HAZOP STUDY

HAZard and OPerability

An introduction

Oct. 3, 2013 Risk Management 2

Content

History

Purpose

Hazards

Deviations

Parameters

Guidewords

Consequences

Safeguards

Application

HAZOP in Dow

HAZOP Process

Nodes

Starting the Study

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Origins of HAZOP

Concept dreamed up by Bert Lawley at I.C.I.

in the late 1960’s

Result of a desire to have structured check

on P. & I.D.s

Spread through I.C.I. in early 1970’s

Endorsed by the “Health and Safety

Directorate” of the U.K. government

NL, Belgian and U.K. etc. governments have

adopted HAZOP

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HAZOP in the 1980’s

U.K. HSE and the Dutch Arbeidsinspectie

began to mandate HAZOP as part of Safety

Report for “Seveso Directive”

I.C.I. by this time were doing HAZOP on

“everything”

Dow incorporated in its Risk Management

process based on its own criteria (focusing

on highest risk)

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Purpose of HAZOP

To identify credible causes, consequences and safeguards before INCIDENTS occur

To define recommendations to minimize the HAZARD by eliminating or controlling the cause or providing “lines of defence”

Provide compatible information for subsequent Process Safety efforts (i.e. LOPA scenarios)

Comply with regulatory Process Safety requirements

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Scope of HAZOP

Review is limited to the piping, instrumentation and equipment shown on the P&ID’s (do not re-design)

Review is limited to deviations from normal operations

Impact of process unit on the utility systems or other process units will be noted as requiring further study

Primary intent is to identify hazards and define action items for additional safeguards if appropriate

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HAZARDS

Fire and Explosion

Reactive Chemicals Incidents

Toxic Exposure

Corrosion

Radiation

Vibration

Mechanical Hazards

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“Deviations”

Hazards are caused by DEVIATIONS

from the DESIGN INTENTION

HAZOP is a method for generating

these “DEVIATIONS” using “GUIDE

WORDS”

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Study is based on

“PARAMETERS”

Flow

Temperature

Pressure

Level

Composition

Agitation

Anything it is important to control

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In combination with “GUIDE

WORDS”

“No”

“Less”

“More”

“Reverse”

“Instead of ” or “Other than” (e.g.

something else or wrong composition)

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Combinations of parameters and

guide words are “DEVIATIONS”

No flow

Less flow

More flow

Reverse flow

Flow of something not planned

More temperature

Less temperature

And so on…...

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Deviations are logical

combinations like...

More temperature

Less pressure

Ignore illogical combinations like….

X Reverse temperature

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Determining the causes for a

deviation

Consider only the causes that originate within the node (consequences may be outside of the node)

Deviations could be caused by: Equipment or process control failure

Human error

Loss of utilities

External events such as fire

Long term processes, e.g. erosion, corrosion, coking

If process instrumentation crosses a node boundary, control malfunction is considered a cause in both nodes

Deviations that require the simultaneous occurrence of two or more unrelated causes are not considered

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Consequences

Describe all consequences, even those that propagate outside the node.

Consequences may include: Personnel injury

Environmental damage

Equipment damage

Property loss

Extended downtime

Operability/Quality problems

Consequences are described assuming there are no safeguards

Describe consequences as a chronological sequence of events

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Safeguards

Safeguards may include: Equipment design

Instrumentation (control, alarm and shutdown)

Pressure relief devices

Administrative procedures

Only list those instrument systems that have at least an alarm as a safeguard

Control instrumentation must automatically correct or mitigate a process deviation

Operator training and administrative procedures should be listed provided they are part of ODMS

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What can HAZOP be applied

to?

Continuous processes

Batch processes

Operating procedures

Maintenance procedures

Any operation where the Design Intention is

defined and deviations are possible

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Recommendations

Recommendations are made to: Eliminate a cause

Prevent or mitigate the consequence

Reduce the likelyhood that the hazard will occur

Examples of recommendations include: Equipment/instrumentation changes/additions

Further study needed

Inspection and maintenance

Training

Administrative systems to manage hazards

Verification of design assumptions

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HAZOP Process

Team maximum 6 persons from (example):

run plant engineer

programmer

process control

process chemist

shift operations team member

study leader/facilitator

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Nodes P&ID’s for the process are broken into manageable

sections called nodes

Nodes generally consists of unit operations and associated piping and connect to upstream and downstream units

Nodes are defined by the HAZOP team and can be redefined as needed

A “Global issues” node can be included to capture hazardous events that can impact the entire process unit. For example:

Loss of containment

Sampling

Utility failure

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Typical nodes

E 201

R 201

P 201

NODE 1

NODE 2

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Nodes

There is no “right” way to define nodes

Usually start with a small node

As experience builds, move to a larger node

Follow the leader’s intuition

If the team gets bored, the node is probably

too small

If the team gets confused, the node is

probably too big

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Starting the study:

The most knowledgeable person describes

the INTENTION of the node

Composition (which chemicals are in the

equipment)

Flow, temperature, pressure, phase,

quantity, agitation etc

…. Anything important to the process

Leader records for study team reference

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Start with Deviation “No Flow”

Team gives all the causes for no flow in the lines and equipment inside the node

Leader prompts their thinking

Team can add but not delete

These causes are recorded in software package

The library in the software can be consulted for possible additional causes

When the ideas “dry up” move on to CONSEQUENCES

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Team decision on “ACTION”

column Team may decide if any new action is

needed

Can record any protective devices or

alarms which become active e.g. PSV’s

Can refer decision outside the team

Can refer serious consequences for

“consequence analysis”

MUST NOT REDESIGN THE PLANT in

the Hazop study session!!

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After “no flow”

Repeat exercise for “less flow”

(usually similar to “no flow”

Repeat exercise for “more flow”

Repeat exercise for “reverse flow”

Repeat exercise for “composition”

(other than expected material

composition)

UNTIL “FLOW” is completely studied

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After “flow”

List causes for “more temperature”

proceed to consequences for “more

temperature”

repeat all steps as for flow

when temperature is studied, go to pressure

after pressure, consider other parameters,

e.g. agitation (use design intention as a

guide)

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When parameters are all done

for node 1

Repeat whole process for node 2

And all the other nodes defined in the

study scope

List actions and responsibility for follow

up