FATAL ACCIDENT INVESTIGATION REPORT - CIP Initiative

192 Pages·2005·1.63 MB·English

FATAL ACCIDENT INVESTIGATION REPORT

FATAL ACCIDENT INVESTIGATION
REPORT

Isomerization Unit Explosion
Final Report

Texas City, Texas, USA

Date of Incident: March 23, 2005
Date of Report: December 9th 2005

Approved for release by J. Mogford, Investigation team leader

FATAL ACCIDENT INVESTIGATION REPORT

Executive Summary

On March 23rd 2005, 15 people were killed and over 170 harmed as the result of a fire and
explosion on the Isomerization plant (ISOM) at the BP Products North America owned and
operated refinery in Texas City, Texas, USA.

On May 17th an interim report was released to quickly spread initial learnings from the
incident and to accelerate implementation of corrective actions. The interim report identified
critical factors. To achieve early publication, the interim report did not address the
underlying root causes leading to the incident.

This final report seeks to deepen understanding of the causes of the incident, and
recommends additional corrective actions to prevent recurrence of a similar incident and to
improve safety performance at the site.

The team’s opinion is that there were four critical factors, as listed in the interim report,
without which the incident would not have happened or would have been of significantly
lower impact.

• LOSS OF CONTAINMENT
• RAFFINATE SPLITTER STARTUP PROCEDURES AND APPLICATION OF
KNOWLEDGE AND SKILLS
• CONTROL OF WORK AND TRAILER SITING
• DESIGN AND ENGINEERING OF THE BLOWDOWN STACK

The incident was an explosion caused by heavier–than-air hydrocarbon vapors combusting
after coming into contact with an ignition source, probably a running vehicle engine. The
hydrocarbons originated from liquid overflow from the F-20 blowdown stack following the
operation of the raffinate splitter overpressure protection system caused by overfilling and
overheating of the tower contents.

The failure to institute liquid rundown from the tower, and the failure to take effective
emergency action, resulted in the loss of containment that preceded the explosion. These
were indicative of the failure to follow many established policies and procedures.
Supervisors assigned to the unit were not present to ensure conformance with established
procedures, which had become custom and practice on what was viewed as a routine
operation.

The severity of the incident was increased by the presence of many people congregated in
and around temporary trailers which were inappropriately sited too close to the source of
relief. Many of those injured could have been warned and left the area safely had warning
been provided by those who were aware of events. It is not clear why those aware of the
process upset failed to sound a warning. The likelihood of this incident could have been
reduced by discontinuing the use of the blowdown stack for light end hydrocarbon service
and installing inherently safer options when they were available.
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The team found no evidence of anyone consciously or intentionally taking actions or
decisions that put others at risk.

While the site management had introduced improvement programs, such as the 1000-day
program, had completed a site-wide Major Accident Risk assessment exercise (MAR) and,
following previous incidents, had begun to introduce many improvements in the areas of
training, audit, and culture, the team found many areas where procedures, policies, and
expected behaviors were not met.

In the course of this investigation, the team found many areas, although not critical factors in
the incident, where practices should be improved and have included recommendations to
achieve this.

The investigation used the BP root cause methodology supplemented by the CCPS (Center
for Chemical Process Safety) guidance. Documentary or instrumentation records were given
credence and where evidence was purely drawn from interviews corroboration has been
sought from at least two parties. Where confirmation could not be gained it has been noted
in the report.

These underlying causes are identified as follows:

• Over the years, the working environment had eroded to one characterized by resistance to
change, and lacking of trust, motivation, and a sense of purpose. Coupled with unclear
expectations around supervisory and management behaviors this meant that rules were
not consistently followed, rigor was lacking and individuals felt disempowered from
suggesting or initiating improvements.
• Process safety, operations performance and systematic risk reduction priorities had not
been set and consistently reinforced by management.
• Many changes in a complex organization had led to the lack of clear accountabilities and
poor communication, which together resulted in confusion in the workforce over roles
and responsibilities.
• A poor level of hazard awareness and understanding of process safety on the site resulted
in people accepting levels of risk that are considerably higher than comparable
installations. One consequence was that temporary office trailers were placed within 150
feet of a blowdown stack which vented heavier than air hydrocarbons to the atmosphere
without questioning the established industry practice.
• Given the poor vertical communication and performance management process, there was
neither adequate early warning system of problems, nor any independent means of
understanding the deteriorating standards in the plant.

The underlying reasons for the behaviors and actions displayed during the incident are
complex, and the team has spent much time trying to understand them.

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It is evident that they had been many years in the making and will require concerted and
committed actions to address.

The interim report made recommendations in the areas of

• People and Procedures
• Control of Work and Trailer Siting
• Design and Engineering

This report augments those recommendations with additional recommendations in these three
areas and new ones in the areas of leadership and underlying systems.

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CONTENTS

Executive Summary.............................................................................................i
Main Body
1. Introduction....................................................................................................1
2. Background....................................................................................................3
3. Description of the Incident...........................................................................7
3.1 Sequence of Events Leading up to the Incident......................................7
3.2 The Incident...........................................................................................12
4. Evidence.......................................................................................................15
4.1 Site Inspections.....................................................................................15
4.2 Witnesses..............................................................................................16
4.3 Samples ................................................................................................16
4.4 Equipment Testing.................................................................................17
4.5 Documentation .....................................................................................20
5. Evidence Analysis.......................................................................................21
5.1 Introduction to Evidence Analysis..........................................................21
5.2 Loss of Containment – Potential Scenarios...........................................22
5.2.1(a) Vapor Pressure/Liquid Carryover..........................................22
5.2.1(b) Steam Generation.................................................................23
5.2.1(c) Nitrogen.................................................................................23
5.2.1(d) Improper Feed.......................................................................24
5.2.2 Sewers........................................................................................24
5.2.3 Scenario Conclusion...................................................................24
5.3 Process Modeling..................................................................................25
5.3.1 Inventory of Liquid in the Raffinate Splitter................................25
5.3.2 Feed Charge into Raffinate Splitter.............................................28
5.3.3 Feed Composition to Raffinate Splitter.......................................30
5.3.4 Heat Input to the Splitter.............................................................31
5.3.5 Feed Preheat and Feed Vaporization to the Splitter...................35
5.3.6 Volume of Hydrocarbon Relieved to Blowdown Drum................36
5.3.7 Volume of Hydrocarbon Released to Sewer...............................37
5.3.8 Volume of Hydrocarbon Released to Atmosphere......................38
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5.3.9 Dynamic Modeling.......................................................................39
5.3.10 Conclusions of Technical Analysis...........................................39
5.4 Release Modeling..................................................................................40
5.4.1 Dispersion of Vapors From Blowdown Drum ..............................40
5.5 Explosion Modeling................................................................................41
5.6 Sewers...................................................................................................45
5.7 Sample Analysis....................................................................................46
5.8 Operations.............................................................................................47
5.8.1 Control Board Indications............................................................47
5.8.2 Intervention.................................................................................53
5.8.3 Indicated vs. True Level in Raffinate Splitter Bottoms.................54
5.8.4 Density Errors for Level Measurement........................................54
5.8.5 Raffinate Splitter Pressure Control..............................................56
5.8.6 Conclusion..................................................................................58
5.8.7 High Level Alarm in the Blowdown Drum....................................59
5.8.8 Satellite Control Room................................................................59
5.8.9 Outside Operators.......................................................................60
5.8.10 Extended Working....................................................................60
5.8.11 Conclusion................................................................................61
5.9 Hazard Studies......................................................................................61
5.9.1 Hazop and Revalidations............................................................61
5.9.2 Major Accident Risk (MAR).........................................................65
5.9.3 Action Tracking...........................................................................66
5.9.4 Conclusions.................................................................................67
5.10 Operating Procedures.........................................................................68
5.10.1 Startup Procedures................................................................68
5.10.2 Use of Startup Procedure......................................................70
5.10.3 Startup Procedure Steps Signed Off......................................71
5.10.4 Normal Startup.......................................................................71
5.10.5 Departures From the Startup Procedure................................73
5.10.6 Departures From the Startup Procedure During
Previous Startups ..................................................................76
5.10.7 Pre-Startup Review................................................................78
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5.10.8 Troubleshooting and Intervention..........................................78
5.10.9 Safe Work Practices..............................................................79
5.10.10 Shift Handover....................................................................80
5.10.11 Operations Upset/Problem Reporting.................................81
5.10.12 Conclusions........................................................................81
5.11 Training (Knowledge and Skills) .........................................................81
5.11.1 Training Program...................................................................81
5.11.2 Training Records...................................................................84
5.11.3 ISOM Operators....................................................................85
5.11.4 ISOM Supervisors (Including Step-Ups)................................86
5.11.5 Gun Drills...............................................................................87
5.11.6 Lack of Simulator...................................................................88
5.11.7 Training in Troubleshooting...................................................88
5.11.8 Training on Emergencies.......................................................89
5.11.9 Process Safety Knowledge and Skills...................................89
5.11.10 Training Program Audits........................................................90
5.11.11 MOC Training........................................................................90
5.11.12 Conclusions...........................................................................90
5.12 Facility Siting.......................................................................................91
5.12.1 Regulation.............................................................................91
5.12.2 Industry Guidance.................................................................91
5.12.3 Amoco Workbook..................................................................91
5.12.4 Texas City Procedure............................................................92
5.12.5 Trailers..................................................................................92
5.12.6 MOC Procedure as it Applies to Turnarounds (TARs)...........96
5.12.7 Trailer Site.............................................................................97
5.12.8 Comparison of Facility Siting Methodologies.........................99
5.12.9 Conclusion...........................................................................103
5.13 Plant Design, Engineering and Operability.......................................103
5.13.1 Raffinate Splitter..................................................................103
5.13.2 Blowdown Drum..................................................................108
5.13.3 Control Room......................................................................112
5.13.4 Hazardous Area Classification ............................................113
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5.13.5 Conclusions.........................................................................114
5.14 Equipment Testing............................................................................114
5.14.1 In-Situ Testing......................................................................114
5.14.2 Shop Testing........................................................................118
5.15 Maintenance/Mechanical Integrity.....................................................121
5.15.1 Maintenance Program .........................................................121
5.15.2 Raffinate Splitter..................................................................121
5.15.3 Blowdown Drum (F-20)........................................................126
5.15.4 Safety Critical Equipment.....................................................127
5.15.5 Internal Inspection ...............................................................128
5.15.6 Conclusions.........................................................................128
5.16 Emergency Response.......................................................................128
5.16.1 Emergency Response Plans................................................129
5.16.2 Evacuation Alarm.................................................................129
5.16.3 Conclusions.........................................................................130
5.17 Previous Incidents.............................................................................130
5.17.1 Raffinate Splitter and Blowdown Drum................................131
5.17.2 Previous Startups ................................................................133
5.17.3 External Incidents................................................................134
5.17.4 Conclusions.........................................................................135
5.18 Audit Programs .................................................................................136
5.18.1 PSM Audits..........................................................................136
5.18.2 gHSEr Audit.........................................................................137
5.18.3 Other Audits.........................................................................137
5.18.4 Corrective Actions................................................................138
5.18.5 Conclusions.........................................................................139
5.19 Risk...................................................................................................139
5.19.1 Risk Awareness...................................................................139
5.19.2 Risk Acceptance..................................................................140
5.19.3 Conclusions.........................................................................141
5.20 Communication.................................................................................141
5.20.1 Operations...........................................................................141
5.20.2 Process Safety.....................................................................142
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