1204518574725 RIL PHA Involving OffSite Consequences Standard

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RIL Group StandardsPHA involving Off-Site Consequences



Document Control Details

Revision Date Reason For Issue Compiled by Approved by

0 Jan’ 08 Corporate Standard Mr. Mahesh Agrawal Dr. Prasad Tipnis

Next Review Date

Dec’ 10

User Notes:- The Centre for Health Safety and Environment Excellence (CHSEE) is the

custodian of this document and is responsible for the Administration and Authorisation of this

Standard. CHSEE is responsible for confirming the accuracy and integrity of content and

proposed changes to the Standard.

Controlled copy of the current version of this document is held at CHSEE and also available on

its portal. Any printed / electronic copy of this document is uncontrolled. It is recommended

that users verify that the version being used by them is the current version by referring to the

controlled version



PHA involving Off-Site Consequences – RIL Group Standard

Acknowledgement

The management acknowledges the contributions of the following individuals for being a part of the inter-site workgroup and for their assistance in preparing this standard (PHA involving Off-Site Consequences) on Process Safety Management.

Location Members

CHSEE − Mr. Mahesh Agrawal

Jamnagar

− Mr. HV Lodhia

− Mr. SL Chichghare

− Mr. AB Jani

Hazira

− Mr. NH Kothari

− Mr. Raskin Damani

− Mr. K Ramesh

Patalganga− Mr. SK Dikshit

− Mr. Mainak Ghosh

Vadodara− Mr. MG Manadan

− Mr. VK Shah

Nagothane− Mr. A Chattopadhyay

− Mr. NS Verma

Gandhar− Mr. PA Shah

− Mr. SP Nigam

The management also acknowledges the guidance and help of the following experts fromDuPont Safety Resources.

Agency Members

DuPont Safety Resources− Mr. Herbert Paans

− Mr. B Subramanian

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Abbreviations

• RIL - Reliance Industries limited

• HSE - Health, Safety and Environment

• CHSEE - Centre for Health, Safety and Environment Excellence

• GMS - Group Manufacturing Services

• PSM - Process Safety Management

• PT - Process Technology

• PHA - Process Hazards Analysis

• PHR - Process Hazards Review

• QA - Quality Assurance

• PSMLT - Corporate PSM Leadership Team

• ERPG - Emergency Response Planning Guidelines

• CCPS - Center for Chemical Process Safety

• IMS - Integrated Management System

• PIAM - Plant Integrity Assurance Manual

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• CMG - Crisis Management Group




Table of Contents

DOCUMENT CONTROL DETAILS ............................................................... 1 ACKNOWLEDGEMENT ..............................................................................2 ABBREVIATIONS.......................................................................................3 TABLE OF CONTENTS................................................................................4 DOCUMENT ISSUE.....................................................................................5 1. INTRODUCTION..................................................................................6 2. BASIC CONCEPT AND SCOPE..............................................................6 3. POLICY AND PUBLIC EXPECTATIONS................................................ 7 4. SEQUENCE OF ACTIVITIES.................................................................8 5. PHA RESOURCES................................................................................9 6. CONSEQUENCE ANALYSIS FOR EVENTS WITH OFF-SITE

POTENTIAL.........................................................................................9 6.1. Introduction ....................................................................................................9 6.2. Initial identification of event scenarios ........................................................ 10 6.3. Consequence evaluation criteria - toxics .......................................................11 6.4. Consequence evaluation criteria – fire./explosion........................................11 6.5. Initial consequence estimation ......................................................................11 6.6. More precise consequence estimation.......................................................... 12

7. CONSEQUENCE ANALYSIS - WORST CASE....................................... 12 7.1. Introduction .................................................................................................. 12

7.2. Worst case Definition.................................................................................... 13

7.3. Identifying the highest vapor and aerosol generation rate candidates........ 13 7.4. Estimating the worst case release consequences.......................................... 14

8. PROCESS HAZARDS REVIEWS (PHAS) ............................................ 14 8.1. Introduction .................................................................................................. 14

8.2. PHA team ...................................................................................................... 15

8.3. Process hazards analysis design meeting ..................................................... 15

8.4. Process Hazards Analysis methods............................................................... 16

9. RISK REDUCTION DECISIONS.......................................................... 16 9.1. Introduction .................................................................................................. 16

9.2. Measures of off-site risk.................................................................................17

9.3. Qualitative evaluation of off-site risk.............................................................17

9.4. Qualitative estimates of off-site risk ..............................................................17

9.5. Effective risk reduction items ....................................................................... 18

9.6. Events with industry crisis potential ............................................................20

9.7. The risk reduction decision-making process ................................................20

10. THE USE OF PHA INFORMATION IN COMMANDING OFF-SITE RISK........ 21

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11. GLOSSARY ........................................................................................22




Document Issue

The PHA involving Off Site Consequences Standard is issued by the Centre for Health, Safety &Environment Excellence (CHSEE), on behalf of Reliance Industries Limited management andform a part of the of Reliance Industries Limited HSE management system.

Name: …………………………...................................................................................................................

Signed: ………………………….................................................................................................................

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Date: ……………………………..................................................................................................................




1. Introduction

This guideline provides information and procedures to help identify, analyze, assess, andcontrol Company activities with potential for episodic off-site harm. The purpose is toensure systematic and consistent attention to potential off-site consequences and risk inProcess Hazards Analysis (PHA) and risk reduction decision-making.

Distinctions between consequences and risk, and their respective roles in the risk reduction decision-making process, are key concepts in the conduct of a Process Hazards Analysis. Consequence analysis takes a potential hazardous event and estimates theunmitigated consequences, without consideration of the frequency or probability of occurrence. Risk is the combination of both the extent of consequences and theiroccurrence frequency.

While consequence reduction is important, risk reduction is the primary objective in therecommended risk reduction decision-making process (Section 9). The dimension of frequency in risk, in certain circumstances, helps avoid incorrect over-emphasis on majorconsequence, worst case hazardous events. If the occurrence frequency is so low that the

risk from this worst case is extremely low, (compared to events with less catastrophicconsequences) then priority belongs on the higher-risk, lower-consequence, events. Asdiscussed in Section 9, risk reduction priorities and decisions should also be responsive topublic perception, within the framework that the primary objective is risk reduction.

2. Basic Concept and Scope

This guideline covers PHA for facilities that are capable of producing results off-site that:

are dangerous to life and health, or

Threaten the environment or property.

Toxic gas releases, explosions, fires, and other hazardous events which could injure peopleoff-site must be considered. Other episodic events, such as a process upset that can causemajor environmental damage or property damage of substantial concern to thecommunity, also need consideration.

To enable analysis of facilities with off-site consequence potential, guidance is provided:

For identifying hazardous events posing an off-site risk, and estimating theirconsequences using methods that provide consistent and technically-sound results.

For assessing risk from activities with potential off-site consequences, and to evaluate

measures that reduce risk by prevention and/or mitigation of hazardous events.

For determining a worst case hazardous event and estimating the vulnerable off-sitearea.

For preparation of off-site consequence and risk information for use incommunications with the public, focusing on interactions with Local CrisisManagement Groups (CMG)

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In PHA, hazardous events with potential off-site consequences should be examined,ranging from events with minimal off-site impact to worst case events. The analysisshould focus on key process safety features and the identification of opportunities forfurther risk reduction.




While there are sound safety reasons for undertaking analysis of extreme and worst caseevents, there is also a potential use for this information in communications to regulators,community leaders, Crisis Management Groups, and others, to ensure the publicunderstands how RIL anticipates and minimizes risk. The recommended safety and risk reduction decision-making process described in Section 9, is intended to aid in respondingto external communication requirements and expectations.

Since hazards and risk analysis activities for hazardous materials distribution aresignificantly different than for fixed facilities, they are not covered in this guideline. This iscovered in Distribution Safety Standard.

3. Policy and Public Expectations

To comply with Company’s policy, we must conduct our business in a way that protectspeople, the environment and property, and continually seek ways to enhance thatprotection. We must also recognize the importance of addressing public concerns over thepotential impact of RIL operations on their lives and property.

The public’s expectations for the performance of chemical plants in their communities are becoming increasingly stringent. Zero exposures off-site to toxic or environmentally hazardous materials is a growing public desire. Tolerance for lesser events, such asnuisance odors in their neighborhoods, is steadily decreasing. Therefore, our off-site risk goal is to design, build and operate our facilities in ways that:

1. Meet or exceed currently applicable legislative and regulatory requirements, andanticipate future criteria.

2. Address the public concerns in a way so as to develop low-risk, environmentally-sound facilities in the communities.

3. Do not add perceptibly to the risk off-site of accidental injury, death, orenvironmental damage.

4. Further reduce the potential for hazardous releases, as feasible, to reduce risk and respond to public concerns.

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Item 3 above, involves consideration and assessment of off-site risk in terms of publicperceptions.




4. Sequence of Activities

Process hazards analysis is an integral element in process safety management, asdescribed in PHA Standard. The information relationships between the PHA activitiesdescribed in this document and the other applicable standards are shown in the followingfigure.

The typical flow of activities in Process Hazards Analysis involving off site consequences isoutlined below. References to applicable sections of this guideline are provided.

Process Safety Management,Management of Change

Pre Start-up Safety Review

Process Technology,Process Hazard Analysis

Consequence Process Hazard

Analysis Review

Can Consequences

occur off-site?

es, apply PHA involving Off-SiteConsequences

No, Apply

1. Define the scope of the Process Hazards Analysis and make an initial identificationof the hazards; define the approximate range of hazardous events from those withminor off-site impact to candidate worst cases.

2. Estimate consequences of initial candidate events for the first PHA meeting.(Reference: Initial Consequence Estimation - Section 6).

3. In the first PHA meeting:

a. Determine whether or not the worst case consequences involve serious impactoff-site. If not, change the PHA to an on-site focus. (Reference: Worst Case –Section7).

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PHA




b. Identify a more thorough set of hazardous events, consider the needs foradditional Consequence Analysis and the value of more precise estimation of consequences. (Reference: More Precise Consequence Estimation - Section 6).

c. Develop a qualitative understanding of off-site risk, in terms of occurrencefrequency for hazardous events, and the potential number and type of injuries.

(Reference: Measures of Off-Site Risk - Section 9).

d. Determine if a limited or more extensive Quantitative Risk Analysis is needed based on initial qualitative risk estimates and other factors. (Reference:Process Hazard Review Methods - Section 8).

4. Complete the items identified for follow-up in Step 3 above; conduct the final PHA,and resolve all risk reduction items per the risk reduction decision-making process.Document PHA activities and the results of the Consequence Analysis, consistent with RIL Standards on Process Safety Management, Process Technology,Management of Change & Pre Start-up Safety Review.

5. PHA Resources

There are a number of Company resources that can assist in evaluating off-site risks:

• Consultants in process safety, explosion hazards, fluid flow and air dispersion canassist in consequence analysis. Consultants in the CHSEE can assist in off-sitequalitative and Quantitative Risk Analysis. Other specialists in the Engineering(Process & Engineering) can help identify and evaluate environmental damagepotential.

• In addition, given the increasingly high profile of off-site risk in the media andgrowing concerns among the public, public relations personnel can assist in

evaluating and measuring existing public attitudes in communities and in helpingstrengthen relations with the community.

6. Consequence analysis for events with off-site potential

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6.1. Introduction

Consequence analysis is an essential element in all process hazards analysis,along with process hazards reviews. A consequence is the direct, undesirableresult of an episodic accident sequence, usually involving a fire, explosion, orrelease of toxic material.

Consequence analysis is the estimation of potential harmful effects resultingfrom these accident sequences. Hypothetical incidents are analyzedindependently of their frequency, or probability, of occurrence. This applicationof consequence analysis should not be used for evaluation of chronic exposuresresulting from company activities; the methods needed for such evaluations are beyond the scope of this guideline.

Consequences from episodic accidental releases of environmentally damagingmaterials should be determined in consultation with an environmental expert.The evaluation and identification methods described in this guideline generally do not adequately apply to environmental consequences. Criteria to evaluatesignificant environmental damage should be developed by consultation with an

environmental specialist and reviewed with site and corporate management.




Consequence analysis focuses on a range of events, extending from ahypothetical worst case to more probable events with only minor effects.Evaluation of events with major impact is usually an iterative process. Italternates between the activities of identifying hazardous events and estimatingthe extent of the harm resulting from these events. As the key factors influencingconsequences become understood by a PHA team additional hazardous events

are frequently identified, requiring additional consequence analysis.

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6.2. Initial identification of event scenarios

Consequence analysis starts with a review of the facilities and activities, withinthe scope of the study, to select an initial range of accidental event scenarios.Most of the events having potential impact off-site will involve the release of atoxic, flammable, or environmentally-damaging material.

Frequently, a set of release scenarios has been identified in previous processhazards reviews. Otherwise, the first step is to identify and survey the hazardspresent to select hazardous events with the potential for consequences beyond

the immediate hazard location (e.g., 100 feet away). Organized hazards analysismethods to identify accidental release scenarios are described later in Section 8, but as a starting point, an informal approach is appropriate.

Hazardous consequences include injuries, substantial property damages, ormajor harm to the environment from episodic events. An initial range of accidental release scenarios should be selected that extends from a major event,thought to be a candidate for worst case consequences, to an event thought toresult in only minor consequences at locations near the release (e.g., 100 feetfrom the release). For emphasis, to help identify releases that can impact off-sitelocations, it is useful to identify a de-minimus release. This is defined as therelease that just causes minor consequences at the closest off-site location.

Events producing smaller releases will not have any direct off-site impact thatexceeds the selected consequence criterion.

For efficient use of resources, an appropriate consequence analysis strategy is toinitially use conservative, simplifying approximations for consequence analysis.Selection of candidate scenarios for worst case consequences should be doneafter reviewing Section 7, which defines worst case, and describes methods andconsiderations used to identify a worst case release. With this information as background, it is appropriate for purposes of selecting initial worst casecandidates to make simplifying approximations. For accident scenarios involvingprolonged toxic or flammable releases, typically the scenario with the greatestrate of vapor and aerosol generation will produce the largest consequences.

There are also circumstances where the worst consequence comes from thelargest quantity released, such as a short duration puff of toxic vapor, or anunconfined spill of evaporating liquid.

Conservative approximations tend to overestimate either the magnitude of theevent, the extent of the consequences, or both. A more complex analysis of consequences only needs to be done when hazards analysis considerations or risk reduction decisions indicate the need for a more precise and realisticconsequence estimate, or when required by regulatory authorities.




6.3. Consequence evaluation criteria - toxics

Consequence analysis for a hypothetical incident, as a minimum, consists of estimating the geographical zone in which consequences could exceed a givenlevel of harm (i.e., a consequence evaluation criterion).

While considerable injury criteria are available for chronic exposure to many toxic chemicals, very limited information is available for acute exposures. The American Industrial Hygiene Association has developed one-hour exposurelimits for chemicals, which are expressed as Emergency Response PlanningGuidelines, or ERPGs. Two acute exposure levels appropriate for off-siteconsequence evaluation are:

ERPG-2 emergency exposure limit; exposure results in minor but notirreversible health effects and individuals are able to take protective action,an evacuation criterion.

ERPG-3 exposure can cause serious health effects and may be life

threatening, an injury criterion. (See Section 11 - Glossary for completeERPG definitions.)

For estimation of locations where consequences of a toxic release can exceedserious injuries, the ERPG-3 concentration should generally be used. WhenERPG-3 values are not available, consult Haskell Du Pont or some other externalexpert for their equivalent recommendation and review with them the possibility of using Immediately Dangerous to Life and Health (IDLH) values as atemporary criterion. It may be appropriate to use criteria more stringent thanERPG-3 depending on local site and community relationships, and CHSEEguidance. For estimation of locations where evacuation and escape activities would be needed, ERPG-2 values should be used.

6.4. Consequence evaluation criteria – fire./explosion

An appropriate initial criterion for estimating possible fire exposure injury is thethermal radiation level where escape within 30 seconds will prevent burninjuries. This radiation level will not ignite most combustible materials even forprolonged exposure.

The appropriate criterion for estimating off-site explosion damage is anoverpressure that causes minor structural damage with possible injuries (e.g.,50% glass breakage can occur at 0.1 psi overpressure). If there are substantialpopulated distances off-site where this level of explosion damage can occur, it

will also be appropriate to evaluate locations where serious injury and majordamage could occur. Because different damage criteria are used for differenttypes of explosions, it is necessary to consult with an expert knowledgeable aboutexplosion when evaluating damage consequences for explosions with potentialoff-site impact (contact the CHSEE).

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6.5. Initial consequence estimation

Complete evaluation of accidental release scenarios can be a complex task involving considerations that include: instantaneous releases, phase changes,transient flow, thermodynamic interactions with the atmosphere, gasmomentum effects, aerosol formation, etc. For initial consequence estimates,simplifying assumptions that err by over-predicting consequences, are called for




(i.e., conservative assumptions). Generally, toxic gas and flammable vapors havethe largest consequences when:

released at or near ground level,

at conditions that produce high vapor and aerosol generation rates,

With low release velocities.

The more dense the gas, the slower it will disperse in air, so release conditionsthat increase the gas density are conservative. For releases of liquefied gasesunder pressure that flash at ambient temperatures, it is conservative to assumethat all of the liquid remaining after the flash will form a stable aerosol and notdeposit out as rain or form a pool.

After developing an initial set of conservatively-estimated release scenarios,computer software should be used to estimate toxic and flammable consequencesper the consequence evaluation criteria described previously.

6.6. More precise consequence estimation

Consequence estimates should always be prepared in a manner that can besubstantiated, particularly in light of regulatory requirements, whereverapplicable.

This means that they should be technically consistent with established methodsthat are widely accepted by experts and err on the conservative side by over-predicting consequences. However, use of the most conservative assumptionscan sometimes result in a gross overestimation of potential consequences. Insome situations, gross overestimates could lead to either unrealistic public

concern or unwarranted, and possibly unsafe, large-scale evacuation planning. Insuch cases, it is recommended that better-refined estimates of consequences beprepared, using more precise and realistic assumptions.

More precise, technically-defensible, consequence estimation is an extremely difficult task, complicated by the limited availability of large-scale test data.There are many different and complex technical approaches to consequenceestimation available. Without an adequate understanding of all the implicitassumptions incorporated in any particular method, inappropriate or outrightmisapplication is likely. Given the growing public and regulatory sensitivity around this issue, it is desirable to achieve an approximate level of consistency inconsequence analysis throughout the Company. To do so, all consequence

analyses using more precise methods or assumptions should be reviewed with aCHSEE consultant prior to documentation.

7. Consequence analysis - worst case

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7.1. Introduction

One of the primary efforts of risk reduction activities for accidental releases is toidentify effective means to reduce the area at risk. A thorough evaluation of the worst case is needed to define the maximum area at risk and gain insight into theimportant factors that determine that area.




Analysis of a worst case release is also an important screening criterion; if theresults of the worst case evaluation indicate the area at risk does not extend off-site, then extensive worst case consequence analysis will not be necessary.

7.2. Worst case Definition

The worst case is the release scenario that results in the greatest off-site distance where the selected consequence evaluation criterion can occur (e.g., the greatestdistance to the ERPG-3 boundary). The worst case accidental release scenario isdetermined by evaluating the following possibilities for each material withpotential adverse consequences beyond the immediate, local release area:

Catastrophic line or hose failure (flow from both ends) including the largestlines and hoses.

Exposure of vessels and equipment to fire if fires can occur, or if flammableor combustible substances are handled or stored nearby.

Venting of pressure relief devices at the relief system design basis.

Catastrophic vessel or container failure.

These possibilities are evaluated under the conditions that all mitigating systemsare failed, such as: flares, scrubbers, isolation valves, excess flow valves, check valves, interlocks, pressure relief valves, cooling systems, operator intervention,etc. A downwind distance to the consequence evaluation criterion is estimatedfor these release scenarios at realistic worst case meteorological conditions thatmaximize the down wind distance at risk. The total area at risk is a circle with thedownwind distance as a radius. Zones in this circle where hazardous impactcannot occur because of geographical barriers, such as mountains, are excluded.

For large sites, it may be necessary to evaluate releases for several materials atdifferent site locations to select several worst cases that encompass the total off-site area at risk.

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7.3. Identifying the highest vapor and aerosol generation ratecandidates

In consequence evaluation, for most toxic or flammable releases with significantconsequence potential, the material at the point of release is estimated as either:all vapor, all liquid, or flashing liquid and vapor. Dust releases can posesignificant toxic and flammable consequences, but they require specialconsequence estimation methods beyond the scope of the methods describedhere. If the release scenario is a sudden catastrophic vessel or container failure,or a release that lasts less than one minute, it is modeled as a puff.

The worst-consequence puff release is the one that produces the largest mass of vapor and aerosol. For flashing-flow puff releases, assume that all of the liquidremaining after the flash forms a stable aerosol and does not deposit out as rainor form a pool.

Puff releases at ground level will be hazardous further downwind than equivalentpuffs released at elevated locations. It may be necessary to compare differentelevated puff results with ground level puffs to identify the one with the greatestdownwind distance at risk. Puff releases that are essentially all liquid with




minimal flashing will form pools that are usually evaluated as a continuousrelease using a pool vaporization model.

The highest temperature pool with the largest surface area will generally have thehighest vapor generation rate. Spills onto surfaces where heat is rapidly transferred to the pool can also have high vapor generation rates.

Releases that last longer than one minute are treated for worst case estimationpurposes as long-term, constant-flow-rate releases (i.e., continuous releases).Determination of worst case release downwind distance, using time-varying,transient computer models, is not warranted in most cases; besides, transientmodeling technology has not currently progressed to a mature, widely-acceptedlevel. All of the conservative assumptions described above for puffs also apply tocontinuous releases.

7.4. Estimating the worst case release consequences

The worst case, conservatively-estimated release scenarios should be evaluated

using computer software.

A consequence analysis should be estimated for worst case candidate scenarios,at realistic meteorological conditions, that produce dangerous concentrations atthe greatest downwind distance. These recommended worst case meteorologicalconditions are site dependent,

8. Process hazards reviews (PHAs)

8.1. Introduction

This section describes special PHA activities and considerations that apply to

PHAs involving off-site consequences.

Recommended methods for these PHAs include, What If /Checklist, HAZOP,Failure Modes and Effects Analysis, Event Tree Analysis, Fault Tree Analysis andQuantitative Risk Analysis. For the purposes of this Guideline, Quantitative Risk Analysis is a study that generates risk contours and F-N graphs as described inSection 9 and defined in the Glossary.

This section assumes the reader has a working knowledge of these methods.Recommended references for these PHA methods, and a description of therelationship of PHA in Process Hazards Analysis and Process Safety Management are:

Process Safety Management

Process Hazard Analysis (PHA)

Center for Chemical Process Safety, Guidelines for Hazard EvaluationProcedures, Second Edition with Worked Examples

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Center for Chemical Process Safety, Guidelines for Chemical ProcessQuantitative Risk Analysis




8.2. PHA team

For many PHAs involving substantial or difficult-to-estimate consequences, thePHA team skills and knowledge should be expanded to include appropriateconsequence analysis expertise. In these cases, PHA team makeup shouldinclude people:

Who have direct responsibility for operating the facility or equipment(Ownership).

Who understand the basic science and technology involved in the processor equipment operation (Process Knowledge).

Who know how the equipment or process should work (DesignKnowledge).

Who have the hands on operating and maintenance experience for theprocess or similar processes (Operating Experience). [This provides the

knowledge of how the equipment or process actually operates, as opposedto how it is intended to operate.]

Who are skilled in PHA methodologies and in conducting PHA meetings(PHA Expertise).

Who understand the basic technology involved in consequence estimationfor this PHA (Consequence Expertise).

Who have other appropriate knowledge or expertise, as may be needed(Others).

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8.3. Process hazards analysis design meeting

Process hazards analysis and PHA activities begin with definition of the boundary limits, and selection of an appropriate, qualified PHA team. It isrecommended that one of the initial activities be a process hazards analysisdesign meeting. The PHA leader and a small group of team members shouldarrange a brief meeting to plan a process hazards analysis strategy and initialactivities, particularly for PHAs for operations that could involve off-siteconsequences.

Planning includes gathering and generating information for the PHR meetings,

including selection of scenarios for initial consequence analysis that bracket the worst case, and lesser releases down to the de-minimus off-site scenario. Thisinitial consequence analysis planning is particularly important for PHAs whereconsequences beyond the immediate hazardous areas, or consequences that aredifficult to estimate, are possible. Outside the planning meeting, consequencesare then estimated for these candidate release cases, prior to the first full PHR team meeting by PHA team.

Making consequence analysis information available to the PHA team prior to theinitial PHR meeting will improve team efficiency to identify hazardous events with far reaching consequences, and improve team effectiveness inunderstanding how consequences vary for different release situations. As

previously described, consequence analysis is typically an iterative process, and




hazardous events identified in the on-going PHR meetings may requireadditional consequence estimates.

8.4. Process Hazards Analysis methods

The recommended PHA methods for reviews involving off-site consequences can

be categorized as qualitative and quantitative. Qualitative methods are What If /Checklist, Failure Modes and Effects Analysis, and HAZOP. Recommendedquantitative methods are Event Tree Analysis, Fault Tree Analysis, andQuantitative Risk Analysis. Generally, for PHAs involving toxic or flammableconsequences, one of the qualitative methods should be used initially with theprimary focus on identifying hazardous releases. The qualitative methods canalso be used to evaluate the likelihood of hazardous release occurrence, identify the seriousness of the consequences, and develop risk reduction candidates.Event Tree Analysis, in combination with a qualitative method, is useful toquantitatively evaluate specific hazardous release situations. The Event Tree Analysis results can improve the evaluation of risk reduction candidates,particularly when a variety or range of risk reduction methods are under

consideration. Fault Tree Analysis is most useful in evaluating complex facilitiesand equipment where the effectiveness of process operation and controls toprevent hazardous releases is difficult to evaluate.

Quantitative Risk Analysis can be applied to the entire facility under study, or aspecific hazardous portion of it, to identify major risk factors and evaluate theeffectiveness of risk reduction candidates. Quantitative Risk Analysis may beappropriate for more complex, high-hazard facilities where a range of risk reduction candidates are under consideration, and for situations wherequantification of off-site risk will significantly improve risk reduction decisions. All the quantitative PHA methods, and the formal qualitative methods, require aqualified expert in hazards analysis with experience and background in that PHR

method.

9. Risk reduction decisions

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9.1. Introduction

Risk reduction decisions must be based upon an understanding of the key contributors to risk for the system under study. Key contributors to risk aretypically a limited group of similar events that account for most of the risk. Therange of off-site consequences and their frequency of occurrence (i.e., risk)provide a focus for development of risk reduction alternatives. During the PHR,all events with off-site consequences should have individual and societal risk

estimated at least qualitatively. Quantitative risk estimates can add significant value in some cases, as discussed in The Risk Reduction Decision-MakingProcess later in this section.

With consideration of risk contribution, effective risk reduction alternativesshould be generated for the range of hazardous events associated with thesystem. Effective alternatives are not always easily identified. Once identified,however, the risk reduction decision-making process evaluates the alternatives interms of their benefits (primarily individual and societal risk reduction andpositive public perception) and penalties (economic impact, implementationdifficulties, etc.).

This provides a means of comparison to identify the best choice. In developingalternatives and making risk reduction decisions, it is important to identify




events with industry crisis potential. These are extremely serious events, havingthe potential for adverse, disproportionate impact on the facility directly responsible for the incident, other plants, and related industry due to negativepublic or regulatory reaction.

9.2. Measures of off-site risk

Risk is the product of event consequences and their occurrence frequency. Thetotal off-site risk from a location / site is the cumulative risk posed by thecomplete set of hazardous events with off-site consequences, and their respectivefrequencies of occurrence. Off-site risk, in terms of individual and societal risk,can be estimated qualitatively and quantitatively, where:

Individual risk = the occurrence frequency of injury to an individual at aspecific off-site location.

Societal risk = risk to a vulnerable group of people, most often expressed interms of the frequency of occurrence of multiple injury consequences.

9.3. Qualitative evaluation of off-site risk

Individual risk can be qualitatively evaluated as the annual probability of injury at the most vulnerable off-site location. The most vulnerable location is generally the off-site point closest to where the hazardous event may occur. For example, achlorine leak from a one-ton cylinder could cause respiratory injuries in calm weather conditions at the site boundary and is estimated to occur infrequently. When PHA activities identify a number of hazardous events with off-site impact,identification of a single most vulnerable location may be more difficult.

Major events, with the potential for consequences to many people, pose risk to

the vulnerable group as a whole (i.e., societal risk). For qualitative evaluations,societal risk should be summarized as frequencies of occurrence for hazardousevents and their respective number and type of injuries. For example, inqualitative terms, societal risk for a given accident can be summarized as:

A likely event in the lifetime of this facility, with consequences that rangefrom a high probability of multiple medical treatment injuries, to a low probability of several life-threatening injuries.

or,

An extremely unlikely event in the lifetime of this facility withconsequences that include a high probability of many life-threateninginjuries.

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9.4. Qualitative estimates of off-site risk

For Quantitative Risk Analysis, QRA, as defined in this guideline, fatal injuriesare commonly used to measure risk (rather than nonfatal injuries). This is because comparative risk data are available for a wide variety of occupationaland industrial activities. Therefore, fatal injuries are recommended to measurerisk in QRA to allow comparison with external global risk criteria. For QRA,individual risk should be estimated as the annual probability of fatal injury at themost vulnerable off-site location.




When a QRA is done, risk contours are used to evaluate individual risk. Risk contours are a series of geographic, asymmetric concentric lines around thehazardous facility. Each contour represents a line of constant individual risk (i.e.,the annual probability of fatal injury). The benefits of risk reduction proposalscan be readily evaluated by comparing the changes in the location of risk contours from the base case.

When QRA is deemed necessary, the preferred metric for evaluation andcomparison of societal risk is an F-N graph. This graph is a log-log plot of F, thefrequency of occurrence of N or more fatalities, versus N. Comparison of F-Ngraphical results, for the purpose of evaluating the benefit of risk reductionproposals, however, is not as straightforward as for individual risk contours. F-Ngraphical results can be difficult to evaluate, and possibly misleading, withoutinput from a CHSEE or appropriate qualified expert.

9.5. Effective risk reduction items

Risk reduction items should be based on sound engineering methods and

practices, and provide integrity and reliability consistent with the risk of thehazardous events they control. The degree of risk reduction and the impact onlong-range business economics, given limited resources, are the key performanceparameters. Elimination, or reduction, of the hazard or consequence at thesource is generally the most effective approach in the long term. Mitigation of theconsequences, once a release has occurred, is an end-of-the-pipe fix. These fixestend to be difficult to maintain in a constant state of readiness.

Protective and preventive methods, such as process interlocks and isolation valves that effectively stop releases, are usually better than consequencemitigation; the assurance of managing and maintaining them for highly reliableoperation is important in estimating their risk reduction performance.

Other desirable attributes of effective risk reduction items, which should beactively searched for, include:

Diversity and independence from other controls, operating equipment, andprocedures. A low probability of failure from the same causes that disableother safety features or controls, and from hazardous event initiatingcauses, is important for effective risk reduction.

Use of equipment that fails safe when de-energized. Systems that fail-safeonly when energized can be designed for high reliability and integrity, butmanagement and maintenance to assure continuing safe performance is

difficult.

Safety equipment and procedures that are practical, easily operated,inspected and maintained to assure correct functioning. The ideal issimplicity and passive operation, with few or no moving parts (i.e., KEEPIT SIMPLE). Items with these features generally have high availability toperform their safety function and require minimal maintenance which benefits long term economics.

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In situations where public perception is, or could be, a significant factor, risk reduction performance should be considered in view of public perception. Thefollowing risk reduction hierarchy categorizes risk reduction concepts in order of

those that offer the best public perception first:




1. ELIMINATE SIGNIFICANT USE OF HAZARDOUS MATERIALS

• How can the process be changed to use a less dangerous material?

• How can the process be changed to eliminate any significant quantity of this dangerous material? Consider process changes such as,

synthesizing the material and consuming it as it is formed, using it in adilute or different form that poses minimal risk, etc.

2. IMPROVE CONTAINMENT OF HAZARDOUS MATERIALS

• Use containment vessel design pressures high enough to avoid the needfor emergency vents and relief valves, for example, on distillationcolumns.

• Consider enclosing process equipment inside equipment with similarpressure rating (i.e., pipes within pipes and vessels within vessels), withleak detection in the annulus.

• Change the process pressures so that air leaks in rather than thehazardous material leaking out. Reduced process pressures close toatmospheric will minimize release rates.

3. MINIMIZE AMOUNT OF HAZARDOUS MATERIALS RELEASED

• Alter the process to minimize the quantity contained.

• Use isolation valves to bottle up all substantial quantities in case of pipeor equipment loss-of-containment accidents.

4.

LIMITED SIZE OF THE EXPOSED AREA

• Consider water sprays where they can substantially reduce the size of the impacted area.

• Consider a depressurization system to decrease the vessel pressure forlarge quantities of hazardous materials. Lowering the pressure cansubstantially reduce potential accidental release flow rates.

• Purchase land or relocate the hazardous materials to increase thedistance from the hazard to populated locations.

• Consider enclosing the equipment containing hazardous materials in a building with a scrubbed exhaust system. Size the system to handle thelargest bottled-up quantity, or study the risk benefits from incrementalscrubbing capacity increases.

5. REDUCE IMPACT ON THE EXPOSED AREA

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• Consider use of a computerized emergency response system to improvedecision making and resource deployment in emergency conditions.Community awareness and education are important considerations,and effective plans should be developed as described in Community Preparedness Standard.




9.6. Events with industry crisis potential

Accidents and near misses, with actual or potential damage to the publiccommunity, can have impacts well beyond the directly-affected victims and theresponsible facility. Major industrial incidents can impact the plant, thecompany, and even related industry with harmful effects far in excess of the

direct damage to victims. These impacts can extend far beyond the affectedparties, and may include significant indirect costs (both monetary andnonmonetary) to the responsible company, and in some cases, to all companiesin the industry.

Examples of incidents with industry crisis impacts include the 1984 Bhopalmethyl iso-cyanate release and the 1991 Texas City hydrogen fluoride (HF)release. Impacts from the Texas City release have gone substantially beyondTexas City. This incident prompted the regulatory authority for the Los Angeles,California, area to pass a rule aimed at immediately reducing, and ultimately eliminating, industrial HF use by business in the area. It is an example of how serious incidents can cause greater scrutiny and greater potential for regulatory

intervention.

As part of PHRs involving off-site consequences, methods of analysis andinsights are needed to identify events with industry crisis potential. This is notintended to be a complex technical process, although there are experts andreferences available for assistance. The recommended reference that describeshow to identify industry crisis events is Ripples in a Pond: Forecasting IndustrialCrises, by Paul Slovic. In many cases, when a worst case event with potentialmultiple off-site and life-threatening injuries is identified, it is reasonable toexpect that this event has industry crisis potential.

Risk reduction efforts for events with industry crisis potential should search for

effective risk reduction items as previously described. In many cases, it may not be practical to eliminate or substantially reduce the consequences, which limitsrisk reduction to searching for methods that lower the frequency of occurrencefor the industry crisis events.

Processes or operations with industry-crisis-potential events should, as aminimum, employ all applicable guidelines, standards, and proven goodengineering practices to reduce the risk. Effective methods that reduce the risk of industrial crisis events also generally assure a sound approach to reducingsocietal risk from lesser events.

9.7. The risk reduction decision-making process

Once the key contributors to risk for the system under study have beenidentified, the risk reduction decision-making process begins. This process isintended to find the best net combination of safety benefits and related penaltiesfrom among the identified alternatives. The process has four iterative steps, asfollows:

1. Identify and define the risk reduction alternatives.

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2. Specify the appropriate measures of effectiveness and estimate to whatdegree they are achieved. The key objective is risk reduction, including bothindividual and societal risk. Other objectives may also be appropriate,

including good public perception, consistency with site practice, conformity




to standards, etc. Benefits other than risk reduction, such as improvementin process yield, etc., should also be identified as part of this step.

3. Identify the penalties associated with each alternative, including long-termeconomic impact on capital and operating/maintenance costs, difficulty of effective implementation, etc.

4. Where appropriate, quantify values, consistent with the continuousimprovement process, and analyze the alternatives to select the best choice.

In this process, risk reduction is limited by the available alternatives. In cases where major off-site risk is present and effective risk reduction alternativesinvolve difficult issues, the risk reduction alternative of phasing out hazardousoperations should be evaluated. This risk reduction decision-making processshould be used for both qualitative and Quantitative Risk Analysis.

Occasionally, substantial concerns regarding off-site safety may persist even afterseveral cycles through the risk reduction decision-making process. In these rare

and highly unusual cases, to evaluate the overall level of safety, it is possible toquantitatively estimate the off-site risk and make comparisons with accreditedregulatory criteria. Development of a Quantitative Risk Analysis for comparison with the Dutch guidelines, as a means to identify and focus priority efforts onimproving high hazard situations, should only be done with the assistance of aPHA expert (Contact CHSEE).

Inadequate evaluation of risk, because of incorrect frequency or consequenceinformation, can lead to poor quality risk reduction decisions.

Example: Focus Only on Consequences

Over-emphasis of consequence reduction involved a desire to reduceconsequences from complete failure of a large chlorine storage tank. The processrequirements were such that several chlorine rail cars connected in parallel couldserve as a replacement for the tank. Consequences for railcar failure weresubstantially less than the tank failure, so this change was recommended. By notevaluating risk, it was not discovered that the process risk would actually increase because more vessels, connections, piping, etc., would increase thefrequency of releases.

Example: Insufficient Estimation of Consequences

Study of another liquid chlorine handling system was based on the consequence

estimate that any release from a one-inch pipe or larger would be extremely bad.Per this estimate, small vessels under low pressure had automatic isolation valves installed on all liquid connections. Similarly, a high-pressure, nitrogen-padded, liquid chlorine tank also had a single isolation valve. Even though thehigh pressure release consequences would be much worse than the low pressurereleases, the risk was thought to be similar because of the incomplete estimationof consequences. As a result, the risk reduction opportunity to install a secondhigh integrity isolation valve, inside the high pressure tank, was not identified.

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10. The use of PHA information in commanding off-site risk

The information generated in the off- site Process Hazards Analysis provides the

foundation for communication to ensure that the public understands how RIL anticipatesand minimizes risk. Risk communication is a complex subject beyond the scope of this




guideline. Several resources exist within RIL to aid sites in the development andimplementation of risk communication programs that can build understanding andmitigate adverse public reaction.

Specifically, the Public Relations personnel can offer hands-on assistance with all aspectsof such efforts. Sites should contact their Public Relations personnel for communications

assistance.

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11. Glossary

Area at risk - the geographical zone in which potential consequences from a hazardousevent could exceed a defined level of harm, selected as the consequence evaluationcriterion.

Consequence - the direct, undesirable result of an accident sequence, usually involving afire, explosion, or release of toxic material.

Consequence analysis - the estimation of potential harmful effects, and the area where

they can occur, resulting from an episodic hazardous event. Consequences are analyzedindependently of the event s probability or frequency of occurrence.

Continuous release - Releases lasting more than one minute are usually treated ascontinuous, for purposes of dispersion calculation.

De minimus release - the release event that causes minor consequences at the closest off-site location. Events producing smaller releases will not have any direct, off-site impact.

Episodic release - a release of limited duration, usually associated with an accident.

ERPG (Emergency Response Planning Guidelines) - a system of guide lines, developed by

a committee of the American Industrial Hygiene Association, which are intended toprovide estimates of concentration ranges where one might reasonably anticipateobserving adverse effects as described in the definitions for ERPG-1, ERPG-2, and ERPG-3, as a consequence of exposure to a specific toxic substance.

ERPG-1 - the maximum airborne concentration below which it is believed that nearly allindividuals could be exposed for up to one hour without experiencing other than mildtransient adverse health effects or perceiving a clearly defined objectionable odor.

ERPG-2 - the maximum airborne concentration below which it is believed that nearly allindividuals could be exposed for up to one hour without experiencing or developingirreversible or other serious health effects or symptoms that could impair their abilities to

take protective action.

ERPG-3 - the maximum airborne concentration below which it is believed that nearly allindividuals could be exposed for up to one hour without experiencing or developing life-threatening health effects.

Event Tree Analysis - A logic model that graphically portrays the combinations of eventsand circumstances, and their probabilities of occurrence in an accident sequence.

F-N graph - a plot of cumulative frequency versus consequences, usually expressed as anumber of fatalities. Used as a measure of societal risk in quantitative risk studies.

Hazard - a chemical or physical property or condition that has the potential for causingharm to people, property, or the environment.




Hazardous event - a specific, unplanned event or sequence of events that leads to physicalharm to people or damage to property or the environment.

Individual risk - the risk of injury to a person at a specific location, including the nature of the injury and the expected frequency of the injury occurring.

Industry crisis potential - a term used to describe an event having the possibility foramplified business, political, and/or regulatory effects beyond the geographic area directly impacted by the precipitating incident (see examples).

Occurrence frequency - the number of occurrences (or estimated occurrences) of an eventper unit time.

Process Hazards Analysis - the combination of a Process Hazards Review and aConsequence Analysis.

Process Hazards Review (PHR) - the systematic, comprehensive study of a process oroperation, using recognized, formal method(s) of analysis, to identify hazards, identify

hazardous events and all of the ways in which each event can occur, and develop practicalrecommendations to eliminate or control the identified hazards.

Puff release - an emission that is short in duration compared with the time required toreach a location of interest. Releases lasting less than one minute are usually treated asinstantaneous, or puff, releases.

Quantitative Risk Analysis - the systematic development of numerical estimates of theexpected frequency and consequences of potential hazardous events associated with afacility or operation, based on engineering evaluation and mathematical techniques. Thisanalysis generates risk contours and F-N graphs using computer programs such asPHASTrisk (DNV Technica) or equivalent.

Risk - the product of the expected occurrence frequency (events/year) and theconsequences (effects/event) for a hazardous event or group of hazardous events.

Risk contours - lines connecting points of equal individual risk around a facility, used inQuantitative Risk Analysis.

Societal risk - a measure of risk to a vulnerable group of people, most often expressed interms of frequency of occurrence distribution of multiple casualty events.

Worst case - the release scenario that results in the greatest off-site distance where theselected consequence evaluation criterion can occur

1204518574725 RIL PHA Involving OffSite Consequences Standard

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