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        2. Home > Operational Area > ELECTRICAL & DCS
          Precautions for Operation of DCS control system

          1. When DCS system is in power failure, the standby power supply shall be automatically switched. If there is any abnormality, the circuit automatic controlled in the system shall be immediately switched into manual operating status. When power supply is normal, first check whether the system operation and system data are normal or not, if there is abnormal phenomenon, it is required to ask the thermal persons to download the configuration again, and check and verify the parameters of DCS control system. Only after everything is confirmed to be in good condition, can the system be  automatically controlled again. 

          2. If the DCS system operation station is in failure, the operation station of other boiler shall be immediately started and the maintenance people of thermal control room shall be informed to indentify the causes and to try to deal with the problems. Only after the thermal control maintenance persons confirm that the operating station is in good condition, can the operating station be automatically controlled. 

          3. The DCS system is ensured to operate stably.

          (1) The controlled parameters are near the center of the normal range, such as: The drum water level is near 0mm.  

          (2) The changing tendency of the controlled parameters is smooth and do not vibrate. 

          (3) Other parameters associated with the controlled parameters do not fluctuate greatly.

          (4) The main process equipment is running normally. 

          (5) The actuator and control valve are working normally and the transmitter and field measurement devices are working normally. 

          (6) All the control loops put into automatic operation must satisfy the smooth running of the system. 

          4. When the  automatic loop for negative pressure control of boiler hearth is put into operation, it is still required to monitor the changing of  negative pressure and bed temperature of boiler hearth in order to maintain stability of negative pressure of boiler hearth, primary air amount, and secondary air amount and the smooth changing, and to avoid excessive large adjusting range. 

          5. Maintenance for operator's passwords There is not any relation between the operator's passwords of each operation, the passwords must be set up separately. The password is the premise of ensuring the safe and normal operation of the system, it must be strictly implemented. 

          6. Historical data is stored in hard disk of operation station, it has nothing to do with factors such as system blackouts. Historical data is an important means of tracing the accident responsibility.

          7. The computer in the operation station is an important part of the system, it must be maintained normal operating and tidy. 

          8. When the card of the system is broken down, the relative control circuit shall be immediately switched back to manual operation, and the fault card shall be immediately replaced. Only after the faults has been checked and cleared, can the system be automatically controlled. 

          9. Selection of signal: 

          (1) In DCS system, the parameters of boiler hearth outlet temperature, materials temperature, drum water level, material layer differential pressure and smoke oxygen content have many measuring points, the operators must confirm its correctness in automatic control.

          (2) When the flue gas hearth outlet temperature and materials bed temperature are selected, the signal of fault shall be eliminated firstly, then the largest signal point shall be selected and participated in control. 

          (3) When the boiler drum water level, materials layer differential pressure and flue gas oxygen content are selected, then the signal in the front shall be selected in control. 

          (4) The operator's selecting reasonable signal point  according to the above principles is the premise of automatic control of DCS system. 

          10. Alarm input: 

          (1) The alarm of steam drum water level, main steam temperature, hearth negative pressure, flue gas oxygen content, main steam pressure and bed temperature, boiler  outlet temperature, coal-feeding interruption,  deaerator pressure and water level signal etc. can be relieved and input. 

          (2) If alarm is given during automatically running,  the operator shall immediately pay attention to what is happening, if necessary, please immediately switch to manual control. 

          (3) For the elimination of alarm of coal-feeding interruption, the alarm input switch must be switched to "Relieve", then only after the alarm is put into use again, can the alarm for coal-feeding interruption be relieved; When the combustion control in "automatic" state, firstly the combustion switch is switched to manual operate, then the alarm input switch is switched to "relieve", and only the alarm switch is put into use again, can the alarm for coal-feeding  interruption be relieved. After the other alarm is eliminated, DCS automation is realized according to actual situation.


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