SIEMENS SIMATIC S7 + WINCC
Boiler Level Control
Boiler Level Control
This mesh allows automatic regulation of the boiler water supply valve (FCV200), ensuring operating stability and ensuring proper operating and safety conditions.
Control is based on the three-element principle, based on water level measurements in the steam pipe (LT200), combined with water flow measurements (FT200) and produced steam (FT300).
The LIC200 Boiler Level Control and FIC200 Boiler Feed Water Flow Control PIDs cascade. The MV output of the PID LIC200 makes up, along with the produced steam flow (FT300), the formula for the PID FIC200 remote setpoint. Formula: FT300 + 3 * (LIC200.MV – 50.0).
• Create FC7 CTR_FIT200 function. Right-click on the Blocks folder and select Insert New Object > Function menu item.
• Create the following variables in the symbol table:
| Name | Address | Type | Description | S7_m_c |
|---|---|---|---|---|
| FIC200_AUX1 | MD28 | Real | FIC200 Auxiliar 1 | |
| FIC200_AUX2 | MD32 | Real | FIC200 Auxiliar 2 | |
| FIC200_AUX3 | MD36 | Real | FIC200 Auxiliar 3 |
• Create a variable for opening the water supply valve to the boiler FCV200 in the symbol table.
| Name | Address | Type | Description | S7_m_c |
|---|---|---|---|---|
| FCV200_RB | MD40 | Real | Feed Water Valve READBACK | True |
• Open CTR_FIC200 function and insert FB_PID function block.
| LIC200 | FB_PID | DB56 |
• Force PID action. In PID automatic mode, when the boiler level increases beyond the level setpoint, the PID MV decreases and, consequently, the value of the remote setpoint of the feed water flow control (FIC200) decreases. In automatic mode, when the boiler level decreases below the level setpoint, the PID MV increases and, consequently, the value of the remote setpoint of the feed water flow control (FIC200) increases.
• When the PID LIC200 is in manual (LIC200.AM = 0), move the value 50.0 to the PID LIC200 MV.
• Formula for the FIC200 PID remote setpoint. Formula: FT300 + 3 * (LIC200.MV - 50). FIC200 PID remote setpoint limited to the range 0 to 300 m3/h.
• Insert FB_PID function block.
| FIC200 | FB_PID | DB57 |
• Move the PID output to the PCV310 control valve on the Profibus-PA network.
• Read the opening value of the FCV200 control valve via the Profibus-PA network.
• Force PID action. When the water flow decreases (PV drops), the valve (MV) must open to maintain the flow in the indicated SP. When the water flow increases (PV increases), the valve (MV) must close to maintain the flow in the indicated SP.
• Move the multiplication factor for converting PV and SP (0 to 300 m3/h) to 0 to 100% at the PID input.
• The selection of automatic/manual mode of the PID LIC200 is made following the automatic/manual mode of the PID FIC200.
• Make the call to FC7 CTR_FIC200 in OB1.
• Select Operator Control and Monitoring for DB55 PIC300.
• Compile AS and OS.
• Create frontal for Boiler Water Level and Flow PIDs in Controle_Nivel.pdl.
C script to show the PW_PID picture window object in the current picture.
LIC200 PID:
The Picture Name property of the PW_PID picture window receives the name of the PID.PDL.
The TagPrefix property of the picture window PW_PID is set to CALD/LIC200. This instruction adds the text “CALD/LIC200” at the beginning of all object dynamizations within the picture window.
The Picture Name property of the PW_PID picture window receives the name of the picture PID.PDL.
The TagPrefix property of the PW_PID picture window is set to CALD/FIC200. This instruction adds the text “CALD/FIC200” at the beginning of all dynamizations of objects within the picture window.