What should operators do if the DCS freezes?

Handling of DCS crash incidents: 1. Contact the thermal control team to arrive immediately, and inform the shift supervisors of Phase 1 and Phase 2 as well as relevant management; if AGC is in operation, inform the dispatching team to maintain the current instructions or to disconnect the system remotely. 2. Maintain stable loads on the adjacent units that are operating normally, avoid making large operational adjustments, and switch the supply source of plant main steam as necessary. Inform the chemistry, ash control, and desulfurization teams to monitor relevant parameters more closely using the instruments at their disposal, with a focus on parameters such as condensate and feedwater flow rates in the chemistry department, as well as the MFT activation signals in the desulfurization unit. Monitor the changes in furnace negative pressure as well as the relevant 6KV bus voltage readings, and strengthen communication with the main unit to report on these values. 3. Accident handling must be carried out under the unified guidance of the shift supervisor and management. Any operation related to the safety of the unit must be ordered by the shift supervisor (except in situations where the procedures specify that actions to prevent threats to human life and equipment safety can be taken on-site by the operators in accordance with the procedures); no other personnel have the authority to give any operational instructions to the operators or to carry out any operations on their own. 4. When some operator stations freeze or lose the ability to display images, other operational operator stations that are functioning properly should be used for monitoring and adjusting parameters (it may be necessary to contact the thermal control team to grant access to the control panel and large screens). Efforts should be made to minimize any adjustments or changes to the displayed images, in order to maintain the stability of the parameters. For systems that have lost monitoring capability, a dedicated person should be assigned immediately to monitor the important instruments on-site and maintain communication links. 5. When all the screens at the control station fail simultaneously and it becomes impossible to monitor the unit parameters, all available personnel (except those responsible for ensuring the normal operation of the unit) should be mobilized immediately. Sufficient communication tools (including walkie-talkies and all phones and mobile devices in the control room) should be prepared, and personnel should be assigned to carry out monitoring and operations on-site. The shift supervisor and the chief operator must remain in the control room to direct and control the operations at the console. 1. One person in the relay protection room (acting as deputy chief), whose main task is to monitor the operation of the protection devices for generators and transformers as well as those for power lines. Any abnormalities should be reported immediately. If a protection device triggers a trip, it is necessary to check that the fast-switching device for station service power is functioning properly and that the voltage on the 6KV bus is normal. It is important to use the “online operation signal for generators and transformers”, the readings from the reactive power meters, and other relevant signals to assess the current operating conditions of these devices. Additionally, the operation of the 110V DC system should also be checked. Once it is confirmed that the generator shutdown procedure is working correctly, one should proceed to the 220V DC section and the UPS room to check the operation of important DC loads. 2. At a distance of 13.7 meters from the turbine head, one person (deputy all-rounder) is responsible for closely monitoring the turbine speed as well as the relevant oil pressure gauges (including the speed and oil pressure of turbines A and B), in order to assess the operating conditions of both the main turbine and the auxiliary turbines. If air guide valve operation is detected, the safety oil pressure drops to 0. It is necessary to immediately report on any changes in the turbine speed as well as the condition of the main valves and control valves. If the turbine speed increases without the system being shut down, it is important to contact the control room to find out whether the generator has been disconnected. If the generator has been disconnected and the control room has issued an order to shut down the turbine but the turbine does not stop operating, then the turbine must be shut down immediately on-site. When the generator remains connected and its speed rises to 3090 rpm, it should be checked that the OPC operates properly. If the unit has been shut down, continue to monitor changes in speed and the closing status of the main valve actuators. If the speed does not decrease but continues to rise, report to the control room so that they can open the vacuum break valve; also check the lubrication oil pressure at the engine head. If the shutdown operation is normal, close the electric outlet valve of #5 low-temperature reheater at #5 low-temperature reheater. If the unit is currently operating stably, increased monitoring of the speed gauges for auxiliary machine A and B should be carried out, and the current feedwater flow rate should be determined based on experience. After the boiler’s MFT occurs, and once it has been confirmed that the main engine has stopped properly, it is necessary to check whether generators A and B also shut down automatically. If not, the control room should be informed so that generators A and B can be shut down urgently either via the control panel or locally. After they are shut down, the valves controlling these generators should be checked to ensure they are functioning properly; the speed of the generators should decrease, and the oil pressure in them should be normal. 3. At a distance of 6.4 meters from the machine room, an operator (Patrol B) initiated the AC lubricating oil pump on the control console in the central control room immediately after the DCS stopped working, in order to check the operation of the oil pump and the oil pressure on-site. If the AC lubricating oil pump operates abnormally or trips, it is necessary to contact the control room promptly to start the DC lubricating oil pump via the console and check that it is functioning properly on-site. After the steam turbine is shut down, check that the check valves for each stage of extraction steam are closed properly. Continue to monitor the operation of the oil pumps, and take note of any changes in the water level of the 6.4M heater when time permits. When the controller issues the command to open the vacuum break door, check whether the local door is already open; if not, open it locally immediately upon receiving the command. Check each stage of the extraction steam electric valve; if not, contact to close it manually. 4. One person should be stationed at 0m in the machine room to monitor the water level of the condenser closely. If an abnormally low water level is detected, the electric valve for supplying water to the condenser can be opened on-site. After the unit is shut down, the vacuum pump should be stopped urgently on-site; the manual valve bypassing the condensate recirculation valve should be opened. (Patrol B) If the recirculation valves for pumps A and B are not opened after those pumps are shut down, the primary pumps A and B should be stopped on-site upon receiving instructions, and close monitoring should be maintained over the operation of the main oil pump of the small unit as well as the oil pressure of the lubrication pump. 5. One person shall be stationed at 0m on the furnace side. Upon receiving notification from the control room that a manual MFT has been initiated, they shall check on-site to ensure that all operating feeders trip; if not, they shall immediately shut down those devices using the emergency switches, and then check whether the primary fan also trips – if not, it should be shut down urgently as well (Patrol A). 6. Another person shall be on the 17M platform on the furnace side. After receiving the notification from the control room about a manual MFT, they shall check to ensure that all operating coal feeders trip; if not, they shall shut them down urgently. They shall then check whether the solenoid valves controlling fuel flow into and out of the fuel main are properly closed; if not, they shall promptly close the manual isolation valves for fuel flow or shut down the fuel pump. 7. One person shall be stationed at the superheater desuperheating water area on the top of the furnace (Patrol B). Their task is to monitor the local pressure gauge for the primary desuperheating water. Under normal conditions, this gauge should show a pressure 1–2 Mpa higher than the pressure at the superheater outlet. When this pressure reaches 32 Mpa, and after confirming that the gauge reading is accurate, they shall check whether the safety valve operates. If the pressure continues to rise even after a MFT is initiated, an immediate MFT should be carried out. After MFT, check that the interlock of the main water cooling valves for stages 1 and 2 of the superheater is functioning properly; if not, close them manually. After closing, go to the main water cooling valve for the reheater to verify whether the interlock is working, and close it manually if necessary. 8. One person per deaerator level (Patrol B) is primarily responsible for monitoring the deaerator water level; any abnormalities must be reported promptly. After shutdown, it is necessary to check whether the electric valve connecting the fourth extraction pump to the deaerator is closed automatically, and if not, it must be closed manually. After units A and B come offline, check whether the recirculation systems of steam pumps A and B are activated; if not, report immediately and arrange to shut down pumps A and B as well. 9. One person in the main PC room (patrol A) is responsible for monitoring the voltage of the 400V busbars at various levels as well as the current consumption of the main loads. Special attention should be paid to the voltage in the two safety circuits, as well as the current usage by the AC lubrication pumps, DC charging supplies, air-side seal oil pumps, and air preheaters. After the unit trips, it is essential to first confirm that the safety circuits are functioning properly and that the currents of all loads are within normal limits. If the plant power is lost and the 400V supplies in the main PC room are disconnected, check whether the diesel generators can take over and provide power; if not, contact the control room immediately so that they can manually start the diesel generators urgently. Also, verify that the backup power supplies for the safety circuits are functioning properly and that all power switches operate correctly. Otherwise, manual switching operations should be carried out in accordance with the principle of electrical switching; the diesel engine should then be started locally to supply power to the critical sections, while some less important loads should be turned off to ensure proper power supply to the essential loads. Additionally, monitoring of the diesel engine’s operation status should be intensified. 10. The personnel in the control room should decide whether to shut down the unit based on the various reports coming from the field, and they must start the AC lubricating oil pump as soon as possible in the control room. In the event of any situation that threatens the safety of the unit, the MFT should be activated manually immediately to shut down the turbine, stop the generator urgently, open the excitation switch, and remove the control panel along with the four sets of buttons. Based on the feedback on site, determine whether to operate the PVC valves and vacuum break valves on the control panel, shut down generators A and B, and start the emergency diesel engine, while ensuring proper coordination and issuance of operational commands. 6. Once the operator station display returns to normal, it is necessary to immediately check the status of all operating equipment and parameters, as well as the operation of interlock protections. The tripped equipment should be reset on the display, and the relevant interlocks should be disabled. If the unit does not trip, efforts should be made to maintain and adjust all parameters to ensure normal operation of the unit, and it should be kept online as much as possible. When it is detected that the relevant operating parameters have exceeded the protection trip value but no action has been taken, manually initiate the protection trip immediately. Apart from some routine on-site inspections, the rest of the personnel returned to the control room to handle the incident. Restore the auxiliary power supplies for each section, verify the status of all protections, determine the cause of the shutdown, and conduct a thorough on-site inspection to ensure that no damages exist that could pose a risk to the startup of the unit; only after that can a report be submitted to the management for approval to restart the unit. 7. In handling this incident, it is necessary to prioritize protecting the safety of personnel, the power grid, and the equipment, to ensure that no boiler fires or explosions occur. It ensures a safe shutdown in the event of serious accidents such as bearing damage due to loss of fuel supply to the turbine, runaway speed, overheating and overpressure of the heating surfaces, water impact, generator demagnetization, or operation without steam due to reverse power, when it is no longer possible to maintain grid-connected operation. 8. As N decreases, start the top shaft oil pump promptly, engage the barring gear, complete other shutdown procedures, or restart and perform a trial run. 9. The personnel operating adjacent units should assist in checking the service pumps and circulation pumps of the utility systems, as well as the operation of the oil pumps, in order to prevent failures that could lead to a loss of plant power and cause the utility equipment to shut down. They must contact relevant parties and report any issues promptly, and take necessary actions. I wonder if I can be of any help to you?

It’s best to base this on the actual conditions of the factory. Once, there was a UPS power failure, which caused all the control computers to shut down; the situation at the site became chaotic