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An AIChE Technology Alliance Risk Analysis Screening Tools (RAST) Overview / Demonstration

April 12, 2019 Slide - 1

Overview of the Risk Analysis Screening Tool


An AIChE Technology Alliance



Risk Analysis Screening Tool (RAST)

Overview and Demonstration

✓ What is RAST?

✓ Identifying and Screening of Chemical and Operational

Hazards

✓ Developing Hazard Scenarios

✓ Consequence Analysis

✓ Frequency Evaluation

✓ Risk Analysis/Layers of Protection Analysis (LOPA)






Risk Analysis Screening Tool (RAST)


Disclaimer:It is sincerely hoped that the information presented in this document will lead to an even better safety

record for the entire industry; however, neither the American Institute of Chemical Engineers, the

European Process Safety Centre, its consultants, CCPS Technical Steering Committee and Subcommittee

members, EPSC members board, their employers, their employers officers and directors, nor The Dow

Chemical Company, and its employees warrant or represent, expressly or by implication, the correctness

or accuracy of the content of the information presented in this document. As between (1) American

Institute of Chemical Engineers, its consultants, CCPS Technical Steering Committee and Subcommittee

members, their employers, their employers officers and directors, and The Dow Chemical Company, and

its employees, and (2) the user of this document, the user accepts any legal liability or responsibility

whatsoever for the consequence of its use or misuse.

RASTRisk Analysis Screening Tools

Version 2

Welcome to RAST (Risk Analaysis Screening Tool).

The RAST software and its associated CHEF documentation were developed through the collaborative

efforts of volunteers from member companies of the Center for Chemical Process Safety (CCPS) and the

European Process Safety Centre (EPSC). Special appreciation is extended to the Dow Chemical Company

for donating RAST/CHEF for global use and for providing the resources to help modify the software and

documentation such that companies can tailor the RAST software to meet their company-specific risk

tolerance levels. It is sincerely hoped that companies using RAST and CHEF during their hazard

identification and risks analysis studies will be able to improve their process safety performance.

Latest Revision Date 3/02/19

Go To Main Menu >>



Go To Instructions >>RAST (Risk Analysis Screening Tool) and

CHEF (Chemical Hazard Engineering

Fundamentals) were made available

through a donation from the Dow

Chemical Company to the Center for

Chemical Process Safety (CCPS) and the

European Process Safety Council (EPSC).

The intent is to make this information

easily available to the chemical industry

to support “cost-effective elimination of

process safety incidents”.




RAST is a collection of “Screening Level” Process Safety

Tools to assist in performing a Hazard Identification and Risk

Analysis study that draws upon basic input information.

What is RAST?




Screening is the evaluation or investigation of something as part of a

methodical survey, to assess suitability for a particular role or purpose.

“Screening Level” Tool

- Oxford Dictionary

RAST is intended to bridge the gap between qualitative and detailed quantitative risk

evaluation. It utilizes many simplifying assumptions, engineering approximations,

and simplified methods to generate “order of magnitude” estimates of consequence,

likelihood, and risk.



❑ RAST contains a data table of chemical properties (for 250 chemicals as of the date of this

manual) that are used for quantifying hazards and in source models to determine leak rate.

Users may enter properties for additional chemicals as needed in the HIRA study.

❑ RAST generates a list of suggested scenarios for consideration by the study team. The

suggested list of scenarios is not intended to represent all scenarios needed for an effective

HIRA study, but a starting point that the evaluation team may build upon.

❑ RAST is intended as a productivity tool to aid evaluation teams in performing Hazard

Identification and Risk Analysis (HIRA) studies to provide consistency among analysis teams

while reinforcing company protocol and criteria. It utilizes simplified and often empirical

methods in quantifying hazards, consequence and risk.

What is RAST?




❑ RAST and the accompanying Chemical Hazards Engineering Fundamentals (CHEF)

materials are based on performing Hazard Identification and Risk Analysis (HIRA) tasks in

a specific order. The order of task execution is based on an overall work flow such that

results of a specific estimate (such as a source model) being available as input for the

subsequent task (such as vapor dispersion). RAST is set up to use minimal information to

get started with the addition of more information over time to improve the analysis and

generate additional reports.

❑ RAST bridges the gap between qualitative and detailed quantitative risk evaluation

allowing application of greater rigor and detail for high risk scenarios. In some cases, other

software or rigorous evaluation methods may be needed beyond the capability of RAST to

meet a company’s risk analysis requirements. For these cases, RAST accommodates the

entry of results from other software or methods (including qualitative estimates) in the

overall study. In other cases, the study team may merely enter qualitative results.

What is RAST?




Hazard Identification and

Risk Analysis (HIRA) Study

Hazard Identification and Risk Analysis (HIRA) is a collective

term that encompasses all activities involved in identifying

hazards and evaluating risk at facilities, throughout their life

cycle, to make certain that risks to employees, the public, or the

environment are consistently controlled within the organization's

risk tolerance.-Center for Chemical Process Safety




The information flow in RAST follows this Overall Work Process


Overall Work Process Steps for Hazard

Identification and Risk Analysis

What are the Hazards?

What can go Wrong?

How Bad could it Be?

How Oftenmight it

Happen?

Is the Risk Tolerable?

Identify Chemical

and ProcessHazards

Estimate Frequency

Analyze Consequences

AnalyzeRisk

IdentifyAdditional Safeguards as Needed

DevelopScenarios

Identify Equipment

or Activity to be Analyzed

Manage Barriers

for Life Cycle of Facility



Hazard Identification and Risk Analysis are the processes whereby hazards are evaluated by answering basic questions:

▪What are the Hazards?

▪What can go wrong?

▪What are the potential consequences?

▪How likely is it to happen?

▪ Is the Risk Tolerable?

Hazard Identification and

Risk Analysis (HIRA) Study


Hazard Identification and Risk Analysis is one of the key elements of CCPS Risk-Based

Process Safety




Incr

easi

ng

Pro

cess

Ris

k

and

Det

ail o

f An

alys

is

Hazard and Operability Study

Layers of Protection Analysis

Barrier Analysis

RAST / CHEF

Fault Tree Analysis

Detailed Dispersion Modeling

Detailed Explosion Modeling

Human Vulnerability Analysis

Process Risk Analysis – Level of Detail

Detailed Quantitative Risk

Method

Simplified Quantitative Risk

Method

Qualitative Risk Method

Hazard and/or Risk Screening Criteria

QRA Criteria

Process Safety Review

Checklist Analysis

Safeguard Recommendations



Screening Tool is a simplified model with limited capabilities, suitable for

screening-level studies.

RAST as a “Screening Level” Tool


-Center for Chemical Process Safety

Screening Criteria: A predetermined measure, standard, or rule (typically

based upon company or regulatory requirements), on which a judgment or

decision can be based.

RAST contains screening criteria, that a company may modify, for process

equipment (or scenarios associated with specific process equipment) when

hazards or risk are not sufficient to warrant beyond a qualitative risk analysis.CCPS does not endorse any specific criteria but provides initial values needed for the

program to run and for the company to consider.




Example Checklist Analysis

Example HAZOP DocumentationScenario

Identification

Initiating Event

+ Enabling Conditions

Lo

ss E

ven

t

Incident Outcome with

Undesired Consequence

Failure of Independent Protective

Layers




Scenario Development within RAST


Scenario: A detailed description of an unplanned event or incident sequence that results in a

loss event and its associated impacts, including the success or failure of safeguards involved

in the incident sequence.

Initiating Cause (or Initiating Event): The operational error, mechanical failure, or external

event or agency that is the first event in an incident sequence and marks the transition from a

normal situation to an abnormal situation.

Loss Event: Point in time in an abnormal situation when an irreversible physical event occurs

that has the potential for loss and harm impacts. Examples include release of a hazardous

material, ignition of flammable vapors or ignitable dust cloud, and over-pressurization rupture

of a tank or vessel.

Incident Outcome: The physical manifestation of the incident: for toxic materials, the incident

outcome is a toxic release, while for flammable materials; the incident outcome could be a

boiling liquid expanding vapor explosion (BLEVE), flash fire, vapor cloud explosion (VCE), etc.




Scenario Development within RAST

In addition to Cause (or Initiating Event) and Consequence (or Incident Outcome),

a RAST scenario contains one unique Loss Event. Details of the Loss Event help

clarify the event sequence for the analysis team. In addition, the Loss Event is

linked to a specific Source Term that allows RAST to perform a simple

Consequence Analysis.

Standardized lists of Initiating Events, Loss Events, and Incident Outcome are

used to develop scenarios in RAST. Common parameter deviations for the type of

equipment being analyzed is used to link some Loss Events with Initiating Events

consistent with a Hazard and Operability Study (HAZOP) approach.




HAZOP Node: HAZOP Design IntentPlant Section =

Equipment Type = Vessel/Tank

Equipment Tag = V-101

LOPA Menu Filters:

Scenario Type Scenario CommentsParameters and

DeviationInitiating Event (Cause) Initiating Event Description Loss Event Outcome

Off-

Site

Tox

ic R

elea

se

On-

Site

Tox

ic R

elea

se

Indo

or T

oxic

Rel

ease

Toxi

c In

filtr

atio

n

Che

mic

al E

xpos

ure

Flas

h Fi

re o

r Fi

reba

ll

Vap

or C

loud

Exp

losi

on

Bui

ldin

g E

xplo

sion

Equ

ipm

ent E

xplo

sion

Pro

pert

y D

amag

e or

Bus

ines

s Lo

ss

Env

iron

men

tal D

amag

e

Drain or Vent Valve Open

Drain or Vent Valve left open following

infrequent maintenance, purging or

cleaning

Flow-Loss of

Containment

Human Failure Action once per

quarter or less

Operator leaves Drain or Vent Open

following infrequent maintenanceDrain or Vent Leak

Off-Site Toxic Release, On-Site

Toxic Release, Toxic Infiltration,

Chemical Exposure, Flash Fire

or Fireball

5 4 4 3 4

Vapor Relief Vent - FireOff-Site Toxic Release, On-Site

Toxic Release, Toxic Infiltration6 5 5

Equipment Rupture at Fire Conditions




or Fireball, Equipment Explosion

6 5 5 4 4 3

Ignitable Headspace

Chemical is Flammable or

Combustible: Maximum Operating,

Mechanical Energy or Heating Media

Temperature exceeds Flash Point

less 5 C

Composition-Wrong

ConcentrationBPCS Instrument Loop Failure

Failure of Pressure or NonCombustible

Atmosphere ControlEquipment Rupture - Deflagration




or Fireball, Equipment Explosion

6 5 5 3 4 3

Mechanical Integrity Failure -

Extremely Large

Largest Pipe or Nozzle Size less than

Extremely Large Hole Size

Flow-Loss of

Containment

IEF=4 as determined by Process

SafetyFailure from corrosion, fatigue, etc. Extremely Large Hole Size Leak




or Fireball, Vapor Cloud

Explosion

6 5 5 3 4 5

Mechanical Integrity Failure -

Medium

Mechanical Integrity Loss of

Containment for Medium Hole Size

Flow-Loss of

Containment


SafetyFailure from corrosion, fatigue, etc. Medium Hole Size Leak




or Fireball

6 5 5 3 4

Mechanical Integrity Failure - Very

Large


Containment for Very Large Hole Size

Flow-Loss of

Containment


SafetyFailure from corrosion, fatigue, etc. Very Large Hole Size Leak





Explosion

6 5 5 3 4 5

Mechanical Integrity Failure - Very

Small


Containment for Very Small Hole Size

Flow-Loss of

Containment


SafetyFailure from corrosion, fatigue, etc. Very Small Hole Size Leak

On-Site Toxic Release, Flash

Fire or Fireball3 4

Overfill Release



Flash Fire or Fireball

6 5 5 4

Equipment Rupture at Operating

Temperature





Explosion

6 5 5 3 5 5

Vacuum DamageRating for Full lVacuum Not Entered

for Low Design Pressure EquipmentPressure-Low BPCS Instrument Loop Failure Failure of Pressure Control

Full Bore Hole Size Leak above

Liquid Level

On-Site Toxic Release, Flash

Fire or Fireball3 4

Excessive Heat Input - Heat

Transfer

No Heating Media Temperature was

notedPressure-High BPCS Instrument Loop Failure Failure of Flow Control

Criteria for Triggering Incidents Not

Met

Excessive Heat Input -

Mechanical

Vapor Pressure plus pad gas

exceeds Maximum Allowable

Working Pressure or Relief Set

Pressure at Maximum Temperature

from Mechanical Energy Input

Pressure-HighHuman Failure Action once per

quarter or less

Agitation or Pump Recirculation left running

for extended time allowing slow temperature

increase

Vapor Relief Vent - Mechanical

Energy

Consequence Does Not Exceed

Threshold Criteria for Continuing

with LOPA

Excessive Pad Gas Pressure

Maximum Pad Gas Pressure Does

Not Exceed the Maximum Allowable


Pressure

Flow-High Regulator FailureRegulator Fails causing high flow or

pressure


Met

Excessive Heat Input - Pool Fire

Exposure

Overfill, Overflow, or Backflow


Safety

BPCS Instrument Loop Failure

Leak of Flammable Material or Material

above its Flash Point which may ignite

Failure of Level Indication with continued

addition of material

Vapor Pressure exceeds Relief Set

or Burst Pressure from Pool Fire

Exposure

Maximum Feed Pressure or

Downstream Equipment Pressure is

not sufficient to active Relief Device

resulting in Overfill

Pressure-High

Level-High or Flow-

Backflow

Potential Outcome / Tolerable Frequency Factors

Suggested Scenarios from the RAST Library

Scenarios in gray were

considered but are excluded for

reason noted

Scenarios with NO IPL's Required will NOT be reported.

V-101 is a Vessel/Tank containing Acrylonitrile that operates at 25 C and 0.01 bar.

The volume is 100 cu m with a maximum allowable working pressure of 0.2 bar.

The maximum feed or flow rate is 400 kg/min.

Off-

Site

Tox

ic R

elea

se

On-

Site

Tox

ic R

elea

se

Indo

or T

oxic

Rel

ease

Toxi

cIn

filtr

atio

n

Che

mic

alE

xpos

ure

Flas

hFi

re o

r Fir

ebal

l

Vap

or C

loud

Exp

losi

on

Bui

ldin

g E

xplo

sion

Equ

ipm

ent E

xplo

sion

Pro

pert

y D

amag

e or

Bus

ines

s Lo

ss

Env

iron

men

tal D

amag

e

Update Go To Scenario Results ><< Go To Main Menu

Create UserScenario

Scenario Type with

Comments or

Description

HAZOP

Parameters and

Deviations

Most Common

Initiating Event

with Description

Loss Event with

Potential Outcome and

Tolerable Frequencies

Scenario Cases where Hazard

Screening does not indicate a need

for further Analysis shown in “Gray”

“Update” command

if accessed directly

by worksheet tabs

RAST Listing of Suggested Scenarios




Consequence: The undesirable result of a loss event, usually measured in

health and safety effects, environmental impacts, loss of property, and

business interruption costs.

Consequence Analysis: The analysis of the expected effects of incident

outcome cases, independent of frequency or probability.

Consequence Analysis with RAST




Containment Dike

Liquid Feed Rate

Liquid Flash and

Aerosol Evaporation

Pool

Evaporation

Vent

Release

Liquid

Release

Vessel or Equipment

Rupture

Inert Feed Rate

Relief Release

Containment Dike

Liquid Feed Rate

Liquid Flash and

Aerosol Evaporation

Pool

Evaporation

Vent

Release

Liquid

Release

Vessel or Equipment

Rupture

Inert Feed Rate

Relief Release

Illustration of Source Models for

Release of Vapor and LiquidRAST uses various source and effect models

from CCPS and other literature sources. Loss

events are categorized as related to hole size

(vapor, liquid, or two-phase), material balance

(such as overfill), heat balance (such as

vaporization resulting from fire exposure), rupture

(instantaneous release) or equipment damage. If

the release is liquid or two-phase, vapor rate is

estimated from simple flashing, aerosol

evaporation and pool evaporation models.

For more information on methods used within

RAST, refer to Chemical Hazard Engineering

Fundamentals (CHEF) documentation.

Consequence Modeling in RAST





Consequence Analysis with RASTRAST Version 1.2

Release Location Outdoors

Airborne Quantity Summary:

Release Temperature, C 25.0 Factor Probability

Release Pressure, barg 0.010

Physical State at Release Conditions Liquid

Heat Input, Kcal/min

Equivalent Hole Size, cm 1.000

Release Rate, Kg/sec 0.45

Release Duration, min 60.00

Spray Distance, m 5.8

Flash + Aerosol Evaporation Fraction 0.003

Estimated Aerosol Droplet Diameter, micron 1225

Pool Area, sq m 159.3

Estimated Pool Temperature, C 8.2

Maximum Pool Evaporation Rate, kg/sec 0.2457

Total Airborne Rate, kg/sec 0.24

Total Airborne Quantity, Kg 447.6

Airborne Quantity Composition:

Mole Fraction Acrylonitrile 1.000

Mole Fraction Pad Gas (at Mw = 29)

ERPG-2 for Vapor Composition, ppm by volume 56.6


LFL for Vapor Composition, % by volume 3.00

CONSEQUENCE SUMMARY Date:

Gasket FailureLoss Event for: Vessel/Tank; V-101 Containing

Acrylonitrile :

with Personnel Not in Immediate Area

Prob of Exposure (proximity based)

Fence Line

Concentration

Exceeds ERPG-2

On-Site Toxic POE

Flash Fire POE

Physical Explosion POE

Chemical Exposure POE

Ground or Work Area

Exceeds Multiple of

LFL or Time-Scaled

ERPG-3

RAST Version 1.2

Dispersion Summary:

Max Distance to Time-Scaled ERPG-2, m 180.4


Max Distance to 1% Lethality for 1.5 F weather, m 350.7

Max Distance to Severe Toxic Impact, m 55.4

Max Distance to 0.5 LFL, m 15.5

Maximum Ground Elevation Concentration, ppm 1000000.0

Concentration at Distance to Fence Line, ppm 56.8

Concentration at Distance to Unrestricted Work Area, ppm 1000000.0

Concentration at Distance to Occupied Bldg 1, ppm 374.9

Concentration at Distance to Occupied Bldg 2, ppm

Concentration within Enclosed Process Area, ppm

Conc within Enclosed Process Area w/Ventilation, ppm

Explosion Summary:

VCE or Building Explosion Distance to 1 psi Overpressure, m 2

Overpressure at Distance to Occupied Building, psi

Overpressure at Center of Occupied Building, psi

Distance to Severe Thermal Radiation Impact, m

Distance to Direct Blast Impact (10 psi), m

Maximum Fragment Range, m 2

Rupture Distance to 1 psi Overpressure, m

Rupture Overpressure at Distance to Occupied Building, psi

Ruture Overpressure at Center of Occupied Building, psi


Gasket FailureLoss Event for: Vessel/Tank; V-101 Containing

Acrylonitrile :

Probability of Ignition (POI)

Probability of Explosion (POX)

Potential Toxic Impact

to Occupied Building

(Conc > ERPG-3)

A Consequence Analysis report is provided for any Loss Event. Each analysis includes a summary of the source model, dispersion model and explosion model if applicable.

Either results of the Consequence Analysis or a Qualitative Consequence Severity may be used for Risk Analysis within RAST




Frequency Evaluation with RASTScenario Frequency in RAST is order-of-magnitude and based on independence of

initiating events, enabling conditions/conditional modifiers and protective layers. Tables

of initiating event frequencies, enabling condition or conditional modifier probabilities

(such as probability of ignition), and probability of failure upon demand (PFD) for

independent protective layers (IPL) are stored as administrative parameters.

Residual failures (those leaks represented by chronic issues such as wear or fatigue

rather than a process upset) are labeled Mechanical Integrity scenarios in RAST with

frequency based on correlation on published leak frequency data. The User may either

include or exclude residual failures in Risk Analysis.

These tables and correlation coefficients may be updated to reflect a company’s specific

frequency values for use in risk analysis. The scenario frequency is simply the product of

the initiating event frequency times the enabling condition or conditional modifierprobability times the failure probability for each IPL appropriate for the scenario.




Risk - A measure of human injury, environmental damage, or economic loss

in terms of both the incident likelihood and the magnitude of the loss or injury.

Risk Analysis - The estimation of scenario, process, facility and/or

organizational risk by identifying potential incident scenarios, then evaluating

and combining the expected frequency and impact of each scenario having a

consequence of concern, then summing the scenario risks, if necessary, to

obtain the total risk estimate for the level at which the risk analysis is being

performed.

Risk and Risk Analysis




Risk Analysis within RAST involves converting the Consequence Severity and

Scenario Frequency to graduated scales representing order-of-magnitude levels.

A tabular Risk Matrix is used to summarize results with each cell in the matrix (at

intersecting values of Consequence Severity and Scenario Frequency)

representing a specific value of scenario risk.

Tolerable Risk may also be summarized in the same tabular Risk Matrix and

compared to scenario risk in determining if further risk reduction is needed.

The values of tolerable frequency for the various Consequence Severity levels are

administrative parameters that should be updated to reflect a specific company’s

risk tolerance criteria. The default parameters provided in RAST should be

considered “examples” as CCPS does not endorse any specific risk criteria.

RAST Analysis within RAST




Example Risk Matrix within RAST


2 3 4 5 6 7

Description Human Harm Environment Business Loss 10^-2/year 10^-3/year 10^-4/year 10^-5/year 10^-6/year 10^-7/year

Reportable Incident to Environmental Agency OR

< 10 kg Very Toxic to Waterway OR < 100 kg NFPA-H4 to Soil

< 100 kg Toxic to Waterway OR < 1000 kg NFPA-H3 to Soil

< 1000 kg Harmful to Waterway OR < 10000 kg NFPA-H2 to Soil

Environmental Contamination Confined to Site OR




Environmental Contamination of Local Groundwater OR




Incident Requiring Significant Off-Site Remediation OR



> 100000 kg Harmful to Waterway OR > 100000 kg NFPA-H2 to Soil

Incident with Significant National Media Attention OR


> 100000 kg Toxic to Waterway OR > 1000000 kg NFPA-H3 to Soil

Acceptable

Tolerable - Offsite

Tolerable - Onsite

Unacceptable

Low

Con

sequ

ence

Hig

h

Con

sequ

ence

Low

Frequency

High

Frequency

Consequence Severity Description Frequency

Severity Level-1

Minor Injury On-site

(or < 0.01 Person Severely Impacted On-site)

Potential for Adverse Local Publicity

Property Damage and

Business Loss < $50M2 Orange Yellow

Green

Green

Yellow> 10 People Severely Impacted On-site

> 1 Person Severely Impacted Off-site

Property Damage and

Business Loss > $50 MM6 Red

Red Red Orange Yellow GreenSeverity Level-41 to 10 People Severely Impacted On-site

0.1 to 1 People Severely Impacted Off-site

Property Damage and

Business Loss $5 MM to

$50 MM

Legend

6

Yellow Green GreenSeverity Level-2

Major Injury On-site

(or 0.01 to 0.1 Person Severely Impacted On-site)

Public Required to Shelter Indoors

(or Minor Injury Off-site)

Property Damage and

Business Loss $50 M to

$500 M

3 Red

Red Orange Yellow GreenSeverity Level-3

Potential Fatality On-site

(or 0.1 to 1 Person Severely Impacted On-site)

or Potential Major Injury Off-site

Property Damage and


$50 MM

4 Red

Severity Level-5

6

Red Orange

5 Red

Risk Matrix: Risk = Consequence Severity times Frequency

Red Red

Green Green Green Green

Orange

Each company determines the acceptable, unacceptable and tolerable

frequencies for the consequence severity of a single scenario



Example Risk Analysis within RAST


A Layers of Protection Analysis (LOPA) workbook within RAST is used to

summarize the risk associated with each scenario to be analyzed. Scenarios are

selected from a list of potential scenarios for risk analysis by the analysis team.

Scenarios of relatively low risk may be screened out from LOPA consideration

based on a company’s risk screening criteria which may be entered as

administrative parameters.

Those scenarios representing “worst cases” are noted (those requiring the greatest

number of protective layers to meet a company’s risk tolerance criteria) to aid the

analysis team in selecting which scenarios to include in the analysis.

During LOPA, the study team adds additional cost effective IPLs until each scenario

is at or below the tolerable risk criteria.



Example LOPA Worksheet within RAST


Study Team updates Initiating Event

Description and assigns Frequency Factor

Study Team enters or updates any Enabling

Condition or Conditional Modifier Probability

Study Team reviews Scenario Description and Updates Consequence Severity

Tolerable Frequency Factor

Study Team enters Description and PFD for all Protective Layers to

be Utilized




Documentation within RASTRAST maintains datasets of new chemicals, suggested scenarios,

consequence analysis results, and layers of protection analysis results for

each equipment item evaluated. These datasets are compatible with and

may be imported into newer versions of the RAST tools to effectively

manage the data and documentation associated with the study. Future

HIRA studies for the facility are easily updated by importing previous

studies into the latest version of RAST, review and update of inputs, and

generation of updated reports.

Key reports include: Summary of Hazards, List of Suggested Scenarios,

Consequence Analysis for Loss Events, and a Layers of ProtectionAnalysis worksheet.




Desired Roles within a HIRA Study using RAST❑ Study Leader – Organizes and facilitates study team meetings. Is

experienced in HIRA studies and ensures study objectives are being met.

❑ Scribe or Note Taker –Documents meeting progress and action items for the

study team.

❑ Participant – Brings knowledge of facility design and/or operation to the study

❑ RAST User – Ensures appropriate inputs are entered into RAST to meet

study objectives. Presents reports and results to the team to address

questions and support decisions.

❑ RAST Technical Administrator – Ensures administrative parameters for

RAST are consistent with company protocol and criteria. (May not necessarily

participate in HIRA studies.)




Chemical Hazard Engineering Fundamentals (CHEF) is intended for newer engineers or

as a refresher for experienced personnel. It describes methodology for performing a

Hazard Identification and Risk Analysis (HIRA) study. There are many simplifying

assumptions used that may not be suitable for every situation. A RAST User should be

familiar with CHEF materials to recognize when a simplifying assumption may not be

appropriate within a specific HIRA study.

Risk Analysis Screening Tools (RAST Users) focuses on how to utilize the software in

helping HIRA study teams to improve productivity, consistency, and quality of the studies.

Various inputs and reports are described in detail with examples.

RAST Technical Administrator is intended to show experienced Process Safety

personnel how to incorporate a company’s specific risk matrix and other screening criteria

into the RAST tools. It is intended for those filling a RAST Technical Administrator role

rather than a RAST User.

RAST Related Training Available




Risk Analysis Screening Tool (RAST)Links to RAST Materials from CCPS Web Site



CAI and Arnel Confined

Space Explosion

DPC Enterprises

Chorine ReleaseT2 Laboratories Runaway

Reaction and Explosion

BP Refinery

Explosion and Fire


Risk Analysis Screening Tool (RAST)Case Studies on the CCPS Web Site




Risk Analysis Screening Tools (RAST)

Case Study – CAI and Arnel



CONFINED SPACE EXPLOSION

Danvers, Massachusetts

November 22, 2006




Case Study – CAI and ArnelHazard Identification and Risk Analysis (HIRA) Study

What are the Hazards?

What can go Wrong?

How Bad could it Be?

How Oftenmight it

Happen?

Is the Risk Tolerable?

Identify Chemical

and ProcessHazards

Estimate Frequency

Analyze Consequences

AnalyzeRisk

IdentifyAdditional Safeguards as Needed

DevelopScenarios

Identify Equipment

or Activity to be Analyzed

Manage Barriers

for Life Cycle of Facility

We begin the study by Identifying the Equipment or Activity for which we intend to perform

an analysis. RAST uses the operation of a specific equipment item containing a specific

chemical or chemical mixture to define the activity. For example, the operation of a storage

tank, a reactor, a piping network, etc. Inputs are chemical data, equipment designinformation, operating conditions, and plant layout.





Process DescriptionThe Danversport , MA plant is a 12000 ft2 ink and paint manufacturing facility jointly owned by CAI and

Arnel Companies. This facility began operations in the early 1960s within a minimally populated

peninsula. Over several years, a large marina and many single family and duplex homes have located

adjacent to the manufacturing plant, some homes as close as 150 ft. away.

The CAI production manager and five employees manufactured solvent-based inks in the Danvers

facility. At the end of each day, they loaded the day’s production of ink products onto a truck and

delivered it to the Georgetown warehouse. CAI stored alcohols, heptane, other solvents, and pigments

and resins in the building and in three 3000-gallon underground storage tanks (USTs).

Nine Arnel employees worked in the Danvers facility, which was the company’s only business location.

Arnel manufactured solvent- and water-based stains, lacquers, coatings, and paints, as well as

polyurethane coatings and adhesives. They stored alcohols and other solvents, pigments, paint resins,

and industrial grade nitrocellulose at the facility.

This is an illustrative example and does not reflect a thorough or complete study.





Process DescriptionCAI and Arnel mixed solvents,

pigments, resins and nitrocellulose

to produce inks and paints in 1000

to 3000 gallon vessels. Vessels

contained top mounted agitators

and a steam heating jacket. Mix

tanks 1 and 2 were fully open on

top while mix tanks 3 and 4 were

equipment with a 12 inch diameter

access hatch to keep debris from

falling into the tank but allowed

vapor or air to pass through the

opening.




The initial mixture of more than 2000 gal. of

heptane and propyl alcohol is added to the tank

from 500 gal. totes. Resin is hand loaded from

fiber drums to the top of the tank. This mixture is

then heated to between 90 and 120oF to dissolve

the resin. Temperature control is achieved by

manually opening a ¼ inch steam valve leading to

the steam heating jacket. Following a quality

control check, the liquid is pumped out the bottom

of the mix tank to smaller pigment mixers, as

needed. Unused resin-solvent mixture would

remain in the mix tank until it was all utilized in

specific ink products.


Process Description






We will start by entering information for the Formulation Mixing Tank. At some point, we may

decide to include other equipment in the study.

One the Main Menu, enter the equipment identification as the Formulation Mixing Tank,

equipment type as Stirred Reactor/Crystallizer and location as Indoors.

Chemical Data – RAST requires a chemical or chemical mixture that is representative of the

hazards. RAST does not perform time-dependent or location-dependent composition

changes (such as within a reactor or distillation column). Where hazards may be

significantly different between reactor feed and products, or distillation overheads versus

bottoms; evaluation of the equipment may be repeated using different composition (such as

Reactor A with feed composition and Reactor B with products composition).



Import from Previous Study

Merge Data from Another Study into this Study

Update Previously Saved Information

Access LOPA Workbook from Scenario Results

Update Notes and Comments for Entire Workbook

Select Default Units: Study File: Case Study - CAI and Arnel Example.pptx.xlsm

Session Date: Participants:

Equipment Identification =

Equipment Type =

Equipment Location =

Data Entry Status or Notes:

Plant Section or Sub-Area:

P&ID Number:

Min

Complete

RAST

Input Data Sufficient to Proceed with Analysis

Input Information

Stirred Reactor/Crystallizer

Indoors

Formulation Mixing Tank

Evaluations and Reports

Risk Analysis Screening Tools (V 2)Latest Revision Date 3/02/19

Import from RAST File

Equipment Parameter Input

Chemical Data Input

Reaction Input and Evaluation

Fire & Explosion Index / Chemical Exposure Index

English Units SI Units

Relief Effluent Screening

Scenario Identification

Check Inputs

Save Inputs toEquipment Table

Go to Equipment Table >

Process Conditions Input

Plant Layout Input

Hazards & Consequences

LOPA Menu >

Clear Input

Update Scenarios for Equipment Loaded

Input Guidance Information

CLEAR EVERYTHING IN WORKBOOK

Pool Fire Evaluation

Merge Data from Another File

Go to Workbook Notes >

Go to Revision Log >

Go To Scenario Results >

Go To Instructions >>


Enter Equipment Identification,

Equipment Type and Location



Begin by entering

information on the Main

Menu worksheet. Start

with the Formulation

Mixing Tank



Chemical Data Input

Equipment Identification: 40 C

Equipment Type: 0.01 bar

Location: 100.8 C

Key Chemical: Reference:

Chemical Comments:

Reg. Agency Considers Toxic?

Heptane 0.450 0.659 1.9374 100.2 800 4900 1.1

Propanol, 1- 0.450 0.340 1.0000 60.07 250 4000 2.0

Dissolved Solids 0.100 0.001 0.0082 100

Sum = 1.00 Vapor Mixture Properties: 81.6 396.7 4440.3 1.4

Mixture azeotrope? No

Melting Point = -126 deg C

Flash Point = -4 deg C

Est Mixture Flash Point = 9.1 deg C

1 Not “Sustained Burning”?

AutoIgnition Temperature = deg C

Ease of Ignition = Normal

Fuel Reactivity = Medium

Dermal Toxicity =

Aquatic Toxicity =

Model as a single Pseudo-Chemical? Mixture NFPA Flammability = 3

Mixture NFPA Health = 1

Reactivity Category =

Mixture NFPA Reactivity = 0

Estimated Boiling Point = 100.5 C Liquid Conductivity = Non-Conductive

Vapor Pressure at Operating Temp = 0.081 atm

Liquid Density at Operating Temp = 0.75 gm/ml

Liq Heat Capacity at Op Temp = 0.59

Liq Heat Capacity at Boiling Point = 0.69 micron

Heat of Vaporization at Op Temp = 118 micron

Heat of Vaporization at Boiling Point = 105 mJoule

Boiling Point at Relief Set or MAWP = 103.3 C

Boiling Point at Burst Pressure = 104.6 C

From the above vapor composition: Estimated 1 hour LC 1 8880.5 ppm Estimated 1 hour LC 50 22201.3 ppm

State Mol Weight ERPG-2 (ppm) ERPG-3 (ppm) LFL (vol %) Flash Pt (C )

Pad Gas Properties Vapor 29

Heat Transfer Fluid Vapor 18

High Viscous Material (for F&EI)?

Mixture Properties

Wt Fraction

Feed

Molecular

Weight

Second Liq

Phase

Relative

Volatility

Wt Fraction

Vapor

User ValuesMixture

Estimates

ERPG-3 (ppm)ERPG-2 (ppm) LFL (vol %)

Liquid

Operating Temperature =

Heptane


Indoors


Second Liq

Phase

Chemicals (the first chemical listed is the 'key'

chemical)

Wt Fraction

Feed

Saturation Temperature =

Physical State =

Operating Pressure (gauge) =

Solids Mean Particle Size =

cal/gmDust Min Ignition Energy =

Name

Water

Dust-flammable hybrid?

Particle Size at 10% Fraction =

Solids Bulk Density >160 g/liter (>10 lb/ft3)?

Summary of Chemical Properties

cal/gm C

Standard Mixture (the key chemical has been

defined as a mixture)

Dust CharacteristicsDust/Solids Hazard Class =

Go To Process Conditions >Save All Input to Equipment TableEnter New Chemical Clear Input

<< Go To Main Menu

Go To Plant Layout >

Show Chemical Details Hide Chemical Details

Go To Equipment Input >



Chemical Data

Saturation temperature is

estimated as the boiling point

at the operating pressure.

The physical state is “liquid”

Fortunately, all the chemicals needed

in this evaluation are already in the

Chemical Data Table internal to RAST.

The solvent mixture concentration is

assumed equal fractions of heptane

and 1-propanol with a small amount of

dissolved solids to represent the

nitrocellulose resin is used as

representative of the hazards.

The operating pressure is essentially

atmospheric such that 0.01 bar gauge

is entered.

RAST allows up to 5

components.

Chemical details may

be shown or hidden

The operating temperature of 40

C represents a mixture at 90 to

120 F. The operating pressure

entered as 0.01 bar gauge



Equipment Input

Equipment Identification:

Equipment Type:

Location:

3000 gal Pipe Length = m

0.1 bar Piping Vulnerable to Damage?

Apply Screwed Connection Penalty?

C

C

3 in Pump Type =

Seal or Containment Type =

Remote Start Pump?

354 kg Pump Automated Suction or Discharge?

kg Estimated User Entry

Pump Volume (including piping to block valves), liter 7.1

Pump Surface (including piping to block valves), m2 0.43

5 HP

Equipment or Piping Connection =

23 sq m

sq m Replacement Cost & Business Loss

m Drum Oven Volume = cu m

mm High Speed Rotating Equipment?

Bellows or Expansion Joint Used?

Sight Glass Used?

Relief Device Identification

Relief Type =

Relief Discharges to:

Relief Set Pressure (gauge) = bar

50 sq ft Relief Size (equiv. diameter) = mm

100 BTU/hr sq ft F Relief Design Actual Flow Rate = kg/min

120 C Release Pipe Diameter = mm

0.5 bar Release Elevation m

Closest Distance From Relief to Elevated Work Area = m

Heat Transfer Fluid Name = Furthest Distance from Relief to Elevated Work Area = m

Vapor Elevation of Nearest Work Area = m

Enter Distances from Relief Location ONLY if Different from Equipment Location

mm Relief Distance to Property Limit or Fence Line = m

Relief Distance to Occupied Bldg 1 or Area = m

sq m Relief Distance to Center of Occ Bldg 1 = m

Kwatt /sq m C Occ Bldg 2 in Same Wind Direction for Relief?

C Relief Distance to Occupied Bldg 2 = m

Relief Distance to Center of Occ Bldg 2 = m

Piping Parameters

Pump / Agitator Parameters

MAWP (gauge) =

Equipment Description

Formulation Mixing Tanks are 8 ft diameter by 10 ft tall.

Equipment Volume =


Equipment Parameters

Full Vacuum Rated?

Estimated High Temperature Failure =

Estimated Embrittlement Temperature =

Equipment Elevation to Surface =

Drain Valve Size


Indoors

Susceptible to Vibration Fatigue?

Motor Power =

User Equipment Max. Wetted Area =

Heat Transfer Fluid State =

Vessel/Tank Parameters

Material of Construction

Internal Corrosive or Stress Cracking Potential?

Equipment Mass =

Number of Flanges or Nozzles =

Nozzle or Pipe Size =

Estimated Equip Mass based on C. Steel

Other Equipment Parameters

Transportation Equipment or Piping Parameters

Tube Failure Release to Atmosphere?

Insulation

Estimated Equipment Max Wetted Area =

Heating Fluid Temperature =

Heating Transfer Area =

Indoors

Tracing ?

Vessel/Tank Geometry?

Insulation Heat Reduction Factor =

Warning: Operating Pressure Greater than Relief Set Pressure

Low Pressure Tank with Weak Seam Roof?

Coolant Temperature =

Conductive Dip Pipe or Bottom Fill?

Cooling Transfer Area =

Tube (or Leak) Diameter =

Quantity Hot Oil Handled (for F&E) =

Cooling Overall U =

Number of Tubes =

Relief Device Parameters

Heat Transfer Parameters

Heating Overall U =

Water

Heat Transfer Fluid Pressure (gauge) =

Vessel/Tank Considered as "Storage"?

Clear InputSave Input to Equipment Table< Go To Chemical Data

<< Go To Main Menu Go To Process Conditions Input >

Go To Plant Layout >

Go To Reaction Input >



Equipment InputThe relief device is essentially

the 12 inch access hatch on

the top of the vessel and

vented “Indoors” which is not

typical.

The vessel jacket/bottom

head is roughly 50 ft2 and

heated by low pressure

steam.

Only minimal data will be

entered at this time.

The equipment volume

and maximum allowable

working pressure

A largest “working” nozzle

of 3 inches is entered

representing the bottom

liquid outlet.

The relief device is

considered the 12 in hatch

which vents indoors.

Heat transfer

information is entered.





Process Conditions

Ambient temperature of 25 C

has been assumed (input left

blank such that the default value

is used).

The maximum flowrate to the

tank is approximately 50

gal/min. from 500 gallon totes.

The maximum liquid height in

the vessel is 8 ft.

Process Conditions Input


Equipment Type:

Location:

Ambient Temperature = Operating Temperature = 40 C

Inventory Limit (blank is unlimited) = kg Operating Pressure (gauge) = 0.01 bar

Liquid Head within Equipment, Dh = 8 ft Physical State =

Limiting Maximum Fill Fraction = Saturation Temperature = 100.8 C

Limiting Minimum Fill Fraction = Contained Mass = 6856 kg

Maximum Feed Press (gauge) = bar Maximum Contained Mass = 8569 kg

Maximum Feed or Flow Rate = 50 gal/min Inventory for Reference = 17139 kg

Maximum Feed Temperature = C

Type of Feed (Batch or Continuous)

Non-Ignitable Atmosphere Maintained?

Potential for Aerosol or Mist?

Pad Gas Name = Percent of Time in Operation =

Max Pad Gas Pressure (gauge)= bar

Maximum Pad Gas Rate = kg/min

Downstream Pressure (gauge) = bar

Maximum Back Flow Rate = kg/min

Equipment Vents to .. =

Use Time-based Release for Equipment Rupture? sec



Process Description

Process/Operating Conditions

Indoors

Summary for Heptane

Frequent Turnaround or Cleanout?

Operating Procedures

Liquid

Review Date:

Review of Operating Procedures for

Selected Equipment Item by:

Centralized Ventilation Shut-Off Bldg 1?

Centralized Ventilation Shut-Off Bldg 2?

Clear InputSave Input to Equipment Table< Go To Chemical Data

Go To Plant Layout ><< Go To Main Menu

< Go To Equipment Input

Go To Reaction Input >



April 12, 2019 Slide - 41Approximately 100 ft


Site Layout

The enclosed production

area (denoted as C, D, and

E) is approximately 10,000

ft3. Areas denoted A and B

contained offices and a

laboratory. Fiber drums of

nitrocellulose were stored in

trailers east of the building.



April 12, 2019 Slide - 42Approximately 500 ft


Site Layout

A marina is adjacent to the

site, approximately 150 ft

east of the manufacturing

area. A residential

community is approximately

100 ft north with the nearest

houses 150 ft away.

The CAI and Arnel facility is

circled in the photograph.





Site LayoutThere is a total of 15 employees

between CAI and Arnel. For now, it is

assumed that during normal work hours,

2 people might be in the production area

and 5 in the offices and laboratory.

There has been assumed to be 10

people located at the marina between

customers, maintenance and sales staff.

The enclosed process area is estimated

to be 200,000 ft3. There are two 6,000

cfm exhaust fans allowing roughly 3.6

air changes per hour when running.

Plant Layout Input


Equipment Type:

Location:

Distance to Property Limit or Fence Line = 100 ft Occupied Building 1 Name =

Furthest Distance to Fence Line ( > 30.48 m ) = m Distance to Occupied Bldg 1 or Area = 50 ft

Max. Onsite Outdoor Population Density people/m2 Elevation of Occ Bldg 1 Ventilation Inlet = m

Personnel Routinely in Immediate Area? Distance to Center of Occupied Bldg 1 = m

Distance to end of Offsite Zone 1 m Occupied Bldg Type =

Offsite Population Density within Zone 1 people/m2 Occupied Bldg Ventilation Rate = changes/hr

Offsite Population Density Beyond Zone 1 people/m2 Number of Building Occupants = 5

Effective Egress from Work Area? Occ Bldg 2 in Same Wind Direction? No

Access for Emergency Services? Occupied Building 2 Name =

Degree of Equipment Congestion in Area? Distance to Occupied Bldg 2 150 ft

Containment or Dike Surface Area = sq m Elevation of Occ Bldg 2 Ventilation Inlet = m

Consider Dike or Bund Failure for Vessel Rupture? Distance to Center of Occ Bldg2 = m

Credit Fire Heat Adsorption for Drainage/Indirect? Occupied Bldg 2 Type =

Distance to Nearest Fired Equipment = Occupied Bldg 2 Ventilation Rate = changes/hr

Quantity of "Other" Flammables in Immediate Area kg Number of Occupants Bldg 2 = 10

Quantity of Flammables in Adjacent Area kg

Adjacent Containment or Dike Surface Area = sq m

Automated EBVs to limit spill quantity?

Spills to Soil Require Remediation?

Potential for Water Contamination?

Enclosed Process Volume = 200000 cu ft High Population Downstream of Facility?

Enclosed Process Ventilation = 3.6 changes/hr

No. Enclosed Area Personnel = 2

Note that Environmental Scenarios are Excluded

Enclosed Process Area Data

Occupied Building DataLocation Information

Environmental Inputs

Marina

Plant Offices and Laboratory



Indoors

Layout Description

Process Areas C, E, and F are approximately 10,000 ft2 by maybe 20 ft

height. Office area B roughly 50 ft from mixing tanks

Clear InputSave Input to Equipment Table< Go To Process Conditions

Go To Reaction Input ><< Go To Main Menu

< Go To Equipment Input

< Go To Chemical Data



Indoor Chemical Processing often intensifies hazards as dilution of

airborne chemicals is minimized. Release quantities to reach

flammable or toxic concentrations may be very small.

An enclosed manufacturing volume of 1000 m3 only requires approximately 40 kg

flammable vapor (such as 38 kg propane) for the entire volume to reach the

lower flammable limit. A chemical with ERPG-3 of 150 ppm would only require

0.15 m3 of toxic vapor (such as 0.23 kg HCl) to reach a potentially toxic

concentration within the enclosed process area.

Chemical Processing Indoors







Input Data for an Equipment Item

stored in one row by Equipment Tag

Retrieve Information for an Equipment

Item by selecting any cell in the desired

row and entering Load Selected

Select Save Inputs to Equipment Table (blue macro button). All Input Information

will be stored in the Equipment Table in a single row identified by a unique Equipment

Identification or Tag.




Risk Matrix


To understand the Consequence

Severity and Tolerable Frequency, the

values for key Study Parameters and a

Risk Matrix may be viewed on the

Workbook Notes worksheet. These

values may be updated on hidden

worksheets and should reflect the

company’s specific risk criteria.

For this case study, the Risk Matrix

(right) has been used. The Human

Harm criteria is based on an estimated

number of people severely impacted

(severe injury including fatality).

2 3 4 5 6 7

Description Human Harm Environment Business Loss 10^-2/year 10^-3/year 10^-4/year 10^-5/year 10^-6/year 10^-7/year

Reportable Incident to Environmental Agency OR




Environmental Contamination Confined to Site OR




Environmental Contamination of Local Groundwater OR




Incident Requiring Significant Off-Site Remediation OR



> 100000 kg Harmful to Waterway OR > 100000 kg NFPA-H2 to Soil

Incident with Significant National Media Attention OR


> 100000 kg Toxic to Waterway OR > 1000000 kg NFPA-H3 to Soil

Acceptable

Tolerable - Offsite

Tolerable - Onsite

Unacceptable

Low

Con

sequ

ence

Hig

h

Con

sequ

ence

Low

Frequency

High

Frequency

Consequence Severity Description Frequency

Severity Level-1

Minor Injury On-site

(or < 0.01 Person Severely Impacted On-site)

Potential for Adverse Local Publicity

Property Damage and

Business Loss < $50M2 Orange Yellow

Green

Green

Yellow> 10 People Severely Impacted On-site

> 1 Person Severely Impacted Off-site

Property Damage and

Business Loss > $50 MM6 Red

Red Red Orange Yellow GreenSeverity Level-41 to 10 People Severely Impacted On-site

0.1 to 1 People Severely Impacted Off-site

Property Damage and


$50 MM

Legend

6

Yellow Green GreenSeverity Level-2

Major Injury On-site

(or 0.01 to 0.1 Person Severely Impacted On-site)

Public Required to Shelter Indoors

(or Minor Injury Off-site)

Property Damage and

Business Loss $50 M to

$500 M

3 Red

Red Orange Yellow GreenSeverity Level-3

Potential Fatality On-site

(or 0.1 to 1 Person Severely Impacted On-site)

or Potential Major Injury Off-site

Property Damage and


$50 MM

4 Red

Severity Level-5

6

Red Orange

5 Red

Risk Matrix: Risk = Consequence Severity times Frequency

Red Red

Green Green Green Green

Orange



HAZOP Node: HAZOP Design IntentPlant Section =

Equipment Type = Stirred

Reactor/Crystallizer

Equipment Tag = Formulation Mixing

Tank

LOPA Menu Filters:

Scenario Type Scenario CommentsParameters and

DeviationInitiating Event (Cause) Initiating Event Description Loss Event Outcome

Off

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Drain or Vent Valve Open

Drain or Vent Valve left open following

infrequent maintenance, purging or

cleaning

Flow-Loss of

Containment

Human Failure Action once per

quarter or less

Operator leaves Drain or Vent Open

following infrequent maintenanceDrain or Vent Leak Flash Fire or Fireball 4

Vapor Relief Vent - Heat TransferFlash Fire or Fireball, Building

Explosion5 6

Equipment Rupture at Saturation

Temperature

Flash Fire or Fireball, Building

Explosion5 6

Vapor Relief Vent - FireIndoor Toxic Release, Flash Fire

or Fireball, Building Explosion5 5 6

Equipment Rupture at Fire Conditions Flash Fire or Fireball 3

Ignitable Headspace

Chemical is Flammable or

Combustible: Maximum Operating,

Mechanical Energy or Heating Media

Temperature exceeds Flash Point

less 5 C

Composition-Wrong

ConcentrationBPCS Instrument Loop Failure

Failure of Pressure or NonCombustible

Atmosphere ControlEquipment Rupture - Deflagration Flash Fire or Fireball 3

Overfill Release Flash Fire or Fireball 5

Equipment Rupture at Operating

Temperature

Flash Fire or Fireball, Building

Explosion5 6

Excessive Heat Input -

Mechanical

Vapor Pressure plus pad gas Does

Not exceed Maximum Allowable


Pressure at Maximum Temperature

from Mechanical Energy Input

Pressure-HighHuman Failure Action once per

quarter or less

Agitation or Pump Recirculation left running

for extended time allowing slow temperature

increase


Met

Excessive Pad Gas Pressure

Maximum Pad Gas Pressure Does

Not Exceed the Maximum Allowable


Pressure

Flow-High Regulator FailureRegulator Fails causing high flow or

pressure


Met

High Temperature Failure

Maximum Feed Temperature Does

Not Exceed Temperature limits of

Equipment

Temperature-High BPCS Instrument Loop Failure Failure of Temperature ControlCriteria for Triggering Incidents Not

Met

Pad Gas Compression

Maximum Feed or Downstream

Pressure does not exceed the

Maximum Allowable Working

Pressure or Relief Set Pressure

Pressure-High BPCS Instrument Loop Failure Failure of Pressure ControlCriteria for Triggering Incidents Not

Met

Piping or Equipment Leak - SmallAssessment Excludes Mechanical

Integrity Scenarios

Flow-Loss of

ContainmentMechanical Failure

Loss of Alignment or Equipment Support

causing Vibration or Excessive Movement


Met

Rotating Equipment DamageMotor Power below Rotating

Equipment Vibration or Damage Limit

Composition-

ContaminantsMechanical Failure

Breakage of rotating blade or internal parts

due to alignment, wear,or fatigue


Met

Seal Leak No Agitator Seal indicatedFlow-Loss of

ContainmentSingle Mechanical Seal Failure

Failure from corrosion, alignment, low flow,

etc.

Mechanical Seal Failure above Liquid

Level



with LOPA

Vacuum DamageRating for Full lVacuum Not Entered

for Low Design Pressure EquipmentPressure-Low BPCS Instrument Loop Failure Failure of Pressure Control

Full Bore Hole Size Leak above

Liquid Level



with LOPA

Excessive Heat Input - Heat

Transfer

Excessive Heat Input - Pool Fire

Exposure

Overfill or Backflow of liquid with spill

rate equal to the feed rate to a

maximum quantity of the available

Level-High or Flow-

BackflowOverfill, Overflow, or Backflow

BPCS Instrument Loop Failure


Safety

Failure of Flow Control

Leak of Flammable Material or Material

above its Flash Point which may ignite

BPCS Instrument Loop FailureFailure of Level Indication with continued

addition of material

Vapor Pressure plus pad gas

exceeds Maximum Allowable


Pressure at Ambient or Heating Media

Vapor Pressure exceeds Relief Set

or Burst Pressure from Pool Fire

Exposure

Pressure-High

Pressure-High

Potential Outcome / Tolerable Frequency Factors

Suggested Scenarios from the RAST Library

Scenarios in gray were

considered but are excluded for

reason noted

Scenarios with NO IPL's Required will NOT be reported.Mechanical Integrity Scenarios will NOT be reported

Formulation Mixing Tank is a Stirred Reactor/Crystallizer containing Heptane Mix

that operates at 40 C and 0.01 bar. The volume is 3000 gal with a maximum

allowable working pressure of 0.1 bar. The maximum feed or flow rate is 50

gal/min.

Off

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Update Go To Scenario Results ><< Go To Main Menu

Create UserScenario



Suggested Scenarios for Formulation Mix Tank

Several scenarios suggest that

the confined process area could

reach a flammable concentration

including vessel overfill and

excessive heating.





Suggested Scenarios for Formulation Mixing Tank

❑ Review the suggested list of scenarios. Do these represent what you

would expect for an indoor mix tank?

❑ Are there scenarios that have been “screened out” (shown in gray) that

should be considered?

❑ Are there scenarios missing? (Possibly similar scenarios with different

Initiating Events)

❑ Do you agree with the “worst” Consequence (Tolerable Frequency

Factor) for the scenario listed?



RAST Version 2

Release Location Indoors

Airborne Quantity Summary:

Release Temperature, C 103.3 Factor Probability

Release Pressure, barg 0.100

Physical State at Release Conditions Vapor

Heat Input, Kcal/min 10.54

Equivalent Hole Size, cm

Release Rate, Kg/sec 0.09

Release Duration, min 60.00

Spray Distance, m 0.0

Flash + Aerosol Evaporation Fraction

Estimated Aerosol Droplet Diameter, micron

Pool Area, sq m 0.0

Estimated Pool Temperature, C

Maximum Pool Evaporation Rate, kg/sec

Total Airborne Rate, kg/sec 0.09

Total Airborne Quantity, Kg 306.9

Airborne Quantity Composition:

Mole Fraction Heptane 0.356

Mole Fraction Propanol, 1- 0.644

Mole Fraction Dissolved Solids 0.000

Mole Fraction Pad Gas (at Mw = 29)



LC-50 Concentration, ppm by volume 52430.0

One-hour ERPG-3 for Vapor Composition, ppm by volume 4280.9

One-hour LC-1 Concentration, ppm by volume 8561.8

LFL for Vapor Composition, % by volume 1.55

Dispersion Summary (Atmospheric Stability Class D with 3 m/sec wind except as noted):



Max Distance to 1% Lethality for 1.5 F weather, m 0.1

Max Distance to Estimated LC-50 Concentration, m 0.1

Max Distance to Flash Fire Impact or 0.5 LFL, m 11.0

Maximum Ground Elevation Concentration, ppm 1000000.0

Concentration at Distance to Fence Line, ppm 455.1

Concentration at Distance to Unrestricted Work Area, ppm

Concentration within Occupied Bldg 1, ppm 677.1

Concentration within Occupied Bldg 2, ppm 101.3

Concentration within Enclosed Process Area, ppm 17817.8

Conc within Enclosed Process Area w/Ventilation, ppm 4925.0

Prob of Exposure (proximity based)

Fence Line

Concentration

Exceeds ERPG-2

On-Site Toxic POE

Flash Fire POE

Physical Explosion POE

Chemical Exposure POE

Enclosed Area

Exceeds 0.5 LFL or

ERPG-3


Vapor Vent - Heat TransferLoss Event for: Stirred Reactor/Crystallizer; Formulation

Mixing Tank Containing Heptane :

Ground or Work Area

Exceeds Multiple of

LFL or Time-Scaled

ERPG-3

with Personnel Not in Immediate Area

RAST Version 2

Explosion Summary:

VCE or Building Explosion Energy, kcal 4.8E+06 1

VCE or Building Explosion Distance to 1 psi Overpressure, m 182.3

Maximum Distance to LFL Concentration, m 7.7

Blast Overpressure at Center of Occupied Building 1, psi 6.6

Blast Overpressure at Center of Occupied Building 2, psi 4.3

Distance to Severe Thermal Radiation Impact, m

Rupture Explosion Energy, kcal

Distance to Direct Blast Impact (10 psi), m 1

Maximum Fragment Range, m

Rupture Distance to 1 psi Overpressure, m

Rupture Overpressure at Center of Occupied Building 1, psi 0.0

Rupture Overpressure at Center of Occupied Building 2, psi 0.0

Incident Outcome and Consequence Summary:

NA

Onsite Toxic Impact based on Indoor Concentration / LC-50 of 0.3 NA

Time to ER-3 without Ventilation ~ 1751 sec; and Time to ER-3 with Ventilation ~ sec

Onsite Flash Fire Impact based on Indoor / LFL Concentration of 1.1 5

Chemical Exposure based on Dermal or Thermal Hazards and Spray Distance of 0 m NA

Onsite Direct Blast Impact based on Distance to 10 psi of 0 m

Onsite Thermal Radation Impact based on Distance from Fireball of 0 m

Occupied Building Toxic Impact No NA

Number of Potential Serious Impacts for Building 1: 0 people


Occupied Building Impact from Building Explosion Yes 6

Number of Potential Serious Impacts for Building 1: 4.5 people

Number of Potential Serious Impacts for Building 2: 7.9 people

1 psi Blast Overpressure Distance exceeds the Fence Line, Consider additional Offsite Impacts

Occupied Building Physical Explosion Impact No



Environmental Impact:

Estimated Number of

People Impacted

Probability of Ignition (POI)

Potential Explosion

Impact to Occupied

Building

Probability of Explosion (POX)

LOPA Tolerable Frequency

Factors Based On


Vapor Vent - Heat TransferLoss Event for: Stirred Reactor/Crystallizer; Formulation

Mixing Tank Containing Heptane :

Impact Assessment with Personnel routinely in the immediate

area

Exceeds Threshold

Criteria

YesOffsite Toxic Impact based on Toxic Integration Method and 30.48 m to Fence Line



Consequence AnalysisFor the Raffinate Splitter, select

Vapor Vent – Heat Transfer as

the Loss Event. This represents

a “worst” Consequence for filling

the enclosed area with

flammable vapor.

Note under the Dispersion

Summary that the enclosed

area concentration is not

estimated to reach the lower

flammable limit if the ventilation

system was running. 1 psi Blast Overpressure is estimated to

183 m (600 ft) and message notes this

exceeds the distance to the fence line





Consequence Analysis

RAST estimated maximum 183 m

(600 ft) to 1 psi blast overpressure

from enclosed process area which

is in excellent agreement with

CSB modeling.

REPORT NO. 2007-03-I-MA , US Chemical Safety Board,

Figure 20. Aerial View showing estimated explosion overpressures



Scenario Definition

Protection

Gap

Scenario /

Cross Ref

Description of Undesired ConsequenceLOPA Tolerable Frequency Factor

(chemicals, quantity involved,

and basis for calculations)

Initiating Event Probability of Ignition Probability of Exposure

(Presence Factor)

Time at Risk or Other

Enabling Factor

New

Instrumented

Protection

Credits

Taken

IPL Status? -->

Safety

AnalysisTolerable Frequency Factor 6 BPCS Instrument Loop Failure POI Probability Factor 1

4 1 11 6 1 1 0

Indoor Release of Flammable

Material-POX

6.01

Failure of Flow Control

Stirred Reactor/Crystallizer, Formulation Mixing Tank,

is involved in an Excessive Heat Input - Heat Transfer

event resulting in a Vapor Relief Vent - Heat Transfer

with subsequent 307 kg airborne release of a Heptane

Mixture at an airborne release rate of 11.3 Lb/min.

Estimated time to relief set pressure is 11 min.

This incident could result in a Building

Explosion with Explosion Distance to 1 psi

Overpressure of 598 ft including Explosion

Overpressure at Typical Construction

Occupied Bldg 1 (psi) of 6.6 psi. 1 psi

Blast Overpresssure exceeds Distance to

the Fence Line of 100 ft. Consider

adjustment for Off-Site Impacts with the

potential for Severity Level-5

< Back to Scenario Results

+

Expand All Collapse All

> Human Error ++ +> Possible IPLs


Risk Analysis / Layers of Protection Analysis (LOPA)


The initial Initiating Event description notes BPCS

flow control failure which should be updated to

Human Error more than 1 per quarter to reflect

that operator failed to close the steam valve.

Select Loss Event of Vapor Relief

Vent-Heat Transfer with Incident

Outcome of Building Explosion

for analysis in LOPA (“Yes”), then

select LOPA Worksheet



Scenario Definition

Protection

Gap

Scenario /

Cross Ref

Description of Undesired ConsequenceLOPA Tolerable Frequency Factor

(chemicals, quantity involved,

and basis for calculations)

Initiating Event Probability of Ignition Probability of Exposure

(Presence Factor)

Time at Risk or Other

Enabling Factor

New

Instrumented

Protection

Credits

Taken

IPL Status? -->

Safety

AnalysisTolerable Frequency Factor 6

Human Failure Action more than

once per quarterPOI Probability Factor 1

4 1 11 6 1 1 0

Indoor Release of Flammable

Material-POX

6.01

Failure to close Steam Valve to

vessel heater upon reaching

desired temperature

Stirred Reactor/Crystallizer, Formulation Mixing Tank,

is involved in an Excessive Heat Input - Heat Transfer

event resulting in a Vapor Relief Vent - Heat Transfer

with subsequent 307 kg airborne release of a Heptane

Mixture at an airborne release rate of 11.3 Lb/min.

Estimated time to relief set pressure is 11 min.

This incident could result in a Building

Explosion with Explosion Distance to 1 psi

Overpressure of 598 ft including Explosion

Overpressure at Typical Construction

Occupied Bldg 1 (psi) of 6.6 psi. 1 psi

Blast Overpresssure exceeds Distance to

the Fence Line of 100 ft. Consider

adjustment for Off-Site Impacts with the

potential for Severity Level-5

< Back to Scenario Results

+

Expand All Collapse All

> Human Error ++ +> Possible IPLs




The probability of ignition in RAST is estimated at 0.1 for an indoor

flammable release into a properly electrically classified area. This is an

administrative parameter on a hidden worksheet that may be updated.

RAST does not estimate offsite flammable

impact directly but notes that the Consequence

Severity may need to be adjusted.



BPCS Control or

Human Response

to Alarm

BPCS Control or

Human Response

to Alarm

SIS Function A SIS Function BPressure Relief Device SRPS 1 SRPS 2 SRPS 3

BPCS Independent of

Initiating Event

1 - Other Safety related

protection systems (PFD=0.1)

1 1

Building ventilation system

capable of preventing

concentration from reaching

the lower flammable limit

Notes / Comments

High Temperature Closes

Heating Media Valve

Not Allowed

+ + + +




The existing safeguards (even if there were a high temperature alarm which automatically

closes the steam valve) were not sufficient to manage a scenario of this consequence severity.

The scenario could have been managed

by having a relief device set at a very

low pressure or open line to vent

outdoors and “sealing” the 12 inch solids

loading hatch when not in use.





Case Study – CAI and ArnelRisk Analysis and Incident Investigation often use similar methods to better

understand the scenario. Risk Analysis “anticipates” what could go wrong

and what the potential consequences may be. For Incident Investigation, the

Incident Outcome and Consequences are known in addition to the actual

weather conditions, wind direction, time of day, and other factors.

For the Formulation Mixing Tank, RAST did suggest column Excessive

Heating as one of many scenarios to consider. RAST also recognized that a

Building Explosion could be a feasible Incident Outcome. The estimate blast

overpressure from RAST was in excellent agreement with CSB modeling.

Fortunately, this incident occurred at night and resulting in no fatalities but 10

injuries, 24 hours and 6 adjacent business destroyed.



Questions?


CCPS An AIChE Technology Alliance · Center for Chemical Process Safety An AIChE Technology...

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