Bleve kills two

NFPA Journal, Nov/Dec 1998 by Wolf, Alisa

On April 9,1998, two volunteer firefighters died in Albert City, Iowa, and six responders were injured when a burning LP-Gas tank exploded in a boiling liquid expanded vapor explosion (BLEVE). According to NFPA's fire investigator Robert Duval, who went to Albert City to speak with the state fire marshal and local sheriff's department and to examine the site of the BLEVE, the factors that led to the Albert City tragedy are worth considering now, while such fires are still relatively rare.

"It's definitely a type of fire that's out of the ordinary," Duval says. "Fires like this don't happen every day. On the other hand, it's not a fluke."

Most Popular Articles in Health: Fuel your workout: exercisers who eat before they work out have more energy ...; Soothe a dry, itchy scalp: 5 easy expert solutions; Cocktails and calories: Beer, wine and liquor calories can really add up. ...; The sour truth about apple cider vinegar - evaluation of therapeutic use; The, six best supplements you've never heard of: these secret weapons can ...; More »

NFPA's fire investigations database turned up two similar fatal fires that took place on farms in 1993 and 1997, the first in Warwick, Quebec, Canada, and the second in Illinois. Like the Albert City fire, these two occurred on farms where propane was used to heat buildings. In each case, the tanks' relief valves were operating when firefighters arrived, but they couldn't stop flames from impinging on the tanks and weakening the tank shells. And in each case, tanks ruptured in BLEVEs that sent pieces of metal flying at high velocities in random directions, killing those caught in their path.

Back in the '60s and '70s, when derailments of rail cars carrying liquid propane posed a real challenge, the railroads, the gases industry, and the fire service all worked to improve LP-Gas storage, handling, and firefighting. One of the best-known railroad incidents occurred in Crescent City, Illinois, in 1970, when 10 tank cars carrying more than 34,000 gallons (128,700 liters) each derailed. Three BLEVEs resulted, generating enough force to blow people, railroad ballast, ties, and track into the street, destroying most of the business district and several homes. Sixty-four people, many of them firefighters, were injured.

After several BLEVEs of this type, the railroad industry retrofit all tank cars carrying liquefied flammable gases by adding thermal protection, which protects against high temperatures that can weaken metal. Shelf couplers were also developed to prevent cars from uncoupling vertically, and head shields were fitted to protect against punctures from the couplers. Since these retrofits were completed in 1980, there have been no BLEVEs of tank cars in the United States.

The three fatal BLEVEs on farms over the past five years point to the need, once again, to train firefighters in the safe handling of LP-Gas fires and to enforce NFPA code requirements addressing the safe storage and handling of LP-Gas that have proven effective over the past two decades.

What is a BLEVE?

A BLEVE is a type of pressure-release explosion that occurs when liquefied gases, which are stored in containers at temperatures above their boiling points, are exposed to the atmosphere, causing rapid vaporization. This happens when a container fails. A BLEVE can occur when flame impinges on the tank shell at a point or points above the liquid level of the tank's contents, or when a tank shell is corroded or gouged. The heat from the fire causes the metal to weaken and fail as the internal pressure increases, and liquid-to-vapor expansion provides the energy that creates cracks in the container, causing the container to fail, and propels pieces of the container outward. The result is the mixing of vapor and air that results in the characteristic fireball that occurs when the fire ignites the vapor. During the process, the container's pressure relief valve operates, creating a large vertical torch and a screaming noise.

Those who experience large burning LP-Gas fires describe flames of up to 100 feet (30 meters) or more that slash the air and can brighten a night sky for miles, creating an eerie daylight. Those who've been close enough to a burning tank to hear the relief valves sound describe ear-piercing shrieks of "near sonic velocity," according to Bill Mahre, a private fire investigator working for the propane company on the scene in Albert City the morning after the blast. Responders described to him a near-deafening, high-pitched noise that competed with human voices on the fireground. When the tank BLEVEd, the sound of it woke people county-wide, and the force of it threw a deputy sheriff standing 200 feet (61 meters) away 15 or 20 feet (5 to 6 meters).

After the Albert City BLEVE on April 9, responders told Mahre that it was "absolutely silent. There was only the noise of the truck engines. It was completely dark and quiet." Responders also reported that only a few spot fires remained on the ground and in the surrounding buildings. The fireball seems to have completely consumed the LP-Gas.

The chain of events

The fire at the Herrig brothers' turkey farm was reported at approximately 11:10 on a Thursday night. Teenagers riding the farm's all-terrain vehicle without permission had driven over two pipelines carrying liquid propane from the 18,000-gallon (68,100-liter) tank to two vaporizer units. Fortunately, the teens were able to escape the vapor unharmed and go to a nearby farmhouse to phone 911. The ensuing vapor cloud that leaked from the ruptured pipes was probably ignited by the pilot light on one of the vaporizers, according to Mahre.

Featured Download

Speak Like a CEO

Health Care Industry

Bleve kills two

NFPA Journal, Nov/Dec 1998 by Wolf, Alisa

Find Research Guides for:

Find Featured Titles for: Arts

Most Popular Articles in Health

Most Popular Publications in Health