1) PRDS Temperature control steam to Gland Sealing (TCV- 905): This control loop is used to control the PRDS temperature. The temperature element (TE-916) senses the PRDS line temperature. The output temperature signal from temperature element is fed to a
temperature indicating controller (TIC-916) as a process variable. The process variable signal is compared with the operator feed manual set point in the temperature indicating controller. The output of the
temperature controller operates the temperature control valve (TCV- 905) on the PRDS line to control the PRDS temperature.
Refer closed loop logic diagram: 1104-02-2820-2
2) PRDS PRESSURE CONTROL STEAM TO GLAND SEALING (PCV- 901): This control loop is used to control the PRDS pressure. The pressure transmitter (PT-916) senses the PRDS line pressure. The output pressure signal is fed to a pressure indicating controller (PIC- 916) as a process variable. The process variable signal is compared with the fixed set point in the pressure indicating controller. The output of the pressure controller operates the PRDS pressure control valve (PCV-901) on the PRDS line to control the PRDS pressure. Refer closed loop logic diagram: 1104-02-2820-3
3) PRDS TEMPERATURE CONTROL STEAM TO PEGGING STEAM (TCV-906): This control loop is used to control the PRDS
temperature. The temperature element (TE-917) senses the PRDS line temperature. The output temperature signal from temperature
element is fed to a temperature indicating controller (TIC-917) as a process variable. The process variable signal is compared with the operator feed manual set point in the temperature indicating controller. The output of the temperature controller operates the temperature control valve (TCV-906) on the PRDS line to control the PRDS temperature.
Refer closed loop logic diagram: 1104-02-2820-4
4) PRDS PRESSURE CONTROL STEAM TO PEGGING STEAM (PCV- 902): This control loop is used to control the PRDS pressure. The pressure transmitter (PT-917) senses the PRDS line pressure. The output pressure signal is fed to a pressure indicating controller (PIC- 917) as a process variable. The process variable signal is compared with the fixed set point in the pressure indicating controller. The output of the pressure controller operates the PRDS pressure control valve (PCV-902) on the PRDS line to control the PRDS pressure.
Refer closed loop logic diagram:p 1104-02-2820-5
5) GLAND SEALING DRAIN TO LP HEATER-1 (FCV 000): This control loop is used to control GLAND SEALING STAM. The pressure transmitter (PT-919) senses GLAND SEALING STEAM PRESSURE is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the GLAND SEALING STEAM PRESSURE comes above the set point, controller will open FCV-000 to maintain the pressure. Refer closed loop logic diagram: 1104-02-2820-6
6) PRDS TEMPERATURE CONTROL STEAM TO AUXILIARY STEAM HEADER (TCV-907): This control loop is used to control the PRDS temperature. The temperature element (TE-59) senses the PRDS line temperature. The output temperature signal from temperature
element is fed to a temperature indicating controller (TIC-59) as a process variable. The process variable signal is compared with the operator feed manual set point in the temperature indicating controller. The output of the temperature controller operates the temperature control valve (TCV-907) on the PRDS line to control the PRDS temperature.
Refer closed loop logic diagram: 1104-02-2820-7
7) PRDS PRESSURE CONTROL STEAM TO AUXILIARY STEAM HEADER (PCV-903): This control loop is used to control the PRDS pressure. The pressure transmitter (PT-60) senses the PRDS line pressure. The output pressure signal is fed to a pressure indicating controller (PIC-60) as a process variable. The process variable signal is compared with the fixed set point in the pressure indicating controller. The output of the pressure controller operates the PRDS pressure control valve (PCV-903) on the PRDS line to control the PRDS pressure.
Refer closed loop logic diagram: 1104-02-2820-8
8) MINIMUM RECIRCULATION TO CONDENSER (FCV-941): This control loop is used to control minimum recirculation to condenser. The flow transmitter (FT-942) senses the line flow from GLAND STEAM VENT CONDESER. The output of flow signal is fed to a flow indicating controller (FIC-941) as a process variable. The process variable signal is compared with the fixed set point in the flow indicating controller. The output of the flow controller operates the flow control valve (FCV- 941) on the minimum recirculation line.
9) Hot Well LEVEL CONTROL (LCV-907): This control loop is used to control the LP HEATER level. The level transmitter (LT-907A, LT- 907B and LT-907C senses the hot well tank level. These signals from three level transmitters are given to a 2 out of 3 logic block. This block output is given to process variable to level controller LIC- 907.The process variable signal is compared with the operator feed manual set point in the controller.
When the hot well level comes above the set point, controller will open LCV-907 to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-10
10) CONDENSATE FROM EXPORT CONTROL VALVE TO COMMON SURGE TANK (LCV-908): This control loop is used to control the Common surge tank level. Two numbers of level transmitters (LT-908 & LT-909) senses the Deaerator tank level. The signals from two level transmitters are given to a 1 out of 2 logic block. The 1 out of 2 output is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the surge tank level comes below the set point, controller will open LCV-908 to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-11
11) COMMON SURGE TANK TO HOT WELL (LCV-907A): This control loop is used to control the hot well level. The level transmitter (LT-907A, LT-907B, and LT-907C (2 OUT OF 3 LOGIC)) senses the hot well level is given as process variable to level controller. The
process variable signal is compared with the operator feed manual set point in the controller. When the surge tank level comes above the set point, controller will open LCV-907A to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-12
12) CONDENSATE TO LP HEATER-2 (LCV-904): This control loop is used to control the level in LP HEATER-2. The level transmitter (LT- 903) senses the LP HEATER-2 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the LP HEATER-2 level comes above the set point, controller will open LCV-904 to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-13
13) LP HEATER-1 LEVEL CONTROL (LCV-904A): This control loop is used to control the LP HEATER-1 level. The level transmitter (LT- 904) senses the LP HEATER-1 level is given as process variable to level controller. The process variable signal is compared with the operator
feed manual set point in the controller. When the LP HEATER-1 level comes above the set point, controller will open LCV-904A to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-14
14) LP HEATER-3 DRAIN TO LP HEATER-2 CONTROL (LCV-902): This control loop is used to control the LP HEATER-3 level. The level transmitter (LT-902) senses the LP HEATER-3 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the LP HEATER-3 level comes above the set point, controller will open LCV- 902 to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-15
15) LP HEATER-3 TO HOT WELL CONTROL (LCV-902A): This control loop is used to control the LP HEATER-3 level. The level
transmitter (LT-902) senses the LP HEATER-3 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the LP HEATER-3 level comes above the set point, controller will open LCV- 902A to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-16
16) LP HEATER-2 DRAIN TO LP HEATER-1 CONTROL (LCV-903): This control loop is used to control the LP HEATER-2 level. The level transmitter (LT-903) senses the LP HEATER-2 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the LP HEATER-2 level comes above the set point, controller will open LCV- 903 to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-17
17) LP HEATER-2 TO LP HOT WELL CONTROL (LCV-903A): This control loop is used to control the LP HEATER-2 level. The level
transmitter (LT-903) senses the LP HEATER-2 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the LP HEATER-2 level comes above the set point, controller will open LCV- 903A to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-18
18) HP HEATER-2 DRAIN TO LP HP HEATER-1 CONTROL (LCV- 905A): This control loop is used to control the HP HEATER-2 level. The level transmitter (LT-905) senses the HP HEATER-2 level is given as
process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the HP HEATER-2 level comes above the set point, controller will open LCV-905A to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-19
19) HP HEATER-2 TO LP HP FLASH TANK CONTROL (LCV-905B): This control loop is used to control the HP HEATER-2 level. The level transmitter (LT-905) senses the HP HEATER-2 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the HP HEATER-2 level comes above the set point, controller will open LCV- 905B to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-20
20) HP HEATER-1 DRAIN TO DEAERATOR CONTROL (LCV-906): This control loop is used to control the HP HEATER-1 level. The level transmitter (LT-906) senses the HP HEATER-1 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the HP HEATER-1 level comes above the set point, controller will open LCV- 906 to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-21
21) HP HEATER-1 DRAIN TO HP FLASH TANK CONTROL (LCV- 906A): This control loop is used to control the HP HEATER-1 level. The level transmitter (LT-906) senses the HP HEATER-1 level is given as process variable to level controller. The process variable signal is compared with the operator feed manual set point in the controller. When the HP HEATER-1 level comes above the set point, controller will open LCV-906A to maintain the level.
Refer closed loop logic diagram: 1104-02-2820-22
22) LUBE OIL OVER PRESSURE CONTROL (PRV-910):
This control loop is used to control LUBE OIL OVER PRESSURE. This pressure transmitter (PT-128) Senses LUBE OIL HEADER PRESSURE and consider as a process variable to pressure controller. The process variable signal is compared with the operated feed manual set point in the controller. When the LUBE OIL HEADER PRESSURE comes above the set point, controller will open PRV-910 to maintain the pressure. Refer Closed Loop Logic Diagram: 1104-02-2820-23