Carbide Leak Tied to Storing Gas in Steam Vessel

Union Carbide is still trying to piece together the events that led to Sunday’s leak of highly toxic aldicarb oxime from its Institute, W. Va., plant, which sickened more than 130 persons. But, by Wednesday, it had become clear that a number of factors--among them unusual storage of the chemical and a tracking computer not programmed to handle this substance--combined to cause the leak and the company’s delay of at least 19 minutes in notifying nearby residents of the danger.

Union Carbide spokesmen say that, as best as they can tell, the leak started when steam somehow entered the jacket surrounding a chemical reactor vessel in which 500 gallons of aldicarb oxime was being stored. That this chemical was being stored in such a container, rather than a normal storage vessel, was unusual: The reactor is designed to be surrounded by steam to control temperatures that spark chemical reactions.

If the aldicarb oxime had been in a regular storage container, company spokesman Thad Epps conceded Wednesday, it was unlikely that it would ever have been exposed to steam.

Moreover, the unit in which the spill occurred--a 40-foot-tall honeycomb of pipes in which several huge tanks are embedded--is being phased out by the plant as it prepares to produce aldicarb in a newer, bigger unit.

Safety Improvements

Union Carbide had undertaken $5 million in safety improvements at the plant after an MIC (methyl isocyanate) leak from its Bhopal, India, plant killed at least 2,000 persons last year. But the improvements had focused on the MIC unit, not on the unit where the aldicarb oxime leak occurred Sunday.

The company says that the incident began at 9:24 a.m., although some nearby residents insist that they smelled an unusually strong and foul odor as much as an hour earlier.

Steam surrounded the vessel, heating the chemicals and building pressure beyond the level for which the container was designed. Some of the chemical burst through an emergency valve and was channeled into a “scrubber” and flare system that made it harmless.

But some broke through three gaskets--seals between the pipes and vessel wall that are similar to the washers on a faucet--and into the atmosphere. And some came through a so-called rupture disk, which is supposed to relieve pressure when it gets too high. The company has not disclosed how much of the chemical escaped.

New Tracking System

One of the plant’s new safety features is a sophisticated $80,000 computer system designed to track and predict the movement of chemical leaks. However, Union Carbide had programmed it for only the three chemicals it considered most dangerous--MIC, phosgene and chlorine--and not aldicarb oxime.

Epps said that no more chemical data was added because the computer was only “a pilot program. We were testing the whole system out.”

Thus, although the company activated the computer and plugged in data for MIC--the best approximation of aldicarb oxime that it could devise--personnel at the time of the leak had to rely largely on eyes and noses to judge how far the gas would spread.

Gary Gelinas, president of Westlake Village-based Safer Emergency Systems, the California company that produced the system, insisted in an interview: “I think our system has proven itself in instances where it has been used successfully, and it’s unfortunate that chemical data for aldicarb (oxime) was not in the system. I think, if it had been, it may have provided better results.”

At first, Epps said, it appeared that the leak would not go far, so the supervisor handling the emergency concentrated on rescuing six workers in the unit. Then, about 19 minutes later, as light, variable winds picked up and spread the cloud across several hundred yards, the supervisor “reassessed the situation and the situation had changed,” so he decided to alert county emergency officials, the spokesman said.

Fear of Crying ‘Wolf’

When asked whether it would not have been more sensible to alert local authorities at the first sign of the leak, Epps had told reporters: “If you overnotify, you get into the position of the little boy who cries wolf, and that could be a very bad situation.”

In Washington, House Energy and Commerce Committee Chairman John D. Dingell (D-Mich.) said he will push for tougher emergency notification requirements in the Superfund chemical cleanup bill.

“I intend to offer amendments to provide even stiffer civil and criminal penalties for inexcusable delays in notification such as occurred at Institute,” he said.

A smaller chemical company may increase its stake in Union Carbide and attempt a “business combination.” Details in Business