Chemical Safety Board Chair Rafael Moure-Eraso and investigator Donald Holmstrom on how the CSB and NFPA are working together to address gas-release practices in industrial settings
NFPA Journal®, May/June 2011
One word comes to mind when Rafael Moure-Eraso, chair of the Chemical Safety Board (CSB), recalls the deaths and injuries from two recent, catastrophic explosions in industrial settings: preventable. Both incidents involved a common yet potentially dangerous practice of intentionally releasing natural gas near work settings, even though safer alternatives exist.
In June 2009, workers at the ConAgra Slim Jim facility in Garner, North Carolina, were connecting a new gas supply pipe to an industrial water heater when they began using natural gas to purge air from the pipe. Workers were unaware of the level of gas buildup inside the facility after a two-and-a-half-hour venting process; the concentration of accumulated gas reached the lower flammable limit and came in contact with an ignition source, resulting in an explosion that killed four workers and injured more than 60. Eight months later, at the under-construction Kleen Energy power plant in Middletown, Connecticut, highly pressurized gas used during a cleaning procedure was being blown through pipes and discharged outdoors. Once again, the gas had accumulated to dangerous levels and found an ignition source, killing six workers and injuring nearly 50 others.
Following the incidents, the CSB, a federal agency based in Washington, D.C., that investigates industrial accidents, supplied the codes-and-standards community with safety recommendations. NFPA reacted promptly to the recommendations related to ConAgra, creating and approving a tentative interim amendment to NFPA 54, National Fuel Gas Code, that addresses both indoor and outdoor purging procedures and creates more stringent safeguards for workers involved in these practices. The amendments are expected to be included in the 2012 edition of NFPA 54. Earlier this year, NFPA formed a technical committee to develop the new NFPA 56, Provisional Standard for the Commissioning and Maintenance of Fuel Gas Piping Systems, which would address the kind of gas blows that occurred at Kleen Energy. The new standard would also address a range of gas process activities, such as pipe cleaning, repair, replacement, and removal procedures at other power plant, industrial, and commercial settings.
As the featured presentation at NFPA’s Conference & Expo June 12–15 in Boston, Moure-Eraso will speak at length about Kleen Energy and its aftermath. NFPA Journal recently spoke with Moure-Eraso, along with Don Holmstrom, CSB investigator and director of the agency’s Western Regional Office, to discuss the inherent dangers of gas-release practices, NFPA’s immediate response to the accidents, and the future of industrial safety.
Describe the process of gas purging and gas blowing, and how they were involved in the ConAgra and Kleen Energy incidents.
Moure-Eraso: In the situation with ConAgra, the indoor purging of new piping occurred during the installation of a gas-fired industrial water heater. Workers used natural gas — a flammable gas — to displace air from a system of piping. With one of the pipes, the gas wasn’t vented outside, but rather inside the plant.
Gas blows are a different situation. You use extraordinarily large volumes of gas at higher pressures to clean out systems of pipes and tubes, mostly in power plants. The volume of gas is so enormous that the venting needs to be directed to safe locations outside. And since there is so much gas, there’s a greater possibility of finding a source of ignition and thus injuring people working in an area near the building.
Were these incidents preventable?
Moure-Eraso: It’s surprising [in the case of Kleen Energy] that someone might think to take as much as 450,000 cubic feet (1,274 cubic meters) of a flammable gas and blow it through a system without giving a lot of thought to what could happen. Employee safety and prevention were totally ignored by following this procedure.
Holmstrom: The other side of that coin is that we found that there really weren’t any standards that applied to this practice. So it really shows how important it is for groups like NFPA to set minimum standards and practices so there are actually requirements out there for people who want to undertake safe practices in order to prevent these accidents from occurring.
During the ConAgra investigation, CSB investigators looked into the practice of purging natural gas indoors. What did they discover?
Holmstrom: With the issue of purging, we found a number of similar incidents that occurred relatively recently. [CSB’s ConAgra investigation report documents six gas purging accidents since 1997.] We also discovered there were several phenomena that can affect people’s ability to use their sense of smell, a common practice in detecting the release of fuel gas. One of the issues is odor fade, where the odorant can react with new gas pipes and containers in a way that can remove or reduce the added odorant from natural gas. There’s also odor fatigue — being exposed to an odor for a long period of time can reduce your ability to detect it.
There are other phenomena that deal with a person’s individual physiology. Some people are more sensitive to detecting odors than others.
One of the lessons learned was not to rely on odor alone to detect the release of fuel gas. We recommended in our report the use of combustible-gas detectors to monitor gas concentrations, even when purging gas to the outside. The bigger lesson learned is to do the purging away from workers, at a safe location, and away from ignition sources.
What are your thoughts on how NFPA responded to CSB’s recommendations to the ConAgra incident?
Holmstrom: We’re very pleased NFPA took such positive action. The staff we dealt with was very dedicated to safety and having all of the safe practices adopted. The response was expeditious. Standard-setting always involves a bit of sausage-making. That being said, what impressed us was the perseverance of NFPA members and staff to make sure to get it right and get those recommendations adopted.
Moure-Eraso: We appreciate that the recommendations we made were picked up by NFPA and were acted upon. NFPA’s new provisions to NFPA 54 would have required the gas pipe at ConAgra to be purged outdoors, away from personnel and ignition sources. Under the new requirements, purging must be monitored using appropriate detection equipment to prevent a significant release of flammable gas. The recent NFPA code change is similar to new safety procedures developed and implemented by both ConAgra and the state of North Carolina in the months following the tragedy.
Just days after the CSB issued recommendations on ConAgra, the Kleen Energy explosion occurred. What was going through your mind at that time?
Moure-Eraso: It was a sense of frustration. Here are these individual situations in which flammable gas, which should be used for energy purposes, was used for something completely different, ignoring the potential for fires and explosions.
Holmstrom: I remember getting the call about the incident. While we didn’t know all the particular circumstances, we knew there are differences between purging and gas blows. The commonality is that there’s flammable gas, a hazardous material, being released in the vicinity of workers and sources of ignition. We believe that sort of activity shouldn’t be conducted.
Was it surprising to discover that gas blows were occurring with some frequency?
Moure-Eraso: What surprised me the most was the high volume of gas that is used for this procedure. Here you have a system of pipes with solid debris and dust. Someone has the idea to clean it out by taking flammable gas at high pressure and blowing it out as hard as they can, not thinking what’s going to happen at the other end. That’s surprising.
Holmstrom: What we found was that gas blows were done for convenience. Many of our staff are from the oil and chemical sector, where the primary principle of chemical safety is to keep the hazardous material inside the piping and equipment, and not release it into the workplace. One thing we found was a misconception about how much force was really needed to remove a sufficient amount of contaminants in piping to clean it. We found much less force was needed than commonly understood.
What also made the gas blows inexplicable in our minds was that the gas blow itself could serve as its own source of ignition. Static electricity or an ejected metal contaminant particle can strike another metal surface, creating a spark. In two of the previous incidents involving gas blows, it was determined that the source of ignition was actually the gas blow itself.
Digging deeper into this issue, we surveyed a group of people who construct power plants called the Combined Cycle Users’ Group. We found that, while gas blows were the single most used technique for cleaning piping, almost 50 percent of people use safer techniques, which was an indication that inherently safer techniques are available and broadly practiced.
What are these safer techniques?
Holmstrom: Less-hazardous alternatives include air blows, nitrogen blows, or using a pig [a cleaning device with bristles that is placed inside a pipe and propelled along the pipe by the inert gas media] that don’t present the fire and explosion hazards of a flammable gas. We think those alternatives are commonly practiced and are not expensive. When we asked those who have performed gas blows why they used a flammable gas instead of a non-flammable one, they never had any technical reason to use a flammable gas. We think it was done because the gas was there and was convenient.
What’s your take on NFPA’s response to the Kleen Energy explosion — establishing a new committee and beginning work on a provisional standard regulating this practice?
Moure-Eraso: The first discussions we had with NFPA were to see if the scope of NFPA 54 should be changed. After much discussion and testimony, we decided that gas blows were a separate issue unto themselves and that a new NFPA committee would be created to specifically address this issue. That’s a very important initial response. I feel we’re moving in the right direction.
Outside of these code provisions, what else should be done to prevent similar incidents from occurring?
Moure-Eraso: We have to look at the power plants themselves. They are running these operations, building these operations to produce electricity using gas. It will be important for them to take the initiative to say that, through the process of construction, gas blows should be forbidden. That will be another aspect of preventing this from happening.
Holmstrom: We just had a discussion on the future of the energy industry, and a point was made that the United States was one of the largest producers of natural gas and that it will increase in years to come. Fuel gas safety will become a much bigger issue, and a number of power plants are going to be converting from coal to natural gas. We identified 150 or so power plants that will be constructed over the next five years. States such as Connecticut have already banned gas blows. When states take that kind of action, which is unusual, it obviously speaks to codes-and-standards-setting bodies following suit. It would be inconceivable to say gas blows can be done safely, but with an asterisk and the words "except within the state of Connecticut."
In other words, these practices must be uniform. That’s the importance of NFPA and the code-making process, and we feel confident NFPA is heading in the right direction, and we’ll end up moving beyond the practice of gas blows and use safer alternatives.
Moure-Eraso: Another preventative strategy is federal regulation. We made recommendations to the Occupational Safety and Health Administration to specifically ban this procedure, and the last thing we heard from OSHA was that they were considering it. We are expecting some movement there.
What do you hope NFPA members take away from your presentation at NFPA’s Conference & Expo?
Moure-Eraso: One of the leading concepts in preventing incidents like these and protecting workers’ health is having inherently safe practices in industrial settings. That’s what we should be looking for, and to avoid taking unnecessary risks. Inherently safe practices do not try to manage the risks, but instead try to avoid them from the beginning.
— Interview conducted by NFPA Journal staff writer Fred Durso, Jr.