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February 3, 2003
Volume 81, Number 5
CENEAR 81 5 pp. 23-26
ISSN 0009-2347


SIMPLY SAFER
'Inherently safer design' promises safer plants through better chemistry and engineering

JEFF JOHNSON, C&EN WASHINGTON

Over the past few years, participants in a sharp national debate have argued long and hard over how best to protect a chemical plant from a terrorist attack.

More guards? More inspections, hide or disguise the plant, study its vulnerability and strengthen the facility? Or maybe just do away with the chemicals and processes most likely to explode or kill or injure people?

Two years ago, Sen. Jon S. Corzine (D-N.J.) and other senators proposed legislation offering the last approach as an antiterrorist option for large plants that handle large volumes of toxic chemicals and are located in urban areas. All heck broke loose during the debate, but Corzine brought new attention to a simple, powerful, yet often misunderstood tool to make plants safer. Coined "inherently safer design" by British chemical engineer Trevor Kletz in the late 1970s, the concept seems simple: It is better to design processes that eliminate chemical plant hazards at the beginning than to engineer "add-on" technologies later to try to control them.

Kletz, who is retired after 38 years with ICI, puts it like this, "The very best way to prevent an explosion is to simply replace the material that explodes with one that does not or at least keep the stock down so low that it hardly matters if it all leaks out."

The concept was seized upon during the terrorism debate as a hazard reduction solution with safety benefits that go beyond terrorists and could include cutting the use of toxic chemicals. Kletz tempers that view by noting that not every process can be made inherently safer.

Industry hated the whole idea, and universally opposed the bill.

Instead, the American Chemistry Council (ACC), which represents major chemical producers, created its own security-based program for its members, and ACC and several company officials called the Corzine bill the latest step in a long road toward government and, particularly, Environmental Protection Agency interference in chemical plant operations (C&EN, Oct. 28, 2002, page 29).

FOUR PATHS FOR INHERENTLY SAFER DESIGNS

* Minimize or intensify. Use smaller quantities of hazardous chemicals. For instance, reduce inventories of in-process intermediates and raw materials or intensify production by increasing reaction efficiencies.

* Substitute. Replace a hazardous chemical with a safer one, such as eliminating hazardous solvents in cleaning operations or in paints and coatings.

* Moderate. Shift to less hazardous processes and chemicals, and modify facilities to minimize the impact of hazardous chemical releases by using, for instance, lower pressure and temperatures.

* Simplify. Design facilities to eliminate unnecessary complexity and make operating errors less likely and more forgiving. For instance, depend more on in situ creation and use for highly reactive toxic chemicals.

SOURCES: Dennis Hendershot: http://home.att.net/
%7Ed.c.hendershot/index.htm
; Trevor Kletz: "Process Plants: A Handbook for Inherently Safer Design"; American Institute of Chemical Engineering: "Inherently Safer Chemical Processes"

INDEED, there has been a long march. In the past 10 or 15 years, communities, environmental groups, academics, and state and federal officials have kept pushing for a string of programs to cut industry's use of toxic chemicals.

With names like toxic use reduction, pollution prevention, or green chemistry, the plans have a common goal of reducing use of toxic materials to make workers, communities, and the environment safer. The programs met lukewarm support at best from the U.S. chemical industry, and they often faced outright hostility.

Corzine's bill, for instance, grew from a law that required "risk management plans" and prompted a huge industry outcry. Under the risk management program, some 15,000 companies were required to present hypothetical worst-case accident scenarios for toxic chemicals they used in large quantities. The idea was to publicize the impact on residents from a hypothetical worst-case disaster at a plant and use public pressure to get companies to cut toxic chemicals stored and used there.

ACC and eventually the Department of Justice led a fight to limit public access to the scenarios, arguing that terrorists could use them as a road map for carnage. They won, and the scenarios are nearly impossible to see today. And if someone publishes them, that person could be sent to jail (C&EN, July 3, 2000, page 16).

On the flip side, even industry admits that the limited public pressure resulting from the risk scenarios did work in many cases. Companies reexamined their processes and cut chemicals in order to get out of the risk-management regime and simply avoid the law (C&EN, Nov. 26, 2001, page 19).

However, many of the same groups that wanted the worst-case scenarios made public then turned to Corzine, figuring that if terrorism is such a big fear, maybe it could be used to reduce toxic chemical use. So far, they are losing again. Corzine's bill died in the last session of Congress after sweeping through a Senate committee. Industry opposition has been intense, and although the senator made efforts to soften the bill last year, it mattered little. However, it was reintroduced last month, and the debate may begin anew (C&EN, Jan. 20, page 24).

Meanwhile, the concept Corzine wanted--inherently safer design--is alive and well, say chemical engineers in industry, academia, and government. And although it appears sometimes to be misunderstood--even by industry--examples abound of its successful applications.


BEFORE AND AFTER In the future, chemical plants might look like conventional manufacturers rather than targets for terrorists by employing higher efficiency and process intensification that comes with inherently safer designs.
DSM IMAGES
 


"The first solution to a process safety problem should always be to get rid of the hazard, not control it."


"THE FIRST SOLUTION to a process safety problem should always be to get rid of the hazard, not control it," says Dennis C. Hendershot, a senior engineer with 32 years at Rohm and Haas. "Engineers like the bells and whistles," he continues, "and sometimes people look at a really complicated control system and say it is really well engineered. I see the opposite. Good engineering is simplicity."

Advocates point to a step process or a kind of hierarchy in using inherently safer design. It begins with designing to remove the hazard; applying passive controls that limit the impact of an accident without human intervention; moving to active controls or the bells and whistles; and finally, adding more operating procedures--but only if all else fails.

They point to pluses such as greater efficiency; less need for large inventories of intermediate chemicals; elimination of expensive active control systems; and less need for complicated, confusing operating procedures. In the end, the result could be a new world of smaller and highly efficient chemical plants.

But does it follow that the best way to curb the impact of terrorists is to simplify and eliminate the chemicals that give terrorists the chance to use a plant as a weapon, as proposed by Corzine? Kletz and Hendershot point out that inherently safer design can't always be done. Sometimes, what makes a product fundamentally useful also makes it hazardous. Would you buy gasoline that won't burn and explode or travel in an airplane that can't leave the ground?

And sometimes there is so much money and experience tied up in a tried-and-true design that a company will fight hard not to change it. And the last person they want to change it for is a government regulator. For these reasons, they also say that inherently safer designs should not be tied to regulations.

However, Kletz, Hendershot, and others with long-time chemical industry experience say industry, academia, and government should do much more to encourage the spread of what may ultimately be the safest, cheapest way to make chemicals.

Exploring that application was the focus of a symposium sponsored in part by the American Chemical Society and moderated by Mary Kirchhoff, assistant director of ACS's Green Chemistry Institute. Kirchhoff described the synergism between green chemistry and inherently safer design, and she singled out two companies that used the tools to eliminate highly toxic intermediates: Bayer replaced hydrogen cyanide in the synthesis of sodium iminodisuccinate, and Asahi Chemical eliminated phosgene in the synthesis of polycarbonate for plastic products.

A unique local program, based on inherently safer designs, was also described by Randall L. Sawyer, a chemical engineer with Contra County Health Services in California, at that same meeting.

Sawyer said the county law and a state accident-prevention program he administers trimmed industry toxic chemical use by more than one-third in the past decade. The local law requires him to conduct safety audits every three years at nine large companies in the county: four refineries and five chemical manufacturers.

The ordinance is new--implementation started in 1999--and it was written following a series of chemical and refinery accidents in the county. One accident--an oleum release--sent 20,000 people to the hospital, he said, and others resulted in worker deaths and national investigations.

In the case of oleum, he added, the responsible company cut its use by 95% and ended 1,000 oleum shipments each year through an inherently safer design review and county support.

Sawyer is one of five chemical engineers working for the health department and conducting process safety audits. They require an inherently safer system analysis audit for all processes covered by the ordinance.

The audits are complex, he says; for instance, at one refinery, county engineers interviewed 200 staff.

The best time to apply the concept, Sawyer says, is when engineers are designing a new process or facility. For new facilities, Sawyer says, the ordinance requires plant engineers to consider inherently safer designs three times: during the initial planning stages when chemical formulations are being discussed; again when equipment is being selected; and lastly, when the final design is subject to process hazard analysis.

Sawyer has limited enforcement powers. He can't fine a company but can turn to the county district attorney if a company fails to comply with a health department order. All this is unlikely, he says, because of the bad publicity that would ensue. But he adds, "Frankly, I think the companies would just as soon not face the ordinance."

Nevertheless, industry helped write the law, but as an alternative to a much more onerous one passed in the wake of community anger over industrial accidents.

 


"Sometimes people look at a really complicated control system and say it is really well engineered. I see the opposite. Good engineering is simplicity."


8105gov.kletzcxd 8105gov.hendercxd1
Kletz Hendershot
SAWYER HAS FOUND that the concept of inherently safe plants is not well understood, and his audits show little consistency in how companies interpret inherently safer approaches; some even identify procedural operating changes and signs as inherently safer designs. In response, Sawyer says the county wrote a guide to explain the concept.

Even chemical engineering experts have misunderstandings over how the concept works.

Illustrating this point is an editorial in the Houston Chronicle a year ago by a well-known designer of chemical industry safety instrumentation systems, who took the Senate to task for the Corzine bill.

To demonstrate the limitations of inherently safer designs, the editorial used as an example automobile seatbelts and airbags, and noted that thousands of people still die in car accidents. The editorial argued that Corzine was now trying to mandate the same design approach for chemical companies.

"The bill is completely unrealistic. Nothing in this world is inherently safe because there always is a human element involved, and mechanical devices do fail."

The editorial was much discussed in the chemical community. And Hendershot wound up offering a response. He particularly took issue with the claim that human or mechanical failure shows that nothing can be inherently safe. The concept's very basis, he said, is that systems do fail and people do make mistakes, but failures can be limited.

Airbags and seatbelts are add-on technologies, he continued, whereas inherently safer technologies for the automobile are energy-absorbing materials, internal protections for fuel tanks, breakaway signposts, or limited-access highways. Inherently safer designs don't end all accidents but are intended to limit their consequences through design.

"The debate," Kletz says, "illustrates that if we are going to urge inherent safety on anyone, we need to make sure they know what it is all about."

 


"It was appallingly bad engineering. It is like an airplane that makes round trips from London to New York and only 6% of the passengers get off."


EVEN FOR KLETZ, like the public in Contra Costa County, the need for inherent safety was driven home by an accident. For him, it was the Flixborough Disaster.

On a June Saturday in 1974, 28 workers were killed in a chemical plant explosion at Flixborough in England. The accident occurred at a nylon plant when cyclohexane ignited after escaping from a large reactor. Fires burned at the site for more than a week, and fatalities would have been much higher had the explosion occurred on a weekday.

"Why so big an explosion?" Kletz asks. He found out that only 6% of the feedstock that exploded was converted to product with each pass through the system. Consequently, some 400 metric tons of an inventory of cyclohexane was stored at the plant. About 40 tons escaped.

Sure, the system failed and leaked, he notes, but the damage would have been much less without the huge inventory.

"It was appallingly bad engineering," he says. "It is like an airplane that makes round trips from London to New York and only 6% of the passengers get off. The rest just stay onboard and enjoy the movies."

This fact was missed for years, Kletz says. Instead, investigators focused on the leak and tightened operating procedures. "In many companies, the gut reaction to an accident is to reroute procedures," he says. "They are starting at the wrong end of the hierarchy."

With a more efficient process,the plant--and the explosion--at Flixborough theoretically could have been one-seventeenth the size, Kletz notes. This potential he calls production intensification. Inefficiency, he says, is one sign of a dangerous design. Such inefficiencies are due to chemical industry expansion of the 1950s and '60s.

"There was a step change in technology," he says. "We were getting bigger plants, operating at higher temperatures and pressures, and if you made a mistake and opened a pipe at the wrong time, you might get away with it in the beginning, but not as the plants got bigger."

Industry's solution to the increasing level of hazard, Kletz says, was more controls. But in the late 1970s, he came to realize the industry needed a whole new approach for finding and fixing hazards, and that was inherently safer designs.

The solution for Kletz and Hendershot is to firmly ingrain the concept into teaching at chemistry and chemical engineering universities so that a new generation of students automatically sees inherently safer design solutions. Both estimate that only a handful of colleges do so now.

They also both push for government programs that provide R&D funding for inherently safe projects and a national awards program to recognize and promote successful technologies.

"There are far, far more opportunities for inherently safer designs than we are making use of today," Kletz adds.



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Chemical & Engineering News
Copyright © 2003 American Chemical Society



 
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