ENGI 9121: Advanced Safety, Risk and Reliability Assessment · Know the instructor MUN 2012 - Asst....

ENGI 9121: Advanced Safety, Risk and Reliability

Assessment

Faisal Khan

Salim Ahmed

Process Engineering

Fall 2012

Know the rules of the game

Be responsible

Learn through intellectual activities (taking class note is NOT one)

The D2L system is the main medium of communication. It is your

responsibility to check for important information about the course.

Be persistent

Nothing is more common than unsuccessful persons with talent

Persistence and determination alone are omnipotent

Know and follow the regulations

Plagiarism

Consult the FEAS/MUN Student Code of Conduct

http://www.engr.mun.ca/policies/codeofconduct.php

http://www.mun.ca/student/home/conduct.php

2 / 30ENGI 9121: Advanced Safety, Risk and Reliability Assessment

N

Know the instructor

MUN

2012 - Asst. Prof./Process Engg.

Qatar University

2008-2012: Asst. Prof./Chemical Engg.

University of Alberta

2006 - 2008: Postdoctoral Fellow

2006 - Ph.D. (Process Control)

BUETa,

2000 - M.Sc. (Chemical Engg.)

1997 - B.Sc. (Chemical Engg.)

aBangladesh University of Engineering & Technology


N

Track me down in the next 5-10 years


N

Preliminary design of a flash distillation process

F1 F2

P1

A1

T1 T2

F4

F5

L1

F3


N

Final design of a fired heater includes a number of

safety measures


N

What makes operations safer?

What are the additional elements in the final diagram?

Why do we need all of these?

How to determine what we need?

How to design what we need?


N

Module 2


N

Design of Safety Measures

Make sure you learn these

By finishing this module, you should be able to

Classify safety systems

Identify the needs for safety systems

Evaluate different systems for a given operation

Design proper safety systems for different operations

Recommend guidelines for the use of safety systems


N

Do the workouts, submit and get feedback

Engagement: we will solve workout problems in-class

Team-work: solve problem as a team

Communication: make sure that you can convey messages to and

read from your team members

Feedback: provide and be provided with feedback


N

Safety systems are the layers of protection


N

Hazard by themselves do not lead to a hazardous event

A combination of triggering effect, that is an isolated incident or a combination

of them lead a hazard to develop into an accident.

Safety systems are the layers of protection to prevent a hazard from leading into

an accident.

Safety is ensured through automation and

redundancy

Equipment, control and operators may fail

Multiple failures may occur

Automation is required for quick, timely and well-defined action

Redundancy is key to account for failure


N

Think about the flash distillation process

Would you like to run it like this?

F1 F2

P1

A1

T1 T2

F4

F5

L1

F3


N

Let’s think about a simple surge tank

LT

LCI/P

The surge tank is a stable

process.

If the inlet flow is changed, the

level goes to a different steady

state.

Can this guarantee that the

tank will not overflow or dry

down?


N

Basic Process Control Systems (BPCS) are implemented for safeoperation.

The first layer of protection is control (BPCS1)

BPCS

Process

1Basic Process Control System


N

Is control enough to ensure safety?

What if the control mechanism fails?

Warm liquid temp too high

Full opening of cooling valve is

not enough

May need to shut down feed

valve

Requires operator intervention


N

How do the operators know when to

intervene?

The alarms act as a layer of protection by warning

operators

Alarms

BPCS

Process


N

No automated action.

Requires analysis by an operator.

What if the operator fails to take the corrective

action?

Reaction runaway

Temperature increases sharply

Not enough time for operator

Requires to stop feed flow


N

Need to shutdown feed flow

automatically.

SISs are placed to automate emergency actions

SIS

Alarms

BPCS

Process

Activates when a critical process variable exceeds specified limits.

Automatic - no operator action required


N

SISs should be independent of the control system


N

When closing/opening the valves is not enough

P1

To effluent handling

Pressure goes beyond the limit

Opening the valve is not

enough

May be unsafe for the

following equipment

Need quick release


N

Need to use a relief device

Relief devices acts as a layer of protection by

diverting materials

Relief devices

SIS

Alarms

BPCS

Process


N

Relief devices are the last preventive layer

Provide an exit path for fluids

Normally used to prevent unusually high pressure

that may cause vessels or pipes to burst

resulting from large disturbance or equipment/power failure

Designed to be activated when control and SISs are not enough

The release is controlled


N

Control, alarm, SIS and relief systems are

prevention layers

Reliefdevices

Divert materialssafely

Safety instrumentedSystems

Shut down partof the process

Alarmsystem

Warn aboutabnormal situations

Basic processcontrol

Maintain variablesat desired values

Process Inherently safedesign

Fo

ur

ind

epen

den

tla

yers

of

pro

tect

ion


N

What to do if all the prevention layers fails and materials/energy is released.

Risk has two components

Risk = Probability × Consequence

Prevention layers

reduce probability


N

Can we do something to reduce consequences?

In case of release of materials/energy,

consequences should be reduced

Containment

Dikes

Emergency management

Procedures for plant personnel

Procedures for community response


N

Containment and emergency procedure act as

layers of protection

Community emergency response

Plant emergency response

Physical protection (dikes)

Relief devices

SIS

Alarms

BPCS

Process


N

Through design, prevention and mitigation safety

is achieved

Community emergencyresponse

Plant emergencyresponse

Physicaldevices

Reliefdevices

Safety instrumentedSystems

Alarmsystem

Basic processcontrol

ProcessPlant design

Process control

Safety control

Containment

Management

Mitigation

Preventionby control

Inherentsafety


N

Each layer contribute to the reduction of risk

Ris

kin

her

ent

ina

pro

cess

BP

CS

Ala

rms

SIS

Re

lief

Oth

ers

Risk reduction

by process control

by alarm system

by SIS

by Mechanical relief

by containmentand emergencymanagement

Risk reductionby reducingprobabilty

Risk reductionby reducingconsequence

Residual risk


N

The layers should be independent

To be considered as an independent protection layer (IPL), asystem should meet the following criteria:

Specificity: An IPL is capable of detecting and preventing or

mitigating the consequences of specified hazardous events.

Independence:

Its performance is not affected by the failure of another layer

Its performance is not affected by the conditions that caused

another layer to fail

The protection layer is independent of the initiating cause

Dependability: Reduces the identified risk by a known specified

amount

Auditability: Designed to permit regular periodic validation of the

protective function


N

ENGI 9121: Advanced Safety, Risk and Reliability Assessment · Know the instructor MUN 2012 - Asst....

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