Hazop Introduction

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    HAZOP STUDY

    HAZard and OPerability

    An introduction

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    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 atI.C.I. in the late 1960s

    Result of a desire to have structured

    check on P. & I.D.s Spread through I.C.I. in early 1970s

    Endorsed by the Health and Safety

    Directorate of the U.K. government Dow started to use in mid 1970s

    NL, Belgian and U.K. government

    adopted HAZOP

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    HAZOP in the 1980s

    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, consequencesand safeguards before INCIDENTS occur

    To define recommendations to minimize theHAZARD by eliminating or controlling thecause or providing lines of defence

    Provide compatible information forsubsequent 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 onthe P&IDs (do not re-design)

    Review is limited to deviations from normaloperations

    Impact of process unit on the utility systemsor other process units will be noted as

    requiring further study Primary intent is to identify hazards and

    define action items for additional safeguardsif 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 generatingthese 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, controlmalfunction is considered a cause in both nodes

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

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    Consequences

    Describe all consequences, even those that propagate outsidethe 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 leastan alarm as a safeguard

    Control instrumentation must automatically corrector mitigate a process deviation

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

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    what can HAZOP be applied

    to?

    Continuous processes

    Batch procsses

    Operating procedures (similar concept

    to Job Safety Analysis)

    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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    Risk Review in DOW today(Process Risk Management Standard 2001)

    Level 1 Risk Review: (Process Hazard

    Analysis (RC-PHA, Fire and Explosion

    Index, Chemical Exposure Index,LOPA target factors)

    Level 2: LOPA, Cause Consequence

    Pairs, Occupied Building Overpressureanalysis

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    Risk review in DOW today

    LEVEL 1

    Fire and Explosion Index < 128

    Chemical Exposure Index < 200 CEI Hazard Distance (3) outside of the

    fence

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    What makes HAZOP

    mandatory?

    TECHNOLOGY IS NEW TO DOW

    New processes

    New chemistry

    New Unit Operations

    These are the ONLY criteria for

    Mandatory HAZOP

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    HAZOP method

    Generic for Chemical Industry

    Dow guideline setting down our special

    needs (\\USN17\ehsaps)

    Based on P.& I.D. or flowsheet study

    with Operating Instructions/Design

    Intention

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    Normal scope of a Dow

    HAZOP

    Based on the operating unit(s)

    generating the highest risk

    Basic Criteria described All stepsfrom start up, through normal running

    to shut down

    Application to Most EffectiveTechnology (M.E.T.)

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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&IDs for the process are broken into manageable

    sections called nodes

    Nodes generally consists of unit operations andassociated 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 capturehazardous 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 leaders 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 thelines 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. PSVs 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

    (ususally similar to no flow

    Repeat exercise for more flow

    Repeat exercise for reverse flow

    Repeat exercise for composition

    (other than expected materialcomposition)

    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