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									Abu Dhabi National Oil Co. ADNOC Technical Institute

INSTRUMENTATION
PROCESS CONTROL FUNDAMENTALS

UNIT 6 PRACTICAL TASKS

PRACTICAL TASKS DATE OF ISSUE 8-DEC-09

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UNITS IN THIS COURSE
UNIT 1 BASIC CONTROL THEORY

UNIT 2

TUNING A CONTROLLER

UNIT 3

INTRODUCTION TO DCS AND PLC

UNIT 4

HONEYWELL TDC 3000 DCS

UNIT 5

FOXBORO IA DCS

UNIT 6

PRACTICAL TASKS

PRACTICAL TASKS DATE OF ISSUE 8-DEC-09

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TABLE OF CONTENTS
Paragraph PRACTICAL TASK 1 PRACTICAL TASK 2 Page 4 9

PRACTICAL TASKS DATE OF ISSUE 8-DEC-09

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PRACTICAL TASK 1 CASCADE CONTROL Introduction The Autodynamics simulator will be used to demonstrate cascade control. The process variable to be controlled is the level in a tank. A liquid storage tank is used to store a liquid before it is sent for downstream processing. The liquid has a variable density. Figure PT 1 shows the PFD and P and ID of the process. The normal operating conditions for the loop are: HCV-431 is open 50% to give a flow rate of 100 TPH entering V-400. The cascade loop maintains the level at 50% (half way) for a flow rate of 100 TPH. Alarm settings FAH/L 402 LAH/L 461 Above 160 TPH or below 60 TPH. Above 75% or below 25%.

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* 50.0 PCT 100.0 TPH

HCV-431 PI-411
0 KG/CM2G

FI-401

LIQUID

V-400

50.0 PCT

LIRC-461

100.0 TPH

HV-432 PI-412

FIRC-402

0.60 KG/CM2 G

Figure PT - 1a Process Flow Diagram (PFD) Level Control.

PRACTICAL TASKS DATE OF ISSUE 8-DEC-09

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HS 401

FI 401

FT 401

ZT HCV

401
PT

ZI 401 PI 401

431 411

LAH/L

461

DRAIN

LT

LIRC

461

461
SP

FAH/L

FIRC

V 400

402

402

O HS 422 C

ZI 432

O C
FV 402

ZS 432 HV 432

FT 402 FV 402

PT 412

PI 412

Figure PT - 1b P & ID Level Control

PRACTICAL TASKS DATE OF ISSUE 8-DEC-09

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PRACTICAL PROCEDURE PART 1 1) Make sure the Autodynamics simulator is operating as designed. Module 4 Level Control. The VDU screen shows: FI-401 FIRC-402 HCV-431 HV-432 LIRC-431 PI-412 READS READS READS READS READS 100 TPH 100 TPH 50% OPEN 50% 0.6 kg/cm2g

2)

a) What happens if you adjust the set point of FIRC-402.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------b) Explain the result of part 2(a). -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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PART 2 1. 2. 3. Place FIRC-402 to manual. Open HCV-431 so that it reads 60 %. Using the manual output control of FIRC-402, try and maintain the level of V-400 at 50%. 4. Estimate the time taken to bring the level under control.

PART 3 1. Return the simulator to normal designed condition, with full automatic control. 2. Increase HCV-431 so that it is 60% open. 3. Estimate the time taken to bring the level under control. 4. Does cascade control produce faster response in the system? -------------------------------------------------------------------------------------------

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PRACTICAL TASK 2 RATIO CONTROL Introduction This task uses the Autodynamic simulator to show the operation of ratio control. Ratio control is used to produce a mixed product for tanker loading. It is possible with the simulation to switch from ratio to cascade operation, using a product analyser. This is also demonstrated. Figure PT 2 gives the VDU display (PFD) and the P & ID for the process. Mixing Operation The mixing operation is used in the in-line blender to mix the available components. The components are blended to meet product demands and product specification. The mixing components for this operation are a heavy product feed and a light product feed. The blended product for loading meets quality specifications using a ratio or cascade control system. Under normal operation the ratio control is used for start up and cascade control for normal running. Ratio control sets the required mixture of heavy and light products. control is run by an analyser. The cascade It makes sure the correct ratio is

maintained after the initial settings are made by the ratio control. Logic Control This simulation has a PLC system added to provide the following safety function. Block valves HV-526 and HV-528 automatically close when the total volume of the respective trucks reaches 20 m3 (2000 litres). All flows stop, and the high volume alarm comes on. To restart the loading of another tanker the system must be reset by switches HS-531 or HS532. These switches must be switched "Off" again after resetting. The PLC logic will not allow the block valve (HV-526 or HV-528) to open if the reset is left "On".

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PRACTICAL TASKS DATE OF ISSUE 8-DEC-09

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PRACTICAL PROCEDURE Introduction To show how ratio control is done, the simulator exercise 5020 Module 5 will be carried out from the closed down position. The object will be to load a tanker with 20m3 (2000 litres) of SG 0.7 product. Note:The ratio calculation is done as follows (this is done automatically by the loading system). Let X = Quantity of Heavy product. Let Y = Quantity of Light product. Then (0.8 x X) +(0.4 x Y) = (X + Y)0.7 0.8X + 0.4 Y = 0.7X + 0.7Y 0.8X - 0.7X = 0.7Y - 0.4Y 0.1X = 0.3Y

3 X 0.3 = = 1 Y 0.1
The ratio of heavy to light product is 3:1 Note:1. The storage tank (slops tank) holds poor quality produce that cannot be sold. HV-526 must not be opened until AIRC-502 reads the correct quality on automatic. When the tanker is fully loaded the system will stop automatically. Make sure you don't open HV525 until the AIRC-502 is on automatic. 2. Remember to reset the totalizer after the tanker is loaded. Otherwise the PLC logic will not allow another tanker to be loaded.

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PART 1 START UP 1) 2) 3) OPEN the storage tank block valve (HV-527). Turn ON HS-515 to start the heavy product feed pump (P-f515). With FIC-501 on manual, increase the output of FIC-501 to 10%. This will open the heavy feed valve (FCV-501). 4) With FIC-503 on manual opens the light product feed valve by increasing the output of FIC-503 to 10%. 5) Adjust the setpoint of FIC-501 to equal its process variable and transfer the controller to AUTOMATIC. 6) Check the value at AIRC-502 for the specific gravity of the mixed liquid. If the specific gravity is undesirable, adjust the light flow through FCV-503. 7) Adjust the ratio of heavy feed to light feed by adjusting the value at HC-20. 8) Switch HS-529 to RATIO CONTROL, and place FIC-503 in the CASCADE mode. 9) Continue to gradually increase the set point of FIC-501 to design (113.6 m3/hr). The ratio controller HC-20 will automatically adjust the light flow through FCV-503. The specific gravity will not change.

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10) Perform a bump less transfer to place AIRC-502 in control in the following manner: a) Divide the measured variable of FIC-501 by the instrument range. b) Multiply that number by the ratio factor set on HC-20. c) Convert that number to output percent by multiplying by a factor of 100. d) This number becomes the required output setting for AIRC-502. e) Adjust the output of AIRC-502 to the number above. f) Switch HS-529 to the FEEDBACK condition. g) Switch AIRC-502 to AUTOMATIC. 11) Begin loading tanker no. 1 by putting HV-526 in the OPEN condition and switching the storage tank block valve (HV-527) to CLOSED.

PART 2 SHUT DOWN 1. OPEN storage tank block valve HV-527, and CLOSE the truck block valves, HV-526 and HV-528, to stop loading the trucks. 2. Reduce the heavy feed flow by placing FIC -501 in MANUAL and gradually decreasing the controller output. 3. When the heavy feed flow is very low, shut down pump P-515 by switching HS-515 to the OFF condition. 4. When all flows drop to zero, transfer AIRC-502 and FIC-503 to MANUAL. 5. CLOSE storage tank block valve HV-527.

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PART 3 Repeat sections 2 and 3 to fill tanker 2 with 20m3 of SG 0.5 product. PART 4 What heavy to light ratio would you expect for a final produce of SG 0.5? -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

PRACTICAL TASKS INSTRUCTOR'S NOTE The object of this task is to convince a student of the effectiveness of ratio and cascade control. The instructor will need to ensure the student can operate the simulator correctly but no special console settings are required. The simulator uses Honeywell TDC 3000 software for the screen displays. To reinforce the basics of the TDC 3000 the instructor should demonstrate the displays available, particularly the trend display. If possible show how the printer can be used to make a hard copy of trends for engineering management.

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