CKB 30103

INDUSTRIAL SAFETY AND HEALTH

[ HAZARD IDENTIFICATION]

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LEARNING OBJECTIVESAt the end of this chapter, you will be able to;

1. Differentiate the methods to identify hazards.

2. Conduct What if-checklist

3. Apply the concept of HAZOP study

4. Construct Event tree & Fault Tree Analysis

5. Understand how to calculate risk assessment

6. Differentiate between Hazard Identification & Risk Assessment

7. Use Event tree & Fault Tree Analysis as probability quantitative risk assessment

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HAZARDS IDENTIFICATION

“the process of recognizing that hazard exists and

defining its characteristics.”

It is essential to identify the hazards and

reduce the risk in advance of an accident

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There are various approaches to hazard

identification:

– Review of documentation from vendor

– Review of legal and other requirements

– Walkthrough / survey / inspection using

prepared;Checklist based reviews

– Experience based reviews / Expert judgments

– Job Safety Analysis

No single tool fits all applications

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There are various approaches to hazard

identification:

– Review of documentation from vendor

Documentation such as………………..

– Review of legal and other requirements

Legal document such as …………………

From Act 514; ……………………………..

From Act 139; ……………………………..

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There are various approaches to hazard

identification:

– Walkthrough / survey / inspection using prepared

Checklist.[workplace inspection checklist]

Such as ……………………………………

– Experience based reviews / Expert judgments.

Learning experience from …………………….

– Job Safety Analysis

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• Used to indicate compliance with standard procedures and to identify common hazards.

• Design of the checklist depends on the intent.

• Checklist :

initial design/process change

process operation/shutdown

Process Hazards Checklist

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• Checklist at design stage» Review characteristic of all materials –

» raw material,

» catalyst,

» intermediate products &

» final products.

– Check for material type;

e.g. flammability

- what is the autoignition temperature,

- what is the flash point, how can a fire be extinguish etc.

e.g. toxicity

- what are the Threshold limit value,

- what PPE is needed etc.

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• Checklist at operation stage

– Review the material – Do all raw material conform to specification,

– What routine test are needed to support plant operations,

– Does the operating staff have access to MSDS

• Checklist at shutdown stage

– Review the material– Has the inventory of all chemical being removed

– Has all equipment been purged or flushed with inert

material

– Has a shutdown plan or schedule been communicated to

appropriate staff.

Job Safety Analysis

• Method / sample form (JSA & HIRARC).

• Video

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– Hazards and Operability study (HAZOP)

– Event Tree Analysis

– Fault Tree Analysis

– Failure Modes and Effects Analysis

(FMEA)

– What If –Checklist reviews

PROCES HAZARD ANALYSIS

Hazard & Operability Study (HAZOP)

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A formal systematic examination of a processing plant for identifying hazards, failures and operability problems, and assessing the consequences from such mal-operation.

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– Perform by A multi-discipline teams.

• Operation personnel; production and maintenance.

• Procurement personnel; production control (purchasing)

• Safety, Health and Environment personnel.

• Supplier ( sometimes)

– Requires a thorough examination of process-flow diagrams & piping and instrumentation diagrams,

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• A systematic method of uncovering if a process can

cope with deviations from indented design goals

e.g. a plant control system is designed to maintain

the temperature in a batch reactor at 65 oC for

2 hours .

what can make the temperature deviate from

65 oC?

Have means (safeguards) been implemented to

handle such deviations?

A block flow diagram of the HAZOP proces

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Refer to

page 448

for HAZOP

Procedure

Guide

words

Deviation Causes Consequences Present

Protection

Recommenda

tion

Company Name

Meeting Date:

Parameter study:

Diagram & Node No:

Team Name & leader:

Project Title:

OSHA Guide words

Meanings Comments

No or Not

The complete negation of these intention

The activity is not carried out or ceases.

More of,

Less of

Quantity increases or

Decreases in activity

These refer to quantities and properties such as flow rates and temperatures as well as activities like ‘HEAT’ and ‘REACT’

As well as

Part of

Another activity occurs as well the original activity

Incomplete performance of an activity

All the design and operating intentions are achieved together with some additional activity

Only some of the intentions are achieved; some are not

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Guide words

Meanings Comments

Reverse

Other than

Sooner / later than

The inversion of an activity

Complete substitution

When activity occurs at the wrong time relative to others.

This is mostly applicable to activities, e.g reverse flow of chemical reaction. It can also be applied to substances, e.g. ‘POISON’ instead of ‘ANTIDOTE’ or ‘D’ instead of ‘L’ optical isomers.

No part of the original intention is acheved. Something quite different.

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• Various parameter like

Flow rate,

Temperature,

Pressure,

Level,

Composition

Physical property like viscosity

and any other variable affecting the process

[ Table 10-3,Table 10-4 & Table 10-5 Page 449-

450]

• Process parameters and guide words suggest

process variables and their causes.

• Example identified causes:

Blockage of pipeline

Incorrect pressure / incorrect pressure

differential

Wrong routing

Incorrect fitted non return valve

Leakage

Vapour lock

Equipmet failure

Run out material in storage tank

Low quality / wrong quality of material

used

• Known cause and deviation, make possible for the

team to evaluate the consequences.

• Example possible consequences, that may rise to

hazardous condition :

Release of flammable/explosive material

Failure to control situation (on alarm)

Dangerous disturbance of plant condition

Failure to recover situation

Process deviation

etc.

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• Consequences of these deviation on the process

are then assessed, and measure needed to

detect and correct the deviations are established

• The results of the HAZOP analysis are the

team's recommendations,

include identification of hazards and the

recommendations for changes in design,

procedures, etc.

to improve the safety of the system.

Deviations during normal, startup,

shutdown, and maintenance operations are

discussed by the team and are included in

the HAZOP.

HAZOP FORM

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• Refer to Table 10-6

• Page 451

• Crowl & Louvar “Chemical Process

Safety- Fundamentals with

Applications

ADVANTAGES OF HAZOP

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1. Diagram (P&ID,PFD etc) are examined line by line

by multidiscipline team; hence HAZID is

comprehensive.

2. Potential problem areas of the design can be

identified to allow early design modification.

3. Promotes extensive dialogue between

designers and operators; hence better

understanding.

DISADVANTAGES OF HAZOP

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1. Excessive time required in review; hence target

time date cannot be achieved.

2. Unmanageable of board documentation,

especially for a complex system

3. Increase in the total capital cost; due to

additional / modification design or

equipment requested by the HAZOP

team

“What if” Analysis• A systematic examination of a process or operation

by asking questions that begin with “ WHAT

IF………”

• This examination include raw material, storage, material handling, operating procedures, management practices, plant security etc.

• Should be used for uncomplicated process.

• This procedure is powerful method of HAZID if being

carried out by experienced staff.

Combination What if / checklist Initial phase involves a brainstorming what if

session

Followed by a standardized checklist analysis

Problem 1: Process flow diagram- exothermic reaction

A+B = C + heat

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Materia l A

storage • Material B

storage

Product C

Reactor

Product C

Storage

AB

C

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Problem 1: Description

1. The chemical reaction involves 2 liquids, A & B, which flow from their

respective storage tanks into the stirred product C reactor.

2. The flow rate of materials A & B is regulated by control valves A & B,

respectively.

3. The liquid phase chemical reaction that results is highly exothermic &

generates considerable quantities of heat, which must be controlled by

cooling water on the jacket of product C reactor.

4. The reaction of materials A & B to produce product C proceeds rapidly,

& product C is drawn off from the bottom of the reactor.

5. Product C flow through valve C into the product C storage vessel to

await shipment.

6. The reactor & each of the storage tanks have pressure-operated relief

valves in case of pressure buildup during the process operation.

7. Temperature, pressure and level indicator are provided in

the product C reactor for use in controlling process

chemistry.

Combination : “What if / Checklist analysis.

What if Consequences Comment

Material A does not

flow to the reactor?

Un reacted material A

will contaminate

product C

Alarm & shutoff VB on

low flow through VA

Reactor temperature

exceeds operating

limit?

Reactor may be

damaged if pressure

relief fails

Supply more cooling

water to reactor; alarm

& shut off valves A & B

when reactor

temperature limit

exceeded.

Material B is

contaminated?

Product may be off-

specification;

undesirable reactions

may occur

May need improve

supplier B quality

control; verify material

B receiving &

procedures.

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Failure Mode and Effect Analysis

(FMEA)• All equipments and process components are

analyzed to identify

– potential failure mode,

– Consequences,

– Operating safeguards,

– Recommended actions to mitigate the hazards.

• List out all the equipment & process component of

the system under study.

• P & ID must be available for the team to study

• Most applicable to project that are well into design

phase.

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THANK YOU