development of a relational chemical...
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DEVELOPMENT OF A RELATIONAL CHEMICAL PROCESS SAFETY
DATABASE AND APPLICATIONS TO SAFETY IMPROVEMENTS
A Thesis
by
FAHAD AL-QURASHI
Submitted to the Office of Graduate Studies ofTexas A&M University
In partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE
December 2000
Major Subject: Chemical Engineering
ABSTRACT
Development of a Relational Chemical Process Safety Database and Applications to
Safety Improvements. (December 2000)
Fahad Al-Qurashi, B.S., Tulsa University
Chair of Advisory Committee: Dr. Sam. Mannan
Industrial accidents still show a major concern to both the public and the environment.
It has been a governmental objective to minimize these accidents. Several rules and
regulations have emerged to reduce the impacts of chemical releases on people and
environment. As a result of these rules, many databases were developed to record
incidents in an attempt to learn from previous mistakes and hence to reduce accidents.
Most of these databases are maintained by federal agencies. However, the taxonomy
inconsistencies of these databases make it difficult to develop a national picture of the
problem of accidental release.
Part of this research presents an analysis of the RMP*Info database, the latest EPA
database, to determine the most significant chemicals released and other trends.
According to this analysis, 85% of the releases in the chemical industry are due to
twelve chemicals. The sources of those releases and their consequences are presented.
In addition, the effects of the chemical type, toxic or flammable, and the number of full
time employees in the facilities are discussed.
To increase the value of the lessons learned from this database, proposed links with
failure rate databases and reactive chemical databases were discussed. The objective of
the relationship among these databases is to bring all relevant information of both
equipment and chemicals into one database. As a result, the new database will make
possible a better understanding by plant personnel about the reliability of plant
equipment and the danger of the chemicals they are dealing with. Consequently,
accidents will be reduced.
This research shows that relationships can be established among the three databases.
Examples were given to demonstrate the procedure of establishing these relationships.
This research is one step in this regard and should be followed by applying the proposed
procedure in a development of a more developed and beneficial relational database that
can help improve the safety performance of industry.
ACKNOWLEDGMENTS
I would like to express my sincere gratitude to my advisor Dr. Sam Mannan for giving
me this opportunity to work on such an interesting topic and all his support and
motivation during my graduate study. I am grateful to Dr. Kenneth Hall and Dr. John
Wagner for serving on my committee. I would like also to express my appreciation to
Dr. William Rogers for his help throughout the course of this research. This work would
not have been completed without all the help and support I received from my wife. I am
also thankful to my wonderful kids, Arwa and Abdulrahman, for their continuous
question “Are you going to school today?” This question inspired me to finish my
research in this short time period. Finally, I would like to thank my parents, especially
my mother, for their prayers and support.
TABLE OF CONTENTS
PageABSTRACT iii
ACKNOWLEDGMENTS v
TABLE OF CONTENTS vi
CHAPTER I Introduction… … … … … … … … … … … … … … … … … … … … .. 1
Accidental Databases… … … … … … … … … … … … … … … … … … . 4 Emergency Response Notification System Database (ERNS) .......... 4 Accidental Release Information Program Database (ARIP) ............. 5 Major Accident Reporting System (MARS) … .....................… ...... 5 Risk Management Program Database (RMP*Info) .......................... 6
CHAPTER II Analysis of the EPA RMP*Info Database .................................. 8
Introduction to the RMP*Info Database ........................................... 8 Analysis of the Top Twelve Chemicals Released ............................. 11 Number of Releases per Year ........................................................... 12 Release Sources ................................................................................. 13 Initiating Events and Contributing Factors ....................................... 15 Toxic vs. Flammable Chemicals ....................................................... 15 Number of Releases per Facility Size ............................................... 16 Conclusions ....................................................................................... 16
CHAPTER III Relationship Between Accidental Databases and Failure Rate Databases… … … … … … … … … … … … … … … … … … … … .. 18
Example ............................................................................................ 22 Problems with the Proposed Relationship ........................................ 23 Modifications to the Current Accidental Databases … ...................... 24
CHAPTER IV Relation Between Accidental Databases and Reactive Chemical Data … … … … … … … … … … … … … … … … … … .. 26
Unstable Molecular Structures .......................................................... 27 Enthalpy of Decomposition/Reaction ............................................... 28 Compatibility with Process Material ................................................. 28 Example ............................................................................................ 29 Problems with the Proposed Relationship ........................................ 30
Modification to Current Accident Databases … ................................ 31
CHAPTER V CONCLUSIONS AND RECOMMENDATIONS ..............… ... 32
LITRUTURE CITED ........................................................................................... 34
APPENDIX A ...................................................................................................... 37
APPENDIX B … .................................................................................................. 41
VITA … … … … … … … … … … … … … … … … … … … … ...… … … … … … … … . 62
CHAPTER I
INTRODUCTION
Accident databases are used to record where, when, and how an accident may have
occurred. This information is being collected by several agencies, both public and
private. This collection of chemical release data is voluntary in some cases and
mandated in others. In many cases, federal laws (e.g., the Clean Air Act) require that
chemical release information be reported to governmental authorities. As a result,
numerous databases have evolved over the years. Most of these databases are
maintained by federal agencies including the Department of Transportation (DOT),
Occupational Safety and Health Administration (OSHA), and Environmental Protection
Agency (EPA).
The inconsistencies of different taxonomy of these databases make it difficult to develop
a national picture of the problem of accidental release. Additional discussion about
these troubles is given in an EPA report to the U.S. Congress[1].
Other problems with current databases include
• They have been developed using inconsistent and faulty data-collecting methods, and the terms
used to describe accidents are often ambiguous.
• The ever-changing reporting requirements prevent comparisons from year to year, making trends
impossible to identify. '
• They provide little to no information about the specifics of accidents, and many accidents are
incorrectly lumped under the heading of chemical accidents[2].
This thesis follows the style of Process Safety Progress
However, that is not to say that the current databases offer no useful information.
In fact, lessons can be learned form current databases to improve the industry safety
practices. See, for example, Accident History Database: An Opportunity by Mannan et
al[3].
The study of accident databases allow for development of realistic programs that are
sensitive to public, environmental, and employee issues, as well as to the chemical
industry’s objectives. Analysis of the current databases will lead to the development of
national safety goals, and will help to refine databases to provide more accurate data for
future evaluation of industry’s safety progress.
The ability to learn from previous incidents has long been regarded as an essential aspect
of any research to reduce the frequency and severity of future incidents. Nonetheless,
many major accidents, which capture media attention, continue to implicate “failure to
learn from previous losses” as a major contributor[4]. Therefore, incidents, once
captured in a database, should be analyzed effectively to raise flags around certain
industry practices to prevent reoccurrence of similar incidents. These effective analyses
cannot be done unless the data included in the database are accurate and truly describe
the incident. For this reason, the database itself must be structured to accomplish this
objective.
The most useful incident databases include both factual and analytical information.
Factual information includes a description of the incident and specific data associated
with the incident such as equipment type, process unit, etc. Analytical information
captures the results of analyses to determine root causes[4]. “Major chemical accidents
cannot be prevented solely through command and control regulatory requirements;
understanding the fundamental root causes of accidents, widely disseminating the
lessons learned, and integrating these lessons learned into safe operations are also
required”[5].
One way to increase the value of a database is to compare its information to that of
another database. Furthermore, the more common facts in different databases, the more
important and valuable these facts are. Therefore, the objective of this project is to
explore three different databases and attempt to link them to increase their value and
hence improve the industry safety performance. These databases are,
• Accidental Databases
• Failure Rate Databases
• Reactive Chemical Databases
Accidental Databases
Several databases have been searched for the linkage. These databases are
• Emergency Response Notification System Database (ERNS)
• Accidental Release Information Program Database (ARIP)
• Major Accidents Reporting System (MARS)
• Risk Management Program Database (RMP*Info)
Emergency Response Notification System Database (ERNS)
Emergency Response Notification System (ERNS) database is an EPA database that was
established in 1986. It contains data on oil and hazardous substances releases. It is a
database of initial notifications made during or immediately after a release occurs. The
quality of the data is limited by four major factors. First, since reports are made during
or immediately after the release, exact details of the release are often unknown, and
therefore the information available in the database may be incomplete or inaccurate.
Second, most of the information in the database have not been verified or validated.
Reports are usually not updated. Third, some of the reports in the database are
duplicates, which may happen when more than one person is reporting a release. And
finally, since reports are taken over the phone, transcription errors may limit the quality
of some data[6].
Accidental Release Information Program Database (ARIP)
Accidental Release Information Program Database (ARIP) is another EPA subsidiary
project. The EPA selects certain significant releases from the ERNS database to be
subjected to the ARIP 23-question survey. Unlike ERNS, data in ARIP database are
considered accurate because information are provided by facilities several months
following the incident. In addition, the database is periodically reviewed for data quality
control. However, the ARIP questionnaire was revised several times and therefore some
information were added and some were deleted. As a result, analysis on some fields of
the database cannot be performed over the entire database. Also, the data collection was
dependent on uneven collection efforts of the EPA regions; therefore, the data do not
reflect the geographical distribution of releases nor represent release trends over time.
Furthermore, because ARIP focuses on significant releases, it is not statistically
representative of all industry releases[6].
Major Accident Reporting System (MARS)
Major Accident Reporting System (MARS) database contains about 400 major accidents
from all of the European Union (EU). The database is well structured and very detailed.
The database may give a good understanding of safety performance if analyzed
collectively. However, analyzing the database per chemical provide few or no useful
conclusions. This is due to the fact that one chemical may result in too few accidents to
produce a general trend.
Risk Management Program Database (RMP*Info)
The United States government formulated new requirements for facilities in an attempt
to prevent, or at least minimize, the consequences of chemical releases. These new
requirements were mandated by the 1990 Clean Air Act Amendments (CAAA) section
112(r)[7]. This law covers facilities that produce, process, handle, or store regulated
substances at or above specified threshold quantities [8]. EPA translated this law into a
rule called Risk Management Programs for Chemical Accidental Release Prevention.
This rule requires relevant facilities to develop a Risk Management Plan (RMP) which
includes three elements; a hazard assessment program, a prevention program, and an
emergency response program.
The hazard assessment program analyzes the consequences associated with an
anticipated worst-case scenario and alternative-case scenario that has higher probability
of occurrence. The hazard assessment program also includes a five-year history of the
facility’s accidental releases.
The prevention program includes safety, maintenance, training, and monitoring
measures to prevent accidents from happening.
The emergency response program describes emergency health care measures and the
procedures of informing the public and response agencies should an accident occur.
This is the latest database and it represents potentially large and useful information that
could be used to analyze and subsequently reduce releases. For this reason, this database
was analyzed and the results were incorporated in chapter II of this study.
CHAPTER II
ANALYSIS OF THE EPA RMP*INFO DATABASE
Introduction to the RMP Database
In 1996, the United States Environmental Protection Agency promulgated the final rule
for Risk Management Programs for Chemical Accident Release Prevention (40 CFR
68)[9,10]. This federal rule is mandated by section 112(r) of the Clean Air Act
Amendments of 1990 and requires regulated facilities to develop and implement
appropriate risk management programs to minimize the frequency and severity of
chemical plant accidents. The EPA rule also requires regulated facilities to develop a
Risk Management Plan (RMP), which includes a description of a hazard assessment, a
prevention program, and an emergency response program. The hazard assessment in
turn must include worst-case scenarios, alternative release scenarios, and a five-year
accident history for the regulated chemicals.
The RMP rule covers facilities that produce, process, handle, or store regulated
substances at or above specified threshold quantities. Notwithstanding the RMP rule
requirements, these facilities “have a general duty to identify hazards which may result
from such releases using appropriate hazard assessment techniques to design and
maintain a safe facility taking such steps as are necessary to prevent releases and
minimize the consequences of accidental releases which do occur[7]”. The regulated
substances are those that if released could cause adverse effects on human health or the
environment.
The hazard assessment program analyzes the consequences associated with an
anticipated worst-case scenario and an alternative release scenario that has higher
probability of occurrence. The hazard assessment program also includes a five-year
history of the facility’s accidental releases.
The prevention program includes safety, maintenance, training, and monitoring
measures to prevent accidents from happening.
The emergency response program describes emergency health care measures and the
procedures for informing the public and response agencies should an accident occur.
This information about the risk management program must be submitted to EPA through
the RMP*Info Database. This database is divided into nine sections as follows:
Section 1: Identification of the facility and its process
Section 2 and 3: Description of worst-case scenarios for toxic and flammable
substances, respectively
Section 4 and 5: Description of alternative release scenarios for toxic and
flammable substances, respectively
Section 6: Five-year accident history
Section 7 and 8: Prevention program description for program 3 and 2 processes,
respectively
Section 9: Emergency response program
Also included in the database is an executive summary of the nature of the facility and
its safety policies.
Since different processes have different levels of risk and impact on human health or the
environment, EPA has adopted three program levels to cover three types of processes.
Program 1 applies to processes that have no off-site accident history and there is no
danger to the public in the case of the worst-case scenarios. Program 3 applies to
processes of higher risk and are already subject to OSHA’s PSM standard. Program 2 is
for processes that are not eligible for Program 1 or 3. It should be noted that each
facility may have more than one process, and each of these processes could be
categorized in program levels depending on the risk involved and the complexity of
operations.
This database is, therefore, more than an accident database. It gives a general overview
of the facility’s risk assessment and helps promotes an effective prevention of accidents.
It also helps reduce chemical risk at the local level and gives response agencies the
necessary information in case of an accident. The general public can benefit from this
database in understanding the chemical hazards in their localities.
As noted above, this database is based on the past 5-year history of each facility. If a
facility has no accident during the 5-year period, then that facility has no entry in
Section 6 of the database; however, they must submit the other information.
Although this database has fewer number of accidents compared to other databases, it
has been submitted to an extensive data review to assure its accuracy, so lessons learned
and conclusions drawn from this database are more meaningful.
Analysis of the Top Twelve Chemicals Released
The following sections discuss an analysis of the top twelve chemicals released
according to the RMP*Info database. These chemicals contributed to 85% of the
releases reported in the database. Lessons learned from the releases of these chemicals
can help improve the safety performance of the chemical industry. These chemicals are
listed below in the order of number of releases, where ammonia has the highest number
of releases.
Ammonia (anhydrous)
Chlorine
Flammable Mixture
Hydrofluoric Acid
Chlorine Dioxide
Propane
Sulfur Dioxide
Ammonia (conc. 20% or greater)
Hydrochloric Acid
Hydrogen
Methane
Butane
Similar to some of the other databases, the EPA 5-year accident history database also
shows ammonia and chlorine as the top two released chemicals. The RMP*Info
database includes a total of 1869 releases from mid-1994 to mid-1999. However, some
releases involve more that one chemical. If each chemical is considered separately, the
total number of releases would be 2004.
Number of Releases per Year
Figure 1 shows the number of accidents per year for all chemicals reported in the
RMP*info database. It should be noted here that the 1994 and 1999 numbers are lower
because these years were only partly within the reporting window[8]. However, there is a
general upward trend in the number of accidents during the period 1995 to 1998. The
same trend is followed if we looked at the number of releases for each chemical per year.
Ammonia and chlorine are shown in Figure 2 as examples.
Release Sources
Looking at the release sources, Figure 3, we see that approximately 50% of all-chemical
releases are associated with failures in valves and piping. More than one-third of the
ammonia releases are associated with valves, whereas piping is the largest source of
releases for chlorine, as shown in Table 1.
Furthermore, if we investigate the initiating event of the ammonia releases due to valves,
we find that 57% of them are due to equipment failure compared to 36% due to human
error, as shown in Table 2. This result suggests that ammonia facilities should give
higher priority to the maintenance and inspection of ammonia valves. This fact is further
emphasized by the knowledge that valves and piping are the sources of most of the
ammonia release deaths, 88% of which is due to valves, as shown in Table 3.
Although the higher number of chlorine releases was due to piping, all chlorine deaths
were due to failures in valves, as shown in Table 3. However, the initiating event of the
valve releases was distributed between equipment failure and human error, 50%
compared to 44%, respectively, as shown in Table 2.
Piping and valves were responsible for more than 70% of the ammonia injuries.
However, process vessels in addition to piping and valves are responsible for 66% of the
chlorine injuries, as shown in Table 5.
If we examine the hydrofluoric releases, we find a similar trend: 50% of the hydrofluoric
acid releases are due to valves (21%) and piping (31%), as shown in Table 1. However,
unlike ammonia and chlorine, 67% of the valve releases were due to human error and the
remainder was due to equipment failure, as shown in Table 2. Although there were no
deaths as a result of hydrofluoric acid releases, 57% of the injuries are due to piping and
valve releases, as shown in Table 5.
The other chemicals have generally similar trends with regard to the importance of
proper maintenance and operation of valves and piping. Therefore, facilities should give
more emphasis to adequate maintenance and operating procedures for valves and piping.
For the top twelve chemical releases, the category “other,” in the release sources section,
ranges from 11-33% depending on the chemical, as shown in Table 1. This indicates
that the multiple choices given for the source of the release works better for some
chemicals than others. For example, 28% of the hydrogen releases fall under the
category “other”. Upon investigation, we see that 50% of the releases under that
category “other” are associated with compressors. Therefore, for hydrogen, the category
compressor is more important than storage vessel, transfer hose, or pump. This suggests
that the choices given should be revised to reflect the wide range of chemicals and
facilities involved. Although the database was designed to include a wide range of
facilities, the choices given are tailored more for manufacturing plants.
Initiating Events and Contributing Factors
More than 90% of the initiating events for each chemical of the top twelve was due
either to equipment failure or human error, which agrees with the general trend of all
chemicals, as shown in Table 6. Equipment failure was the primary cause of most
releases. According to this database, equipment failure resulted in 52 – 77% of the
releases, depending on the chemical released. Mannan et al [3] reported a similar
conclusion from an analysis of the EPA’s Accidental Release Information Program
database.
Equipment failure and human error are listed as an initiating event and contributing
factor. This may lead to confusion for the reporter because of the inability to
differentiate between the initiating event and contributing factor. In fact if we look at
Table 7, we find that the highest percentage occurred where the contributing factor was
the same as the initiating event.
Toxic vs. Flammable Chemicals
The RMP*info database has 77 toxic chemicals and 63 flammables. 81% of the releases
reported to RMP*Info database are from toxic substances. Although most of the
releases reported are toxic, the probability that a toxic release will result in a fatality is
3.7%. However, this percentage increases to 4.5% for the case of a flammable release,
as shown in Table 8.
Looking at the subject chemicals, we find that all flammable chemicals, except butane,
have fatalities; however, three of the toxic chemicals released resulted in no deaths.
These chemicals are hydrofluoric acid, chlorine dioxide, and hydrochloric acid, as
shown in Table 9. It is also interesting to note that all fatalities and almost all injuries
due to flammable substance releases affected on-site workers or contractors, as shown in
Table 4.
Number of Releases per Facility Size
Table 10 shows the relationship between the size of the facility and the number of
releases in which for eleven out of the twelve chemicals, the highest number of releases
were in large facilities, where the number of full-time employees was greater than one
hundred.
Conclusions
1. Analysis of the EPA RMP*Info database indicates that 85% of the releases were
caused by twelve chemicals.
2. 49% of the releases reported in the database are associated with failures in valves
and piping. Valves are responsible for most of the fatalities in the ammonia
environment and all fatalities in the chlorine environment.
3. The category “other” has high number of releases, because it is believed that the
database does not reflect the wide range of chemicals reported and facilities
reporting.
4. The primary initiating event for valve and piping releases is either equipment
failure or human error depending on the chemical released. For example,
equipment failure was the primary initiating event for ammonia and chlorine
releases. On the other hand, human error is the primary initiating event for
hydrofluoric acid releases, which were associated with piping and valves.
5. Although most of the releases reported in the database are toxic, flammable
substances showed a higher probability that a release would result in a fatality.
All of these fatalities were on-site workers and contractors.
6. Most releases occurred in facilities where the number of full-time employees was
100 – 1000.
CHAPTER III
RELATIONSHIP BETWEEN ACCIDENT DATABASES AND FAILURE RATE
DATABASES
As mentioned before, one way to increase the value of a database is to compare its
information to that of another database. Here, the author proposes a relationship
between the information found in the accident databases with those found in the failure
rate databases. A brief introduction to failure rate data is given first.
There are two types of failure rate data available: time-related failure rates and demand-
related failure rates. Time-related failure rates, presented as failures per million hours,
are for equipment that is normally functioning. The failure rate is calculated based on
the following equation,
hours exposure totalequipment failuresequipment related- timeofnumber totalRate Failure = (1)
Demand-related failure rates are presented in failures per one thousand demands and are
for equipment that is normally static but is called upon to operate at indeterminate
intervals. The following equation is used to calculated demand-related failure rate,
equipment upon the demand totalfailuresequipment related-demand ofnumber totalRate Failure = (2)
There are two sources for failure rate data, plant-specific data and generic data. Plant-
specific failure rate data are generated from equipment failure experience at a plant. A
characteristic of plant-specific data is that they reflect the plant’s process, environment,
maintenance practices, and choice and operation of equipment. Generic failure rate data,
on the other hand, are accumulated and aggregated from a variety of plants and
industries, such as nuclear power plants, chemical process industries or offshore
petroleum platforms. Hence, generic data are derived from equipment of many
manufacturers, a number of processes, and many plants with various operating
strategies. Consequently, they are much less specific and detailed, but they are
frequently adequate to identify the major risk contributors in a process or plant. [11]
Failure rate data can be obtained from the following resources:
AIChE CCPS publication, “Guidelines for Process Equipment Reliability Data
with Data Tables”
Offshore Reliability Data (OREDA)
Government Industry Data Exchange Program (GIDEP)
IEEE Standard 500-1984
United Kingdom Atomic Energy Authority (UKAEA)
Since the AIChE CCPS failure rate data are the primary data for the chemical process
industry, it is the one that was used in the study to illustrate the proposed relationship.
Table 11 shows the CCPS failure rate data input form.
It is always preferred, when using failure rate data, to have valid historical data from the
identical equipment in the same application. In most cases, however, plant-specific data
are unavailable or may be of low confidence level to be used without supporting data.
The supporting data in this case are the generic data. [12]
There are many variables that affect the confidence level of plant-specific data. Process
conditions and/or maintenance practices can fluctuate throughout a study period and
have a major influence on the results: “intensified preventive maintenance can lower and
eliminate failures; changes in process conditions may severely aggravate fouling
tendencies or corrosion rates; equipment may be upgraded or even replaced thereby
extending operating life during the study; many failures may have been missed; many
failures may be wrongly recorded such as a reported pump failure when the push button
was really at fault” [12]. Plant-specific data may be heavily biased by the variations noted
and result in data of little statistical confidence.
There are several factors that are not incorporated in failure rate data. Some of these
factors are
1. External environment such as vibration, temperature, humidity, etc
2. Materials of construction
3. Maintenance and inspection strategies
4. Process internal temperature or pressure
5. Design standards
6. Equipment manufacturer [12]
Information in failure rate data can help plant engineers identify the plant major
deficiencies and focus on them. For example, if certain facility have a pump failure rate
above the upper value reported in failure rate data and a valve failure rate below the
mean value, then this facility should give more attention to pump reliability than valves.
Similarly, if this facility showed a higher number of incidents attributed to pumps in
accident databases, then this fact is further emphasized.
One way to do this relationship is as follows:
1. Pick a facility from the RMP*Info database
2. Count the number of failures for certain equipment during 5 years
3. Convert (2) to failures per million hours
4. Compare (3) with the reported failure rates in failure rate databases for that
specific equipment
5. If (3) is below the mean, this equipment is not a major source of accidents
6. Otherwise, if (3) is above the mean, this equipment is a major source of accidents
and the facility should do something to lower this rate.
Facilities should strive to meet the mean failure rate for all of their equipment. This goal
is more achievable and practical than the “industry best practice” idea implemented by
industry. As facilities meet the mean of the equipment failure rate, the mean will keep
going down. Consequently, equipment reliability should improve and failure rates
should decrease.
The steps above can be summarized in the following equation.
Q * Z* Y
1000,000 * X hoursMillion per Failures = (3)
Where,
X = Number of equipment failures
Y = Number of years covered
Z = Number of days the equipment is operational per year
Q = Number of working hours per day
Example
Facility ID = 1118
Facility Name = Harcros Chemicals Inc. -- St. Gabriel
Number of years covered = 5 years
Number of valve failures = 1
Assumptions
1. Number of days the equipment is operational = 365 days
2. Number of working hours per day = 24 hours
Therefore, Failures per million hours = 22.83
However, when we compare this number with valve failure rate data, we encounter
several problems. These problems are listed below.
Problems with the Proposed Relationship
1. To accurately determine the failure rate for any equipment in a plant, the equipment
population in that facility is necessary. We need to divide by the population number
to calculate the failures per million hours per equipment. Unfortunately, this
information is not available in the RMP*Info database.
2. Failures in accident databases do not have the same subdivisions as in the failure rate
databases. For example, accidents may be reported under valves in accident
databases. However in failure rate databases, valves are divided into check valves,
manual valves, and operated valves. In this case, the analyst does not know under
which type of valves that accident falls.
3. Another problem is that the analyst cannot know if the equipment that caused the
incident in accident databases was being used continuously or intermittently. This
distinction is important if the failure is time-related or demand-related.
4. Failure mode is another important category in failure rate data. Catastrophic,
degraded, and incipient are the types of failure modes in failure rate databases.
Failure data are reported based on their failure modes, but this information is not
included in accidental databases.
5. Comparing the failure rates of equipment with failure rate databases should be done
with caution. The analyst may choose to use the data if the equipment design,
process condition, properties of the chemicals being processed, severity of duty or
quality of the facility maintenance regime, etc. are similar to the equipment being
studied. Since most failure rate data are generic, they are derived from equipment of
many manufacturers, a number of processes, and many plants with various operating
strategies, these factors will usually be different. To account for these differences,
the analyst should use his or her own expertise to adjust failure rate data to his or her
needs.
Because of these problems, it is difficult to compare the valve failures in the above
example with failure rate data. We do not know what type of valve it is, what is the
population of similar valves is in that facility, whether this valve is being used
continuously or intermittently, etc. These data are necessary for accurate comparisons.
To account for the population of equipment in a facility, equation 3 can be modified as
follows:
N*Q * Z* Y
1000,000 * X hoursMillion per Failures = (4)
Where N is the population of that particular equipment in the facility.
Modifications to the Current Accidental Databases
For a more efficient application of this relationship, the following modifications to
accident databases are proposed:
1. Introduce new fields in accidental databases to indicate the type of equipment that
failed. These new fields should be subdivided based on the subdivisions found in
failure rate data. Table 12 shows an example of such subdivisions.
2. Accident databases should also include a new field to specify the type of operation of
the equipment (i.e. continuous or per demand). This segregation is important for
comparing accidental databases with failure rate data.
3. Accident databases should include a brief description of the accident. The
description should include the mode of failure of the equipment. For example, in
case of valve failure, the description should indicate what type of valve it is and how
it failed (e.g. fails to close, fails to open, external leakage, etc).
4. A field should also be added for the total number of similar equipment in use at the
facility at the time of the incident.
CHAPTER IV
RELATIONSHIP BETWEEN ACCIDENT DATABASES AND REACTIVE
CHEMICAL DATA
In chapter III we discussed how accidental databases can be linked to failure rate
databases. Here, we consider another proposed linkage, i.e. relating accidental
databases to reactivity data. Knowledge of the chemical reactivity and applying this
knowledge in the design, operation, and maintenance of chemical processes can help
prevent many accidents.
The most catastrophic accident in the history of industry occurred in December 1984
in Bhopal, India. More than 6000 civilians were killed as a result of a release of a
reactive, toxic, and volatile chemical, methyl isocyanate (MIC). MIC is an
intermediate step of pesticide production in that plant and it demonstrates a number
of potentially dangerous physical properties. Its boiling point at atmospheric
pressure is 39.1 oC, its vapor pressure is 348 mmHg at 20 oC, its vapor is heavier
than air, it reacts exothermally with water, and the maximum exposure concentration
for an eight-hour period is only 0.02 ppm. Since we know these properties of MIC,
an alternative reaction scheme could have been used in that plant with a less
dangerous chloroformate intermediate[13]. If this knowledge was applied in the
design of that plant, the consequences of the accident may have been less
catastrophic.
“Hazardous chemical reactivity is any chemical reaction with the potential to exhibit
rates of increase in temperature and/or pressure too high to be absorbed by the
environment surrounding the system.” [14]
There are several ways potential hazards of a reactive chemical can be identified.
Some of these are,
1. Literature reviews of chemical properties and past incidents
2. Unstable molecular structure
3. Enthalpy of decomposition/reaction
4. Compatibility with process materials [14]
Initially, literature should be searched for relevant data on the chemical in question.
These data should include physical-chemical properties, thermodynamics, past
incidents, case studies, etc. If available information is insufficient, a parallel
investigation of the remaining three approaches should be carried out for the
chemical under investigation.
Unstable Molecular Structures
Substances with a positive enthalpy of formation will always release energy during
their decomposition. Energetic substances can in general be identified by the
presence of hazardous molecular structures. Bretherick [15] published a compilation
of energetic groups that can release substantial energy upon cleavage. However,
there are two deficiencies with these listings:
1. The presence of one of the mentioned groups in the molecule does not
necessarily imply that the substance is hazardous. The presence of such
active groups in a high molecular weight compound reduces the explosive
potential.
2. In addition, the absence of these active groups is no guarantee for long-term
stability of the compound. Some aldehydes, for example, which are not
present in these tables, can be converted to peroxides, which are unstable, by
reacting with oxygen [14,16].
Enthalpy of Decomposition/Reaction
Correlating the computations of about 200 different compounds of various hazard
potential concluded that a reaction with a maximum change in enthalpy less than
- 0.7 kcal/g can be potentially explosive [16]. The 200 chemicals included substances
known to have caused explosions and mixtures considered to be non-hazardous.
Table 13 summarizes these findings.
Compatibility with the Process Material
In case a substance is stable in itself, it can be dangerous when mixed with other
process materials. Information about the possibility of such incompatibilities
problem is available in the National Fire Protection Association (NFPA) Manual [17].
Table 14 gives an example of such reactions.
Even if the substance is considered to be a non-explosion hazard, both non-energetic
and compatible with the process-common materials, it still should be subjected to
screening tests to ensure the absence of instabilities and the potential of a runaway
reaction [14]. Also, the presence of catalysts and contaminants or changes in process
conditions can alter the reaction and lead to dangerous by-products.
Example
Acetylene is one of the compounds listed in the RMP*Info database. This
compound will be used to illustrate the above procedures. Its formula is C2H2 and its
molecular weight is 26.04.
• Molecular Structure:
This molecular structure is one of the high-energy molecular structures listed in
the reactive chemical data.
• Enthalpy of Decomposition/Reaction
Let us consider the following reaction,
I2 (g) + C2H2 (g) à C2H2I2 (g)
This reaction has an enthalpy of reaction, at standard conditions, equals to
– 0.764 kcal/g. Since the enthalpy of reaction is less than - 0.7 kcal/g, it is
H - C C - H
considered violently exothermic and can lead to catastrophic accidents if not
handled properly.
• Compatibility with Process Material
We have indicated above that acetylene can react explosively with iodine.
Furthermore, looking at Table 13, we find that acetylene in contact with copper will
produce copper acetylide, which is sensitive to shock and friction.
The above example illustrates the fact that if this information was incorporated in a
database, plant personnel would be more acquainted of the danger of acetylene and
strive to minimize its impacts.
Problems with the Proposed Relationship
1. The required information, especially enthalpy of reaction and compatibility, is
not available for every chemical. Experiments and chemical computations must
be conducted to determine the missing data.
2. This proposal is valid under normal plant operation conditions. A more
dangerous situation could result in case of abnormal conditions, i.e. high
temperature, high pressure, presence of contaminants, etc., where
experimentation or chemical computation to obtain the missing data could be
more difficult.
Modification to Current Accidental Databases
New fields can be added to accident databases to incorporate reactivity data. The
needed fields are the chemical molecular structure, known enthalpy of formations
and reactions, and known compatibility problems. Of course, it is impossible to
include all possible reactions for each chemical in a database, but reactions that
industry consider important or known to have caused accidents in the past must be
included.
CHAPTER V
CONCLUSIONS AND RECOMMENDATIONS
1. Current accident databases do not represent the safety performance and safety
trend of the chemical industry.
2. Although there are still areas of improvements, there has been much effort
given to the RMP*Info database, which makes it a good candidate for safety
performance analysis.
3. Equipment failures constitute the primary initiating event of industrial
accidents.
4. Facilities are urged to compare their equipment failure rates with equipment
failure rate data and develop procedure for improvement.
5. Accident database can be linked to both failure rate data and reactivity data.
This paper is a step forward in this regard.
6. Available failure rate data are not comprehensive. There are several types of
data that are not available.
7. To better utilize the relational aspects between accident databases and failure
rate data, the procedure proposed here is recommended.
8. Reactivity data are not available for every chemical. As a result, to optimize
the linkage between accidental databases and reactivity data, the missing
information must be made available. Experiments and chemical computation
should be conducted to achieve this goal.
9. If linkages are established among the three databases, it will give a better
understanding to plant personnel about the reliability of plant equipment and
the danger of the chemicals they are dealing with. Consequently, accidents
will be reduced.
LITERATURE CITED
1. US EPA, “A Review of Federal Authorities for Hazardous Materials Accident
Safety”, US EPA-550-R-93-002, (December 1993).
2. McCray, E.T; “ Chemical Accident Databases: What They Tell Us and How They
Can Be Improved to Establish National Safety Goals.” MS Thesis, Texas A&M
University, (May 2000).
3. Mannan, M. S., O’Connor, M., West, H. H., “Accidental History Databases: An Opportunity”,
Environmental Progress, 18, No. 1, pp 1 – 6, (Spring 1999).
4. Vaughan, R., Kelly, B.,“CCPS Process Safety Incident Database (PSID)”, online, available:
www.aiche.org/ccps/lldb.htm. Accessed: Feb 2000.
5. US EPA, “Prevention of Reactive Chemical Explosions”, www.epa.gov, (April 2000).
6. US EPA, “User’s Guide to Federal Accidental Release Databases”, EPA-550-B-95-001, (September
1995).
7. Clean Air Act, Title III-section 112 (r): Hazardous Air Pollutants, Prevention of Accidental Releases,
online, available: www.epa.gov. Accessed: March 2000.
8. Kleindorfer, P. R.; Feldman, H.; Lowe, R. A., “Accident Epidemiology and U.S. Chemical
Industry: Preliminary results from RMP*Info”, Working Paper 00-01-University of Pennsylvania,
(March 6, 2000).
9. US EPA, “Risk Management Programs for Chemical Accidental Release Prevention; Final Rule”, (40
CFR Part 68), Federal Register, 61, No. 120, pp. 31667-31732, Washington, DC, (June 20, 1996)
10. US EPA, “List of Regulated Substances and Thresholds for Accidental Release Prevention and Risk
Management Programs for chemical Accidental Release Prevention; Final Rule and Notice”, (40 CFR
Parts 9 and 68), Federal Register, 59, No. 20, pp. 4478-4501, Washington, DC, (January 31, 1994)
11. Center for Chemical Process Safety: “Guidelines for Process Equipment Reliability Data with Data
Tables”, American Institute of Chemical Engineers, (1989).
12. Greenberg, H. R. and Cramer, J. J., “Risk Assessment and Risk Management for the Chemical
Process Industry”, Van Nostrand Reinhold, New York, (1991).
13. Daniel A. Crowl and Joseph F. Louvar, “Chemical Process Safety: Fundamentals with
Applications”, Prentice Hall PTR, Englewood Cliffs, NJ, (1990).
14. Center for Chemical Process Safety, “Guidelines for Chemical Reactivity Evaluation and
Application to Process Design”, American Institute of Chemical Engineers, (1995).
15. Bretherick, L., “Handbook of Reactive Chemical Hazard”, Butterworth-Heinemann, Stoneham, MA,
(1990).
16. Howard H. Fawcett and William S. Wood, “Safety and Accident Prevention in Chemical
Operations”, John Wiley & Sons, New York, (1982).
17. National Fire Protection Association, “Manual of Hazardous Chemical Reactions”, NFPA, 491M,
Quincy, MA, (1991).
APPENDIX A
Table 1. Release Sources per Chemical
Ammonia (Anhhydrous)Number Percent
Storage Vessel 55 9Piping 141 22Process Vessel 62 10Transfer Hose 67 11Valve 213 34Pump 41 7Joint 18 3Other 76 12Total 630 107
ChlorineNumber Percent
Storage Vessel 76 15Piping 142 28Process Vessel 66 13Transfer Hose 50 10Valve 117 23Pump 6 1Joint 41 8Other 71 14Total 511 111
Flammable MixtureNumber Percent
Storage Vessel 8 8Piping 35 35Process Vessel 15 15Transfer Hose 4 4Valve 14 14Pump 7 7Joint 4 4Other 25 25Total 100 112
HydrofloricAcid
Number PercentStorage Vessel 6 6Piping 30 31Process Vessel 9 9Transfer Hose 6 6Valve 21 21Pump 17 17Joint 3 3Other 12 12Total 98 106
Chlorine DioxideNumber Percent
Storage Vessel 1 2Piping 13 22Process Vessel 28 48Transfer Hose 0 0Valve 4 7Pump 2 3Joint 4 7Other 7 12Total 58 102
PropaneNumber Percent
Storage Vessel 1 2Piping 18 35Process Vessel 9 17Transfer Hose 5 10Valve 16 31Pump 6 12Joint 2 4Other 7 13Total 52 123
HydrogenNumber Percent
Storage Vessel 0 0Piping 11 34Process Vessel 10 31Transfer Hose 0 0Valve 4 13Pump 0 0Joint 3 9Other 9 28Total 32 116
MethaneNumber Percent
Storage Vessel 0 0Piping 9 33Process Vessel 5 19Transfer Hose 1 4Valve 4 15Pump 0 0Joint 0 0Other 3 11Total 27 81
ButaneNumber Percent
Storage Vessel 4 16Piping 8 32Process Vessel 4 16Transfer Hose 1 4Valve 2 8Pump 2 8Joint 1 4Other 5 20Total 25 108
AllNumber Percent
Storage Vessel 204 11Piping 482 26Process Vessel 285 15Transfer Hose 167 9Valve 438 23Pump 102 5Joint 95 5Other 278 15Total 1869 110
Percent adds to more than 100% due to multiple causes.
Table 4. Consequnces of Releases per Chemical
Ammonia (Anhydrouse)Workers/Contractors 7
Deaths Public Responders 0Public 0Workers/Contractors 629
Injuries Public Responders 17Public 18
On-Site Property Damage $341,765,401Deaths 0Hospitalization 48
Off-site Other Medical Treatments 415Evacuation 7,977Sheltered in Place 10,779Property Damage $1,653,014
ChlorineWorkers/Contractors 0
Deaths Public Responders 0Public 0Workers/Contractors 495
Injuries Public Responders 30Public 3
On-Site Property Damage $8,745,633Deaths 0Hospitalization 39
Off-site Other Medical Treatments 109Evacuation 6,214Sheltered in Place 107,416Property Damage $99,976
Flammable MixtureWorkers/Contractors 8
Deaths Public Responders 0Public 0Workers/Contractors 88
Injuries Public Responders 0Public 0
On-Site Property Damage $447,121,831Deaths 0Hospitalization 0
Off-site Other Medical Treatments 219Evacuation 30Sheltered in Place 2,500Property Damage $7,125,132
Hydrofloric AcidWorkers/Contractors 0
Deaths Public Responders 0Public 0Workers/Contractors 98
Injuries Public Responders 1Public 1
On-Site Property Damage $21,048,285Deaths 0Hospitalization 0
Off-site Other Medical Treatments 34Evacuation 675Sheltered in Place 1,500Property Damage $420,000
Chlorine dioxideWorkers/Contractors 0
Deaths Public Responders 0Public 0Workers/Contractors 91
Injuries Public Responders 3Public 0
On-Site Property Damage $202,000Deaths 0Hospitalization 0
Off-site Other Medical Treatments 1Evacuation 0Sheltered in Place 0Property Damage $0
PropaneWorkers/Contractors 1
Deaths Public Responders 0Public 0Workers/Contractors 62
Injuries Public Responders 1Public 0
On-Site Property Damage $59,691,784Deaths 0Hospitalization 0
Off-site Other Medical Treatments 1Evacuation 104Sheltered in Place 379Property Damage $0
Sulfur dioxideWorkers/Contractors 1
Deaths Public Responders 0Public 0Workers/Contractors 25
Injuries Public Responders 0Public 0
On-Site Property Damage $2,275,000Deaths 0Hospitalization 2
Off-site Other Medical Treatments 89Evacuation 1,150Sheltered in Place 2,430Property Damage $1,725
Ammonia (conc. 20% or greater)Workers/Contractors 0
Deaths Public Responders 0Public 0Workers/Contractors 11
Injuries Public Responders 0Public 2
On-Site Property Damage $992,000Deaths 0Hospitalization 0
Off-site Other Medical Treatments 3Evacuation 121Sheltered in Place 2,215Property Damage $0
Hydrochloric AcidWorkers/Contractors 0
Deaths Public Responders 0Public 0Workers/Contractors 80
Injuries Public Responders 0Public 0
On-Site Property Damage $26,126,200Deaths 0Hospitalization 2
Off-site Other Medical Treatments 112Evacuation 655Sheltered in Place 20,864Property Damage $467,973
HydrogenWorkers/Contractors 2
Deaths Public Responders 0Public 0Workers/Contractors 44
Injuries Public Responders 0Public 0
On-Site Property Damage $71,785,940Deaths 0Hospitalization 0
Off-site Other Medical Treatments 0Evacuation 0Sheltered in Place 10Property Damage $200,000
MethaneWorkers/Contractors 1
Deaths Public Responders 0Public 0Workers/Contractors 50
Injuries Public Responders 0Public 0
On-Site Property Damage $83,739,100Deaths 0Hospitalization 1
Off-site Other Medical Treatments 1Evacuation 300Sheltered in Place 0Property Damage $2,300
ButaneWorkers/Contractors 0
Deaths Public Responders 0Public 0Workers/Contractors 35
Injuries Public Responders 0Public 0
On-Site Property Damage $61,337,950Deaths 0Hospitalization 0
Off-site Other Medical Treatments 0Evacuation 450Sheltered in Place 0Property Damage $0
AllWorkers/Contractors 26
Deaths Public Responders 0Public 0Workers/Contractors 1,715
Injuries Public Responders 58Public 24
On-Site Property Damage $1,000,877,807Deaths 0Hospitalization 192
Off-site Other Medical Treatments 5,580Evacuation 22,011Sheltered in Place 196,570Property Damage $10,871,363
Table 6. Releases Initiating Events per Chemical
Ammonia (Anhydrous)Number Percent
Equipment Failure 353 56Human Error 223 35Natural 21 3Unknown 32 5Total 630 100
ChlorineNumber Percent
Equipment Failure 275 54Human Error 214 42Natural 5 1Unknown 17 3Total 511 100
Flammable MixtureNumber Percent
Equipment Failure 71 71Human Error 26 26Natural 0 0Unknown 3 3Total 100 100
Hydrofloric AcidNumber Percent
Equipment Failure 51 52Human Error 42 43Natural 2 2Unknown 3 3Total 98 100
Chlorine DioxideNumber Percent
Equipment Failure 36 62Human Error 18 31Natural 1 2Unknown 3 5Total 58 100
PropaneNumber Percent
Equipment Failure 28 54Human Error 20 38Natural 2 4Unknown 2 4Total 52 100
Sulfur DioxideNumber Percent
Equipment Failure 30 63Human Error 18 38Natural 0 0Unknown 0 0Total 48 100
Ammonia (conc. 20% or greater)Number Percent
Equipment Failure 21 54Human Error 16 41Natural 0 0Unknown 2 5Total 39 100
Hydrochloric AcidNumber Percent
Equipment Failure 24 73Human Error 7 21Natural 2 6Unknown 0 0Total 33 100
HydrogenNumber Percent
Equipment Failure 24 75Human Error 8 25Natural 0 0Unknown 0 0Total 32 100
MethaneNumber Percent
Equipment Failure 21 78Human Error 6 22Natural 0 0Unknown 0 0Total 27 100
ButaneNumber Percent
Equipment Failure 16 64Human Error 8 32Natural 0 0Unknown 1 4Total 25 100
AllNumber Percent
Equipment Failure 1053 56Human Error 698 37Natural 37 2Unknown 81 4Total 1869 100
Table 7. Releases Primary and Contributing Causes
Ammonia (Anhydrous)Contributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 254 40 28 4Human Error 56 9 152 24Improper Procedure 28 4 96 15Overpressurization 43 7 23 4Upset Condition 16 3 2 0By pass 3 0 1 0Maintenance 43 7 44 7Process Design Failure 22 3 14 2Unsuitable Equipment 15 2 8 1Unusual Weather 4 1 0 0Management Error 9 1 7 1Other 33 5 20 3Total Releases 630
ChlorineContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 188 37 25 5Human Error 56 11 148 29Improper Procedure 30 6 86 17Overpressurization 19 4 7 1Upset Condition 18 4 7 1By pass 16 3 2 0Maintenance 48 9 39 8Process Design Failure 11 2 8 2Unsuitable Equipment 14 3 4 1Unusual Weather 4 1 1 0Management Error 0 0 17 3Other 26 5 23 5Total Releases 511
Flammable MixtureContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 39 39 11 11Human Error 19 19 21 21Improper Procedure 14 14 12 12Overpressurization 5 5 4 4Upset Condition 14 14 2 2By pass 3 3 1 1Maintenance 11 11 7 7Process Design Failure 13 13 3 3Unsuitable Equipment 7 7 2 2Unusual Weather 3 3 2 2Management Error 5 5 4 4Other 13 13 1 1Total Releases 100
Hydrofloric AcidContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 37 38 2 2Human Error 20 20 26 27Improper Procedure 14 14 18 18Overpressurization 1 1 0 0Upset Condition 4 4 0 0By pass 1 1 0 0Maintenance 16 16 18 18Process Design Failure 3 3 0 0Unsuitable Equipment 10 10 2 2Unusual Weather 0 0 1 1Management Error 4 4 1 1Other 4 4 5 5Total Releases 98
Chlorine DioxideContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 20 34 0 0Human Error 8 14 6 10Improper Procedure 9 16 8 14Overpressurization 7 12 2 3Upset Condition 18 31 6 10By pass 1 2 0 0Maintenance 5 9 10 17Process Design Failure 3 5 1 2Unsuitable Equipment 2 3 1 2Unusual Weather 0 0 0 0Management Error 1 2 1 2Other 7 12 2 3Total Releases 58
PropaneContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 17 33 4 8Human Error 10 19 16 31Improper Procedure 6 12 7 13Overpressurization 3 6 1 2Upset Condition 2 4 1 2By pass 0 0 1 2Maintenance 8 15 7 13Process Design Failure 6 12 0 0Unsuitable Equipment 3 6 1 2Unusual Weather 2 4 0 0Management Error 1 2 0 0Other 3 6 0 0Total Releases 52
Sulfure DioxideContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 24 50 3 6Human Error 5 10 13 27Improper Procedure 6 13 5 10Overpressurization 1 2 0 0Upset Condition 5 10 1 2By pass 0 0 0 0Maintenance 2 4 2 4Process Design Failure 4 8 2 4Unsuitable Equipment 1 2 1 2Unusual Weather 0 0 0 0Management Error 0 0 0 0Other 5 10 1 2Total Releases 48
Ammonia (conc. 20% or greater)Contributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 16 41 1 3Human Error 3 8 10 26Improper Procedure 1 3 6 15Overpressurization 3 8 0 0Upset Condition 2 5 0 0By pass 1 3 1 3Maintenance 4 10 3 8Process Design Failure 3 8 1 3Unsuitable Equipment 2 5 0 0Unusual Weather 1 3 1 3Management Error 0 0 0 0Other 1 3 1 3Total Releases 39
Hydrochloric AcidContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 17 52 3 9Human Error 4 12 5 15Improper Procedure 4 12 2 6Overpressurization 8 24 3 9Upset Condition 2 6 2 6By pass 0 0 0 0Maintenance 4 12 0 0Process Design Failure 1 3 2 6Unsuitable Equipment 3 9 1 3Unusual Weather 0 0 1 3Management Error 2 6 1 3Other 1 3 1 3Total Releases 33
HydrogenContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 13 41 1 3Human Error 4 13 5 16Improper Procedure 3 9 5 16Overpressurization 4 13 1 3Upset Condition 5 16 1 3By pass 2 6 0 0Maintenance 4 13 2 6Process Design Failure 5 16 2 6Unsuitable Equipment 4 13 0 0Unusual Weather 0 0 1 3Management Error 1 3 1 3Other 2 6 0 0Total Releases 32
MethaneContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 13 48 3 11Human Error 8 30 4 15Improper Procedure 8 30 5 19Overpressurization 4 15 1 4Upset Condition 3 11 2 7By pass 1 4 0 0Maintenance 3 11 2 7Process Design Failure 7 26 1 4Unsuitable Equipment 1 4 0 0Unusual Weather 0 0 2 7Management Error 0 0 2 7Other 0 0 0 0Total Releases 27
ButaneContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 8 32 2 8Human Error 5 20 7 28Improper Procedure 2 8 0 0Overpressurization 0 0 1 4Upset Condition 0 0 1 4By pass 0 0 0 0Maintenance 5 20 0 0Process Design Failure 2 8 0 0Unsuitable Equipment 3 12 0 0Unusual Weather 1 4 0 0Management Error 0 0 0 0Other 0 0 0 0Total Releases 25
AllContributing Factor Initiating Event
Equipment Failure Percent Human Error PercentEquipment Failure 724 39 96 5Human Error 204 11 478 26Improper Procedure 131 7 293 16Overpressurization 104 6 50 3Upset Condition 99 5 25 1By pass 32 2 10 1Maintenance 162 9 157 8Process Design Failure 83 4 46 2Unsuitable Equipment 71 4 28 1Unusual Weather 18 1 8 0Management Error 29 2 40 2Other 111 6 64 3Total Releases 1869Percent adds to more than 100% due to multiple causes.
Table 10. Relationship Between the Size of Facilities and Number of Releases
Ammonia (Anhydrous)Full Time Employees Number Percent1 - 10 115 1811 - 100 128 20101 - 1000 295 471001 + 85 13
630 99
ChlorineFull Time Employees Number Percent1 - 10 63 1211 - 100 216 42101 - 1000 171 331001 + 53 10
511 98
Flammable MixtureFull Time Employees Number Percent1 - 10 6 611 - 100 19 19101 - 1000 59 591001 + 15 15
100 99
Hydrofloric AcidFull Time Employees Number Percent1 - 10 1 111 - 100 6 6101 - 1000 81 831001 + 10 10
98 100
ChlorineDioxide
Full Time Employees Number Percent1 - 10 0 011 - 100 0 0101 - 1000 31 531001 + 27 47
58 100
PropaneFull Time Employees Number Percent1 - 10 3 611 - 100 13 25101 - 1000 33 631001 + 3 6
52 100
Sulfur DioxideFull Time Employees Number Percent1 - 10 2 411 - 100 15 31101 - 1000 27 561001 + 4 8
48 100
Ammonia (conc. 20% or greater)Full Time Employees Number Percent1 - 10 12 3111 - 100 9 23101 - 1000 15 381001 + 3 8
39 100
Hydrochloric AcidFull Time Employees Number Percent1 - 10 0 011 - 100 11 33101 - 1000 17 521001 + 5 15
33 100
HydrogenFull Time Employees Number Percent1 - 10 0 011 - 100 2 6101 - 1000 20 631001 + 10 31
32 100
MethaneFull Time Employees Number Percent1 - 10 5 1911 - 100 6 22101 - 1000 12 441001 + 4 15
27 100
ButaneFull Time Employees Number Percent1 - 10 0 011 - 100 3 12101 - 1000 19 761001 + 3 12
25 100
AllFull Time Employees Number Percent1 - 10 209 1111 - 100 494 26101 - 1000 897 481001 + 254 14
1869 99
Figure 1. Number of Releases per Year
0
50
100
150
200
250
300
350
400
450
500
1994* 1995 1996 1997 1998 1999*
Year
Num
ber o
f Rel
ease
s
* incomplete data
Ref: Kleindorfer, P. R. et al, "Accident Epidemiology and U.S. Chemical Industry: Preliminary results from RMP*Info"
Figure 2. Number of Ammonia and Chlorine Releases per Year
0
20
40
60
80
100
120
140
160
180
1994* 1995 1996 1997 1998 1999*
Year
Num
ber o
f Rel
ease
s
Ammonia (anhydrous) Chlorine
* incomplete data
Figure 3. Percent of Total Releases vs. Release Source
0
5
10
15
20
25
30
StorageVessel
Piping ProcessVessel
TransferHose
Valve Pump Joint Other
Release Source
Per
cent
of T
otal
Rel
ease
s
APPENDIX B
Table 2. The Primary Initiating Event for Valve Releases per Chemical
Equipment Failure (%) Human Error (%)Ammonia (Anhydrouse) 57 36
Chlorine 50 44Flammable Mixture 71 29
Hydrofloric Acid 33 67Chlorine Dioxide 75 25
Propane 50 44Sulfur Dioxide 20 80
Ammonia (conc. 20% or greater) 50 50Hydrochloric Acid 100 0
Hydrogen 100 0Methane 75 25Butane 50 50
Table 3. Percent Deaths due to Valve and Piping Releases
Valve (%) Piping (%) Process Vessel (%) Sum (%)Ammonia (Anhydrouse) 88 28 13 128
Chlorine 100 0 0 100Flammable Mixture 13 75 13 100
Hydrofloric Acid 0 0 0 0Chlorine Dioxide 0 0 0 0
Propane 0 100 100 200Sulfur Dioxide 0 0 100 100
Ammonia (conc. 20% or greater) 100 0 0 100Hydrochloric Acid 0 0 0 0
Hydrogen 0 100 100 200Methane 0 100 100 200Butane 0 0 0 0
Percent adds to more than 100% due to multiple causes.
Table 5. Percent Injuries due to Valve, Piping and Process VesselReleases
Valve (%) Piping (%) Process Vessle (%) Sum (%)Ammonia (Anhydrouse) 30 41 9 80
Chlorine 18 29 18 66Flammable Mixture 22 47 19 88
Hydrofloric Acid 19 38 9 66Chlorine Dioxide 10 23 50 83
Propane 32 49 41 122Sulfur Dioxide 32 32 28 92
Ammonia (conc. 20% or greater) 15 15 15 46Hydrochloric Acid 0 3 11 14
Hydrogen 30 48 55 132Methane 26 46 44 116Butane 34 34 46 114
Percent adds to more than 100% due to multiple causes.
Table 8. Percent of Occurrence of Fatality per Chemical Type
Chemical Type Number of Releases Number of Deaths Percent of Death OccurrenceToxic ( T ) 1624 60 3.7%Flammable (F) 380 17 4.5%
Table 9. The Effect of the ChemicalType on the Number of Releases and Number of Deaths
Type Number of Releases Number of DeathsAmmonia (Anhydrous) T 630 37
Chlorine T 511 9Flammable Mixture F 100 8
Hydrofloric Acid T 98 0Chlorine Dioxide T 58 0
Propane F 52 1Sulfur Dioxide T 48 1
Ammonia (conc. 20% or greater) T 39 5Hydrochloric Acid T 33 0
Hydrogen F 32 2Methane F 27 1Butane F 25 0
VITA
Fahad Alqurashi was born in Taif, Kingdom of Saudi Arabia, on July 31, 1973.
After completing his schooling in Dhahran High School, he pursued his B. S. degree in
Chemical Engineering at Tulsa University from 1991 to 1995. Prior to continuing his
education, he worked for Saudi Aramco Oil Company. In August 1999, he entered the
Chemical Engineering Department at Texas A&M University to pursue his master’s
degree. He will be working for Saudi Aramco Oil Company, Saudi Arabia on January 1,
2001.
Permanent address:
Kingdom of Saudi ArabiaSaudi Aramco Oil CompanyUthmaniyah Gas Plant DepartmentEngineering DivisionProcess Unit