This document describes the deaerator level control auto loop. It maintains the correct level in the deaerator to ensure high quality feedwater. There is a main CV and auxiliary CV for level control. Control can operate in single element or three element mode depending on steam flow. It outlines the set points, measurements, control elements, and control modes for the main and auxiliary CVs. It also lists conditions that would cause the control valves to switch to manual or have their output overridden.

1. DEAERATOR LEVEL CONTROL AUTO LOOP
26/03/2021
ITPCL/IMD/0011 Arun kumar.J

2.  Maintaining correct level in the deaerator is very important when ensuring high
quality feed water.
 The deaerator level control valve needs to be operated with high rangeability and
protection from cavitation at low flows.
 For Deaerator Level control we one MAIN CV and one AUX CV
 There are 2 mode of control
 single element control( when steam flow<30%)
 3 element control (when steam flow>30%)
DEAERATOR LEVEL CONTROL

3. Set point
Process Value
Measurement
Final Control Element
SET POINT IS SET BY
OPERATOR
3 DEARATOR LEVEL TX USED
FOR MEASUREMENT
3-TX LOGIC(MEDIAN) IS
USED
Fed to DEAERATOR LEVEL
MAIN / AUX CONTROL
VALVE
DEAERATOR LEVEL CONTROL

4. DEAERATOR LEVEL CONTROL
Δ
PI
A
M
Set by Operator
PV
OP
DEAERATOR LEVEL
MEDIAN OF 3 TX
DEAERATOR LEVEL
MAIN CV
SP
SET BY
OPERATOR
K 0.1
Kp .75
Ki 0.5
MAIN CV SINGLE ELEMENT (1E)

5. DEAERATOR LEVEL CONTROL
Δ
PI
A
M
Set by Operator
PV
OP
DEA. INLET FLOW
MEDIAN OF 3 TX
DEAERATOR LEVEL
MAIN CV
SP
K 1
Kp 0.5
Ki 1.8
MAIN CV THREE ELEMENT (3E)
Δ
PI
PV
DEAERATOR LEVEL
MEDIAN OF 3 TX
SP
SET BY
OPERATOR
SUM
OP
TOTAL FEED
WATER FLOW
MEDIAN OF 3 TX
F(X)
K 0.1
Kp 1.5
Ki 0.3
INPUT OUTPUT
0 0
100 4
2500 100
3000 120
F(X)
INPUT OUTPUT
0 0
100 4
2500 100
OP

6. Condition in which deaerator Level control main CV comes out of Auto to
Manual mode
 3E SELECTED AND FEED WATER FLOW TX OR CONDENSATE FLOW TX BAD QUALITY
 ALL DEAERATOR LEVEL TX BAD QUALITY.
 FCB AND RUN BACK NOT ACTIVE AND SET POINT TO P.V. DEVIATION +/- 200 mm.
 LEVEL CONTROL CV COMMAND AND FEEDBACK DEVIATION +/- 15%.
 DEAERATOR LEVEL AUX CV IN AUTO
DEAERATOR LEVEL CONTROL
Condition in which Control valve output override
 0% - DEAERATOR LEVEL > 1000 mm.

7. DEAERATOR LEVEL CONTROL
Δ
PI
A
M
Set by Operator
PV
OP
DEAERATOR LEVEL
MEDIAN OF 3 TX
DEAERATOR LEVEL
AUX CV
SP
SET BY
OPERATOR
K 0.2
Kp 1
Ki 0.5
AUX CV SINGLE ELEMENT (1E)

8. DEAERATOR LEVEL CONTROL
Δ
PI
A
M
Set by Operator
PV
OP
DEA. INLET FLOW
MEDIAN OF 3 TX
DEAERATOR LEVEL
AUX CV
SP
K 1
Kp 1.4
Ki 1.8
AUX CV THREE ELEMENT (3E)
Δ
PI
PV
DEAERATOR
LEVEL SP
SET POINT
GIVEN BY
OPERATOR
SUM
OP
TOTAL FEED
WATER FLOW
MEDIAN OF 3 TX
F(X)
K 0.1
Kp 1.5
Ki 0.3
INPUT OUTPUT
0 0
100 4
2500 100
3000 120
F(X)
INPUT OUTPUT
0 0
100 4
2500 100
OP

9. Condition in which deaerator Level control AUX CV comes out of Auto to Manual
mode
 3E SELECTED AND FEED WATER FLOW TX OR CONDENSATE FLOW TX BAD QUALITY
 ALL DEAERATOR LEVEL TX BAD QUALITY.
 FCB AND RUN BACK NOT ACTIVE AND SET POINT TO P.V. DEVIATION +/- 500 mm.
 LEVEL CONTROL CV COMMAND AND FEEDBACK DEVIATION +/- 50 %.
 DEAERATOR LEVEL MAIN CV IN AUTO
DEAERATOR LEVEL CONTROL
Condition in which Control valve output override
 0% - DEAERATOR LEVEL > 1000 mm.