2013 Honeywell Users Group Americas

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Using Honeywell UniSim Design to Simulate Transition and Faults

M. A. Kader Rasel, Ph.D Student, Lamar University

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Overview

• Process Transition

– Monitoring

– Fault detection

• Transition Simulation

– Honeywell UniSim Design

– Dynamic Simulation of equipment changeover

• Analysis and Fault Detection

– Trend Analysis

– Fault detection for different scenario

• Results and discussion

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Process Transition

• Transition Types

– Process state changes (like startup and shutdown)

– Equipment changeover (like furnace, absorbers, pumps, compressors etc)

• Common in day-to-day process operation

• Ensures safe and continuous operability

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Process Transition

• Process state change

– feedstock

– Throughput

– change in operation mode.

• Equipment changeover

– Maintenance

– Regeneration

• Minimal upset of process state is desired

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Process Transition

• Fault during transition

– Process fault (equipment failure)

– Human factor (operator fault)

• Upset the steady state for longer time

• Off spec product

• Accidents

• Early and automated detection can prevent prolonged transition and unexpected situation

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Process Transition

• Transition Monitoring

• Consistent transition operation

• Adherence to SOP

• Operator Performance

• Operation index

• Improve plant safety and reliability

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• Study of transition by simulation

– Dynamic simulation

– Analysis of transition trends.

– Simulation of different fault scenario

– Effectiveness of transition fault detection

• Robustness of the simulation program

• Honeywell UniSim Design

Transition Simulation

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• For Simulation case, a simple reflux pump changeover in a distillation tower is chosen.

Reflux pumps

Reflux flow

controller

Transition Simulation

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• Characteristics (equipment changeover)

– One or more variables changes

– Controllers are in automatic mode

– Process try to maintain steady state

– Controller output can be used to monitor the transition pattern.

• Standard operating procedure (SOP) is followed to minimize process upset

Transition Simulation

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Transition Simulation

• Standard Operating Procedure

1) Open the inlet valve of the reserve pump

2) Start the reserve pump

3) Make sure of the pressure build up in the pump outlet

4) Start opening the reserve pump outlet valve, simultaneously closing the running pump outlet valve

5) Make sure the reserve pump outlet valve is fully open

6) And the running pump outlet valve is fully closed

7) Stop the previously running pump

8) Close the inlet valve of previously running pump Reflux pumps

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Transition Simulation

• Possible fault during transition steps

I. (@1) Reserve pump inlet valve is not opened

II. (@1) Opened the wrong valve instead of inlet valve

III. (@2,3) Pump failed to start/No pressure buildup

IV. (@4) Asynchronous opening and closing of the outlet valves

V. (@4) Wrong valve operation during opening and closing of the outlet valves

VI. (@5) Pump outlet valve partially opened / did not opened

VII.(@8) Closing the wrong valve

Reflux pumps

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Transition Simulation

• Response for SOP (normal transition)

– Reflux flow controller (PV, OP, SP)

– Top stage pressure

– Temperature

• FC-RFX-OP has distinct change in pattern

– Used as a monitoring variable

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Analysis and Fault Detection

• Transition Analysis for SOP

• Matlab is used to plot several linear lines in the trend changes

• Transition monitoring was performed comparing with the fitted line

0 10 20 30 40 50 60 70 800

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Analysis and Fault Detection

• Trend Analysis and monitoring

• Transition monitoring is performed using enhanced trend comparison [ref 1], based on

– Shape matching degree

– Magnitude matching degree

– Duration matching degree

• Fault is detected if magnitude of the above indexes exceeds threshold limit

0 10 20 30 40 50 60 70 800

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80Input data and fitted function

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Analysis and Fault Detection

• Transition Fault

– Pump failure

– Similar trend for opening wrong valve instead of the reserve pump outlet valve

• Fault is detected in phase 2 due to shape mismatch

0 10 20 30 40 50 60 70 80 900

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Trend Change

Real Time

SOP

Fault Detected

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Analysis and Fault Detection

• Transition Fault - unsynchronized pump swapping (type I)

– closing the valve of running pump takes longer that the opening the reserve outlet valve

• Fault is detected in phase 3 due to mismatch in duration

0 10 20 30 40 50 60 70 80 90 1000

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Trend Change

Real Time

SOP

Fault Detected

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Analysis and Fault Detection

• Analysis for unsynchronized pump swapping (type II)

– Opening the valve of reserve pump takes longer that the opening the running outlet valve

• Fault is detected in phase 4 due to mismatch in magnitude

0 10 20 30 40 50 60 70 800

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Trend Change

Real Time

SOP

Fault Detected

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Results and Discussion

• In this work

• Transition simulation using Honeywell UniSim Design

• Using the simulated data, trend analysis is performed

• Enhanced trend comparison is used for monitoring transition

• Simulation of different fault scenario

• Equipment failure and human error in transition is performed and tested with the fault detection method

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Acknowledgement and Reference

• Acknowledgement

– Lamar University, Department of Chemical Engineering

– Dr. Peyton C. Richmond, Advisor

• Reference

– [1] Sundarraman, A., Srinivasan, R. (2003). Monitoring transitions in chemical plants using enhanced trend analysis. Computers & Chemical Engineering, volume 27, 1455-1472.

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