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Equipo de LOPA

Identificación Escenario y Desarrollo Documentación

Eventos iniciadores y modificadores frecuencia

Escenarios, eventos de iniciación, y modificadores de frecuencia

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Proceso LOPA

STEP 5:

EVALUATINGFURTHER R ISK

REDUCTIONSUGGESTIONS

PASO 1:

STEP 6: PASOTEP 2 :

STEP 3:

STEP 4:

IDENTIFICAR

ESCENARIO DE INTERES

IDENTIFY CONSEQUENCES

& TARGET FACTOR

IDENTIFICAR EVENTOS`INICIADO

RES

IDENTIFY NON-SIS

IPL’S

MAKE RISK DECISIONS & DOCUMENT

SELECT THE NEXT INITIATING EVENT

ADD SIF IF NEEDED

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¿Qué es un Escenario de LOPA?“Evento o secuencia de eventos que desencadenan una consecuencia no

deseada.”

Diferentes Consecuencias EscenariosDiferentes Eventos Inicadores con las mismas

Consecuencias Casos

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Cualquier Escenario LOPA debe tener CLARAMENTE definidas sus partes

4. Consecuencias (nube tóxica, VCE, fuego, etc.)

2. Material afectado (etileno,cloro, etc.)1. Equipamiento afectado(reactor, cañería, etc.)

5. Evento iniciador (error operativo, falla de instrumento,falla de control, etc.)

Ocasionalmente …6. Requisitos especiales (probabilidad de ignición.

área normalmente desocupada, etc.)

3. Punto de Salida (PSV, cañería, sello bomba, etc…)

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Desarrollo del Escenario

• HAZOP• OSS (hUCC)• Experiencia (incidentes pasados) • Qué Pasa Si• FMEA• Listas de Verificacíón

“ Al desarrollar un escenario , es un buen punto de arranque una evaluación cualitativa del peligro.”

“ Algunas de las siguientes metodologías son utilizadas en la industria para estas evaluaciones de peligros”

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Desarrollo de un Escenario Típico (Caso) explicado

• Comenzar con información sobre la identificación del peligro

• Identificar las consecuencias (escenarios) que serán estuudiados (daños personales, al medio ambiente , a la propiedad)

• Confirmar que el escenario ha sido desarrollado con el alcance necesario

• Si hay algo que no está seguro, incluirlo también• Identificar todas las causas listadas y encontrar el evento

incial que domina el riesgo• Identificar otros eventos inciadores que pueden conducir a

la misma consecuencia• Identificar otros factores que afectan al reisgo (probabilidad

de incendio o de presencia de una persona en el área)

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El valor de una correcta escritura de los escenarios

no se reconoce adecuadamente

Se puede perder mucho tiempo si el texto no es el

correcto

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Desarrollo de Escenarios para LOPA

LOPA no es una herramienta para identificar escenarios

El Escenario, junto con la cupla Causa-Consecuencia son entradas para LOPA y deben desarrollarse antes que pueda empezar el LOPA

LOPA comienza con la identificación del Factor Objetivo de LOPA

La identificación del escenario y el Valor objetivo del LOPA son iterativos y efectuarán varios ciclos antes de completarse

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Haga participar al personal adecuado Que conozca el Procesoe Personal de Ingeniería de Procesos y Control Otros recursos técnicos Personal de Operación de Planta El facilitador LOPA y quien administra los

tiempos » Líder de Tecnología de Seguridad de Procesos» Coach de SIS » Experto de Business LOPA del Negocio

Cómo comenzar con los Escenarios

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Matriz de Habilidades del Equipo LOPA LOPA Team Skills Matrix

Learning Objective

(Description of Knowledge or Training Needed)LOPA

Facilitator

Process Operations

Expert

Process Technology

Expert

Plant Process Control Expert

Process Safety Expert

100 LOPA Work Process

LOPA/SIS Work Process and requirements Expert Aware Competent Aware - Competent Expert

200 LOPA Fundamentals

Has introductory understanding of LOPA concepts,

methodology, terminology, rules Expert Aware Competent Aware Expert

Thorough understanding of LOPA Guidelines and

Workbook Expert Competent Aware - Competent Expert

Understands LOPA documentation requirements (as defined by other sub-team) Expert Aware Aware Aware Expert

300 Scenario Development

Experience in multiple plants and processes Competent Aware Competent

Thorough knowledge of important process safety

considerations for the plant Competent Expert Competent Expert

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Conseguir la información correcta Experiencias de Planta HAZOPS anteriores, listas Qué Pasa Si ( What-if) o

cualquier otro tipo de evaluación cualitativa. Revisiones y auditorías de Productos Químicos

Reactivos Experiencia de la Industria Invetigación de Causa Raíz (RCI)

Cómo comenzar con los Escenarios

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• Evaluación de la posibilidad de peligro del proceso

• CEI, F&EI, US EPA RMP Comp program, other triggers that you may invent

• Identificación de un tema de Peligro Potencial• Por ejemplo, un tanque, bomba o reactor que exceden los

criterios de screening


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Elección del Nodo de la Unidad

D-1R-1B D-8

R-2B

P-2A/B P-5A/B P-23A/B

E-1 E-2Temp ControlledWater from E-11BTemperature

Controlled Waterfrom E- 24B

To EO RecoveryAcrylic Acid

RiverWater

AtmVent

Ditch

To D-14

N2

Recycle EO

Ethylene Oxide Storage

Reaction SystemSugerencia: ‘HAZOP’ o

‘What if’ las áreas de más riesgos de manera

sistemática

Sugerencia: Use brainstorming en áreas

menos peligrosas

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Enfoque en la Unidad Elegida

Tail Reactor

R-1B D-8

P-5A/B

E-1

TemperatureControlled Waterfrom E- 24B

RiverWater

AtmVent

DitchAcrylic Acid

Ethylene Oxide

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• Uso de Brainstorming : • Get the right people in the room• HAZOP, What if, Check list of events, Whatever’s effective

– Describe the scenario (what’s going to happen) and the amount of material involved.

• Can it really happen?– Are the conditions necessary and sufficient?– Does it pass a sanity check? (Challenging since you need to

mentally turn the existing protection layers off )• Is it clearly understood? The “cause” must be readily visible.

If its not, develop further


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Desarrollo del Escenario– Estimate the consequence of the scenario.

– What’s the bad stuff?– consequence analysis or hazard look up tables based on material hazard

and quantity involved• Is this a consequence of concern?

– If YES, continue. Otherwise stop, identify another scenario or go to the next item of concern

– Identify the Initiating Events (causes) that can lead to the consequences

– There may be several– A check list of typical initiating events is useful

– Ask what else can happen?– Repeat the above as needed

continuación

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Scenario Development

– Identify special requirements or conditions– Probability of ignition, time at risk, presence factor...

• Now repeat until you get it right.• First write it so you understand it• then write it so “they” understand it• finally, write it so EVERYONE understand it

• Identify next item of concern and repeat the brainstorming

continued

And Finally, You’re done

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Scenario DevelopmentCheck for Clarity

Write a sentence using LOPA Workbook inputs to uncover unintended implications.

‘Initiating Event’ …happens which causes...

‘Description of Undesired Consequence’resulting in…

‘LOPA Target Factor’

.

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¿Es Probabilidad o Frecuencia?• Probabilidad – Posibilidad de ocurrencia de un

evento o secuencia de eventos. Es adimensional, y se califica entre 0 y 1.

• Frecuencia – Número de ocurencias de un evento por unidad de tiempo. Es un número entre 0 y 1, y sus unidades son “ocurrencias por hora o año”. Por ejemplo, fallas por año.

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Based on Dow & Industry Experience

Initiating Event Factor (IEF) TableDOW RESTRICTED

Initiating Event Factors for Layers of Protection Analysis

Initiating Event Initiating Event Frequency (per year)

Initiating Event Factor

BPCS Instrument Loop Failure 1.E-01 1

Regulator failure 1.E-01 1

Operator Failure Action more than once per quarter 1.E-01 1

Operator Failure Action once per quarter or less 1.E-02 2

Pump Failure Loss of Flow 1.E-01 1

Single Mechanical Pump Seal Failure 1.E-01 1

Double Mechanical Pump Seal Failure with announcement 1.E-02 2

Canned/Magnetic Drive Pump Failure 1.E-02 2

Cooling Water Failure 1.E-01 1

Loss of electrical power 1.E-01 1

General Utility Failure 1.E-01 1

Greg Schultz

Is this the most current version?

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Based on Dow & Industry Experience

Initiating Event Factor (IEF) Table(cont’d)

DOW RESTRICTED

Initiating Event Factors for Layers of Protection Analysis

Initiating Event Initiating Event Frequency (per year)

Initiating Event Factor

3rd Party Intervention 1.E-02 2

Lightning Strike as an Initiating Event 1.E-03 3

Unloading/Loading Hose Failure 1.E-01 1

Expansion Joint Fails 1.E-02 2

Heat Exch. tube leak <100 tube 1.E-02 2

Heat Exch. tube leak >100 tubes 1.E-01 1

IEF=0 as determined by Tech Center & Process Safety 1.E+00 0

IEF=1 as determined by Tech Center & Process Safety 1.E-01 1





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Gut Check on Initiating Event Factors

Does the Initiating Event occur more frequently than the IEF table indicates?

If so you may not be able to justify any credit!

Example: I’m assuming my pressure transmitter fails only once/10 yrs as the IEF table indicates but in reality we have to unplug the impulse line every year…

… FACTOR IS ZERO!

(Reverse argument does not apply)

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When are you finished identifying Scenarios?

• There is no single answer to this issue since there are multiple ways to ID cause-consequence pairs.– Use a proven effective method– Involve the right people– Complete the process– Query the experts

Have you missed something?

If the answer is No, you are finished!for now

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Should you evaluate the scenario…

IF…?• The initiating event has never occurred in the

plant? Dow history? Industry history?• The initiating event has occurred but some

safeguard has always stopped the scenario?

If you remove all protection layers and one failure will lead to the consequence then yes it should be considered.

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Modificadores y Condiciones especiales

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LOPA - Step Three (modifiers)

Modifiers

STEP 5:

EVALUATINGFURTHER R ISK

REDUCTIONSUGGESTIONS

STEP 1:

STEP 6: STEP 2:

STEP 3:

STEP 4:

IDENTIFY SCENARIO OF

INTEREST

IDENTIFY CONSEQUECES

& TARGET FACTOR

IDENTIFY NON-SIS

IPL’S

MAKE RISK DECISIONS & DOCUMENT

SELECT THE NEXT INITIATING EVENT

IDENTIFY INITIATING EVENT(S)

ADD SIF IF NEEDED

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A LOPA WorkbookDOW RESTRICTED

Layer of Protection Analysis WorksheetProtection Scenario Definition Independent Protection Layers

Gap Description of Undesired Consequence LOPA Target Factor Initiating Event Factor Enabling Factor Probability of Exposure

Target is0 or less

Scenario And Case Number

Give a complete Description of the undesired consequence

List chemicals and quantity involved Describe the initiating event Record the Probability of

Ignition or Toxic Enabling Factor.

Describe the condition of probability of

exposure

Safety AnalysisBusiness Analysis

HELP For Consequence HELP For TF HELP For Initiating Event HELP For Enabling Factor HELP For POE

Layer of Protection Analysis WorksheetIndependent Protection Layers Notes

Each independent instrument layer must have separate sensors, logic solvers and final elements. Other safety related protection systems

Plant Integrity Design

(Mechanical Integrity Issues)

BPCS Control Action

Operator responds to alarms and

written procedures

SIS Function A SIS Function BPressure

Relief Device

SRPS 1 SRPS 2 SRPS 3

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Enabling Event

• Enabling event or condition - An event or condition that makes possible another event. – does not cause scenario– must be present for the scenario to develop– usually expressed as a probability

• Example– Probability of ignition - a gas release ignites becoming

a fire or explosion. – Toxic enabling factor – people are present and not

protected before they can become exposed to a toxic gas cloud.

Greg Schultz

Is this where TEF belongs?

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Probability of Ignition

• What is the probability of ignition if the release occurs outdoors?– POI based on quantity in vapor cloud (vaporized in 15 minutes)

• In building Ignition?A. Class 1, Division 2 Electrical Classification with 6 or more air

exchanges / per hour POI = .1, Credit =1B. For all others, POI =1, Credit = 0

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DOW RESTRICTED

Enabling Factors for Layers of Protection Analysis Enabling Factor Probability of

IgnitionEnabling

Factor

POI <100# vaporized 1.E-02 2

POI <1,000# vaporized Elevated Ignition Probability Material 1.E-01 1

POI >1,000# vaporized Elevated Ignition Probability Material 1.E+00 0

POI <1,000# vaporized Normal Ignition Probability Material 1.E-02 2

POI <10,000# vaporized Normal Ignition Probability Material 1.E-01 1

POI >10,000# vaporized 1.E+00 0

POI due to static in closed ungrounded vessel ordinary hydrocarbon 1.E-01 1

TEF = -1 -1

TEF = 0 0

TEF = 1 1

TEF = 2 2

None 0

POI=Probability Of Ignition

Use for outdoor releases only. Indoor releases will generally be further evaluations.

Probability of Ignition Workbook Tab

The amount ‘vaporized’, is the amount flashed or otherwise contributes to the flammable

cloud (i.e. droplets)

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Low (<1%): ammonia, methylene chloride, trichloroethylene, etc…

Normal (1-10%): n-butane, propylene, acetone, methane, methanol, etc…

Elevated (10-90%): hydrogen, acetylene, propylene oxide, ethylene, HCN, acetaldehyde, acrolein, 1,3-butadiene, carbon disulfide, diethyl ether, propadiene, etc...

High (>90%): silane and various alkyl aluminum compounds (normally described as pyrophoric).

• Full list found at…Shortcut to LGB Sensitive Vapors.doc.lnk

Ignition Categories

NOTE: Items in red have changed categories

updated

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Toxic Enabling Factor

Old Concepts With a New Application

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Example #1

Outcome:• 2000 - 6000 fatalities offsite• 100,000+ injuries

Just after midnight on December 3, 1984, a Union Carbide pesticide plant in Bhopal, India accidentally released approximately 40 metric tons (88,000 lbs) of methyl isocyanate into the atmosphere.

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Example #2

Outcome:• No fatalities • 63 medical evaluations

On August 14, 2002, a chlorine transfer hose ruptured during a rail car unloading operation at the DPC Enterprises chlorine

repackaging facility near Festus, Missouri, USA. The hose

rupture ultimately led to the release of 48,000 pounds of

chlorine.

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What Differentiates the Outcome of Similar Toxic Release Incidents?

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Comparison

• Both are ‘B’ Chemicals in LOPA

• Airborne quantities are similar– MIC released as vapor due to hot reaction– Chlorine vaporizes due to low BP

Something was VERY different…

ChlorineChlorineERPG3 ERPG3 20 ppm 20 ppm Boiling Point Boiling Point -34 -34 degCdegC

MethylisocyanateMethylisocyanateERPG3 ERPG3 5 ppm5 ppmBoiling PointBoiling Point 38 38 degCdegC

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Differences

1. Number of people near the plant2. Distance between people and the release3. Shelters or lack thereof4. Warning

There may be others… but these are the ones we plan to study

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Basis for Chemical Target Factors

The Chemical Specific Target Factor Table was originally developed using

‘TYPICAL’ conditions affecting the probable impact of a toxic release to the

surrounding community.Population density of 3885 people/sq. mi.Greenbelt distance of 1500 ft.

Dispersion modeling used to adjust for Dispersion modeling used to adjust for situations significantly different than situations significantly different than these.these.

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What is the Toxic Enabling Factor?

Can impact LOPAanalysis by factorof 2,1,0,or -1

Rules:Applies to toxics using Chemical Table

Looks at all of these parameters, Geographic PSTL will provide these

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Consider these ‘New’ Concepts

• Population has not been used in LOPA– but it is used in SVA audits and RMP

submission (and QRA, with greater precision)• Greenbelt distance not previously used

– fenceline has been the Level 2 sensitivity

– ‘Distance to non-company plant or business’ recorded in CEI (Level 1)

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Other ‘New’ Concepts

• Shelter Quality new to LOPA– but is counted in QRA – real issue in Bhopal

• Community Emergency Response not previously credited in any risk assessment

• Wind direction ignored (use circles)

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Applying the TEFRULES

1. Applies only where Chemical Specific TF Table used to determine Target Factor

2. Weighting is as follows1. Population – 40%2. Greenbelt – 30%3. Shelter Quality – 15%4. Community Emergency Response – 15%

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Toxic Enabling Factor Database

Site Plant or Building

Toxic Enabling

FactorDistance Qualifier

Toxic Enabling

FactorDistance Qualifier

Midland ONE 1 none 1

Midland 244 1 none 1






Midland 477 1 < 18 miles 0 > 18 miles


Midland 564 1 < 1 mile 0 > 1 miles



This only represents a portion of the information in the workbook

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Applying the TEFImplementation

• Process Safety Technology Leaders will do much of the population work for you on a site basis.

• You will need to look up TEF on a spreadsheet for your plant (possibly depending on HD-2 distance)

• If TF is 7 may only apply TEF of <= 1, if TF is <=6 may not apply TEF

• Suggest reviewing results with site Responsible Care Leader and Site Leader to gain buy-in (PSTL will do this).

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Probability of Exposure

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Probability of Exposure(2-types)

• Time at Risk - The fraction of time per year a potential hazard can exist.– Applies to all risk – A specialty batch plant makes a hazardous product

5 weeks a year (0.1)– A loading / unloading operation occurs 100 hours

per year or less– Does not apply to startup or shutdown– Apply at plant capacity

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Probability of Exposure(continued)

• Potential for exposure - The fraction of time per year a person can be exposed to a hazard. – Generally applies to personal injury / fatality– The hazardous area is remote from normal work

areas. A few visits per year for a short time.• The hazard is there all the time but the people are not.• Eg., Salt Dome

– The hazardous area is barricaded or chained preventing access.

• A sulfuric acid drying tower in a chained off area

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Probability of Exposure Workbook Tab

Probability of Exposure for Layers of Protection AnalysisProbability of Exposure

Frequency Range from Literature

(/yr.)

Enabling Factor

Probability

Enabling Factor

Probability of Exposure allowed for processes in operation for less than 5 weeks/yr or when personnel are seldom present in area.

1x10-1 1

Probability of Exposure for rare processing events (occurs less than 1% of the time) or in remote locations. Tech. Center and Process Safety concurrance required to use this factor.

1x10-2 2

Probability of Exposure credits allowed for Start-up and Shut Down events. 0

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Layer of Protection Analysis WorksheetProtection

Gap Scenario Definition Independent Protection Layers

Target is 0 or less

Scenario and Case Number

Description of Undesired Consequence LOPA Target FactorInitiating Event

FactorEnabling Factor

Probability of Exposure

Plant Design

BPCS Control Action

Operator responds to alarms and

written procedures

SIS Function A

SIS Function B

Give a complete description of the undesired consequence

List chemicals and quantity involved.

Describe the initiating Event.

Record the Probability of

Ignition.


exposure.

Each independent instrument layer must have separate sensors, logic solvers and final elements.

3.1 Reactor vessel failure due to polyol decomposition reaction

Vessel fragmentation causes multiple

fatalities, Consequence Specific

Target Factor

No or Very Little catalyst present

due to acid leaking into reactor and neutralizing

catalyst

At least two people present on

the plant at all times.

6 Safety Analysis 7 1 0

0 Business Analysis

DOW RESTRICTED

Layer of Protection Analysis WorksheetProtection Scenario Definition Independent Protection Layers

GapDescription of Undesired

Consequence LOPA Target Factor Initiating Event Factor Enabling Factor Probability of Exposure Each independent instrument layer must have separate sensors, logic solvers and final elements.

Target is0 or less

Scenario And Case Number

Give a complete Description of the undesired consequence

List chemicals and quantity involved Describe the initiating event Record the Probability of

Ignition or Toxic Enabling Factor.


exposure

3.1

Reactor vessel failure due to

polyol decomposition

reaction

Vessel fragmentation

causes multiple fatalities,

consequence specific

Target Factor

No or very little catalyst present due to acid leaking into

reactor and neutralizing catalyst

At least two people present on the plant at

all times.

HELP For Consequence HELP For TF HELP For Initiating Event HELP For Enabling Factor HELP For POE

LOPA Workbook Example

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