U.S. CHEMICAL SAFETY AND HAZARD INVESTIGATION BOARD

INVESTIGATION REPORT

CHEMICAL MANUFACTURING INCIDENT

(9 INJURED)

Morton International, Inc.

Paterson, NJ

April 8, 1998

Report No. 1998-06-I-NJ Photo by Bill Tompkins

KEY ISSUES:

● INTERNAL HAZARD COMMUNICATION

AND PROCESS SAFETY INFORMATION

● REACTIVE HAZARD MANAGEMENT

● PROCESS SAFETY MANAGEMENT
ABSTRACT

This report explains the explosion and fire that occurred on April 8, 1998, at the Morton International,

Inc. (now Rohm & Haas) plant in Paterson, New Jersey. The explosion and fire were the consequence

of a runaway reaction, which over-pressured a 2000-gallon capacity chemical reactor vessel and released

flammable material that ignited. Nine employees were injured, including two seriously, and potentially

hazardous materials were released into the community. The key safety issue covered in this report was

reactive chemical process safety management. Recommendations concerning this issue were made to

Morton International, Inc. (a wholly owned subsidiary of Rohm & Haas Company); Morton

International, Inc.’s Paterson, New Jersey Plant; the Occupational Safety and Health Administration

(OSHA); the Environmental Protection Agency (EPA); the American Chemical Council; the Center for

Chemical Process Safety (CCPS); the Paper, Allied-Industrial, Chemical & Energy Workers International

Union (PACE); and the Synthetic Organic Chemical Manufacturer’s Association (SOCMA). 

The U.S. Chemical Safety and Hazard Investigation Board (CSB) is an independent federal agency

whose mission is to ensure the safety of workers and the public by preventing or minimizing the effects

of chemical accidents. The CSB is a scientific investigatory organization; it is not an enforcement or

regulatory body. Established by the Clean Air Act Amendments of 1990, the CSB is responsible for

determining the root and contributing causes of incidents, issuing safety recommendations, studying

chemical safety issues, and evaluating the effectiveness of other government agencies involved with

chemical safety. No part of the conclusions, findings, or recommendations of the CSB relating to any

chemical incident may be admitted as evidence or used in any action or suit for damages arising out of

any matter mentioned in an investigation report. See 42 U.S.C. § 7412(r)(6)(G). The CSB makes public

its actions and decisions through investigation reports, summary reports, safety studies, safety

recommendations, special technical publications, and statistical reviews. More information about the

CSB may be found on the World Wide Web at http://www.chemsafety.gov.

Information about CSB publications may be obtained by contacting:

U.S. Chemical Safety and Hazard Investigation Board

Office of External Relations

2175 K Street, N.W., Suite 400

Washington, DC 20037

(202) 261-7600

CSB publications may be purchased from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

(703) 487-4600

For this report, refer to NTIS number PB2000-107721

Salus Populi Est Lex Suprema

People’s Safety Is the Highest Law
TABLE OF CONTENTS

EXECUTIVE SUMMARY ..........................................................................................................................1

ES.1 INTRODUCTION ........................................................................................................................................1

ES.2 INCIDENT ....................................................................................................................................................1

ES.3 KEY FINDINGS ..........................................................................................................................................2

ES.4 RECOMMENDATIONS ..............................................................................................................................8

1.0 INTRODUCTION ..............................................................................................................................11

1.1 BACKGROUND ............................................................................................................................................11

1.2 INVESTIGATION PROCESS ......................................................................................................................12

1.3 PLANT FACILITIES ....................................................................................................................................13

1.4 LAYOUT AND COMPONENTS ..................................................................................................................14

1.4.1 Kettle Description ..................................................................................................................................14

1.4.2 Kettle System ..........................................................................................................................................15

2.0 DESCRIPTION OF THE INCIDENT ..................................................................................................18

2.1 INCIDENT EVENTS ....................................................................................................................................18

2.2 EMERGENCY RESPONSE ........................................................................................................................26

2.3 OFF-SITE IMPACTS ....................................................................................................................................27

2.4 PROPERTY DAMAGE ................................................................................................................................28

3.0 ANALYSIS OF PROCESS CHEMISTRY ........................................................................................29

3.1 REACTIVE CHEMICAL ANALYSIS ..........................................................................................................29

3.2 TESTS OF RAW MATERIALS ....................................................................................................................33

4.0 ANALYSIS OF PROCESS DEVELOPMENT PROGRAM ................................................................34

5.0 ANALYSIS OF PROCESS SAFETY MANAGEMENT PROGRAM ................................................38

5.1 PROCESS SAFETY INFORMATION ........................................................................................................38

5.2 PROCESS HAZARD ANALYSIS ................................................................................................................40

5.3 INVESTIGATION OF PROBLEMS WITH PREVIOUS BATCHES ..........................................................43

5.4 MANAGEMENT OF CHANGE ..................................................................................................................45

5.5 OPERATING PROCEDURES AND TRAINING ........................................................................................46

6.0 REGULATORY OVERSIGHT ANALYSIS ........................................................................................49

6.1 REGULATORY COVERAGE ......................................................................................................................49

6.2 MORTON PSM PROGRAM ........................................................................................................................51

6.3 GOOD PRACTICE GUIDELINES ..............................................................................................................52

6.4 RECENT CATASTROPHIC REACTIVE CHEMICAL INCIDENTS ........................................................53

7.0 ROOT AND CONTRIBUTING CAUSES ........................................................................................56

7.1 ROOT CAUSES ............................................................................................................................................56

7.2 CONTRIBUTING CAUSES ........................................................................................................................57

8.0 RECOMMENDATIONS ....................................................................................................................59

i
9.0 REFERENCES ................................................................................................................................62

APPENDIX A: INCIDENT TIMELINE......................................................................................................63

APPENDIX B: DEVELOPMENT TIMELINE............................................................................................69

APPENDIX C: ROOT CAUSE ANALYSIS DIAGRAM............................................................................70

APPENDIX D: MATERIAL SAFETY DATA SHEETS ............................................................................71

TABLE OF FIGURES

FIGURE 1: AERIAL VIEW OF THE PATERSON PLANT ..........................................................................................11

FIGURE 2: PLOT PLAN ..........................................................................................................................................13

FIGURE 3: ANNOTATED RENDERING OF A CHEMICAL REACTOR HEAD SIMILAR TO KETTLE SEVEN ..........15

FIGURE 4: SIMPLIFIED PROCESS FLOW DIAGRAM..............................................................................................16

FIGURE 5: TEMPERATURE CHART AND DIGITAL DISPLAY ................................................................................17

FIGURE 6: MANWAY HATCH IN PLACE ..............................................................................................................19

FIGURE 7: CONDENSER AND VENT PIPING ........................................................................................................20

FIGURE 8: GLASS SECTION OF 8-INCH LINE TO CONDENSER ..........................................................................22

FIGURE 9: RUPTURE DISK ASSEMBLY RECOVERED FROM K-7 AFTER THE INCIDENT ....................................23

FIGURE 10: EXTRUDED HEAD GASKET ................................................................................................................24

FIGURE 11: RECOVERED INSPECTION MANWAY COVER ....................................................................................24

FIGURE 12: POST-ACCIDENT PHOTO OF THE KETTLE ........................................................................................25

FIGURE 13: BUILDING 11’S BLOWOUT PANELS AND WINDOW FRAMES ............................................................28

FIGURE 14: HEAT GENERATION VERSUS HEAT REMOVAL RATE ........................................................................31

ii
EXECUTIVE SUMMARY

ES.1 INTRODUCTION

On Wednesday, April 8, 1998, at 8:18 pm, an explosion and fire occurred during the production

of Automate Yellow 96 Dye at the Morton International, Inc. (now Rohm & Haas1) Plant (the

plant) in Paterson, New Jersey. The explosion and fire were the consequence of a runaway

reaction, which over-pressured a 2000-gallon capacity chemical reactor vessel (or kettle) and

released flammable material that ignited. Because of the serious nature of the incident,

including injuries to nine employees, the release of potentially hazardous materials into the

community, and extensive damage to the plant, the U.S. Chemical Safety and Hazard

Investigation Board (CSB) initiated an incident investigation. The purpose of the investigation

was to identify the root causes of the incident and make recommendations to prevent similar

incidents.

ES.2 INCIDENT

The Paterson plant manufactures a series of dye products. Yellow 96 Dye was produced by the

mixing and reaction of two chemicals, ortho-nitrochlorobenzene (o-NCB) and

2-ethylhexylamine (2-EHA). The dye was used to tint petroleum fuel products.

The investigation team determined that the reaction accelerated beyond the heat-removal

capability of the kettle. The resulting high temperature led to a secondary runaway

1

1 In February 1999, Rohm and Haas Company, of Philadelphia, PA, purchased Morton International. Morton is

currently a wholly owned subsidiary of Rohm and Haas.
decomposition reaction causing an explosion, which blew the hatch off the kettle and allowed

the release of the kettle contents. The initial runaway reaction was most likely caused by a

combination of the following factors: (1) the reaction was started at a temperature higher than

normal, (2) the steam used to initiate the reaction was left on for too long, and (3) the use of

cooling water to control the reaction rate was not initiated soon enough.

The explosion ejected flammable vapors from the kettle into the second floor of the production

building. The explosion and flash fires inside the building injured nine workers. The flashing

eruption of chemicals broke through the building roof, ignited and formed a large fireball above

the building, and spattered the adjacent neighborhood with a yellow-brown mixture of

compounds that included Yellow 96 Dye and o-NCB.

Workers’ injuries included burns, contusions, and twisted joints. Two employees were badly

burned and required extended hospitalization. All of the employees were able, some with

assistance, to escape the site of the explosion.

ES.3 KEY FINDINGS

1. Morton’s initial research and development for the Yellow 96 process identified the existence

and described the two exothermic chemical reactions2 that can occur when the chemicals

used to produce Yellow 96 are mixed and heated:

● The desired exothermic reaction, to form Yellow 96, which is initiated at an onset

temperature3 of 38°C (100°F) and begins to proceed rapidly at a temperature of

approximately 75°C (167°F), and 

2

2 An exothermic reaction, or “exotherm,” generates heat as a by-product of a chemical reaction. Since reactions

usually proceed faster at higher temperatures, the heat generated is typically removed from the reacting mixture by

a medium such as cooling water, to allow the reaction to proceed at the desired constant temperature.

3 The onset temperature of a reaction is the lowest temperature at which exothermic activity is observed. 
● the undesired, exothermic reaction that results from the thermal decomposition4 of the

Yellow 96 product, which is initiated at an onset temperature 195°C (383°F). 

2. The Paterson facility was not aware of the decomposition reaction. The Process Safety

Information (PSI) package, which was used at the Paterson plant to design the Yellow 96

production process in 1990 and which served as the basis for a Process Hazard Analysis

(PHA) conducted in 1995, noted the desired exothermic reaction, but did not include

information on the decomposition reaction.

3. Neither o-NCB nor 2-EHA, individually, demonstrates exothermic activity at the normal

Yellow 96 process temperatures.

4. Two discrepancies in Morton’s Material Safety Data Sheet (MSDS) for the Yellow 96

product were identified:

● The National Fire Protection Association (NFPA) Reactivity Rating was listed as 0 (on a

0 to 4 scale, with 4 being the most reactive). The CSB determined that the proper

reactivity rating for Yellow 96 is 1.

● The Yellow 96 boiling point was listed as 100°C. The CSB determined that the boiling

point was approximately 330°C, or greater than the decomposition temperature.

5. Morton did not follow up on two recommendations made by its researchers in 1989: (1) to

conduct additional reactive chemical laboratory tests to determine “the rate of reaction

under the worst reaction conditions ... the rate of decomposition of the finished product ...

[and] pressure rise data which could be used to size emergency venting equipment ...” and,

(2) to install specific control and safety devices on the Yellow 96 production vessels such as

an emergency shutdown system.

3

4 A thermal decomposition reaction occurs when a chemical breaks up into smaller molecules during exposure to

an elevated temperature for a sufficient period of time. The liberation of large amounts of heat and generation of

high pressure may accompany decomposition reactions.
6. In scaling up the process from the laboratory phase to production-scale, Morton revised the

process from a semi-batch process, in which the o-NCB was added in incremental stages to

the full amount of 2-EHA already in the reactor, to a batch process, in which the entire

quantities of the reactants were added to the reactor at the outset, and staged heating was

then applied. Morton did not take into account that this change resulted in a potentially

more thermally hazardous operation.5 The heat output from a semi-batch process is easier to

control than is that from a batch process. In the batch process, heating the entire mass of

reactants at the start of the reaction increases the likelihood of exceeding the heat removal

capacity of a kettle.

7. The kettle was not equipped with safety equipment, such as a quench or reactor dump

system, to shut down the process in case of a runaway reaction emergency. Also, pressure

relief devices (rupture disks) were too small to safely vent the kettle in case of a runaway

reaction. 

8. The operators controlled process temperature manually by opening and closing steam and

cooling water valves. Operating procedures, however, required that the process run at

temperatures (150 to 153°C) that were near the temperature at which the reaction could

become uncontrollable (195°C). Thus, normal variations in the operators’ responses to the

batch temperature or delays in adjusting valves could result in overheating or undercooling,

with the result that the heat generated by the reaction would exceed the cooling capacity of

the kettle. In several previous instances, the operators documented on the process batch

sheets that the process temperature rose at a faster-than-expected rate and exceeded the

upper limit specified in the operating procedures in spite of the operators’ efforts. The

temperature of these batches eventually returned to the operating limits. Management did

not investigate the causes of these events. 

9. In 1996, Morton transferred the Yellow 96 process from 1000-gallon to 2000-gallon kettles

and increased the amount of raw materials used per batch by approximately 9 percent

4

5 While this change minimized the potential for toxic effects due to employee exposure to o-NCB, it also resulted

in a more thermally hazardous operation.
without using their existing Management of Change procedures. Morton did not assess the

effects of these changes. While 20 percent of the 25 batches of Yellow 96 made before these

changes exhibited temperature excursions, half of the 6 batches made after the changes had

temperature excursions.

10. The Occupational Safety and Health Administration (OSHA) Process Safety Management

(PSM) standard did not cover the Yellow 96 process. Morton covered the process under its

internal PSM program, which was applied to OSHA-regulated processes and certain other

processes. The CSB did not find that lack of OSHA PSM coverage directly contributed to

causing the incident. The Yellow 96 process would not have been covered by the

Environmental Protection Agency’s (EPA) Risk Management Program rule, which went into

effect in June 1999.

11. The OSHA PSM standard covers only a limited number of reactive chemicals. EPA’s Risk

Management Program rule does not cover reactive chemicals as a class. These standards

provide only minimum requirements for process safety management and provide little

guidance on reactive chemical process safety management issues, such as the use of

chemical screening techniques, and the proper design of pressure relief, emergency cooling,

and safety interlock systems.

12. Morton’s PSM program did not require adherence to a number of industry good practice

guidelines for the safe management of reactive chemical processes such as those published

by the Center for Chemical Process Safety or Lees’s Loss Prevention in the Process

Industries.

13. Morton also did not effectively implement the requirements of its internal PSM program.

The PHA conducted for the process and the operating procedures (batch sheets) did not

address the consequences of potential deviations such as excessive heating, a runaway

reaction, or the inability to provide enough cooling to maintain temperatures in a safe

operating range. Batch sheets did not list the actions operators should take to correct or

avoid deviations. Operators’ reports of significant deviations in controlling batch

temperature were not acted on by management.

5
6

Root Causes

1. Neither the preliminary hazard assessment conducted by Morton in Paterson during

the design phase in 1990 nor the process hazard analysis conducted in 1995 addressed

the reactive hazards of the Yellow 96 process.

Not addressing these hazards resulted in the following design, operational, and training

deficiencies:

● The kettle cooling system could not safely control the exothermic Yellow 96 synthesis

reaction. 

● The kettle was not equipped with safety equipment, such as a quench system or a

reactor dump system, to stop the process to avoid a runaway reaction. 

● Rupture disks were too small to safely vent high pressure in the kettle in the event of

either of the two foreseeable runaway reactions.

● Morton converted its Yellow 96 production from a staged, incremental addition (semibatch) process to a staged heating (batch) process without assessing the possible hazards

of this change, e.g., the increased difficulty of controlling heat output. 

● Operating procedures did not cover the safety consequences of deviations from normal

operating limits, such as runaway reactions, or specify steps to be taken to avoid or

recover from such deviations.

● Training did not address the possibility of a runaway reaction and how operators should

respond to avoid injury if a runaway reaction could not be controlled.

2. Process safety information provided to plant operations personnel and the process

hazard analysis team did not warn them of the potential for a dangerous runaway

chemical reaction.
Morton internal memoranda had documented that the desired reaction to form Yellow 96

from o-NCB and 2-EHA was exothermic and that Yellow 96 would begin to decompose

rapidly (runaway) at temperatures close to the upper operating temperature. Morton

researchers also had identified several situations, such as loss of cooling, which might give

rise to temperatures capable of causing violent decompositions. Although information on the

reactive hazards was contained in plant files, operators and supervisors were unaware that a

dangerous decomposition reaction was possible.

Contributing Causes

1. The hazards of previous operational deviations were not evaluated.

Management did not investigate evidence in numerous completed batch sheets and

temperature charts of high temperature excursions beyond the normal operating range.

Investigation of these incidents likely would have provided an opportunity to uncover the

process’s reactive hazards and correct design and other problems.

2. Morton did not follow their Management of Change procedures to review changes

made in reaction kettle and batch size.

Morton changed the Yellow 96 processing equipment from 1000-gallon to 2000-gallon

kettles and also increased the batch size by 9 percent in 1996. Morton did not follow its

Management of Change procedures and did not review the changes for possible safety

consequences. A Management of Change review likely would have provided another

opportunity for Morton to uncover the process’s reactive hazards and correct design

problems. The review likely would have also revealed that the changes made resulted in a

decrease of 10 percent in the heat transfer area per gallon of reactants. Half of the batches

made after this change exhibited temperature excursions versus 20 percent in the batches

made before the change. 

7
ES.4 RECOMMENDATIONS

Morton International, Inc. (a wholly owned subsidiary of Rohm and Haas Company)

Establish a program that ensures reactive chemical process safety information and operating

experience are collected and shared with all relevant units of the company. 

Morton International, Inc.’s Paterson, New Jersey Plant

1. Revalidate PHAs for all reactive chemical processes in light of the findings of the CSB

report and upgrade, as needed, equipment, operating procedures, and training. 

2. Evaluate pressure relief requirements for all reaction vessels using appropriate technology,

such as the Design Institute for Emergency Relief Systems (DIERS)6 method and test

apparatus and upgrade equipment as needed.

3. Evaluate the need for and install, as necessary, devices, such as alarms, added safety

instrumentation, and quench or reactor dump systems to safely manage reactive chemical

process hazards. 

4. Revise operating procedures and training for reactive chemical processes as needed, to

include descriptions of the possible consequences of deviations from normal operational

limits and steps that should be taken to correct these deviations, including emergency

response actions.

5. Implement a program to ensure that deviations from normal operational limits for reactive

chemical processes that could have resulted in significant incidents are documented and

investigated and necessary safety improvements are implemented.

8

6 DIERS is a consortium of companies, formed in 1976 by the American Institute of Chemical Engineers, to

develop methods for the design of emergency relief systems to handle runaway reactions. The DIERS group has

developed computer programs and a bench-scale test apparatus for assessing the venting requirements of runaway

reactions and two-phase flow.
6. Revise the Yellow 96 Material Safety Data Sheet (MSDS) to show the proper boiling point

and NFPA reactivity rating. Communicate the MSDS changes to current and past customers

(who may retain inventories of these products).

Occupational Safety and Health Administration (OSHA) and 

Environmental Protection Agency (EPA)

1. Issue joint guidelines on good practices for handling reactive chemical process hazards.

Ensure that these guidelines, at a minimum, address the following issues:

● The evaluation of reactive hazards and the consequences of reasonably foreseeable and

worst-case deviations from normal operations.

● The importance of reporting and investigating deviations from normal operations.

● The determination of proper design for pressure relief capability, emergency cooling,

process controls, alarms, and safety interlocks, as well as other good-practice design

features for handling reactive substances.

● The appropriate use of chemical screening techniques such as differential scanning

calorimetry.

2. Participate in a hazard investigation of reactive chemical process safety conducted by the

CSB. The objectives of the hazard investigation will include:

● Determine the frequency and severity of reactive chemical incidents.

● Examine how industry, OSHA, and EPA are currently addressing reactive chemical

hazards. Determine the differences, if any, between large/medium/small companies with

regard to reactive chemical policies, practices, in-house reactivity research, testing, and

process engineering.

● Analyze the effectiveness of industry and OSHA use of the National Fire Protection

Association Reactivity Rating system for process safety management purposes. 

9
● Develop recommendations for reducing the number and severity of reactive chemical

incidents.

American Chemistry Council; Center for Chemical Process Safety (CCPS); Paper, AlliedIndustrial, Chemical & Energy Workers International Union (PACE); Synthetic Organic

Chemical Manufacturer’s Association (SOCMA)

Communicate the findings of this report to your membership.

10
1.0 INTRODUCTION

1.1 BACKGROUND

On Wednesday, April 8, 1998, at 8:18 pm, nine workers were injured in an explosion and fire at

the Morton International, Inc. (now Rohm and Haas Company) plant in Paterson, New Jersey.7

This incident was the result of a runaway chemical reaction during the production of Automate

Yellow 96 Dye. Because of the serious nature of the incident, which caused the hospitalization of

two employees, the release of chemicals into the community, and damage to the plant, the U.S.

Chemical Safety and Hazard Investigation Board (CSB) sent a team to investigate the incident.

Morton International, Inc. is a major salt producer and maker of specialty chemicals for a

variety of applications. Morton developed the Automate Yellow 96 Dye product in the 1980s.

11

7 Morton International, Inc. was purchased in the spring of 1999 as a wholly owned subsidiary of Rohm and Haas

Company, which is a publicly held Fortune 500 company.

Figure 1: Aerial View of the Paterson Plant
Combined with other dyes, Automate Yellow 96 produced bright green shades of tinting for

fuels. Initial laboratory testing and pilot plant scale-up were conducted at Morton facilities in

Hounslow, England in 1986–1989. During this development phase, Morton researchers

observed exothermic activity and determined that batch temperature control was key to

preventing the reaction from reaching runaway conditions. In 1988 and 1989, the Morton

research groups in Paterson, New Jersey, and Ringwood, Illinois, developed a staged heating

process for Yellow 96 and reported no temperature control problems during laboratory and

pilot-scale work. The first production-scale batch of Yellow 96 was manufactured at Paterson on

September 6, 1990.

1.2 INVESTIGATION PROCESS

The CSB received and shared information with the Occupational Safety and Health

Administration (OSHA), the Environmental Protection Agency (EPA), and local emergency

response organizations. The CSB examined physical evidence from the incident, conducted

interviews with Morton personnel, and reviewed relevant documents obtained from Morton.

The CSB was assisted in its initial field investigation work by contractors from the Department

of Energy’s Oak Ridge National Laboratory and the National Aeronautics and Space

Administration’s (NASA) White Sands Test Facility.8 Calorimetric testing of the Yellow 96

process and process materials was conducted for the CSB by both the White Sands Test Facility

and Chilworth Technology, Inc.

12

8 The field phase of the investigation was delayed by approximately 6 weeks due to problems between the CSB

and Morton in obtaining proper credentials for the contract investigators. This delay did not affect the CSB’s key

findings or conclusions regarding the causes of the Morton incident.
1.3 PLANT FACILITIES

The Paterson facility is located in Passaic County, on a seven-acre site surrounded by other

industrial establishments and residential homes. On-site support facilities include offices,

laboratories, shops, lunchrooms, and locker rooms. The plant is bordered on the west by New

Jersey Route 20 (McLean Blvd.) and on the east by the Passaic River (Figure 1).

The incident occurred in Building 11 (B-11), a three-floor building on the east end of the

complex. A facility plot plan is provided in Figure 2. The plot plan identifies the location of

each of the process buildings, the K-7 chemical reactor vessel used on April 8 to produce

Yellow 96, and the hot box, which was used to preheat the ortho-nitrochlorobenzene (o-NCB)

for use in the Yellow 96 process. 

13

OFFICES SHIPPING

PAVED PARKING AREA

TANK FARM

LUNCH AND

LOCKER ROOMS

LAB

AND

OFFICES

PRODUCTION

MAINT.

SHOP

WAREHOUSE

UTILITY

BUILDING 11

PRODUCTION

LAB & OFFICES

THERMAL

OXIDIZER

PRODUCTION

DRUM PAD

HAZ WASTE

ELECT.

SUBSTATION

McLEAN BLVD. NJ ROUTE 20

PASSAIC RIVER

STORAGE

K-7

HOT

BOX

15

Figure 2: Plot Plan
Industrial dye products were manufactured at the plant via batch processing. Various raw

materials were mixed in reaction vessels (kettles) and heat was applied to drive the reaction

process. The resulting dyes were further processed after the reaction steps to remove residual

chemicals and waste products. The final product was put into drums or transferred to product

storage tanks to be shipped off-site or blended with other products to produce different colors as

final products.

1.4 LAYOUT AND COMPONENTS

1.4.1 Kettle Description

From 1990 to 1996, Morton produced Yellow 96 in 1000-gallon kettles. In September 1996,

Morton switched production to 2000-gallon kettles to minimize color contamination between

different dyes produced in the same kettles. Kettle number seven (K-7), which was involved in

the incident, was one of the 2000-gallon kettles. 

Kettle K-7 was designed and manufactured in 1962 (Figure 3 is a drawing of a kettle similar to

K-7). The interior of the kettle was glass lined to prevent corrosion of the carbon steel shell and

heads. The inside diameter of the kettle was 78 inches and the height was about 107 inches. The

kettle heads were dished, with nominal thicknesses of 7/8 inch and 15/16 inch for the top and

bottom heads, respectively. The nominal thickness of the shell was 15/16 inch. A heating and

cooling jacket, or outer case, extended from the top head-to-shell weld downward to the middle

of the bottom head and surrounded the outside of the kettle. The kettle had a Maximum

Allowable Working Pressure9 (MAWP) of 100 psig. The MAWP for the jacket was 90 psig.

Kettle rupture disks were set at 10 psig.10

14

9 The Maximum Allowable Working Pressure (MAWP) is the maximum pressure at which a vessel is designed to

operate safely. Typically, vessels are operated at pressures significantly below the MAWP to provide a margin of

safety. 

10 Rupture disks are emergency safety devices designed to open to relieve high pressure in vessels and protect

equipment and personnel from catastrophic failure of the vessel.
Nozzles were located in the jacket and on the top head of the kettle to provide piping

connections. The nozzle at the bottom of the vessel served as a drain. The most pronounced

feature of the top head was a 30-inch-diameter bolted closure. A glass-coated, single-speed

agitator was attached to the top surface of the bolted closure. The bolted closure contained a

14- by 18-inch elliptical manway secured by four C-type clamps. 

The CSB determined that the kettle and jacket

design, fabrication, inspection, hydro testing,

and registration stamping met the

requirements of the American Society of

Mechanical Engineers, Section VIII, Boiler

and Pressure Vessel Code.

1.4.2 Kettle System

The entire K-7 process system, with the

exception of the thermal oxidizer and

pressure-relief catch tank, was located inside

Building 11. The kettle extended vertically

from the ground level to the second floor.

The operators had access to the kettle’s top

head and associated nozzles on the second

floor where the raw materials were added.

Valve handles and temperature readout and

recording instruments were also located on

the second floor.

Ground-level valve handles were modified to

extend up through the second-story floor

grating, allowing the operators to control

15

Figure 3: Annotated Rendering of a Chemical

Reactor Head Similar to Kettle Seven

Besides the agitator bolted closure,

the chemical reactor’s head had the following:

(A) a 14- x 18-inch elliptical inspection manway,

(B) a penetration for the thermocouple,

(C) an 8-inch nozzle to the rupture disks and the

10-inch pressure manifold leading to the

catch-all tank,

(D) a connection for the liquid condensate return,

from the liquid separator,

(E) an acid feed line into the kettle,

(F) a direct kettle vent line to the B-11 manifold

that collected organic vapors and delivered

them to the site’s thermal oxidizer,

(G) an 8-inch line to the condenser on the third

floor of B-11. A raw material feed nozzle is

located behind the 15-hp. electric agitator

motor.

(http://www.pfaudler.com/gle/vessels.html)

A

C B

D

E

F

G
each valve manually from the second floor. The third floor housed the condenser and exhaust

piping leading outside to the thermal oxidizer and pressure-relief catch tank.

Temperature in the vessel was controlled by adjusting the flow of cooling water and steam

piped to the kettle’s jacket with manually operated valves. The operators determined the degree

to which these valves were opened based on their experience in running the process. The timing

of switching from heating to cooling or vice versa was also based on the operators’ experience.

The cooling-water inlet was located at the bottom and the steam inlet was located at the top of

the jacket. The water outlet was shared with the steam outlet at the top of the jacket. Steam that

condensed during heating operations was drained from the bottom of the jacket and directed to

the boiler condensate return. Figure 4 is a simplified flow diagram of the K-7 reactor system.

16

Figure 4: Simplified Process Flow Diagram

SEP.

T

PI

TI

REACTOR K-7

CONDENSER

CATCH TANK

RECEIVER

RUPTURE DISKS -

10PSI

COOLING WATER

IN

CONDENSATE

OUT

PRODUCT OUT

COOLING

WATER

OUT

STEAM

IN

TO THERMAL

OXIDIZER

CW OUT CW IN

MANWAY RAW

MATERIAL

ADDITION

MANIFOLD

VACUUM

ADDITIONS

LINE

TO VACUUM

PUMPS

RECYCLE OR

WASTE TREATMENT

11/12/99

SECOND

LEVEL

FLOOR

VALVE

HANDLE

EXTENSION
Reactor instrumentation provided measurements of reactor temperature, reactor pressure, and

cooling water pressure. Reactor temperature was measured by one thermocouple11 connected to

two temperature readouts: a digital display and a circular recording chart. The recording chart

could not record temperatures greater than 150°C, although the digital readout continued to

display temperatures above 150°C (see Figure 5). The kettle was not equipped with temperature

or pressure alarms and there were no automatic shutdown devices.

17

11 A thermocouple measures temperature. A thermocouple is composed of two dissimilar metals fused together;

the junction between the two metals generates a voltage that is a function of temperature. 

Figure 5: Temperature Chart and Digital Display

The round window in the aluminum box contained the

temperature chart. The rectangular cutout above and to the

left of the chart contained the digital temperature readout.
2.0 DESCRIPTION OF THE INCIDENT

2.1 INCIDENT EVENTS12

On April 8, 1998, the second work shift began at 4:00 pm. During this shift, Yellow 96 was

scheduled to be prepared in K-7, a 2000-gallon jacketed kettle located at the east end of

Building 11 (B-11). Plant batches of Yellow 96 had been numbered sequentially from the

beginning of production in 1990 and this was to be batch #32. The supervisor assigned two

chemical operators to the production and provided them with the batch sheets for Yellow 96.

Operators used batch sheets for step-by-step direction in performing the process. The batch

sheets were written and approved by plant management, and supervision and operations

personnel. The Yellow 96 batch sheet was nine pages long and had abbreviated safety data

sheets (listing only the key health hazards and protective equipment) for the raw materials and

products as well as a list of raw materials.13 The batch sheets outlined the procedures for each

step in the process. Operators were required to record the time when each step began and ended,

the temperature of the kettle contents, and their initials. Each batch was assigned a sequential

lot number. The lead operator performing the process controlled the batch sheets throughout the

production of Yellow 96. Upon completion of the batch, the operator returned the sheets to the

supervisor along with the temperature recording charts generated during the batch.

Both operators involved in the incident had made Yellow 96 before. The lead operator had 31

years of plant experience and the assistant operator had more than 3 years of experience.

Before beginning batch 32, the operators inspected the kettle through the manway to ensure that

it was clean. The lead operator recalled that the temperature of the kettle was approximately 20

to 30°C (68 to 86°F) during and after the inspection. Once the inspection was completed, the

18

12 This narrative can be followed on the Incident Timeline in Appendix A. It describes the actions taken by the

operators working on the second floor operating deck of B-11 and the subsequent emergency response activities.

13 Complete Material Safety Data Sheets for Yellow 96, o-NCB, and 2-EHA may be found in Appendix C.
19

manway cover was closed and clamped

onto the kettle using four C-type clamps

(see Figure 6).

The first processing step was the addition

of ortho-nitrochlorobenzene (o-NCB) to

the kettle. Because o-NCB has a melting

point of 32°C (89°F), the drums required

for a batch were placed in a hot box for

several days to be melted before use. The

hot box was an enclosed room, with a

steam heater, large enough to contain the

drums (the hot box is shown in Figure 2,

to the west of Building 11).

The operators prepared to transfer the o-NCB from the drums by ensuring that all kettle valves

were closed, except for the vacuum valve, and the agitator was started. A vacuum was used to

draw the o-NCB from the supply drum to the kettle through a combination of piping and

flexible hose. This operation was repeated until all drums were empty. The transfer of the

o-NCB was normal, taking approximately 30 minutes (until 5:15 pm) indicating that the

vacuum was adequate and the o-NCB was well liquefied. Once the transfer of the o-NCB was

completed, the temperature of the o-NCB inside the kettle was reported by the lead operator to

be “60-something degrees, almost 70°C” (158°F), while the second operator recalled that it was

“about 44°C.” The U.S. Chemical Safety and Hazard Investigation Board (CSB) determined

through interviews that the operators did not adjust the initial mix temperature to between 40 to

42°C (104 to 108°F) as required by the batch sheet. This temperature-reduction step would have

reduced the initial rate of the reaction to produce Yellow 96.

The next processing step was the addition of the 2-ethylhexylamine (2-EHA). The operators

readied the kettle by ensuring the vacuum valves and drain isolation valves to the kettle were

closed. They opened the kettle vent to ensure there was no buildup of pressure when the 2-EHA

Figure 6: Manway Hatch in Place

As seen in this photograph of a similar kettle, four clamps 

hold the inspection manway hatch in place.

1

2

3

4
was added. The operators left this vent

valve open for the duration of the

operation, allowing the process to be

performed at atmospheric pressure (see

Figure 7).

Next, the operators added 2-EHA to the

kettle. The 2-EHA was pumped into the

kettle from an underground storage tank

through a meter that stopped the flow

when the preset amount of 2-EHA had

been pumped. The kettle agitator

continued to operate during the 2-EHA

addition. The transfer took approximately

25 minutes. After adding the 2-EHA, the

operators left the building for dinner,

returning at approximately 7:35 pm.

After the addition of the 2-EHA, which was at ambient temperature, the operators stated that

the temperature of the mixture was approximately 44 to 48°C (111 to 118°F). Since the onset

temperature for the reaction was 38°C, it is likely that the reaction to produce Yellow 96 was

already occurring at a very low rate at this time.

2-EHA is a combustible material, with a flash point14 of 52°C (126°F). o-NCB has a flash point

of 127°C (261°F). Thus, both substances were above their flash points during a portion of the

normal process and during the runaway incident.

The staged heating procedure used by Morton to produce Yellow 96 started with an initial

heatup of the reaction mixture to 90°C, with gradual increases thereafter to 150 to 153°C. With

20

14 Flash point is the minimum temperature at which a liquid gives off sufficient vapor to form an ignitable mixture

with air near the surface of the liquid.

Figure 7: Condenser and Vent Piping

The system’s vent to the atmosphere was through the top 

of the condensate collection end of the condenser.

Condenser

Vent

Condensate

Return
both the o-NCB and the 2-EHA now in the kettle, the operators slowly raised the temperature to

initiate the reaction by opening and closing valves to allow steam to enter the kettle jacket in

short bursts, typically lasting several minutes. This processing step was designed to raise the

temperature slowly. The expected reaction time for a batch was 6 to 8 hours.

At approximately 7:40 pm, the lead operator began to raise the temperature of the mixture by

introducing steam to the kettle’s jacket. The operating procedures stated that the heating process

was necessary to start the exothermic reaction used to produce the dye. To introduce steam to

the kettle’s jacket, the operator opened the kettle jacket’s steam-outlet and steam-inlet valves

and watched for steam to appear at the steam blow-off line. The steam and cooling-water valves

were grouped on opposite sides of the kettle and were operated by hand-wheels on extension

rods to the valve bodies below the operating deck. Once the jacket was filled with steam, the

steam-outlet valve was closed. The lead operator applied steam to the kettle for about 10

minutes, stopping when the jacket’s pressure gauge read 5 to 10 psig. He repeated this step two

more times, watching the digital temperature readout. As the temperature rose, he noticed that

the rate of the kettle’s temperature rise was unusually fast. He recalled that the temperature of

the batch rose quickly from 70 to 80°C (158 to 176°F) and that the tenths decimal reading on

the digital temperature indicator was “moving very fast.” This rapid temperature rise began

within the first 15 minutes after the start of heating. The typical heat-up rate during this phase

of the process was 1–2 degrees per minute.

At approximately 8:05 pm, with the temperature at 100°C (212°F) and rising rapidly, the

operators switched from heating the reactor to cooling by closing the jacket steam valves and

opening the cooling water valves. 

Three other experienced operators became aware of the problem and came to assist. They

inquired if the cooling water was on, and at least one of them confirmed the valve positions.

The lead operator re-verified the positioning of the valves to ensure that the cooling-water inlet

and outlet valves were full open and that the steam-inlet and steam-condensate valves were

closed. The operators stated in interviews that they had heard the sound of the cooling water

flowing through the piping, another indicator they used to ensure cooling water flow. The CSB

21
confirmed that the valves had been

working properly.

Approximately 2 minutes passed. The

operators called the supervisor to assist

and he also verified that all valves were

configured properly. The temperature chart

recorder, which had a maximum reading

of 150°C, was now off scale and of no use

to the operators, but the digital gauge

showed that the temperature continued to

rise. The kettle began to vibrate and very

turbulent vapor appeared in the glass

section of pipe above the kettle leading to

the condenser (Figure 8). This vapor was

composed of 2-EHA and gases generated

by the decomposition reaction.

The kettle’s emergency relief system,

consisting of two 6-inch rupture disks set

to open at 10 psig, activated. The

operators estimated that the temperature at

the time the rupture disks vented was

about 180 to 190°C (356 to 374°F).

Figure 9 shows the recovered dual rupture

disk assembly. The rupture disks were

installed on the top of the kettle in a 6-inch

diameter line that vented into a 10-inch diameter manifold. This manifold dumped the vapor

and liquid aerosol flow into a catch tank outside Building 11. A total of 100 gallons of various

chemicals were recovered from this tank after the incident. However, without information on

22

Figure 8: Glass Section of 8-inch Line to Condenser

The 8-inch line to the condenser had a glass section above

the kettle head in which turbulent, refluxing vapor could be

seen in Yellow 96 batch 32.
the contents of the tank before the incident, the CSB could not determine which materials were

vented during the event.

The batch temperature continued to increase rapidly, passing the Yellow 96 decomposition onset

temperature of 195°C (383°F). The kettle began to rumble and shake more violently. One

operator noticed that material was being blown up from the kettle and into the condensate

return separator, indicating that the boiling of 2-EHA and the generation of gases from the

reactions had exceeded the capacity of the condenser. The condenser’s tubes were flooded with

liquid, and the system was trying to relieve its pressure by backward flow up the condensate

return line and through the condenser vent.

At the point of the disk failure, an operator who was standing near the kettle reported that he

saw the digital temperature reading increase from 190 to 260°C in less than 30 seconds. He

then shouted to several other operators and started to run towards an exit. As he reached the top

of the stairs located in the middle of the second floor, he heard additional sounds, including a

gush of air, which he associated with the failure of the glass condensate return separator

assembly. At ground level, he shouted a warning to three more workers who were unaware of

the danger. They all ran toward an exit.

23

Figure 9: Rupture Disk Assembly Recovered from 

K-7 after the Incident (both disks blown)

Disk 2 Disk 1
At almost the same time, the operator and supervisor still at the kettle reported in interviews

that they observed the temperature on the digital temperature readout at about 200°C (392°F).

They remained unaware that the batch temperature was above the decomposition temperature of

the Yellow 96 product. At this point, the operator and supervisor ran toward the second-floor

northeast exit. The reaction in the kettle was vibrating the second-floor steel decking and there

was a very loud rumbling, which other workers on the site thought was the sound of a train

passing.

At 8:18 pm, the pressure in the kettle blew the inspection manway off the vessel. The manway

was found 15 feet from the kettle, and the heat and pressure extruded the head gasket of the

vessel through the bolted connection of the

30-inch bolted closure with the top head of

the kettle (Figures 10 and 11).

From the open vessel manway, a jet of hot

reactants erupted, emptying the vessel. The

ejected material penetrated the third floor and

the roof. An aerosol mixture of gas and liquid

shot above the roof and spattered the adjacent

neighborhood with a yellow-brown mixture

of compounds including Yellow 96 and

24

Figure 10: Extruded Head Gasket

This was a result of the heat and pressure that developed

during the explosions.

Figure 11: Recovered Inspection Manway Cover

This photo shows the scars where the clamp tore away.

Extruded

Head

Gasket

Clamp Scar

Clamp Scar
o-NCB. This aerosol plume ignited forming a large fireball above the roof. The recoil from the

expanding gases of the explosion twisted the kettle off its mounts. The kettle dropped 4 feet

onto the ground level below and was found leaning against a cinder block wall. Figure 12

shows the final resting position of the vessel after the blasts and fire.

As the operator and supervisor reached the second-floor exit landing, the explosion blew them

to the mid-level landing and flash fires spread throughout the building. The building’s wall

panels and windows were blown out by the blast, absorbing much of the explosion’s energy and

preventing greater damage. The lead operator and the supervisor were blown off the mid-level

stair landing onto to the ground. They suffered second- and third-degree burns, requiring their

hospitalization in intensive care for 5 days. Injuries to the other workers included first-, second-,

and third-degree burns, contusions, abrasions, lacerations, and muscle strains.

25

Figure 12: Post-accident Photo of the Kettle

The kettle is leaning against the east-west concrete block wall that divided the

building. (The second floor grating is visible at the right edge of the photo.)

(The color balance of this photo has been altered in order to show 

detail in the dark shadows.)
2.2 EMERGENCY RESPONSE

The Paterson Fire Department (PFD) arrived at 8:24 pm. The Paterson fire chief assumed

command of the fire-fighting effort and called for the Hazardous Materials (HazMat) team. Fire

was visible burning through the roof of the building. Before the PFD began their attack, plant

personnel assembled the necessary information on the location and materials involved in the fire

and the Paterson fire chief determined whether the presence of water-reactive chemicals

precluded the use of water to fight the fire. 

Once determined safe, water was applied to the fire. The flames were suppressed in about

1 hour, but the PFD continued the water deluge to facilitate the HazMat Team’s entry and initial

survey at 9:44 pm. The HazMat Team conducted a primary and secondary search throughout

the building, which indicated that all workers had escaped. The PFD team then entered the east

end of the building on the second floor with a portable dry chemical fire-extinguishing unit to

extinguish the remaining fires. The firewater was stopped as soon as possible to prevent

washing contaminants into the Passaic River, which borders the plant’s eastern side. The fire

was reported under control at 11:27 pm. The K-7 fire-suppression system, located over the top

of the kettle, and the B-11 fixed fire-water deluge system were damaged by the explosion and

did not aid fire suppression.

Morton collected on-site approximately 310,000 gallons of contaminated water from firefighting operations and next-day rain. Less than 10,000 gallons of contaminated

firewater/stormwater reached the Passaic River, according to an estimate by Morton.15

26

15 Morton International, Inc., to NJ Department of Environmental Protection, “Discharge Confirmation Report,”

May 7, 1998, page 7.
2.3 OFF-SITE IMPACTS

During the fire, the ambient temperature was about 40°F. It was a clear night, with light winds

mostly from the northeast, switching to the southeast. These winds blew the plumes of

reactants, products, and smoke off the plant site. The fallout was mainly to the west of the plant.

Spots were reported on cars in the neighborhood, at an adjacent candy factory, and at a car

dealership one-half mile away.

Nearby residents were ordered to shelter in-place during and immediately after the fire-fighting

attacks. The shelter-in-place was conducted by the Paterson Police Department and

encompassed a 10-block by 10-block area around the plant. The shelter-in-place lasted for

approximately 2 to 3 hours.

During and following the fire, air monitoring was performed by various organizations, including

the Passaic County Department of Health, Paterson Office of Emergency Management, the

Environmental Protection Agency, and Morton. Tests conducted during the fire by the Passaic

County Department of Health were negative for benzene, halogenated hydrocarbons, and

nitrous compounds.

Workers at two neighboring businesses and fire fighters reported throat irritation and a slight

burning in their eyes and on their skin. Several odor complaints were also received from

community members.

Approximately 20 hours after the incident, a health warning statement, prepared by the Passaic

County Department of Health and issued jointly with the Paterson Mayor’s office, was

distributed to the local community. It advised residents to avoid contact with the deposited

material, listed steps to be taken in case of health effects, and instructed residents on how to

handle contaminated items.

Wipe samples were taken of visible material deposited on automobiles and buildings near the

Morton facility. These samples contained measurable quantities of Yellow 96 Dye and o-NCB.

27
2.4 PROPERTY DAMAGE

The open flooring in B-11, in conjunction with the blowout walls and windows, minimized the

fire and blast damage to the load-bearing structure of the building. 

The blast blew out the windows, doors, and blowout walls of B-11 (Figure 13). While there was

some blast damage in the immediate vicinity of this reactor vessel, most of the damage was

caused by the ensuing fire. The second blast was outside, above the roof. 

Structural consultants subsequently determined that the load-bearing columns were not severely

damaged. Overall, the building was still structurally sound and some of the equipment was

salvageable.

28

Figure 13: Building 11’s Blowout Panels and Window Frames
3.0 ANALYSIS OF PROCESS CHEMISTRY

3.1 REACTIVE CHEMICAL ANALYSIS

The runaway chemical reaction incident in the Yellow 96 process involved two reactions: (1) the

desired synthesis reaction to form the product, and (2) the undesired decomposition reaction of

the product.

The heat produced by the exothermic reaction that formed the product exceeded the heatremoval capacity of the kettle and rapidly raised the temperature of the batch. That heat

generation caused the vapor pressure of the 2-ethylhexylamine (2-EHA) to rise until it boiled

and the reaction released additional gases, pressurizing the vessel. The heat released also raised

the temperature of the batch above the decomposition temperature of Yellow 96, at which point

the gaseous products of the decomposition reaction resulted in even greater pressure,

culminating in the explosion and the final release of material from the kettle.

Chilworth Technology, Inc., of Monmouth Junction, New Jersey, was hired by the the U.S.

Chemical Safety and Hazard Investigation Board (CSB) to conduct a battery of calorimetric

tests analyzing the Yellow 96 synthesis and decomposition reactions. Two exothermic reactions

were observed: Reaction 1, the desired reaction of 2-EHA with ortho-nitrochlorobenzene

(o-NCB) to form Yellow 96 had an onset temperature (To) of 38°C. Reaction 2, the

decomposition reaction of the Yellow 96 had an onset temperature of 195°C. (The onset

temperature is the lowest temperature at which exothermic activity is observed.) Chilworth also

determined that the onset temperatures for the generation of permanent gases were 139°C for

the desired synthesis reaction and 201°C for the decomposition reaction.16

29

16 Chilworth Technology, Inc., to U.S. Chemical Safety and Hazard Investigation Board, Report No.

R/2713BR/0400/DYK, “Closed Tube Test (Carius Tube Test) Measurement Results and Interpretation for the

Thermal Decomposition of the Formation of Automate Yellow 96,” April 14, 2000.
The heat released during the synthesis reaction raised the temperature of the reaction mixture.

The rate of the temperature rise depended on the balance between the reaction rate, the heat

capacity of the chemicals, and the rate of heat removal by the reactor’s cooling water jacket. To

hold a constant temperature in the kettle after the synthesis reaction had begun, the operators

manually adjusted the flow of cooling water through the water jacket, trying to balance the heat

removal rate with the heat generation rate. Without any indicators for water-flow rate or for

cooling-water inlet and outlet temperatures, the operators controlled the kettle’s temperature

based on in-house training and experience. The operators also had to take into consideration a

time lag in the temperature response of the reaction mixture to the manual adjustments in the

cooling-water flow. 

The released heat not only raised the batch temperature but also accelerated the reaction rate,

making the temperature rise more difficult to control. The accelerating reaction rate made it

more likely that the heat generated by the reaction would exceed the rate of heat removal for

which the kettle was designed, resulting in a runaway, uncontrollable condition. The runaway

condition occurs because the rate at which heat is removed through the jacket increases linearly

with increasing temperature, while the rate at which heat is generated by the reaction increases

exponentially (see Figure 14).

The reaction rate is determined both by the volumetric concentrations of the two reactants and

the temperature. The rate of a reaction increases exponentially with temperature. At the

beginning of the reaction, the reactants are at their maximum concentrations. As the reaction

proceeds to completion, the starting materials are depleted and the reaction slows down.

Therefore, at the start of the batch, with a high inventory of reactants, the influence of

temperature on the heat generation rate is greatest and there is the most danger of overrunning

the heat removal capacity of the kettle. As will be discussed in Section 4.0, Analysis of Process

Development Program, use of a semi-batch process instead of a batch process, could have

provided the operators with more control over the reaction.

The operating procedures for Yellow 96 stated that the operators should heat the reactant

mixture to 90°C to initiate the reaction; however, in the operators’ experience, following the

30
operating procedures resulted in a temperature increase that was difficult to control. The

operators believed that the reaction between 2-EHA and o-NCB started as early as 75°C

(167°F) and so most operators turned the steam heating off when the reaction temperature

reached approximately 70 to 80°C. The CSB confirmed the operators’ observations:

calorimetric testing determined that the onset temperature for the Yellow 96 synthesis reaction

was 38°C. Therefore, the reaction would proceed slowly even at temperatures lower than was

thought by the operators. 

The operating procedure required that the operators should begin the heating process from a

temperature of 40 to 42°C (104 to 108°F), but the operators usually started heating the initial

mixture at whatever the batch temperature was after the addition of the 2-EHA to the o-NCB.

The review of completed batch sheets as well as interviews showed that the starting temperature

was greater than 40 to 42°C (104 to 108°F) in a number of cases, including batch 32 (as

determined in interviews). Since the reaction began at 38°C, starting from a lower temperature

and a correspondingly lower initial reaction rate would have given the operators more time to

react and possibly control the rising temperature before the heat generation rate overran K-7’s

31

Figure 14: Heat Generation versus Heat Removal Rate

If the reaction temperature exceeds point A, the rate of heat generation exceeds 

the rate of heat removal and the reaction will run away. 

(HSE, Designing and Operating Safe Chemical Reaction Processes, page 10)

Temperature

Rate of heat production/removal

Heat production

Heat removal

A
cooling capacities. The operators had been able to do just that during previous batches that

exhibited temperature excursions (see Section 5.3).

If the cooling water is incapable of removing all of the heat generated by the reaction, the

temperature rises and accelerates the reaction rate. In batch 32, the accelerating synthesis

reaction continued to generate heat, raising the temperature. As a result of this heating, the

residual 2-EHA in the kettle began to vaporize rapidly as was observed in the 8-inch glass line

between the kettle and the condenser by the operators. 

In some batch operations evaporation and condensation (refluxing) can be an effective heatremoval technique. Heat generated by the reaction is used to boil a solvent or other materials

in the reactor. This vaporized material is then cooled and converted back to liquid in a

condenser. The heat is thus transferred to the water used to cool the condenser and removed

from the process. The Yellow 96 researchers in the United Kingdom considered using

evaporation and condensation as a heat-removal mechanism but it was not considered in the

Paterson plant design. Vaporization and condensation, however, did occur in batch 32, but the

vaporization proceeded at too fast a rate for all the materials to condense, while additional

noncondensable gases were also being generated. Operators had seen vigorous refluxing

during the reaction in only one previous batch (batch 31), a high-temperature excursion

beyond the normal operating limit.

As the reaction temperature approached 195°C (383°F), the undesired exothermic

decomposition reaction of Yellow 96 began producing more heat and noncondensable gases,

which further pressurized the vessel. The pressure in the vessel rose higher than the rupture

disk pressure setting (10 psig). At about 180 to 190°C (356 to 374°F), the rupture disks

vented, allowing material to escape to the catch tank and to the atmosphere. However, the

venting area available through the rupture disks was insufficient to relieve the pressure being

generated by the reaction, so the pressure in the kettle continued to rise. The 8-inch glass line

to the condenser (see Figure 9) and the glass 2.5-inch condensate return line shattered, also

venting reactants. 

32
The pressure resulting from the Yellow 96 decomposition continued to increase rapidly and

exceeded the kettle’s ability to relieve through the several now-opened lines. This pressurization

eventually caused the manway inspection hatch to be blown off. The expanding vapors and the

decomposition gases propelled the reaction mixture through the third floor and roof as a twophase flow of vapors and liquid.17

3.2 TESTS OF RAW MATERIALS

NASA’s White Sands Test Facility18 and Chilworth19 conducted differential thermal analysis20

tests for the CSB on the two raw materials. No exothermic reactions or pressure spikes were

detected for the individual reactants until temperatures were above the maximum Yellow 96

operating temperature (160°C). After the incident, the Occupational Safety and Health

Administration (OSHA), the Environmental Protection Agency (EPA), and Morton analyzed the

unused raw materials and determined that the reactants used were within the expected quality

range. These tests confirmed that the runaway reaction was not the result of contamination from

the raw materials.

33

17 An analogy for the eruption of two-phase flow from the kettle is the release of gas, liquid, and foam observed

when a container of carbonated beverage is shaken and then opened.

18 NASA, White Sands Test Facility, “NASA Analyses of the Reaction of ortho-Nitrochlorobenzene with

2-Ethylhexylamine,” September 1998.

19 Chilworth Technology, Inc., to U.S. Chemical Safety and Hazard Investigation Board, Report No.

R/2713/0600/BC, “Differential Scanning Calorimetry of 2-Ethylhexylamine, chloronitrobenzene and Automate

Yellow 96 (Crude and Pure),” June 2, 2000.

20 Differential Thermal Analysis (DTA) is a preliminary screening test, similar to the Differential Scanning

Calorimetry (DSC) performed by Morton in 1987. DTA is used to determine whether an exotherm occurs, the

exothermic onset temperature, and the amount of heat generated. The DTA test used small samples, e.g., several

milligrams. The sample is heated at a controlled rate. The onset temperature, To, is the temperature at which the

sample first shows an observable thermal response due to reaction or decomposition.
4.0 ANALYSIS OF PROCESS DEVELOPMENT

PROGRAM

The Yellow 96 process went through several research phases at different branches of Morton.

(The Timeline in Appendix B summarizes important dates in the development and production of

Yellow 96.) The company began its research with small-scale reactions in 1986 at their

Hounslow, England, facility. Larger experimental batches of Yellow 96 were produced in 1987

and 1988. Morton researchers observed exothermic activity in these tests. Morton contracted

Brunel University in the United Kingdom to perform differential scanning calorimetry (a typical

screening test for exothermic activity) on the reaction in 1987. In these tests, “the material was

found to decompose with considerable generation of heat at above 220°C.”21 Morton developed

a semi-batch, staged addition process to control the exothermic reaction rate in these early

trials. The researchers added the ortho-nitrochlorobenzene (o-NCB) to the 2-ethylhexylamine

(2-EHA) in four equal portions and allowed the reaction to run its course and subside between

o-NCB additions.22

In 1989, the researchers at Hounslow wrote a review of the process in which they made a

number of recommendations regarding the reaction control and safety. This review was faxed to

the Paterson plant on April 28, 1989.23 Among other things, the researchers recommended

controlled cooling-water addition directly into the reactor as an emergency method to stop a

runaway reaction. 

This process review memo also included the recommendation that accelerating rate calorimetry

testing be performed to determine “the rate of reaction under the worst reaction conditions ...

the rate of decomposition of the finished product ... [and] pressure rise data which could be

34

21 CSB-NJ249, CSBINSP002548, Morton Internal Memorandum, R. Pollington to C.J. Bird, et al., “Thermal

Stability of Yellow 152,” April 8, 1988.

22 During much of the development work, Morton referred to the Yellow 96 material as “Liquid Yellow 152” or

“Sudan Yellow 152.” 23 CSB-NJ248, CSBINSP002476, fax message, A. Pearce to J.J. Fuerholzer, April 28, 1989.
used to size emergency venting equipment ....”24 Morton did not perform these additional tests

or install the recommended safety equipment.

In late 1989, Morton transferred its research effort on Yellow 96 to the United States. Initial

research was conducted at the Paterson plant. Paterson revised the process from semi-batch to a

full-batch process in order to minimize employee exposure to o-NCB. In the batch process, the

full amounts of o-NCB and 2-EHA were added to the reactor first, and heat was then applied to

initiate the reaction and drive it to completion. This procedure, with one total addition of

o-NCB versus the four partial additions in the semi-batch process, was used throughout Yellow

96 production at Paterson. Morton did not take into account that switching from their initial,

semi-batch process to the full-batch process resulted in a more hazardous condition.

In Inherently Safer Chemical Processes, the Center for Chemical Process Safety notes: “Semibatch or gradual addition batch processes [Morton’s initial process design] limit the supply of

one or more reactants, and increase safety when compared to batch processes in which all

reactants are included in the initial batch charges [Morton’s production process]. For an

exothermic reaction, the total energy of reaction available in the reactor at any time is

minimized.”25 The U.K. Health and Safety Executive (HSE) writes in a recent publication that

semi-batch processes “reduce the quantity of reactant present and controlling the addition rate

may stop the reaction in the event of a hazard arising.”26 At the start of the batch process, when

the reactant concentrations were at their maximum levels, the influence of temperature on the

rate of heat generation was greatest, and there was the most danger of exceeding the heat

removal capacity of the kettles.

Paterson’s research did not specifically test for the exothermic reactions and their lab-scale

work did not reveal the runaway potential of these reactions. After receiving additional

35

24 CSB-NJ249, Morton Internal Memorandum, R. Pollington to C.B. Bird, et al., “LY 152 Process Review,”

April 8, 1989.

25 Center for Chemical Process Safety. Inherently Safer Chemical Processes, A Life Cycle Approach; American

Institute of Chemical Engineers: New York, 1996, 44.

26 Health and Safety Executive. “Designing and Operating Safe Chemical Reaction Processes,” HSE Books:

Norwich, U.K., 2000, 16–17.
documentation from Hounslow alerting them to the possibility of a runaway exothermic

reaction, including the process review memo noted above, Paterson researchers performed

further experiments and determined that they could adjust the temperatures of the reaction to

“reduce the potential for overheating the mixture.”

Morton also conducted research at its Ringwood, Illinois, semiworks facility, producing six trial

batches of material, in sizes of 80 to 425 gallons. In these pilot-scale batches, Morton was able

to control the exothermic reaction within operating limits.

Paterson staff used a “Premanufacturing Process Review Checklist” as a guide for bringing

Yellow 96 to full-scale production in 1990. The Yellow 96 checklist contained an information

package (process transmittal) received from the Ringwood semiworks facility. The information

included batch sheets from the Ringwood batches, material safety data sheets (MSDSs) for the

materials used in the process, and several memos and notes relating to the process. The memos

noted the presence of an exothermic reaction but stated that the process could be controlled by

correctly following the operating steps.

Morton did not conduct a preliminary hazard assessment when they brought Yellow 96 to

production in 1990. Preliminary hazard assessment and Process Hazard Analysis techniques

were in use throughout the chemical process industries at this time and had been gathered and

published by the Center for Chemical Process Safety in 1989, 3 years before OSHA’s

promulgation of the Process Safety Management rule.27,28

The observations by the Morton researchers of the several laboratory and pilot-scale batches

performed in the United States were the determining factor in Paterson’s analysis of the safety

of the process. To design a safe reaction process, certain basic information is required. The

36

27 Center for Chemical Process Safety. Guidelines for Hazard Evaluation Procedures, American Institute of

Chemical Engineers: New York, 1985.

28 Center for Chemical Process Safety. Guidelines for Technical Management of Chemical Process Safety,

American Institute of Chemical Engineers: New York, 1989.
empirical ability to control the process in laboratory and pilot plant should have been

augmented by additional key engineering work, such as:

● Conducting additional calorimetric testing when the process was changed from staged

addition of o-NCB to staged heating of the entire reaction mass.

● Calculating a heat and mass balance to determine if there was sufficient heat removal

capability in the reactors to handle foreseeable events and to determine the influence of

reactor vessel size on this function.

● Determining the worst case venting scenario and sizing the reactor’s safety relief devices

accordingly. The pressure relief devices on the Paterson reactors had been sized for the

scenario of an external fire that would boil xylene in the kettle. Morton did not run

calculations to determine if the relief devices could safely vent the pressure generated by a

runaway exothermic reaction or if the reaction vessels were strong enough to safely contain

the maximum expected pressure.

37
5.0 ANALYSIS OF PROCESS SAFETY MANAGEMENT

PROGRAM

Morton’s Process Safety Management (PSM) program did not require adherence to a number of

industry good practice guidelines for the safe management of reactive chemical processes.

Morton also did not effectively implement important requirements of their internal PSM

program. Deviations in the following areas were important factors leading to the accident:

● Process Safety Information

● Process Hazard Analysis

● Investigation of Problems with Previous Batches

● Management of Change

● Operating Procedures and Training

5.1 PROCESS SAFETY INFORMATION

Paterson facility personnel were not aware of the existence of the decomposition reaction. The

Process Safety Information (PSI) package, which was used by the Paterson personnel to design

the Yellow 96 production process in 1990 and which served as the basis for a Process Hazard

Analysis (PHA) conducted in 1995, noted the desired exothermic synthesis reaction, but did not

include information on the undesired exothermic decomposition reaction.

The Yellow 96 process safety information package did not contain details of the research on the

exothermic reactions performed at Hounslow nor did it contain the recommendations made by

Hounslow for process safety, control, and additional testing in the “LY 152 Process Review”

memo, which had been faxed to Paterson on April 28, 1989. Inclusion of this information in the

process safety information package was a requirement of Morton’s PSM program.

38
Morton’s Material Safety Data Sheet (MSDS) for Yellow 96 Dye stated that the National Fire

Protection Association (NFPA) Reactivity Hazard Rating29 for this material was a 0 (on a 0 to 4

scale, with 4 being the most reactive). The U.S. Chemical Safety and Hazard Investigation

Board (CSB) has determined that the proper reactivity rating for Yellow 96 Dye is 1.30,31 The

reactivity rating is a ranking of the “degree of susceptibility of materials to energy release.

Some materials are capable of rapid release of energy by themselves, through self-reaction or

polymerization, or can undergo violent explosive reaction through contact with water or other

extinguishing agents or with certain other materials.”32 The NFPA defines 0 materials as

“materials that in themselves are normally stable, even under fire conditions,” while 1 materials

are “normally stable, but ... can become unstable at elevated temperatures and pressures.”33 The

NFPA ratings are used by emergency responders, employees, and customers, as an indicator for

the degree of hazard associated with a chemical. Erroneous information regarding reactive

hazards can result in errors in handling or responding to emergencies. In this incident, the

difference did not affect the emergency response activities.

The Yellow 96 Dye MSDS also stated that the compound’s boiling point was 100°C. The CSB

determined that the boiling point is actually much higher, approximately, 330°C, which is

greater than the decomposition onset temperature of 195°C. While not contributing to causing

the incident, the foregoing MSDS discrepancies are examples of shortcomings in Morton’s

Process Safety Information package.

39

29 NFPA704, “Standard System for the Identification of the Hazards of Materials for Emergency Response,” 1996

edition, pages 704–707. The NFPA hazard rating system is intended to provide basic information for fire fighters

and emergency responders. In addition to reactivity, the NFPA system rates fire and health hazards on the same 0

to 4 scale.

30 Chilworth Technology, Inc., to U.S. Chemical Safety and Hazard Investigation Board, Report No.

R/2785/0600/BC, “Instantaneous Power Density via Differential Scanning Calorimetry,” June 26, 2000.

31 Based on determination of the Instantaneous Power Density (IPD) of Yellow 96 per the method of NFPA 704,

1996 edition.

32 NFPA704, “Standard System for the Identification of the Hazards of Materials for Emergency Response,” 1996

edition, pages 704–707.

33 Ibid., pages 704–708. 
5.2 PROCESS HAZARD ANALYSIS

Process hazard analysis (PHA) is a structured, in-depth examination of a chemical plant

process. The objectives of a PHA are to:

● identify the factors in the process that have the potential to cause undesired events (process

hazards); 

● uncover the foreseeable sequences of events (scenarios) that could lead to the realization of

these hazards; 

● evaluate the consequences of these scenarios should they occur; 

● propose improvements, as warranted, to equipment and procedures that either reduce or

eliminate the hazards, prevent the scenarios from occurring or mitigate their consequences. 

The PHA conducted for the Yellow 96 process did not address the consequences of potential

deviations such as excessive heating, a runaway reaction, or the inability to provide enough

cooling to maintain temperatures in a safe operating range. 

The formal PHA for Yellow 96 was conducted in January 1995, approximately 4 years after the

first batch was produced at Paterson. The PHA was performed using the “What If?” method of

analysis. The PHA team analyzed the raw material storage tanks; the weigh tanks; the kettle

vessel/agitation/instrumentation; the kettle condensers, receivers, piping, valves, and pumps; the

elevator and pallet jack; the water scrubber; the dye coupling tanks; and the various site support

systems. The PHA did not specifically address the processing of Yellow 96 in K-7 but generally

covered all of the reactor kettles, both 1000- and 2000-gallon capacity.

As noted earlier, the Paterson Plant received a number of memos from the Ringwood facility

that indicated the potential for a thermal runaway in the Yellow 96 process. Ringwood stated,

“If the batch [ortho-nitrochlorobenzene (o-NCB) charge to the kettle] is left to warm, then it

40
will exotherm strongly upon the addition of the 2-ethylhexylamine.”34 In another memo,

referring to the first 100-gallon, pilot-scale batch, Ringwood noted, “The concern about

exothermic conditions as expressed by... [the Morton Hounslow facility] had been seen

previously during the initial R&D [research and development] work. This can easily be handled

by starting the reaction at ambient temperature and proceed with staged heat-up with holds at

predetermined temperature ranges.”35

When the question, “What if runaway reaction occurs?” was asked, the PHA team recorded the

hazard and consequences as “Not Applicable.” The PHA team relied on the information from

the Ringwood pilot plant and the success of the pilot batches and the apparent success of the

Paterson batches to reach this conclusion. As noted earlier, PHA team members stated that they

were not aware of the work done in Hounslow to characterize the exothermic reactions although

this work had been sent to Paterson in 1989. The PHA team did not take into consideration the

potential for a runaway reaction, although the potential was evident in the product development

information. 

An effective PHA program requires examination of deviations from normal operations that

could turn an exothermic reaction into a runaway situation. The PHA team should have

considered such deviations as: “What if the o-NCB is warmer than specified prior to 2-EHA

addition?” and “What if the predetermined temperature ranges of the staged heat-up process

cannot be met due to equipment or instrumentation malfunction?” The PHA addressed the

question of the failure of the heating system, but it did not ask the question, “What if there is

inadequate cooling?”

The PHA team did not consider the potential ramifications of the high temperature excursions

in batches 3, 5, 14, and 15 (see Section 5.3 – Investigation of Problems with Previous Batches).

Investigation of these occurrences would have provided an opportunity to correct design

problems, which likely would have prevented the incident.

41

34 CSB-NJ250, CSBINSP002395, Morton Internal Document, Automate Yellow 96, Process Suggestions.

35 CSB-NJ250, CSBINSP002414, Morton Internal Memorandum, M. Friswell to J.J. Fuerholzer, May 18, 1989.
As a result of not recognizing the potential for a runaway reaction, the PHA team did not

consider the need for additional safeguards, such as the ones Hounslow recommended in the

1989 process review memo. These recommendations included: temperature alarm, agitator

failure alarm, level alarm, pressure alarm, and emergency cooling water addition directly into

the reactor.36

The late Frank P. Lees, an internationally recognized process safety expert, stated, with regard

to emergency safety measures:

There are a number of emergency measures that can be taken if a process

deviation occurs which threatens to lead to a runaway reaction. The prime

measures are:

(1) inhibition of reaction;

(2) quenching of reaction;

(3) dumping.

The reaction may be stopped by the addition of an inhibitor, or short stop. This

involves the use of an inhibitor specific to the reaction in question....

Quenching involves adding a quenching agent, usually water under gravity, to

the reaction mass to cool and dilute it....

The third method is dumping, which involves dropping the reactor charge under

gravity into a quench vessel beneath which contains a quench liquid.

Other methods, which can be used to slow the reaction but are not generally

ranked as prime emergency safety measures, include:

(1) shut-off of feed;

(2) direct removal of heat;

(3) indirect removal of heat;

(a) full normal cooling;

(b) emergency cooling.37

The Hounslow recommendations of 1989 did suggest controlled quenching of the reaction with

water as an emergency safety measure. The Lees publication does not list the measures actually

used at Paterson (direct removal of heat and full normal cooling) as prime emergency safety

42

36 CSB-NJ249, Morton Internal Memorandum, R. Pollington to C.B. Bird, et al., “LY 152 Process Review,”

April 8, 1989.

37 Lees, Frank P. Loss Prevention in the Process Industries; Hazard Identification, Assessment and Control,

Volume 1, 2nd Edition, Butterworth-Heinemann: Oxford, 1996, 11/59–60.
measures. Quenching with water may not have been appropriate given the fact that the process

was being run above the boiling point of water (condenser and relief vents would have had to be

sized to safely handle the water vapor generated as the heat of reaction was removed from the

kettle); however, this is another example of a possible safety improvement that should have

been considered during the process design effort.

The PHA team also did not question whether the relief device sizing was adequate. Effective

PSM programs require that PHA teams consider scenarios that might require pressure relief,

such as runaway reactions, loss of cooling, loss of agitation, or errors in the addition of

reactants. The necessary venting area is then determined through laboratory testing and

calculations. Venting scenarios such as these were not discussed during the Yellow 96 PHA.

Instead, the PHA participants relied on the information they had received from the Ringwood

pilot plant that a runaway situation was not expected. As a result, the kettle’s venting systems

were not designed to handle the pressure generation rate of the runaway reaction but had

instead been sized for a scenario of an external fire that would boil xylene in the kettle.

After the incident, Morton calculated that a vent area of 116 square inches would have been

required to properly vent the two-phase flow mixture that resulted from the decomposition

reaction.38 On K-7, the 6-inch rupture disk had a venting area of only 28.3 square inches.

5.3 INVESTIGATION OF PROBLEMS WITH PREVIOUS BATCHES

A number of previous batches of Yellow 96 had exhibited unexpected exothermic activity as

shown by high temperature excursions beyond the normal operating range. These batches

exhibited unusual temperature profiles or exceeded the maximum operating temperatures. In

43

38 Morton calculated the required vent area using the DIERS methodology. DIERS (Design Institute of Emergency

Relief Systems) is a consortium of companies, formed in 1976 by the American Institute of Chemical Engineers, to

develop methods for the design of emergency relief systems to handle runaway reactions. The DIERS group has

developed computer programs and a bench-scale test apparatus for assessing the venting requirements of runaway

reactions and two-phase flow.
each of these incidents, the operators were able to regain control of the batch temperature and

complete the batch. Management did not investigate these warning events in the processing

history of Yellow 96 and did not consider these previous incidents during the PHA. 

Significant prior incidents involving 1000-gallon reactor vessels included the following:

● Batch 3 (1991):39 The operators noted on the batch sheet “cooling not controlling temp.”

The operators recorded a temperature of 134°C during the step for heating the batch from

90 to 110°C.

● Batch 5 (November 1991): The operators noted “Temp override to 120 ... cooling

inadequate to control temp” during a specified temperature hold at 108 to 110°C.

● Batches 14, 15, and 18 (July and September 1994, and September 1995): The temperature

recording charts for these batches indicate that the temperature rose quickly and remained

off-scale (greater than 150°C) for approximately 30 minutes for batches 14 and 15 and 75

minutes for batch 18.

Starting with batch 25 in 1996, Morton began producing Yellow 96 in 2000-gallon reactor

vessels. Significant occurrences following this change included:

● Batch 28 (April 1997): The operators noted on the batch sheet “cooling water of no use,”

when trying to maintain the batch temperature at 110°C. The batch sheets indicate that

batch temperature rose much more quickly than expected. 

● Batch 30 (October 1997): The temperature of this batch rose quickly and remained off the

temperature recording chart (maximum temperature of 150°C) for approximately 30

minutes.

44

39 Two Morton batch sheets were labeled as batch 3. The batch in question was labeled CSBINSP003200-3213 in

the data received from Morton.
● Batch 31 (March 1998): As in batch 30, the reactor temperature rose quickly and remained

off the chart for approximately 45 minutes. Based on operators’ comments during

interviews, the temperature of this batch reached 180–200°C.

The operators’ written notes in the batch sheets, detailed above, should have served as

notification to management of the temperature control problems and prompted the supervisors

to investigate these problems. However, the operators did not always record high temperatures

on the batch sheets and they did not verbally inform supervisors of the temperature excursions

when they were able to regain control of a batch. One operator reported in an interview that he

had brought these issues to the attention of his supervisor, but no supervisors recalled this

contact. Several supervisors were aware that high temperatures had occurred in the past.

However, supervisors stated in interviews that high temperatures were considered a quality

concern, not a safety issue. The batch sheets for Yellow 96 mirrored this quality concern,

stating, “DO NOT heat batch above 160°C or yield and quality will be lower.”

5.4 MANAGEMENT OF CHANGE

Beginning with batch 25, in 1996, Paterson began producing Yellow 96 in 2000-gallon kettles

versus the 1000-gallon kettles that had been used for the first 24 batches. At that time, Paterson

also scaled-up the Yellow 96 batch size by approximately 9 percent. The CSB determined that

the combination of these two changes resulted in a reduction of approximately 10 percent in

available heat transfer area per gallon of material. Therefore, the batches produced in the 2000-

gallon kettles had less cooling per gallon of reacting material than batches made in the 1000-

gallon kettles. Given the fact that the reaction was being run at temperatures very close to the

runaway conditions, it was less likely that the operators would be able to control the process in

the larger kettles.

Paterson did not use its management of change procedures to review the safety of these changes

even though they met the definition of a change in Paterson’s PSM program. The batch sheets

45
were never modified to reflect the use of 2000-gallon kettles. The batch sheet in use at the time

of the April 1998, incident was last revised in August 1996. It specified the use of a 1000-gallon

kettle. The scaled up volumes of o-NCB and 2-EHA were indicated on the batch sheets by

crossing-out the old volumes and writing in the increased amounts.

5.5 OPERATING PROCEDURES AND TRAINING

The Yellow 96 batch sheet contained little direction for the operators on how to manage the

exothermic reaction between o-NCB and 2-EHA. As a result, each operator ran the Yellow 96

process slightly differently. This lack of direction had safety consequences, as discussed in the

examples below.

● The batch sheet stated, after adding o-NCB to the kettle, to “Adjust temperature of kettle to

40–42°C with mixing.” With an onset temperature of 38°C, higher temperatures could lead

to early initiation of the reaction and make it less likely that the operators could control the

reaction.

● The batch sheet stated, after adding the 2-EHA, to “Make sure cooling water is on the

condenser then carefully heat batch to 90°C. Note: DO NOT overheat or batch will start to

exotherm.” The next step was to “[c]arefully give batch small shots of steam to raise the

temperature 2–3°C if necessary. Watch batch temperature carefully as batch will exotherm

from 90°C–110°C over 10 minutes.” There were no instructions on how much steam to use

or how long to apply steam. Consequently, each operator had their own technique and

looked for different temperature milestones to determine when to switch from steam to

cooling water. The operators who ran batch 32 stated that they let steam enter the vessel

jacket to heat up the batch for 5 to 10 minutes with 5 to 10 pounds of steam pressure on the

jacket. They did not apply cooling water until the batch reached a temperature of 100 to

110°C. This was contrary to the experience of other operators and supervisors who stated

46
that the amount of steam admitted into the jacket should be minimal, lasting 1 to 5 minutes,

and cooling water should be applied when the batch temperature reached 70 to 80°C. 

● A note following the final reaction step stated, “DO NOT heat batch above 160°C or yield

and quality will be lower.” Operators and supervisors stated during interviews that they had

not been trained regarding the risk of a runaway exothermic reaction in the Yellow 96

process. They believed that temperatures higher than the maximum temperature of 160°C

would result only in quality problems with the finished product. In addition, the temperature

chart could not record temperatures above 150°C, limiting Morton’s ability to document the

temperature profile of a batch and identify abnormal temperature deviations. 

The additional steam used in batch 32 raised the reaction rate of the Yellow 96 synthesis

reaction to a point at which it was generating heat faster than it could be removed by cooling

water. The immediate cause of the incident highlights the dangerous circumstances under which

the operators were instructed to run the Yellow 96 process:

● The batch sheet provided incomplete information on how much heating the batch required.

New operators were trained on-the-job by working with an experienced operator, but

batches of Yellow 96 were made infrequently, and so on-the-job training was infrequent.

Each operator used their own experience as their guide. 

● There was no instrumentation that operators could use to measure the amount of steam

being used or cooling water temperatures to ensure consistency of batch temperatures from

batch to batch.

● While the operators and supervisors knew the batch was sensitive to heat, they were

unaware of the possible outcomes of a runaway reaction.

Plant operating procedures (batch sheets) did not address the handling of emergency situations

in the kettles. Operators were not sufficiently trained to understand fully, or to react

appropriately, to the runaway reaction. Other than the instruction to ensure that the cooling

water was on, the operators were given no other direction for emergency situations. They were

47
not trained to recognize the hazards associated with the Yellow 96 process and consequently did

not recognize when they should have evacuated the building. Operators were instructed to

obtain help from supervision when unusual events occurred.

On the evening of the incident, the supervisor, the two principle operators, and two other

chemical operators stayed by the runaway kettle while: (1) the rapidly rising batch temperature

exceeded the operating procedure limit of 160°C, (2) the residual 2-EHA started boiling and the

reaction generated additional gases, (3) the violently boiling mixture flooded the condenser,

(4) the kettle rupture disks actuated because of the vessel’s pressurization, (5) the kettle began

rumbling and shaking, and (6) the kettle temperature exceeded the decomposition onset

temperature range for Yellow 96 of 195°C. After the operators established that heating was off,

full cooling was on and the temperature of the batch continued to rise, their presence could not

contribute anything to preventing an incident such as the one that occurred.

48
6.0 REGULATORY OVERSIGHT ANALYSIS

The Occupational Safety and Health Administration’s (OSHA) Process Safety Management

(PSM) standard (29 CFR 1910.119) provides only minimum requirements for process safety

management and provides little guidance with respect to reactive chemical process safety

management. The lack of guidance did not contribute directly to causing the incident. However,

additional guidelines in such areas as reporting and investigating deviations from normal

operations, the use of chemical screening techniques, and proper design for pressure relief,

emergency cooling, and safety interlock systems would likely have helped the Morton Paterson

staff to recognize the hazards of the Yellow 96 process and take steps to avoid the incident.

6.1 REGULATORY COVERAGE

The OSHA PSM standard did not cover the Yellow 96 process. However, Morton included the

process under its internal PSM program, which was applied to OSHA-regulated processes and

certain other processes. In most respects, Morton patterned its program after the OSHA

standard; however, there were significant omissions and differences. Also, the Morton program

did not require adherence to a number of industry good practices for the safe management of

reactive chemical processes. 

OSHA only refers to reactivity hazards as two of the information requirements in the PSM

standard’s Process Safety Information element subheading, “Information pertaining to the

hazards of the highly hazardous chemicals in the process,” 1910.119(d)(1): “(iv) Reactivity data

[and] (vi) Thermal and chemical stability data.” In addition, the Non-Mandatory Appendix to

the standard states,

“The information to be compiled about the chemicals, including process

intermediates, needs to be comprehensive enough for an accurate assessment of

the fire and explosion characteristics, reactivity hazards, the safety and health

hazards to workers, and the corrosion and erosion effects on the process

equipment and monitoring tools. Current material safety data sheet (MSDS)

49
information can be used to help meet this requirement which must be

supplemented with process chemistry information including runaway reaction

and over pressure hazards if applicable.”

The OSHA PSM standard covers certain reactive chemicals ranked as 3 and 4 under the

National Fire Protection Association’s (NFPA) 0 to 4 reactivity ranking system.40 Reactive

chemicals are not covered under the Environmental Protection Agency’s (EPA) Risk

Management Plan rule. Some reactive chemicals are listed by the EPA because they qualify for

inclusion due to their toxic or flammable properties. The raw materials and the Yellow 96 Dye

were all assigned a 0 reactivity rating on their respective material safety data sheets. However,

as was the case with the Yellow 96 process, many chemicals with low reactivity rankings can be

very reactive in combination with other chemicals or at temperatures that are reached only as a

result of deviations from normal operating conditions.

In 1995, OSHA received a petition41 to promulgate an Emergency Temporary Standard (ETS) as

the result of an incident at Napp Technologies, Inc., in Lodi, New Jersey, on April 21, 1995, that

killed five people. The petition stated that the PSM standard “fails to comprehensively cover

reactive chemicals” and requested that OSHA reopen the standard. As of August 2000, OSHA

has not acted on this petition.

50

40 In NFPA 704, the NFPA defines “3s” as “materials that in themselves are capable of detonation or explosive

reaction, but that require a strong initiating source or that must be heated under confinement before initiation.”

“4s” are defined as “materials that in themselves are capable of detonation or explosive reaction at normal

temperatures and pressures.” 41 Eric Frumin, et al., to Mr. Joe Dear, Asst. Secretary for Occupational Safety and Health, “Petition for

Emergency Revision of Standards on Process Safety Management and Emergency Response,” October 23, 1995.

The petitioners were Union of Needletrades, Industrial and Textile Employees; United Steelworkers of America;

Oil, Chemical and Atomic Workers; AFL-CIO; International Association of Fire Fighters and International

Chemical Workers Union.
6.2 MORTON PSM PROGRAM

Morton’s written Process Safety Management program did not include a number of OSHA

PSM requirements. The U.S. Chemical Safety and Hazard Investigation Board (CSB) also

identified areas in which Morton did not implement their PSM program.

Examples of inadequacies in Paterson’s PSM program included the following:

● Under the requirements for what the Process Hazard Analysis (PHA) shall address, the

Morton program did not include the OSHA requirement for “The identification of any

previous incident which had a likely potential for catastrophic consequences in the

workplace.” As stated earlier, investigation of these occurrences would have provided an

opportunity to correct design problems, which likely would have prevented the incident.

● Under OSHA PSM requirements, an operating procedure is required for Emergency

Shutdown. Morton’s program simply lists “Emergency Shutdown” in a list of required

procedures and omitted OSHA’s requirements that the procedures should state the

conditions under which shutdown is required and the operator’s responsibilities. Inclusion of

this information in operating procedures and training likely would have led the operators to

evacuate sooner, thus preventing their injuries.

Examples of inadequacies in Paterson’s implementation of its PSM program included the

following:

● Morton’s program required that the process safety information package should contain

“Copies of any laboratory, pilot plant, or other testing work (including that performed

outside the company) which pertains to the hazards posed by the chemicals used in the

process.” There were a number of memos and notes that touched on the exothermic nature

of the Yellow 96 process, but the testing results and memos that explicitly discussed the

runaway potential were not provided to the PHA team or used to inform operations

personnel. Using this information in process reviews and in training would have made

personnel more aware of the hazards of the process.

51
● Morton’s program required information on chemical reactions and equations for primary

and important secondary, or side reactions addressing all chemicals associated with the

process, including discharge and by-products. Also required, if available, were kinetics data

for important process reactions, including order, rate constants vs. time, approach to

equilibrium, and kinetics data for undesirable reactions, such as decompositions and

autopolymerizations. This information was not compiled for the Yellow 96 process although

the information had been developed and was available.

● The change from the 1000-gallon to the 2000-gallon kettle was not approved through a

Management of Change process, although the change met Morton’s definition of a change.

A change of this magnitude should also have been reviewed in a PHA per Morton’s

procedure. Again, Morton missed an opportunity to assess the hazards of the process and

take steps to avoid an incident.

6.3 GOOD PRACTICE GUIDELINES

Good practice guidelines, such as the Center for Chemical Process Safety publications,42,43 were

available prior to the startup of Yellow 96 production in 1990. Other guidelines (see References)

became available prior to the Yellow 96 Process Hazard Review in 1995. Use of these

guidelines would have provided the Morton Paterson staff with information on the means to

identify the potential reactive hazards and would likely have led them to take steps to prevent

the incident.

Additional guidelines are now available from the Center for Chemical Process Safety’s books

on reactive chemicals (see References), Lees’s Loss Prevention in the Process Industries44 and

52

42 Center for Chemical Process Safety. Guidelines for Hazard Evaluation Procedures, American Institute of

Chemical Engineers: New York, 1985.

43 Center for Chemical Process Safety. Guidelines for Technical Management of Chemical Process Safety,

American Institute of Chemical Engineers: New York, 1989.

44 Lees, Frank P. Loss Prevention in the Process Industries; Hazard Identification, Assessment and Control, 2nd

Edition, Butterworth-Heinemann: Oxford, 1996.
the U.K. Health and Safety Executive’s booklet, “Designing and Operating Safe Chemical

Reaction Processes.”45 The U.K. guidelines, published in May 2000, are a consensus product of

government, industry, and labor. Use of these types of guidance documents by Morton staff

could have provided them with sufficient information and awareness of the reactive hazards that

likely would have helped them to take actions to prevent the incident. 

Government-issued safety guidelines on other topics, such as those issued by OSHA and EPA,

have been used extensively by industry. For example, the EPA’s Off-Site Consequence Analysis

Guidance is used by industry in complying with the EPA’s Risk Management Plan requirements.

6.4 RECENT CATASTROPHIC REACTIVE CHEMICAL INCIDENTS

The Chemical Safety Board, and safety professionals in general, currently face limitations in

their ability to obtain information on reactive chemical incidents. Detailed analysis of root

causes is only available for several major incidents in recent years. Expanded information on

the root causes of incidents would provide data on trends in reactive chemical process safety

management and on the effects of federal and state regulations and consensus standards on the

frequency and severity of reactive chemical incidents. 

Napp Technologies Incident46

The 1995 Napp explosion and fire in Lodi, New Jersey resulted in five deaths as well as injuries,

public evacuations, and serious damage both on and off the site. A joint EPA/OSHA team

investigated this event. At the time of the incident, Napp was conducting a mixing operation

involving water-reactive chemicals. The operation, which should have been completed in less

53

45 Health and Safety Executive. “Designing and Operating Safe Chemical Reaction Processes,” HSE Books:

Norwich U.K., 2000.

46 EPA/OSHA Joint Chemical Accident Investigation Report, Napp Technologies, Inc., Lodi, New Jersey, EPA

550-R-97-002, October 1997.
than 1 hour, continued for nearly 24 hours. Operators noticed an unexpected reaction taking

place in the blender, producing heat and the release of a foul-smelling gas. During an emergency

operation to remove the contents of the blender, the material ignited and a deflagration occurred

that resulted in the deaths of the employees and the destruction of the facility.

According to the EPA/OSHA report, the most likely cause of the incident was the inadvertent

introduction of water into water-reactive materials (aluminum powder and sodium hydrosulfite)

during the mixing operation. The water caused the sodium hydrosulfite in the blender to

decompose, generating heat, sulfur dioxide, and additional water. The decomposition process,

once started, was self-sustaining. The reaction generated sufficient heat to cause the aluminum

powder to react rapidly with the other ingredients and generate more heat, until the point of

deflagration was reached. As in the Morton case, the chemicals and chemical reactions involved

in the Napp incident were not covered under the OSHA PSM standard.

Georgia-Pacific Resins Incident47

In 1997, an explosion at a resins production unit at Georgia-Pacific Resins, Inc. in Columbus,

Ohio, killed one worker and injured four others. This explosion was caused by a runaway

reaction. As detailed in an EPA Chemical Safety Case Study on this event, “the runaway was

triggered when, contrary to standard operating procedures, all the raw materials and catalyst

were charged to the reactor at once followed by the addition of heat. Under the runaway

conditions, the heat generated exceeded the cooling capacity of the system and the pressure

generated could not be vented through the emergency relief system causing the reactor to

explode.”

The PHA conducted for the Georgia-Pacific process did not consider the failure to control the

rate of chemical addition to the process. In addition, the pressure relief system was not sized to

handle the pressure rise from such an event.48

54

47 U.S. Environmental Protection Agency. “How to Prevent Runaway Reactions, Case Study: PhenolFormaldehyde Reaction Hazards,” EPA 550-F99-004, August 1999.

48 Belke, James C. “Recurring Causes of Recent Chemical Accidents,” proceedings of the International Conference

and Workshop on Reliability and Risk Management, September 15–18, 1998, page 463.
Napp, Morton, and Georgia-Pacific were three of the most significant and highly studied

reactive chemical incidents to occur in the United States in recent years but they were not the

only incidents:

● In its Safety Alert on the Georgia-Pacific incident, EPA noted six other phenolformaldehyde reaction incidents that had occurred since 1989.49

● Databases such as the EPA’s Emergency Response Notification System, OSHA’s incident

statistics, and the U.K. Institution of Chemical Engineers’ incident database contain over

30 events in the last decade that were characterized by keywords such as “exothermic

reaction” or “runaway reaction.”

55

49 U.S. Environmental Protection Agency. “How to Prevent Runaway Reactions, Case Study: PhenolFormaldehyde Reaction Hazards,” EPA 550-F99-004, August 1999, page 2. 
56

7.0 ROOT AND CONTRIBUTING CAUSES 

7.1 ROOT CAUSES

1. Neither the preliminary hazard assessment conducted by Morton in Paterson during

the design phase in 1990 nor the process hazard analysis conducted in 1995 addressed

the reactive hazards of the Yellow 96 process.

Not addressing these hazards resulted in the following design, operational, and training

deficiencies:

● The kettle cooling system could not safely control the exothermic Yellow 96 synthesis

reaction. 

● The kettle was not equipped with safety equipment, such as a quench system or a

reactor dump system, to stop the process to avoid a runaway reaction. 

● Rupture disks were too small to safely vent high pressure in the kettle in the event of

either of the two foreseeable runaway reactions.

● Morton converted its Yellow 96 production from a staged, incremental addition (semibatch) process to a staged heating (batch) process without assessing the possible hazards

of this change, e.g., the increased difficulty of controlling heat output.

● Operating procedures did not cover the safety consequences of deviations from normal

operating limits, such as runaway reactions, or specify steps to be taken to avoid or

recover from such deviations.

● Training did not address the possibility of a runaway reaction and how operators should

respond to avoid injury if a runaway reaction could not be controlled.
2. Process safety information provided to plant operations personnel and the process

hazard analysis team did not warn them of the potential for a dangerous runaway

chemical reaction.

Morton internal memoranda had documented that the desired reaction to form Yellow 96

from ortho-nitrochlorobenzene (o-NCB) and 2-ethylhexylamine (2-EHA) was exothermic

and that Yellow 96 would begin to decompose rapidly (runaway) at temperatures close to

the upper operating temperature. Morton researchers also had identified several situations,

such as loss of cooling, that might give rise to temperatures capable of causing violent

decompositions. Although information on the reactive hazards was contained in plant files,

operators and supervisors were unaware that a dangerous decomposition reaction was

possible.

7.2 CONTRIBUTING CAUSES

1. The hazards of previous operational deviations were not evaluated. 

Management did not investigate evidence in numerous completed batch sheets and

temperature charts of high temperature excursions beyond the normal operating range.

Investigation of these incidents likely would have provided an opportunity to uncover the

process’s reactive hazards and correct design and other problems.

2. Morton did not follow their Management of Change procedures to review changes

made in reaction kettle and batch size.

Morton changed the Yellow 96 processing equipment from 1000-gallon to 2000-gallon

kettles and also increased the batch size by 9 percent in 1996. Morton did not follow its

Management of Change procedures and did not review the changes for possible safety

consequences. A Management of Change review likely would have provided another

57
opportunity for Morton to uncover the process’s reactive hazards and correct design

problems. The review likely would have also revealed that the changes made resulted in a

decrease of 10 percent in the heat transfer area per gallon of reactants. Half of the batches

made after this change exhibited temperature excursions versus 20 percent in the batches

made before the change.

58
8.0 RECOMMENDATIONS

Morton International, Inc. (a wholly owned subsidiary of Rohm and Haas Company)

Establish a program that ensures that reactive chemical process safety information and

operating experience are collected and shared with all relevant units of the company

(98-006-I-NJ-R01).

Morton International, Inc.’s Paterson, New Jersey Plant

1. Revalidate Process Hazard Analyses for all reactive chemical processes in light of the

findings of the U.S. Chemical Safety and Hazard Investigation Board (CSB) report and

upgrade, as needed, equipment, operating procedures, and training (98-006-I-NJ-R02).

2. Evaluate pressure relief requirements for all reaction vessels using appropriate technology,

such as the Design Institute for Emergency Relief Systems (DIERS)50 method and test

apparatus and upgrade equipment as needed (98-006-I-NJ-R03).

3. Evaluate the need for and install, as necessary, devices, such as alarms, added safety

instrumentation, and quench or reactor dump systems to safely manage reactive chemical

process hazards (98-006-I-NJ-R04). 

4. Revise operating procedures and training for reactive chemical processes as needed, to

include descriptions of the possible consequences of deviations from normal operational

limits and steps that should be taken to correct these deviations, including emergency

response actions (98-006-I-NJ-R05).

59

50 DIERS is a consortium of companies, formed in 1976 by the American Institute of Chemical Engineers to

develop methods for the design of emergency relief systems to handle runaway reactions. The DIERS group has

developed computer programs and a bench-scale test apparatus for assessing the venting requirements of runaway

reactions and two-phase flow.
5. Implement a program to ensure that deviations from normal operational limits for reactive

chemical processes that could have resulted in significant incidents are documented and

investigated and necessary safety improvements are implemented (98-006-I-NJ-R06).

6. Revise the Yellow 96 Material Safety Data Sheet (MSDS) to show the proper boiling point

and National Fire Protection Association reactivity rating. Evaluate the need for and change,

as necessary, the MSDSs for other Morton dyes. Communicate the MSDS changes to current

and past customers (who may retain inventories of these products) (98-006-I-NJ-R07).

Occupational Safety and Health Administration (OSHA) and 

Environmental Protection Agency (EPA)

1. Issue joint guidelines on good practices for handling reactive chemical process hazards

(98-006-I-NJ-R08). 

Ensure that these guidelines, at a minimum, address the following issues:

● The evaluation of reactive hazards and the consequences of reasonably foreseeable and

worst-case deviations from normal operations.

● The importance of reporting and investigating deviations from normal operations.

● The determination of proper design for pressure relief capability, emergency cooling,

process controls, alarms, and safety interlocks, as well as other good-practice design

features for handling reactive substances.

● The appropriate use of chemical screening techniques such as differential scanning

calorimetry.

2. Participate in a hazard investigation of reactive chemical process safety conducted by the

CSB (98-006-I-NJ-R09). 

60
The objectives of the special investigation will include:

● Determine the frequency and severity of reactive chemical incidents.

● Examine how industry, OSHA, and EPA are currently addressing reactive chemical

hazards. Determine the differences, if any, between large/medium/small companies with

regard to reactive chemical policies, practices, in-house reactivity research, testing, and

process engineering.

● Analyze the effectiveness of industry and OSHA use of the National Fire Protection

Association Reactivity Rating system for process safety management purposes. 

● Develop recommendations for reducing the number and severity of reactive chemical

incidents.

American Chemistry Council; Center for Chemical Process Safety (CCPS); Paper, AlliedIndustrial, Chemical & Energy Workers International Union (PACE); Synthetic Organic

Chemical Manufacturer’s Association (SOCMA)

Communicate the findings of this report to your membership (98-006-I-NJ-R10).

61
BY THE CHEMICAL SAFETY AND HAZARD

INVESTIGATION BOARD

Gerald V. Poje

Member

Andrea Kidd Taylor

Member

Isadore Rosenthal

Member

August 16, 2000

62
63

9.0 REFERENCES

Barton, J. A., and Nolan, P. F. “Incidents in the Chemical Industry Due to Thermal-Runaway

Chemical Reactions, IChemE Symposium Series, No. 115, 1989.

Barton, John and Rogers, Richard. Chemical Reaction Hazards, 2nd edition, Institution of

Chemical Engineers: Rugby, Warwickshire, 1997.

Belke, James C. “Recurring Causes of Recent Chemical Accidents,” proceedings of the

International Conference and Workshop on Reliability and Risk Management, September 15–18,

1998, page 463.

Center for Chemical Process Safety of the American Institute of Chemical Engineers. Guidelines

for Chemical Reactivity Evaluation and Application to Process Design, American Institute of

Chemical Engineers: New York, 1995.

Center for Chemical Process Safety of the American Institute of Chemical Engineers. Guidelines

for Hazard Evaluation Procedures, American Institute of Chemical Engineers: New York, 1985.

Center for Chemical Process Safety of the American Institute of Chemical Engineers. Guidelines

for Process Safety in Batch Reaction Systems, American Institute of Chemical Engineers: New

York, 1999.

Center for Chemical Process Safety of the American Institute of Chemical Engineers. Guidelines

for Safe Storage and Handling of Reactive Materials, American Institute of Chemical Engineers:

New York, 1995.

Center for Chemical Process Safety. Guidelines for Technical Management of Chemical Process

Safety, American Institute of Chemical Engineers: New York, 1989.

Center for Chemical Process Safety of the American Institute of Chemical Engineers. Inherently

Safer Chemical Processes, A Life Cycle Approach, American Institute of Chemical Engineers:

New York, 1996.

EPA/OSHA Joint Chemical Accident Investigation Report, Napp Technologies, Inc., Lodi, New

Jersey, EPA 550-R-97-002, October 1997.

Health and Safety Executive. Chemical Reaction Hazards and the Risk of Thermal Runaway,

http://www.open.gov.uk/hse/pubns/indg254.htm, 1999.

Health and Safety Executive. “Designing and Operating Safe Chemical Reaction Processes,”

HSE Books: Norwich U.K., 2000.

Lees, Frank P. Loss Prevention in the Process Industries; Hazard Identification, Assessment and

Control, 2nd Edition, Butterworth-Heinemann: Oxford, 1996.

U.S. Environmental Protection Agency. “How to Prevent Runaway Reactions, Case Study:

Phenol-Formaldehyde Reaction Hazards,” EPA 550-F99-004, August 1999.
64

APPENDIX A: INCIDENT TIMELINE B-11 evacuation

REVISED – 7/5/2000 

Shift starts at

1600,

April 8, 1998

Second-shift foremanassigns Operators1 & 2 to K-7 inin Building 11 (B-11)and gives themAutomate Yellow 96 Dye batch sheets.

Operators 1 &2 inspect K-7and prepare tostart batch 32of Yellow 96.

Three-man teammakes finalpreparation toload orthonitrochlorobenzene(o-NCB).

Operators 1 &2 secureinspectionmanway hatchon the head ofK-7.

1

Start

Operator 1 held

over from first shift

in the normal

overtime rotation.

The B-11

supervisor and

1st-shift foreman

schedules

production and

work assignments.

K-7 empty and

clean.

Temperature of

empty K-7 is 20 to

30oC (ambient).

for the loading of

o-NCB.

Inspection

manway hatch is

secured with four

C clamps.

Laborer suits up in

protective clothing

with air-purifying

respirator.

Operators 1 & 2

suit up in

protective clothing

with supplied air.

B-11 is evacuated,

except for three

workers.

This is to be the

32nd plant batch of

Automate Yellow 96

Dye.

This is to be the

fourth batch of

Automate Yellow

96 Dye to be

prepared in K-7.

Kettle 7 (K-7) is a

2,000-gallon

chemical reactor.

Note: All times are expressed

as military time

Shift foreman

schedules forklift

operator and
65

REVISED 

–7/5/2000 

On second floor,laborer bringsdrums of o-NCB

from elevator toK-7. (1645)

Operator 1aligns valveson K-7 feedmanifold to dip tube.

K-7 vacuumpulls o-NCB

through diptube and feedmanifold.(1715)

Operators 1 & 2 leave B-11 for airing outperiod. (1730)

K-7 feedmanifold anddip tubeflushed with 5 gallons ofdetergentsolution.(1720)

2 1

A hand-pulled

forktruck is used to

bring the pallet of

drums from elevator

to kettle on second

floor of B-11.

The pallet of drums

is brought to the

second floor of 

B-11 by an elevator

Forklift operator

brings pallet of 

at the west end.

o-NCB drums from

hot-box to B-11

elevator.

K-7 agitator is

turned on.

Transfer of o-NCB

takes about 25

minutes and is

uneventful.

Rapid smooth

transfer indicates

that the o-NCB is

well heated and

liquefied.

A laborer has

prepared a solution

of water and

detergent in 

5-gallon pail.

Pallet of empty drums is

returned to B-11

elevator.

B-11 unoccupied

for mandatory 30

minutes while

"airing out."

Team unsuits.

Temperature after

loading o-NCB was

reported by

operators as from

"about 44" to

almost 70."

Vacuum system is

working. Vacuum

gauge on head of K-7.

No unusual occurrences

noted.

Temperature of

drums is too hot tohandle with gloved

hand.

"60-something
66

Shots of steam are

added by opening

the steam-in valve

for a few minutes.

REVISED 

–7/5/2000 

Operators 1 & 2return to charge2-ethylhexylamine(2-EHA). (1800)

2-EHA flowsinto K-7through feedmanifold fromundergroundstorage tanks.(1830)

Operator 1adds firststeam to K-7jacket. (1940)

Operator 1adds one ortwo more shotsof steam.

Operator 1 fillsK-7 jacket withsteam.

3 2

Other operators and

laborers return to

B-11.

Based on 

experience,

Operator 1 aligns

valves and sets

2-EHA feed 

Digital meter is set for

2-EHA charge and

controls remote pump

at storage tank.

Vent to condenser

above K-7 is open.

Operators estimate

that loading 2-EHA

takes 25 minutes.

At the beginning of

heating, the temperature

of the 2-EHA and o-NCB

mixture is at 44 oC.

 0perators know

that Yellow 96 has

a very difficult

exotherm to

control.

One line in operating

instructions in batch

sheet says only,

"heat carefully to

90oC."

Operators and

supervisors know

that exotherm of

Yellow 96 starts

before 90 oC.

Jacket steam

pressure is 5 to 10

psi on dial gauge.

Lag time between

temperature rise in

kettle and steam

addition is a few

minutes.

There are no

temperature or

flow indicators on

steam supply.

Operators'dinner break.(1900–1935)

Exact time depends 

on operator

experience and

preference.

operators

work from

experience and

develop their own

batch heating

techniques.

Individual 

meter.
67

REVISED 

–7/5/2000 

K-7temperaturerises rapidly to100° to 110°C.

(2000)

Operatorsinitiate coolingwater flow toK-7 jacket.(2005)

K-7 temperaturerises rapidly toover 150°C and

keeps risingrapidly.

K-7 starts tovibrate thesecond-floordecking.

K-7 temperaturerises to over175°C. (2015)

4 3

Operators 1 & 2

estimate about 15

minutes have

passed since

steam addition

began.

Operators' past

experience

indicates that the

exotherm of

Automate Yellow

96 may begin

around 75oC.

The heat of the

reaction of the

2-EHA amine and

the o-NCB is now

rapidly heating

K-7.

Valves are grouped

on opposite sides

of K-7.

Operators hear

water flow and

steam bumping in

K-7 jacket

verifying water is

on.

Operators estimate

that it takes

2 minutes to switch

to cooling water.

Operator 1 and other

operators recheck

cooling water valve

positions and find 

them correct.

The cooling water

line-in or line-out

have no temperature

Operators 1 & 2

or flow indicators.

see shift supervisor

on his rounds and

call to him to come

over.

Three other

operators on the

second floor of B-11

are now aware that

K-7 has a problem

and start over to see.

The shift supervisor

arrives and rechecks

valves.

Other second-floor

operators have

gathered around in the

aisle next to K-7.

The temperature in

K-7 has exceeded the

boiling point of

The experienced

residual 2-EHA.

operators have never

before observed a

significant condensate

return in a Yellow 96

batch.

Cooling water to K-7

confirmed to be fullon. Cooling water

pressure is normal.

Turbulent vapor is in

the K-7 condenserline glass and there is

deluge of yellowish

condensate return in

the glass separator.

Permanent gases are

being generated by

the reaction.
68

REVISED 

–7/5/2000 

Two 6-inchrupture disksin series popin 6-inch linefrom K-7reactor head toB-11 catchtank. (2015)

K-7temperatureclimbs to over200oC.

Remaininggroup ofoperators andshift foremanrun toward B-11 exits bydifferentroutes.

Aerosol plume ofK-7 reactants andproducts blowsthrough the thirdfloor and roof ofB-11 and ignites.

K-7 contents eruptfrom manway,starting flash firesthat catch workerstrying to escapesecond floor, B-11.(2018)

5 4

To this point, the

only pressure relief

for K-7 was the

2.5-inch condenser

vent line through

ball valve to

receiver vented to

catch tank.

The temperature in

K-7 is between

180o and 190oC.

Heat removal by

condensing vapors

in the condenser

and returning reflux

to the kettle cannot

keep up with

reaction heat.

On all other

occasions, the

Yellow 96 batches

had recovered

from these

temperature

excursions.

K-7 rumbling

violently as mix's

boiling rate rapidly

increases.

Last K-7

temperatures

observed were

between 200o and

260oC.

K-3 operator

shouts "get out"

and runs to stairs

toward the west

end of B11.

An experienced

observing operator

reads digital

temperature gauge

at 260oC.

Operator 1 and

shift foreman at

second floor east

end door are blown

down steps to

landing.

Secondary ignition

of aerosol release

blows them off

landing onto

ground.

They suffer

severe thirddegree burns

and require

intensive care.

Witness observes

large fire ball above

roof. Rupture disks are set for 10 psi.

There is a loud roar;

other plant workers

think that a train is

passing the plant.

Manway coveris blown offkettle. (2018)

Mixture in K-7 is

above theYellow

Dye decomposition

exotherm onset

temperature of

175–195 C. o

(2017)
69

REVISED –7/5/2000 

Call to Paterson

Fire Department

(PFD) at 2020.

Battalion 1

arrives on

scene at 2024.

PFD positions ladder pipetruck and begins placing

water on west end of B-11

roof.

Fire undercontrol at 2327.

PFD repositions ladder

pipe truck, increases

pressure, and douses

east end of B11 roof.

End 5

Multiple 911 calls.

Structure fire on the

roof at the east end

of B-11.

Sounds second

alarm for more

equipment. (2044)

Nine injured workers

assemble at the

McLean Blvd. plant

entrance.

Victims are sent by

ambulance to threearea hospitals, two

most serious to St.

Joseph's.

All plant personnel

accounted for.

Uncertain as to

whether chemicals

involved are water

reactive.

Full protective gear

used.

Fire knocked down at

2144, but water flow

maintained to cover entry

teams.

Light vapor fires put out with

wheeled dry chemical unit.

Primary and secondary

building searches are

completed.

HAZMAT and fire teams

suit up for entry.

All firemen decontaminated

before returning. No ill effects.

One fireman punctures

boot and is exposed to

site chemicals.

Investigative teams begin.

Water flow from ladder pipe is

stopped to prevent washing

contaminants into Passaic

River.

Fire units remain in

case of hot spots.

Site secured as a

crime scene by

Paterson police.
70

APPENDIX B: DEVELOPMENT TIMELINE

Revised 7/5/2000 

1996

11/14/91 9/13/94

9/14/95

1991

June/July 1986 10/2/87 4/8/88 4/8/89 4/28/89

5/1/89 5/12/89 6/25/90 8/22/90 9/6/90

7/27/94 January 1995

4/2/97 3/31/98 4/8/98

Batch 5

Process Change to

2000-gal kettles and

increased batch size

—High Temp

occurrence

—1000-gal kettle

"Cooling inadequate

to control temp"

Batch 15

—High Temp

occurrence

 1000-gal kettle

Batch 18

—High Temp

occurrence

Batch 4

 1000-gal kettle

—High Temp

occurrence

—1000-gal kettle

"Cooling not

controlling temp"

Initial Lab

Experiments at

Hounslow, UK

Differential Scanning

Calorimetry testing in

UK identified

decomposition

exotherm

Memo, "Thermal

Stability of Liquid

Yellow 152,"

Discussion of thermal

stability work at

Brunel University

Handwritten Memo

—

"LY 152 Process

Review"

recommending

additional testing and

safety instrumentation

"LY 152 Process

Review" transmitted to

Paterson/Ringwood

Development of stepwise heating process

to minimize exposure to

ortho-nitrochlorobenzene

First Ringwood Batch

—100 gallons

Ringwood Batch 90-

9495

Operator's Note: "This

batch wants to run,

112-133C"

Ringwood Semiworks

Process Transmittal

sent to Paterson

First Paterson batch

Batch 14

—High Temp

occurrence

 1000-gal kettle

PROCESS

HAZARD

ANALYSIS

Batch 28

—High Temp

occurrence

 2000-gal kettle

Batch 31

—High Temp

occurrence

 2000-gal kettle

Batch 32—Explosion

and Fire

K-7—2000-gal kettle
71

APPENDIX C: ROOT CAUSE ANALYSIS DIAGRAM Injuries and Physical Damage Gas pressure exceeds strength of manway clamps Employees present at kettle side Employees attempt to salvage product Employees unaware of hazards Inadequate hazard assessments

—fails

to identify hazards

Inadequate mgmt.

of change

—fails to

identify hazards

Employees had

saved previous

batches

Majority of batches

had been smaller

—

better heat transfer

(1000 vs 2000 gal)

Timing of steam/

cooling water had

been favorable

Venting capacity

insufficient to

relieve pressure Runaway reaction generates

permanent gases

and boiling of 

2-EHA

Cooling

water system

unable to control

heat of reaction

Reaction heatup

rate too fast

Steam added at

too high a rate

Switchover to

cooling water too

late

Operating

procedures/training

inadequate

Operating

procedures/training

inadequate

Inadequate design

—no heat/mat'l

balance

Not required by

Morton PSM

program

Desigers did not

identify proper

worst-case venting

scenario

PHA team did not

identify proper

worst-case venting

scenario

Inadequate

guidance on

hazard

assessments

Inadequate

implementation of

plant programs

REVISED - 7/8/2000

Inadequate

transfer of

research

information

Inadequate

transfer of

research

information

Inadequate

guidance on

design

Inadequate

guidance on

hazard

assessments
72

APPENDIX D: MATERIAL SAFETY DATA SHEETS
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92