CAUSE OF TANK EXPLOSIONS DURING TANK WORK

Chemical Safety Board urges caution for hot work

Board says hot work accidents have become ‘one of the most significant types of incidents’ investigated

Earlier this month a team of CSB investigators deployed to the Omega Protein facility in Moss Point, Mississippi, where a tank explosion on July 28, 2014, killed a contract worker and severely injured another. Our team, working alongside federal OSHA inspectors, found that the incident occurred during hot work on or near a tank containing eight inches of a slurry of water and fish matter known as “stickwater.”

The explosion blew the lid off the 30-foot-high tank, fatally injuring a contract worker who was on top of the tank. A second contract worker on the tank was severely injured. CSB investigators commissioned laboratory testing of the stickwater and found telltale signs of microbial activity in the samples, such as the presence of volatile fatty acids in the liquid samples and offgassing of flammable methane and hydrogen sulfide.

The stickwater inside of the storage tank had been thought to be nonhazardous. No combustible gas testing was done on the contents of the tank before the hot work commenced.

This tragedy underscores the extreme importance of careful hot work planning, hazard evaluation, and procedures for all storage tanks, whether or not flammable material is expected to be present. Hot work dangers are not limited to the oil, gas, and chemical sectors where flammability hazards are commonplace.

The CSB has now examined three serious hot work incidents—all with fatalities—involving hot work on tanks of biological or organic matter. At the Packaging Corporation of America (PCA), three workers were killed on July 29, 2008, as they were performing hot work on a catwalk above an 80-foot-tall tank of “white water,” a slurry of pulp fiber waste and water. CSB laboratory testing identified anaerobic, hydrogen-producing bacteria in the tank. The hydrogen gas ignited, ripping open the tank lid and sending workers tumbling to their deaths.

On February 16, 2009, a welding contractor was killed while repairing a water clarifier tank at the ConAgra Foods facility in Boardman, Oregon. The tank held water and waste from potato washing; the CSB investigation found that water and organic material had built up beneath the base of the tank and decayed through microbial action, producing flammable gas that exploded.

Mixtures of water with fish, potatoes, or cardboard waste could understandably be assumed to be benign and pose little safety risk to workers. It is vital that companies, contract firms, and maintenance personnel recognize that in the confines of a storage tank, seemingly non-hazardous organic substances can release flammable gases at levels that cause the vapor space to exceed the lower flammability limit. Under those conditions, a simple spark or even conducted heat from hot work can prove disastrous.

In November of 2011 two contractors at a facility located in Buffalo, New York were performing welding atop a 10,000 gallon slurry tank when hot sparks ignited flammable vapors inside the tank, causing an explosion that killed one contractor and seriously injured another. The CSB's final report and safety video entitled “Hot Work: Hidden Hazards” were released at an April 19, 2012, public meeting. The CSB said a primary cause of the blast was the failure of the company to require that the interior of storage tanks on which hot work is to be performed be monitored for flammable vapor. A proposed recommendation urges the company to require monitoring the inside of storage tanks — and the area around tanks — before performing any hot work.

I urge all companies to follow the positive example set by the DuPont Corporation, after a fatal hot work tragedy occurred at a DuPont chemical site near Buffalo, New York. Following CSB recommendations from 2012, DuPont instituted a series of reforms to hot work safety practices on a global basis, including requirements for combustible gas monitoring when planning for welding or other hot work on or near storage tanks or adjacent spaces.

Combustible gas testing is simple, safe, and affordable. It is a recommended practice of the National Fire Protection Association, The American Petroleum Institute, FM Global, and other safety organizations that produce hot work guidance. Combustible gas testing is important on tanks that hold or have held flammables, but it is equally important—if not more so—for tanks where flammables are not understood to be present. It will save lives.

Metropolitan identifies seven key lessons aimed at preventing worker deaths during hot work in and around storage tanks containing flammable materials which include:

1. Use alternatives - Whenever possible, avoid hot work and consider alternative methods.

2. Analyze the hazards - Prior to the initiation of hot work, perform a hazard assessment that identifies the scope of the work, potential hazards, and methods of hazard control.

3. Monitor the atmosphere - Conduct effective gas monitoring in the work area using a properly calibrated combustible gas detector prior to and during hot work activities, even in areas where a flammable atmosphere is not anticipated.

4. Test the area - In work areas where flammable liquids and gases are stored or handled, drain and/or purge all equipment and piping before hot work is conducted. When welding on or in the vicinity of storage tanks and other containers, properly test and if necessary continuously monitor all surrounding tanks or adjacent spaces (not just the tank or container being worked on) for the presence of flammables and eliminate potential sources of flammables.

5. Use written permits - Ensure that qualified personnel familiar with the specific site hazards review and authorize all hot work and issue permits specifically identifying the work to be conducted and the required precautions.

6. Train thoroughly - Train personnel on hot work policies/procedures, proper use and calibration of combustible gas detectors, safety equipment, and job specific hazards and controls in a language understood by the workforce.

7. Supervise contractors - Provide safety supervision for outside contractors conducting hot work. Inform contractors about site-specific hazards including the presence of flammable materials.

Safety Videos, Safety Bulletin and Accident Investigations Call Attention to the Hazards of Welding or Cutting Near Storage Tanks

Washington, DC, August 6, 2014 – The U.S. Chemical Safety Board (CSB) today emphasized the hot work safety resources available free of charge through the agency’s website at www.csb.gov. The Board previously released safety videos, a safety bulletin, and accident investigations all warning of the hazards of welding, cutting, grinding, and other hot work activities in and around storage tanks containing flammable materials.

Of particular interest is the CSB’s safety video entitled “Dangers of Hot Work,” which presents key lessons from the CSB’s hot work safety bulletin, released on March 4, 2010, in Wausau, Wisconsin, near the Packaging Corporation of America (PCA) facility where three workers were killed in July 2008 during a hot work-related explosion.

CSB Chairperson Rafael Moure-Eraso said, “The CSB has examined multiple deadly hot work accidents. Our call to industry is to follow effective hazard analysis and combustible gas monitoring procedures when welding and cutting in and around storage tanks. These simple steps will save many lives.”

Hot work is defined as burning, welding, or similar spark-producing operations that can ignite fires or explosions. The CSB has conducted numerous investigations into fatal hot work accidents, with final reports which are available at the following links:

E. I. DuPont De Nemours Co. Fatal Hot Work Explosion

Partridge Raleigh Oilfield Explosion and Fire

Bethune Point Wastewater Plant Explosion

Motiva Enterprises Sulfuric Acid Tank Explosion

The CSB’s “Dangers of Hot work” safety video uses 3-D computer animations to depict three of the hot work accidents summarized in the bulletin - Partridge-Raleigh, an oil production site in Central Mississippi; the Bethune Waste Water Treatment Plant in Daytona Beach, Florida; and the Motiva Enterprises Refinery in Delaware City, Delaware.

Hot work accidents occur throughout many industries in the U.S., including food processing, pulp and paper manufacturing, oil production, fuel storage, and waste treatment.

CSB Investigations Supervisor Donald Holmstrom states in the video, “We typically hear about hot work accidents weekly. It has become one of the most significant types of incidents the CSB investigates, in terms of deaths, in terms of frequency.”

The CSB began investigating hot work hazards following a July 17, 2001, explosion at the Motiva Enterprises refinery in Delaware City, Delaware. A work crew had been repairing a catwalk above a sulfuric acid storage tank farm when a spark from their hot work ignited flammable vapors in one of the tanks. Following the a July 29, 2008, accident at the Packaging Corporation of America (PCA) n Tomahawk, Wisconsin - which killed three maintenance workers and injured another - the CSB began systematically tracking hotwork incidents. The CSB determined the explosion resulted from welding above an 80-foot-tall storage tank that contained highly flammable hydrogen gas – the product of bacterial decomposition of organic fiber waste inside the tank.

In the ten months following the explosion at Packaging Corporation, the CSB deployed investigators to five other sites where hot work ignited flammable gas or vapor, including an explosion at MAR Oil in La Rue, Ohio, that killed two contractors in October 2008; an explosion that killed one and injured another at EMC Used Oil in Miami, Florida, in December 2008; an explosion that killed a contract welder at ConAgra Foods in Boardman, Oregon, in February 2009; an explosion at A.V. Thomas Produce in Atwater, California, in March 2009 that severely burned two employees; and the explosion of a massive gasoline storage tank that killed three workers at a TEPPCO Partners fuel distribution facility in Garner, Arkansas, in May 2009.

In November of 2011 two contractors at the E. I. DuPont De Nemours Co. located in Buffalo, NY were performing welding atop a 10,000 gallon slurry tank when hot sparks ignited flammable vapors inside the tank, causing an explosion that killed one contractor and seriously injured another. The CSB’s final report and safety video entitled “Hot Work: Hidden Hazards” were released at an April 19, 2012, public meeting. The CSB said a primary cause of the blast was the failure of the company to require that the interior of storage tanks – on which hot work is to be performed ­– be monitored for flammable vapor. A proposed recommendation urges DuPont to require monitoring the inside of storage tanks ­– and the area around tanks – before performing any hot work, which is defined as welding, cutting, grinding, or other spark-producing activities.

Just last week there was a deadly accident in Moss Point, MS. According to media report one man was killed and three others injured while performing welding working on a tank that was supposed to be empty. The CSB is following up on this incident and is in the process of gathering additional information.

METROPOLITAN ENGINEERING, CONSULTING & FORENSICS (MECF)

Providing Competent, Expert and Objective Investigative Engineering and Consulting Services

P.O. Box 520

Tenafly, NJ 07670-0520

Tel.: (973) 897-8162

Fax: (973) 810-0440

E-mail: metroforensics@gmail.com

Web pages: https://sites.google.com/site/metropolitanforensics/

We are happy to announce the launch of our twitter account. Please make sure to follow us at @MetropForensics

To unsubscribe from future technical blogs and announcements, please reply to this email with the word “unsubscribe” in the subject line.

Metropolitan appreciates your business.

Feel free to recommend our services to your friends and colleagues.