Category: Current Events
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Initial reports are that it was at a terminal facility: Here a news story …
When is a safety incident a crime? Would making it a corporate crime improve corporate and management behavior?July 29th, 2015 by Mark Paradies
I think we all agree that a fatality is a very unfortunate event. But it may not be a criminal act.
When one asks after an accident if a crime has been committed, the answer depends on the country where the accident occurred. A crime in China may not be a crime in the UK. A crime in the UK may not be a crime in the USA. And a crime in the USA may not be a crime in China.
Even experts may disagree on what constitutes a crime. For example, University of Maryland Law Professor Rena Steinzor wrote an article on her blog titled: “Kill a Worker? You’re Not a Criminal. Steal a Worker’s Pay? You Are One.” Her belief is that Du Pont and Du Pont’s managers should have faced criminal prosecution after an accident at their LaPorte, Texas, facility. She cited behavior by Du Pont’s management as “extraordinarily reckless.”
OSHA Chief David Michaels disagrees with Professor Steinzor. He is quoted in a different article as saying during a press conference that Professor Steinzor’s conclusions and article are, “… simply wrong.”
The debate should raise a significant question: Is making an accident – especially a fatal accident – a corporate crime a good way to change corporate/management behavior and improve worker safety?
Having worked for Du Pont back in the late 1980’s, I know that management was very concerned about safety. They really took safety to heart. I don’t know if that attitude changed as Du Pont transformed itself to increase return on equity … Perhaps they lost their way. But would making poor management decisions a crime make Du Pont a safer place to work?
Making accidents a crime would definitely making performing an accident investigation more difficult. Would employees and managers cooperate with ANY investigation (internal, OSHA, or criminal) IF the outcome could be a jail sentence? I can picture every interviewee consulting with their attorney prior to answering an investigator’s question.
I believe the lack of cooperation would make finding and fixing root causes much more difficult. And finding and fixing the root causes of accidents is extremely important when trying to improve safety. Thus, I believe increased criminalization of accidents would actually work against improving safety.
I believe that Du Pont will take action to turn around safety performance after a series of serious and sometimes fatal accidents. I think they will do this out of concern for their employees. I don’t think the potential for managers going to jail would improve the odds that this improvement will occur.
What do you think? Do you agree or disagree. Or better yet, do you have evidence of criminal proceedings improving or hindering safety improvement?
Let me know by leaving a comment below.
I overheard a senior executive talking about the problems his company was facing:
- Prices for their commodity were down, yet costs for production were up.
- Cost overruns and schedule slippages were too common.
- HSE performance was stagnant despite improvement goals.
- They had several recent quality issues that had caused customer complaints.
- They were cutting “unnecessary” spending like training and travel to make up for revenue shortfalls.
I thought to myself …
“How many times have I heard this story?”
I felt like interrupting him and explaining how he could stop at least some of his PAIN.
I can’t do anything about low commodity prices. The price of oil, copper, gold, coal, or iron ore is beyond my control. And he can’t control these either.
But he was doing things that were making his problems (pain) worse.
For example, if you want to stop cost overruns, you need to analyze and fix the root causes of cost overruns.
How do you do that? With TapRooT®.
And how would people learn about TapRooT®? By going to training.
And what had he eliminated? The training budget!
How about the stagnant HSE performance?
To improve performance his company needs to do something different. They need to learn best practices from other industry leaders from their industry AND from other industries.
Where could his folks learn this stuff? At the TapRooT® Summit.
His folks didn’t attend because they didn’t have a training or travel budget!
And the quality issues? He could have his people use the same advanced root cause analysis tools (TapRooT®) to attack them that they were already using for cost, schedule, and HSE incidents. Oh, wait. His people don’t know about TapRooT®. They didn’t attend training.
This reminds me of a VP at a company that at the end of a presentation about a major accident that cost his company big $$$$ and could have caused multiple fatalities (but they were lucky that day). The accident had causes that were directly linked to a cost cutting/downsizing initiative that the VP had initiated for his division. The cost cutting initiative had been suggested by consultants to make the company more competitive in a down economy with low commodity prices. At the end of the presentation he said:
“If anybody would have told me the impacts of these cuts, I wouldn’t have made them!”
Yup. Imaging that. Those bad people didn’t tell him he was causing bad performance by cutting the people and budget they needed to make the place work.
That accident and quote occurred almost 20 years ago.
Yes, this isn’t the first time we have faced a poor economy, dropping commodity prices, or performance issues. The more things change, the more they stay the same!
But what can you do?
Share this story!
And let your management know how TapRooT® Root Cause Analysis can help them alleviate their PAIN!
Once they understand how TapRooT®’s systematic problem solving can help them improve performance even in a down economy, they will realize that the small investment required is well worth it compared to the headaches they will avoid and the performance improvement they can achieve.
Because in bad times it is especially true that:
“You can stop spending bad money
or start spending good money
When it comes to root cause analysis, more people (over 14,000) are linked to Mark Paradies than anyone else on the internet.
Mark also has thousands of colleges that have endorsed him for the skill “root cause analysis”.
See his LinkedIn profile at:
If you would like to link up with Mark on LinkedIn, click on the link above and send him an invitation to connect. Also, please feel free to recognize Mark for his root cause analysis skills by recommending him for his work on root cause analysis.
The Associated Press reported that the US Department of Justice is warning food companies that they could face civil and criminal charges if they poison their customers.
POISON THEIR CUSTOMERS!
Yes, you read it right.
We are again testing the fine line between accidents and criminal behavior.
How does a company know that they have gone over the line? The FDA stops showing up and the FBI puts boundary tape around your facilities.
Are you in the food business? Think it is time to start taking root cause analysis of food safety incidents seriously? You betcha!
Your company can’t afford a Blue Bell Ice Cream incident. You need to effectively analyze and learn from smaller incidents to stop the big accidents from happening.
What tool should you use for effective root cause analysis? The TapRooT® Root Cause Analysis System.
Why choose TapRooT® Root Cause Analysis?
Because it has proven itself effective in a wide number of industries around the world. That’s why industry leaders use it and recommend it to their suppliers.
Find out more about the TapRooT® System at:
And then attend one of our public courses held around the world.
You can attend at no risk because of our iron-clad guarantee:
Attend a TapRooT® Course, go back to work, and use what you have learned to analyze accidents, incidents, near-misses, equipment failures, operating issues, or quality problems. If you don’t find root causes that you previously would have overlooked and if you and your management don’t agree that the corrective actions that you recommend are much more effective, just return your course materials/software and we will refund the entire course fee.
Get started NOW because you can’t afford to wait for the FBI to knock on your door with a warrant in their hand.
I love to use Safeguard Analysis to examine incidents and determine Causal Factors.
What were the Safeguards keeping this officer safe and how did they fail? (A failed Safeguard is usually a Causal Factor.)
Watch and leave a comment about your ideas …
United grounds all of their flights for two hours due to “computer problems” (see the CNBC story).
The NYSE stops trading for over three hours due to an “internal technical issue” (see the CNBC story).
Computer issues can cost companies big bucks and cause public relations headaches. Do you think they should be applying state of the art root cause analysis tools both reactively and proactively to prevent and avoid future problems?
TapRooT® has been used to improve computer reliability and security by performing root cause analysis of computer/IT related events and developing effective corrective actions. The first TapRooT® uses for computer/high reliability network problems where banking and communication service providers that started using TapRooT® in the late 1990’s. The first computer security application of TapRooT® that we knew about was in the early 2000s.
Need to improve your root cause analysis of computer and IT issues? Attend one of our TapRooT® Root Cause Analysis Courses. See the upcoming course schedule at:
The 22-year-old man died in hospital after the accident at a plant in Baunatal, 100km north of Frankfurt. He was working as part of a team of contractors installing the robot when it grabbed him, according to the German car manufacturer. Volkswagen’s Heiko Hillwig said it seemed that human error was to blame.
A worker grabs the wrong thing and often gets asked, “what were you thinking?” A robot picks up the wrong thing and we start looking for root causes.
Read the article below to learn more about the fatality and ask why would we not always look for root causes once we identify the actions that occurred?
For those outside the USA, on the 4th of July we are off celebrating our God given freedoms that are guaranteed in the US Constitution that resulted from declaring our independence from the British crown. On July 4, 1776, the Continental Congress approved the final wording of the Declaration of Independence. That act continued the progress of the revolt that had started back in April of 1775 and resulted in the founding of the United States and the US Constitution.
For more information about the US Constitution, see: http://www.constitutionfacts.com
See you next week!
It is the largest environmental settlement ever.
BP will pay the US Government,Alabama, Florida, Louisiana,Mississippi, and Texas $18.7 billion to compensate for environmental damage done by the Deepwater Horizon spill.
The Chicago Tribune reported “Fall from ladder nets Merrillville man $2.4 million jury verdict.”
Part of the reason that the company was found liable is that the ladder was “out of code.” It had been produced before standards for ladders were developed.
Have any old ladders out there that need to be replaced?
We can all remember some type of major product recall that affected us in the past (tires, brakes, medicine….) or recalls that may be impacting us today (air bags). These recalls all have a major theme, a company made something and somebody got hurt or worse. This is a theme of “them verses those” perception.
Now stop and ask, when is the last time quality and safety was discussed as one topic in your current company’s operations?
You received a defective tool or product….
- You issued a defective tool or product….
- A customer complained….
- A customer was hurt….
Each of the occurrences above often triggers an owner for each type of problem:
- The supplier…
- The vendor…
- The contractor…
- The manufacturer….
- The end user….
Now stop and ask, who would investigate each type of problem? What tools would each group use to investigate? What are their expertise and experiences in investigation, evidence collection, root cause analysis, corrective action development or corrective action implementation?
This is where we create our own internal silo’s for problem solving; each problem often has it’s own department as listed in the company’s organizational chart:
- Customer Service (Quality)
- Manufacturing (Quality or Engineering)
- Supplier Management (Supply or Quality)
- EHS (Safety)
- Risk (Quality)
- Compliance (?)
The investigations then take the shape of the tools and experiences of those departments training and experiences.
Does anyone besides me see a problem or an opportunity here?
John Lehman, the youngest Secretary of the Navy who fired the oldest admiral ever, says that Obama’s decision to promote the head of the Nuclear Navy after just two years will put the best safety record in the world at risk.
Here’s a link to the article: http://www.wsj.com/articles/obama-torpedoes-the-nuclear-navy-1432591747
What do you think?
Accident News: The Washington Times Reports “Amtrak train from D.C. derails in Philadelphia; 6 dead, dozens injured”May 13th, 2015 by Mark Paradies
I read an article in the Houston Chronicle about failed corrective actions at Blue Bell® Ice Cream.
It made me wonder:
“Did Blue Bell perform an adequate root cause analysis?”
Sometimes people jump tp conclusions and implement inadequate corrective actions because they don’t address the root causes of the problem.
Its hard to tell without more information, but better root cause analysis sure couldn’t have hurt.
Find out how TapRooT® Root Cause Analysis can help find and fix the root causes of problems by reading about TapRooT®’s history at:
As a stockholder, I was reading The CB&I 2014 Annual Report. The section on “Safety” caught my eye. Here is a quote from that section:
“Everything at CB&I begins with safety; it is our most important core value and the foundation for our success. In 2014, our employees maintained a lost-time incident rate of 0.03 for more than 160 million work-hours. This equals one lost-time incident for every 6.2 million hours on the job. These numbers are a testament to our safety record and a reason why we are in the top tier of safest companies in the industry.”
CB&I’s lost time incident rate is 50 times better than the industry average (.03 compared to 1.5). That might make you wonder, how do they do that?
Answering that question is learning from a lack of accidents!
Here are a couple of thoughts that I have…
First, when you see this kind of success, you know it is because of management, supervisory, and employee involvement in accomplishing a safe workplace. Everybody has to be involved. There can’t be finger pointing and blame. Everybody has to work together.
Second, I know CB&I is a TapRooT® User. CB&I has trained TapRooT® Investigators to find and fix the root causes of incidents and, thereby, keep major accidents (LTI’s and fatalities) from occurring.
So, congratulations CB&I on your excellent performance! Congratulations on the lives you have saved and the injuries you have avoided!
If you are interested in having industry leading safety performance, perhaps you should get your folks trained to find and fix the root causes of problems by using advanced TapRooT® root cause analysis. Find out about our courses at THIS LINK.
And consider attending the 2015 Global TapRooT® Summit on June 1-5 in Las Vegas. You can:
- meet industry leaders who are achieving world-class performance
- benchmark your programs with their programs
- learn industry leading best practices
- get motivated to take your safety performance to the next level.
See the 2015 Global TapRooT® Summit schedule at:
A press release from the UK RAIB:
RAIB is investigating an incident that occurred at 17:25 hrs on Saturday 7 March 2015, in which train reporting number 1Z67, the 16:35 hrs service from Bristol Temple Meads to Southend, passed a signal at danger on the approach to Wootton Bassett junction, Wiltshire. The train subsequently came to a stand across the junction. The signal was being maintained at danger in order to protect the movement of a previous train. However, at the time that the SPAD occurred, this previous train had already passed through the junction and was continuing on its journey. No injuries, damage or derailment occurred as a result of the SPAD.
Wootton Bassett junction is situated between Chippenham and Swindon stations on the Great Western main line and is the point at which the line from Bristol, via Bath, converges with the line from South Wales. It is a double track high speed junction which also features low speed crossovers between the up and down main lines (see figure below for detail).
Wootton Bassett junction in 2012 – the lines shown from left to right are the Up Goods,
Up Badminton, Down Badminton, Up Main and Down Main (image courtesy of Network Rail)
The junction is protected from trains approaching on the up main from Chippenham by signal number SN45, which is equipped with both the Automatic Warning System (AWS) and the Train Protection and Warning System (TPWS). This signal is preceded on the up main by signal SN43, which is also equipped with AWS and TPWS. The maximum permitted line speed for trains approaching the junction from this direction is normally 125 mph. However, on 7 March, a temporary speed restriction (TSR) of 85 mph was in place on the approach to signal SN45. A temporary AWS magnet had been placed on the approach to signal SN43 to warn drivers of this TSR.
A diagram of the layout of Wootton Bassett junction – note that some features have been omitted for clarity (not to scale)
The train which passed signal SN45 at danger consisted of steam locomotive number 34067 ‘Tangmere’, and its tender, coupled to 13 coaches. The locomotive is equipped with AWS and TPWS equipment.
The RAIB’s preliminary examination has shown that, at around 17:24 hrs, train 1Z67 was approaching signal SN43 at 59 mph, when it passed over the temporary AWS magnet associated with the TSR. This created both an audible and visual warning in the locomotive’s cab. However, as the driver did not acknowledge this warning within 2.7 seconds, the AWS system on the locomotive automatically applied the train’s brakes. This brake application should have resulted in the train being brought to a stand. In these circumstances, the railway rule book requires that the driver immediately contact the signaller.
The RAIB has found evidence that the driver of 1Z67 did not bring the train to a stand and contact the signaller after experiencing this brake application. Evidence shows that the driver and fireman instead took an action which cancelled the effect of the AWS braking demand after a short period and a reduction in train speed of only around 8 mph. The action taken also had the effect of making subsequent AWS or TPWS brake demands ineffective.
Shortly after passing the AWS magnet for the TSR, the train passed signal SN43, which was at caution. Although the AWS warning associated with this signal was acknowledged by the driver, the speed of the train was not then reduced appropriately on the approach to the next signal, SN45, which was at danger. Because of the earlier actions of the driver and fireman, the TPWS equipment associated with signal SN45 was unable to control the speed of the train on approach to this signal.
As train 1Z67 approached signal SN45, the driver saw that it was at danger and fully applied the train’s brakes. However, by this point there was insufficient distance remaining to bring the train to a stand before it reached the junction beyond SN45. The train subsequently stopped, standing on both the crossovers and the up and down Badminton lines, at around 17:26 hrs. The signalling system had already set the points at the junction in anticipation of the later movement of 1Z67 across it; this meant that no damage was sustained to either the train or the infrastructure as a result of the SPAD.
The RAIB has found no evidence of any malfunction of the signalling, AWS or TPWS equipment involved in the incident.
The RAIB’s investigation will consider the factors that contributed to signal SN45 being passed at danger, including the position of the temporary AWS magnet associated with the TSR. The investigation will also examine the factors that influenced the actions of the train crew, the adequacy of the safety systems installed on the locomotive and the safety management arrangements.
RAIB’s investigation is independent of any investigation by the Office of Rail Regulation.
We will publish our findings, including any recommendations to improve safety, at the conclusion of our investigation.
These findings will be available on the our website.
The UK Rail Accident Investigation Branch announced the start of two rail incident investigations.
The first is an investigation of the injury of a passenger that fell between a London Underground train while being dragged by the train. See the preliminary information at:
This is an accident that was prevented from being worse by the alert actions of the train’s operator.
The second incident was container blown off a freight train. The preliminary information can be found here:
Monday Accident & Lessons Learned: Crane Accident at Tata Steel Plant in the UK brings £200,000 Guilty VerdictMarch 16th, 2015 by Mark Paradies
Tata Steel was found guilty of violating section 2(1) of the Health and Safety at Work etc. Act 1974. The result? A fine of £200,000 plus court costs of £11,190.
HSE Inspector Joanne carter said:
“Given the potential consequences of a ladle holding 300 tonnes of molten metal spilling its load onto the floor, control measures should be watertight. The incident could have been avoided had the safety measures introduced afterwards been in place at the time.”
The article listed the following corrective action:
“Tata has since installed a new camera system, improved lighting, and managers now scrutinise all pre-use checks. If the camera system fails, spotters are put in place to ensure crane hooks are properly latched onto ladle handles.
Here are my thoughts…
- Stating that corrective actions would have prevented an accident is hindsight bias. The question should be, should they have learned these lessons from previous near-misses?
- Reviewing the corrective actions, I’m still left with the question … Should the crane be allowed to operate without the camera system working? Are spotters a good temporary fix? How long should a temporary fix be allowed before the operation is shut down?
- What allows the latches to fail? Shouldn’t this be fixed as well?
What do you think? Is there more to learn from this accident? Leave your comments here.
The International Business Times reports that a Ukraine coal mine that recently had an accident that killed 34 miners is responsible for 300 fatalities since 1999. See the story at:
The whole rescue process is being complicated by the fighting in the Ukraine.
Another story claim that investment in “safety technology” could have prevented the methane blast at the mine.
Press Release from the UK Rail Accident Investigation Branch: Bridge strike and collision between a train and fallen debris at Froxfield, Wiltshire, 22 February 2015March 11th, 2015 by Mark Paradies
Image of debris on track before the collision, looking east.
Train 1C89 approached on the right-hand track
(image courtesy of a member of the public)
Bridge strike and collision between a train and fallen debris at Froxfield, Wiltshire, 22 February 2015
RAIB is investigating a collision between a high speed train (HST) and a bridge parapet which had fallen onto the railway at Oak Hill, an unclassified road off the A4 on the edge of the village of Froxfield, between Hungerford and Bedwyn. The accident occurred at about 17:31 hrs on Sunday 22 February 2015, when the heavily loaded 16:34 hrs First Great Western service from London Paddington to Penzance (train reporting number 1C89) hit brick debris while travelling at about 90 mph (145 km/h). The train driver had no opportunity to brake before hitting the debris, and the impact lifted the front of the train. Fortunately, the train did not derail, and the driver applied the emergency brake. The train stopped after travelling a further 730 metres (800 yards). There were no injuries. The leading power car sustained underframe damage and there was damage to the train’s braking system.
The bridge parapet had originally been struck at about 17:20 hrs by a reversing articulated lorry. The lorry driver had turned off the A4 at a junction just north of the railway bridge, and crossed over the railway before encountering a canal bridge 40 metres further on which he considered to be too narrow for his vehicle. A pair of road signs located just south of the A4 junction warn vehicle drivers of a hump back bridge and double bends but there were no weight or width restriction signs. The lorry driver stopped before the canal bridge and attempted to reverse round a bend and back over the railway bridge without assistance, and was unaware when the rear of his trailer first made contact with, and then toppled, the brick parapet on the east side of the railway bridge. The entire parapet, weighing around 13 tonnes, fell onto the railway, obstructing both tracks. This was witnessed by a car driver who was travelling behind the lorry. The car driver left his vehicle to alert the lorry driver and he then contacted the emergency services by dialing 999 on his mobile phone at about 17:21 hrs.
RAIB’s investigation will consider the sequence of events and factors that led to the accident. The investigation will include a review of the adequacy of road signage and the overall response to the emergency call made by the motorist who witnessed the collapse of the bridge parapet. It will identify any safety lessons from the accident and post-accident response.
RAIB’s investigation is independent of any investigations by the railway industry or safety authority.
The RAIB will publish the findings at the conclusion of the investigation on it’s website.
Press Release from the Chemical Safety Board: CSB Releases Technical Analysis Detailing Likely Causes of 2010 Zinc Explosion and Fire at the Former Horsehead Zinc Facility in Monaca, Pennsylvania, that Killed Two Operators, Injured a ThirdMarch 11th, 2015 by Mark Paradies
CSB Releases Technical Analysis Detailing Likely Causes of 2010 Zinc Explosion and Fire at the Former Horsehead Zinc Facility in Monaca, Pennsylvania, that Killed Two Operators, Injured a Third
Washington, DC, March 11, 2015 – The July 2010 explosion and fire at the former Horsehead zinc refinery in Monaca, Pennsylvania, likely resulted from a buildup of superheated liquid zinc inside a ceramic zinc distillation column, which then “explosively decompressed” and ignited, according to a technical analysis released today by the U.S. Chemical Safety Board (CSB).
Two Horsehead operators, James Taylor and Corey Keller, were killed when the column violently ruptured inside the facility’s refinery building, where multiple zinc distillation columns were operating. The rupture released a large amount of zinc vapor, which at high temperatures combusts spontaneously in the presence of air. The two men had been performing unrelated maintenance work on another nearby column when the explosion and fire occurred. A third operator was seriously injured and could not return to work.
The incident was investigated by multiple agencies including the CSB and the U.S. Occupational Safety and Health Administration, but its underlying cause had remained unexplained. In the fall of 2014, CSB contracted with an internationally known zinc distillation expert to conduct a comprehensive review of the evidence file, including witness interviews, company documents, site photographs, surveillance videos, laboratory test results, and data from the facility’s distributed control system (DCS). The 57-page report of this analysis, prepared by Mr. William Hunter of the United Kingdom, was released today by the CSB. Draft versions of the report were reviewed by Horsehead and by the United Steelworkers local that represented Horsehead workers in Monaca; their comments are included in the final report as appendices.
In the years following the 2010 incident, the Horsehead facility in Monaca was shut down and dismantled. The “New Jersey” zinc process, a distillation-based method that was first developed in the 1920’s and was used for decades in Monaca, is no longer practiced anywhere in the United States, although a number of overseas companies, especially in China, continue to use it.
“Although this particular zinc technology has ceased being used in the U.S., we felt it was important to finally determine why this tragedy occurred,” said CSB Chairperson Dr. Rafael Moure-Eraso. “Our hope is that this will at last provide a measure of closure to family members, as well as inform the safety efforts of overseas companies using similar production methods.”
The Hunter report was based on expert professional opinion, and did not involve any onsite examination of the evidence. CSB investigators made several short deployments to the Horsehead site in 2010 following the incident, interviewing a number of witnesses and documenting conditions at the site.
The explosion involved an indoor distillation column several stories tall. The column consisted of a vertical stack of 48 silicon carbide trays, topped by a reflux tower, and assembled by bricklayers using a specialized mortar. The bottom half of the column was surrounded by a masonry combustion chamber fueled by natural gas and carbon monoxide waste gas. Horsehead typically operated columns of this type for up to 500 days, at which time the columns were dismantled and rebuilt using new trays.
The explosion on July 22, 2010, occurred just 12 days after the construction and startup of “Column B.” Column B was used to separate zinc – which flowed as a liquid from the bottom of the column – from lower-boiling impurities such as cadmium, which exited as a vapor from the overhead line. The column, which operated at more than 1600 °F, normally has only small amounts of liquid metals in the various trays, but flooding of the column creates a very hazardous condition, the analysis noted. Such flooding likely occurred on July 22, 2010.
“Under extreme pressure the tray wall(s) eventually failed, releasing a large volume of zinc vapor and superheated zinc that would flash to vapor, and this pressure pushed out the combustion chamber blast panels,” Mr. Hunter’s report concluded. “The zinc spray and vapor now had access to large amounts of workplace air and this created a massive zinc flame across the workplace.”
After examining all the data, the report determined that the explosion likely occurred because of a partial obstruction of the column sump, a drain-like masonry structure at the base of the column that had not been replaced when the column was rebuilt in June 2010. The previous column that used this sump had to be shut down prematurely due to sump drainage problems, the analysis found. These problems were never adequately corrected, and various problems with the sump were observed during the July 2010 startup of the new Column B. Over at least an hour preceding the explosion, DCS data indicate a gradual warming at the base of Column B, as liquid zinc likely built up and flooded the lower trays, while vapor flow to the overhead condenser ceased.
Ten minutes before the explosion, an alarm sounded in the control room due to a high rate of temperature change in the column waste gases, as zinc likely began leaking out of the column into the combustion chamber, but by then it was probably too late to avert an explosion, according to the analysis. Control room operators responded to the alarm by cutting the flow of fuel gas to Column B but did not reduce the flow of zinc into the column. The unsafe condition of Column B was not understood, and operators inside the building were not warned of the imminent danger.
The technical analysis determined that there was likely an underlying design flaw in the Column B sump involving a structure known as an “underflow” – similar to the liquid U-trap under a domestic sink. The small clearance in the underflow – just 65 millimeters or the height on one brick – had been implicated in other zinc column explosions around the world, and likely allowed dross and other solids to partially obstruct the sump and cause a gradual accumulation of liquid zinc in the column. Liquid zinc in the column causes a dangerous pressure build-up at the bottom and impairs the normal evaporation of vapor, which would otherwise cool the liquid zinc. Instead the liquid zinc becomes superheated by the heat from the combustion chamber, with the pressure eventually rupturing the column and allowing the “explosive decompression.”
The report noted that the Column B sump had previously been used with a different type of column that had a much lower rate of liquid run-off through the sump, so the problem with the sump was only exacerbated when Column B was constructed to separate zinc from cadmium, increasing the liquid flow rate into the sump by a factor of four to five.
The report concluded that Horsehead may have missed several opportunities to avoid the accident, overlooking symptoms of a blocked column sump that were evident days before the accident. “Missing these critical points indicates that, in large measure, hazardous conditions at Monaca had been ‘normalized’ and that process management had become desensitized to what was going on. This raises the question whether sufficient technical support was provided to the plant on a regular basis,” according to Mr. Hunter.
The report noted that New Jersey-type zinc distillation columns have been involved in numerous serious incidents around the world. In 1993 and 1994, two column explosions at a former French zinc factory killed a total of 11 workers. An international committee of experts who investigated the incidents in France identified up to 10 other major incidents at other sites attributable to sump drainage problems. The Monaca facility had suffered five documented column explosions prior to 2010, but none with fatalities, according to the CSB-commissioned report.
For more information, contact Daniel Horowitz at (202) 261-7613 or (202) 441-6074 cell.