’s control system is regulated by the PCV8056 pressure control valve, so that the oil pressure remains at 0.7–0.9 MPa (G); meanwhile, any excess oil flows back to the tank through this valve. (2) Adjustment of lubricating oil pressure: Once the oil pressure has been adjusted to the normal level, the adjustment of the lubricating oil pressure begins. The pressure in the main lubricating oil supply line is regulated by the PCV8053 pressure control valve; it is absolutely not allowed to manually adjust the main valve in the lubricating oil outlet line. This valve must remain in an open state during operation, and measures should be taken to prevent it from being accidentally closed. 1.2 Oil pressure alarm test and adjustment: (1) The low-pressure alarm of the governor and the automatic start-up of the auxiliary oil pump are used to check the performance of the pressure switch. The testing method involves bringing the main oil pump pressure to 1.1 MPa (G), with the control oil pressure within the range of 0.7–0.9 MPa (G); when the oil pressure drops below 0.6 MPa (G), an alarm signal should be generated, and the auxiliary oil pump should immediately start operating automatically. When the main oil pump reaches 0.7–0.9 MPa (G), fully open the bypass valve from the pump outlet to the oil return tank, or manually adjust the oil inlet valve to reduce the oil pressure below 0.5 MPa (G); an alarm signal should be issued, and the auxiliary oil pump should start operating immediately. (2) Low-pressure alarm and shutdown of the lubricating oil system are intended to check the performance of the pressure switch. The procedure involves reducing the valve opening in the oil pipeline of the unit while the main oil pump is running, and when the pressure in the main lubricating oil line reaches 0.25 MPa (G), an alarm signal should be generated once the pressure gauge reading reaches 0.15 MPa (G); at this point, the auxiliary oil pump should start operating automatically. When the valve is closed and the oil pressure drops to 0.1 MPa (G), a stop signal should be issued. (3) Liquid level alarm and oil temperature alarm: An alarm signal should be generated when the level of the lubricating oil in the tank is more than 1165 mm above the top of the tank ； The method is to drain oil from the tank to lower the liquid level and check the alarm value. Hot well level alarm: high limit alarm at +150mm, low level alarm at -150mm. (4) Condensate pump automatic start-up test: Reset the emergency stop button for Pump 1#, start Pump 1#, and switch Pump 1# to main operation mode in the control room. The emergency stop button for pump 2’s motor has been reset, and both pumps are now operating. Similarly, when pump 2’s motor is in operation, the emergency stop button for pump 1 is reset; in the control room, pump 2 is set to the main operating mode while pump 1 is set to the standby mode. The emergency stop button for pump 1 is then reset, and pump 1 starts up automatically, resulting in both pumps operating. After the test is complete, and once the backflow drainage has returned to normal, turn off the backflow valve. Then open the atmospheric safety valve and the water filling valve for the water seal, adjusting their opening degrees so that no large amount of water flows out from the exhaust port of the atmospheric safety valve. Stop pump No. 2 in the control room and designate pump No. 2 as the standby pump. (5) Emergency oil pump auto-start interlock test: Check that the emergency oil pump is set to automatic mode, reset the local and DCS emergency stop buttons, supply power to the emergency oil pump motor, start the main oil pump, and ensure that the lubricating oil pressure is normal. Contact the electrical staff to turn off switches 1# and 2# from the power distribution room. The main oil pump stops due to power loss; the PISA8057 alarm is triggered, and the low oil supply pressure interlock activates, causing the emergency oil pump to start automatically. Once this is confirmed, the electrical staff are notified to restore power to lines 1# and 2#. Start the main oil pump to restore normal operation of the oil system, and shut down the emergency oil pump. (6) Test of turbine emergency shut-off valve closure: A. When the oil system is in normal operation with oil circulation, open the emergency shut-off valve, activate the manual solenoid valve in the control room to reduce the oil pressure, and check whether the valve closes quickly. B. Adjust the bypass valve near the lubricating oil pressure outlet of the manual filter using hand; when the oil pressure is reduced to 0.1 MPa (G), the low-pressure trip diaphragm valve opens, causing the pressure in the trip oil line to drop, and check whether the quick-shut valve closes promptly. C. Open the test valve on-site; the pressure oil flows toward the test piston, which in turn pushes the quick-close valve piston, causing both the piston and the valve stem to move in the closing direction. At this point, the test pressure can be read from the test pressure gauge. The allowable test pressure for this process is: PI ≤ A + B (P2 – 1), where A = 1.869 (bar) and B = 0.68 (bar); P2 represents the actual value of the quick-close valve pressure. If the quick-close valve pressure P2 differs from P1, it indicates that there is salt or oil residue deposited on the valve stem. To restore normal operation, this test process must be repeated multiple times. If the test pressure P2 still decreases and does not reach the specified limit value, then it is necessary to address the issue during shutdown. Note: It is required that designated personnel conduct this test regularly during unit operation. (7) Vacuum level trip test: Verify that the condensate pump is operating properly. Contact the site to start the turning gear at 505; the specific steps are as follows: check that the emergency stop button of the turning gear pump has been reset. 505 Crankshaft rotation fault reset. Observe that the cranking preparation light is on. Press the start button of the crank pump; the start light of the crank pump will turn on and the pump will begin to operate. Set the crank knob to automatic and start cranking. Check whether the tie rod position indicator light is correct, and inspect the travel of the turning gear on site. Open the steam valve on site. Open the extraction valve of the extraction pump, monitor the DCS vacuum level, and record the data once the alarm is cleared. Switch DCS to the main interlock diagram to confirm that the vacuum level interlock is online. Stop the train system and open the quick shut-off valve. Stop the steam extraction, and slowly turn the handwheel of the atmospheric safety valve to break the vacuum. Record the data when a vacuum level alarm is triggered. The quick-close valve closes. Resume extraction steam, restore normal vacuum level, and resume barring. On-site, adjust the water filling valve of the atmospheric safety valve to ensure that water flows out from the water seal overflow port. (8) Vacuum extraction in the turbine condenser: During the startup of the turbine, the condensate system in the condenser is brought into operation; the minimum required vacuum level in the condenser is 375–400 mmHg, while the normal operating vacuum level is 640–660 mmHg. Startup steps for the turbine: 2.1 Warming up the pipes: Warm up the steam pipeline ahead of the steam valve, and drain any condensate present in that pipeline. Then, warm up the steam pipeline in front of the control steam valve, specifically: (1) Close the control steam valve ； (2) Open the upper and lower drain valves at the front of the quick-shut valve ； (3) Pass medium-pressure steam in front of the steam stop valve ； (4) Slightly open the steam cut-off valve at the root to warm up the pipeline ahead of the control valve; pay attention to the opening degree required for the upper seat drain valve located in front of the quick-close valve. Initially, keep the pressure at 0.2–0.3 MPa (G). After 20 minutes, increase the pressure at a rate of 0.2 MPa (G) per minute and 5–10°C per minute, until it reaches 3.2 MPa (G) or 280°C. The upper seat drain valve at the front of the quick-shut valve remains open before the turbine starts to rotate. After completing the pipe warming process, open the steam stop valve to half of its travel. 2.2 Heating the steam for sealing (1) Open the drain valve on the sealing steam pipeline. (2) Maintain the sealing steam pressure at 0.014 MPa (G). (3) Open all the drain valves of the turbine cylinder. 2.3 Evacuating the steam turbine cylinder (1) Close the safety valve on the turbine’s exhaust vent line, open the water supply valve, and maintain the water seal; under normal conditions, water should be visible coming out of the drain valve. (2) Close the valve on the turbine exhaust pipeline. (3) First, perform shaft turning, then open the seal steam supply valve, and supply seal steam at a pressure of 0.014 MPa (A). (4) Start the steam extractor of the steam seal condenser to maintain the vacuum level of the steam seal condenser at 132 mm of water column. 2.4 Prime motion: Start the barring gear, then start the auxiliary extractor. When the vacuum level inside the turbine cylinder reaches 375–400 mmHg, the steam cut-off valve can be slightly opened to urge the rotor into motion; once the steam cut-off valve is opened, the rotor should start rotating. It is absolutely not allowed for the rotor to fail to rotate even after the steam cut-off valve has been opened. If it is observed that the rotor is not rotating, the steam cut-off valve must be closed immediately and reopened in order to urge the rotor into motion. When the vacuum level reaches 450 mmHg, the main pump can be started, while the unit’s drain valve should be closed. When the vacuum level reaches 500 mmHg, the auxiliary pump can be shut down. When the unit speeds up and the steam doing work on the blades is sufficient to maintain the speed, the barring device is stopped at this point. 3 Warm-up and acceleration 3.1 Low-speed warm-up: Open the steam cut-off valve, observe the tachometer, and use a vibration tachometer to verify the accuracy of the tachometer on the equipment. At a constant speed of 1000 revolutions per minute for 1 hour ； Check the oil pressure, oil temperature, vibration, and for any abnormal noises inside the machine. When the lubricating oil pressure is 1.1 MPa (G), the speed control oil pressure should be between 0.7–0.9 MPa (G). The bearing temperature rise should be between 14–17°C, the radial vibration of the bearings should be within 0.025 mm, and the axial displacement should be 0.25 mm. 3.2 Turbine speed increase: After reaching 1000 revolutions per minute, the speed is increased to 1500 revolutions per minute over a period of two minutes, after which the turbine operates at this speed for 20 minutes. The inspections carried out are the same as those during low-speed warming up. Once it is confirmed that everything is operating normally, the speed is increased again to 2500 revolutions per minute over two minutes, with the turbine running at this speed for another 20 minutes; the inspections remain the same as those during low-speed warming up. Once it is confirmed that the turbine is functioning properly, preparations are made to exceed the critical speed – the speed is increased to 4200 revolutions per minute within one minute, thereby exceeding the critical speed of 2900 revolutions per minute. After passing the critical speed, the turbine operates at this speed for 20 minutes, with inspections conducted as before. Once it is confirmed that the turbine is working correctly, the speed is increased further to 5476 revolutions per minute, with the turbine running at this speed for 20 minutes more to assess its performance. If all is normal, the speed can be increased further. At this point, the 505 governor can be used to adjust the speed, and the steam cut-off valve should be fully opened so that the turbine can operate at 7666 revolutions per minute for one hour. During this time, parameters such as oil pressure, oil temperature, vibration, thermal expansion, and exhaust pressure are monitored and checked. Once these values are found to be satisfactory, the next step in the overspeed testing is carried out. 3.3 Over-speed test: Use the 505 governor to increase the speed further, and observe and record the speed at which the control system trips once the rated speed is exceeded. The speed at which the control system trips was 8433 revolutions per minute. After the first trip, reopen the speed control valve; after passing the critical speed, the speed should be increased at a rate of 1000–1200 revolutions per minute until the governor activates. Then, conduct another over-speed test using the 505 governor. This over-speed test should be carried out three times, with proper recording of the results. 4 Shutdown of the turbine: When the turbine is operating normally at its rated speed, it can be shut down by adjusting the opening degree of the manual steam cut-off valve. (1) Gradually reduce the opening degree of the steam cut-off valve ； (2) Quickly pass through the first critical speed of 2900 revolutions per minute ； (3) When the turbine stops rotating, first activate the barring device, and then start the auxiliary oil pump to keep it running. Based on the temperature of the bearing lubricant, it is advisable to reduce the bearing oil temperature to 40°C; then stop the operation of the oil pump and cease the shaft turning ； (4) Stop the supply of sealing steam ； (5) Stop the operation of the steam seal condenser ； (6) Close the exhaust valve and bypass valve ； (7) Open the cylinder drain valve ； (8) Close the steam shut-off valve ； (9) Open the drain valve at the front of the quick-shut valve and the drain valve on the steam pipeline ； (10) Close the safety valve of the turbine exhaust vent line and the water seal supply valve. Is that detailed enough?

It’s indeed very detailed. We are back-pressure type. What is the appropriate negative pressure for the steam seal cooler? Please advise.

Once the pressure-raising heating process is complete, the vacuum system is operating properly, and the conditions for starting the turbine and compressor are met, the start oil switch and the quick-shut oil switch can be activated. This ensures that the levels of start oil, quick-shut oil, and secondary oil pressure are within normal ranges; after that, the start oil switch is turned off and the quick-shut valve is opened in preparation for starting up the equipment.