Module 9: Practical Distributed Control Systems
Written Assessment
Total Marks: 97 marks
Assessment Points:
• Supply the required answers below in a blue font (not red or black).
• You must submit this assessment along with the practical component.
• Answer all the questions.
Module 9 Critical Questions:
• Question 1 & Question 20.
• These questions are mandatory to assess Module competency.
• Questions must be answered completely correctly to be assessed as competent with a score for this module.
Que 1: Explain the differences between DCS and SCADA systems.
Note – This question is mandatory. It should be answered and students are expected to get this question completely right to be assessed as competent with a score for this module.
Ans1:
Q2: Name the five (5) essential levels of SCADA systems.
A2:
Q3: Explain the meaning of smart instruments in a DCS system. And give a simple diagram where smart instruments are used to a computer based system using PLC and digital data communications.
A3:
Q4: What are the requirements of the operator interface within the DCS?
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Q5: What should be done when the DCS operator wants to see data? How a field communications failure is handled in a SCADA system?
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Q6: Draw a typical layout of the data communications paths in a DCS system, where a number of PLC’s collect the data from field devices and share that data with operator stations via LAN.
A6:
Q7: Discuss the importance of “redundancy” in a DCS system.
Hint: Think about sharing data between SCADA and DCS
A7:
Q8: Briefly describe and give a simple diagram for a cold standby SCADA system.
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Q9: Compare the functions of DCS and PLC in a SCADA system.
A9:
Q10: Explain the main differences between DCS and PLC/SCADA systems.
A10:
Q11: What are the advantages of “STAR” and “RING” topologies?
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Q12: Explain how digital inputs are used in a SCADA system and what applications they normally perform.
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Q13: Briefly describe the function of “Packet Switching Systems”?
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Q14: Explain how industrial Ethernet can be incorporated in DCS systems.
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Q15: Explain the “Bastion” model of security.
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Q16: What are the five (5) important industrial network security issues?
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Q17: Briefly describe “Polled” communication philosophy.
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Q18: How can we efficiently avoid collisions in a “CSMA/CD” communication technique?
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Q19: What are the functions of the DCS central processing unit. Also, include in your answer a simple diagram for a “Control Program” which is used as a loop (or iteration).
A19:
Q20: Describe discrete & logic control. What is a “Ladder Logic Diagram”?
Note – This question is mandatory. It should be answered and students are expected to get this question completely right to be assessed as competent with a score for this module.
A20:
Q21: What is meant by sequential & batch control?
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Q22: Sketch a simple diagram showing the algorithm for a continuous control system which uses PID controllers.
A22:
Q23: Discuss in detail your understanding about a PID control algorithm and its components.
Include in your answer a simple diagram including set point processing, output processing, operator, and processor.
A23:
Q24: Briefly explain the meaning of “tagged slot”, and give at least five (5) examples of data points.
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Q25: What is meant by “Timer Point” in a DCS system? What does it do?
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Q26: What are the six (6) basic network security measures?
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Q27: What is the main disadvantage of traditional firewalls?
A27:
Q28: Define what is meant by a “trend window”? What are the functions?
A28:
Q29: What are the three (3) main types of HMI screens?
A29:
Q30: Discuss human and ergonomic factors in alarm systems. Include in your answer a simple figure showing correct position of the operator to the system.
A30:
Q31: Ergonomic design and studies should ensure that important environmental parameters are appropriate to the requirements of the human operator.
Name at least five (5) such parameters.
A31:
Q32: An alarm system can assist the human operator in some areas.
Name at least four (4) such important areas.
A32:
Q33: By means of a simple diagram, show typical operator activities during an abnormal condition of the plant.
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Q34: Explain the concept of Safety Integrity Level (SIL).
Give a typical and simple diagram for “Discrete Safety Integrity Levels” vs PFD avg.
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Q35: Explain in detail the meaning of SIL2 category of safety integrity.
A35:
Q36: Name the activities involved in designing of an alarm system.
A36:
Q37: Explain how alarms are prioritized. Name at least two (2) factors.
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Q38: What are the benefits of “logging repeating alarms?
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Q39: In regard to alarm reporting, describe the four (4) features of “alarm annunciator display?
A39:
Q40: In regard to maintenance, explain your understanding of dependability of a DCS system?
A40:
Q41: What are the two basic requirements in terms of DCS in-built diagnostics?
A41:
Q42: Explain in detail the self-diagnosis concepts of a DCS system?
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Q43: Discuss in detail the three (3) reasons why UPS’s are essential for DCS control systems.
A43:
Q44: What actions does the “gateway interfacing module”, “controllers” and “history storage module” perform in the recovery of a DCS system?
A44:
Q45: a) From the table below prepare an alarm tag list with appropriate tag names and classify each tag as an important (i.e. actionable) or warning alarm. (10 marks)
Tag Name Description Range Units U_Limit L_Limit
AI-1000 Limestone crusher D.E. Opacity Monitor 0-50 ug/m3 35 0
AI-1100 Screen House D.E. Opacity Monitor 0-50 ug/m3 35 0
TIC-2000 Mill Inlet Temperature 0-120 Deg C 100 60
PDC-2000 Mill Differential Pressure 0-400 mm Wg 275 125
TIC-2010 Mill Outlet Temperature 0-150 Deg C 120 80
WC-2000 Mill Raw Material Feed / flow rate 0-225 tph 220 180
WIC-2010 High Grade Limestone Feed / flow rate 0-50 tph 45 0
WIC-2020 Feedable Grade Limeston Feed/Flow rate 0-180 tph 170 0
WIC-2030 Low Grade Limestone Feed / flow rate 0-50 tph 40 0
WIC-2040 Additives Feed/flow rate 0-20 tph 18 0
b) Explain the reason(s) for classifying the alarms as either important or warning. (10 marks)
c) Tag WC-2000 is the sum of the total feed / flow to the mill. Explain what tags are used to calculate this tag and how the calculation would be done using Function Block Diagram language. (10 marks).
A45:
Q46: Design an Effective Alarm Management system using MATLAB simulink for the following data.
Consider a Cement Grinding Ball Mill Bearings Lubrication System (as shown in fig) consists of an oil reservoir, two pumps – either of them supplies (other remains as stand-by) lubrication oil to the Ball Mill inlet and outlet bearings.
Sl.no. FAULTS
1 Pump-1 failure
2 Pump-1 power supply failure
3 Pump-1 oil filter Diff.Pressure High
4 Pump-2 failure
5 Pump-2 power supply failure
6 Pump-2 oil filter Diff.Pressure High
7 Inlet Bearing Oil Flow Low
8 Outlet Bearing Oil Flow Low
9 Lub. Oil reservoir Temperature High
10 Reservoir Lub. Oil Level Low
Design a simple and effective alarm management system for the above faults using MATLAB. For every fault condition, identify the alarm and also display corrective actions. 1or 0 can be used as input parameter to trigger certain faults like pump 1 failure… etc. Assume some fault conditions.
Provide Snapshots for before and after alarm trigger by running the MATLAB file.
PLEASE UPLOAD SIMULINK FILE.
Sample:
A46:
Please Provide IEEE references:
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