Automatic Stratup of the Steam Boiler
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Details:


Objective: Automatic startup for Boiler No.3;
Beneficiary: LUKOIL ENERGY AND GAS ROMANIA- Power Plant;
Used Software: Emerson Ovation 3.5;
Location: Ploiesti, Romania.

Tasks performed:

  • Control system design;
  • Engineering;
  • Commissioning;
Purpose, task and area of use:

 Automatic Startup of Boiler No.3 was executed for improving the automatic starting system and increasing operational safety; improve adjustment of all boiler parameters according to the final setpoint of the desired steam characteristics.
Fan start order:

• VAAp - only one of the 2 fans (selected in working mode) is started, the other remaining in reserve. The VAAp discharge valve opens depending on the selected function; after 5 seconds from starting the fan.
• VGA starts; after 30 seconds from the start, the corresponding steering unit opens at 20%;
• VA1 starts, after 30 seconds the corresponding device opens at 20%;
• VA2 starts, after 30 seconds the corresponding device opens at 20%;
The fan starts will take place successively, at an interval of 30 seconds. Shutters related to VGA, VA 1, VA 2 enter automatic operation.
Preventing is considered performed if for 10 minutes, on each of the 2 air channels on the suction of the air fans of the boiler, an air flow of at least 30000 m3N / h is circulated.
If no burner has been started for 10 minutes after the end of the pre-ventilation, the “finished and non-canceled pre-ventilation” signal is canceled, requiring a new pre-ventilation.

Safety Valve tightness check conditions:

The program includes the following sequences:

I. Pressurize the pipe to Safety Valve 1 for burners 1-9, at a value of 1.2 bar.
Safety Valve generally closes automatically when the value of 1.2 bar is exceeded.
A time interval is expected for pressure value stabilization (1.1 -1.2 bar).
The sequence is considered successful if within 3 minutes there are no variations greater than 50 mbar in the gas pipeline.

II. The pressure on the pipe is reduced by automatic pulses, up to the value of 0.5 bar.
A time interval is expected for pressure value stabilization (0.5 bar).
The sequence is considered successful if within 3 minutes there are no variations greater than 50 mbar in the gas pipeline.
After checking the tightness of Safety Valve in DCS, the following signals are mentioned in HMI interface: "successful operation".
General Safty Valve opens, the pressure is automatically adjusted to the value of 0.4 bar with the help of the ventilation downstream of the Safety Valve (command executed in impulses), the main Regulation Valve remains open at preset value.
The first burner start command is executed automatically (set as priority “1”).
If the start of the first burner is considered successful, the boiler burners in priority mode are started successively, one after the other.
Automatic Startup of the Steam Boiler:
Nitrogen leak test when the boiler is in reserve:

Stage I with a pressure of 1.2 bar up to general Safety Valve:
- the nitrogen valve opens before Safety Valve, closes automatically when the pressure exceeds 1.2 bar;
- the pressure is adjusted to a value between 1.1 bar and 1.2 bar with the help of ventilation valve situated before Safety Valve.
- wait for pressure stabilization, then for 3 minutes perform the tightness test before Safety Valve.
If the pressure value does not change more than 50 mbar, it is considered a successful test and proceeds to stage II; otherwise the sequence is reset and the leak-proof circuit alarm is displayed.

Stage II with the pressure of 1.2 bar and 0.5 bar for pipe circuit after Safety Valve:
- the nitrogen valve opens after the Safety Valve, it closes automatically when the pressure of 1.2 bar is exceeded;
- the pressure is adjusted to a value between 1.1 bar and 1.2 bar with the help ventilation valve after Safety Valve.
- wait for pressure stabilization, then for 3 minutes the tightness test is performed after Safety Valve.
If the value of the pressure does not change more than 50 mbar, the test is considered successful and it is passed to the next sequence, tightness at 0.5 bar.
- the pressure is reduced with the help of ventilation Valve after Savety Valve to a value of approximately 0.5 bar;
- resume the previous tightness sequence, wait for pressure stabilization and 3 minutes for the tightness test.
If the pressure value does not change more than 50 mbar, the test is considered successful; otherwise the sequence is reset and the leak-proof circuit alarm is displayed.
The nitrogen sealing sequence is automatically resumed at 12 hours only if the “START” button is engaged and boiler stopped.
Sequence can also be executed manually by the Operator by pressing “START” button.