Root Causes of Propane Tank Explosion Near Albert City, Iowa


		AcuSafe -> June 2000 Newsletter
		Root Causes of Propane Tank Explosion Near Albert City, Iowa

This article is based upon a Chemical Safety Board investigation report dated June 23, 1999, and represents the findings of fact and conclusions of this document.

On April 9, 1998, at approximately 11:28 pm, an 18,000-gallon propane tank exploded at the Herrig Brothers Feather Creek Farm (the farm) in Albert City, Iowa. The farm raised turkeys, which were housed in seven barns. Space heaters and furnaces provided heat for these turkey barns. Fuel for these space heaters and furnaces was supplied by a propane storage and handling system that included the propane tank that exploded.

On the evening of the incident, a group of teens gathered at the farm for a party. As part of the festivities, two of the youths began driving an all-terrain vehicle (ATV) around the property. After some time the ATV was heading east between the propane tank and a turkey barn when it struck two aboveground propane pipes (liquid and vapor lines) that ran parallel to one another from the propane tank to direct-fired vaporizers approximately 37 feet to the north of the tank. (The direct-fired vaporizers were components of the system that used heat to transform liquid from the tank into a gas that was piped to space heaters and furnaces on the farm.) The ATV damaged both the liquid and vapor lines.

The liquid line, which measured approximately 3/4-inch inside diameter, was completely severed from the tank at the location where it was connected to a manual shut-off valve directly beneath the tank. An excess flow valve protecting the liquid line failed to function, and propane leaked out of the tank at the point of the break. As the liquid propane sprayed out of the tank, it rapidly changed to vapor. Propane vapor may have also leaked from the damaged vapor line. Within a few minutes, propane from the damaged lines ignited, most likely when it reached one of the direct-fired vaporizers approximately 37 feet away.

After the teenagers summoned the fire department, twenty members of the Albert City Volunteer Fire Department and two Buena Vista County Sheriff Deputies were the first responders to reach the farm. Upon arrival at about 11:21 pm, the fire fighters observed flames originating from two primary locations: from under the west end of the tank and from the pressure relief valve pipes located on the top of the tank. At approximately 11:28 pm, as fire-fighting equipment was being moved into position, the tank exploded, scattering metal tank fragments in all directions. One large piece of the tank traveled in a northwesterly direction, striking and killing two volunteer firemen. Seven other emergency personnel sustained injuries as a result of the explosion.

The CSB identified several root causes and one contributing cause to the incident:

ROOT CAUSES

1. Protection for aboveground piping was inadequate.
Two aboveground pipes (liquid and vapor lines) that ran from the propane storage tank to its vaporizers were not protected from potential physical damage from vehicles. Lack of piping protection allowed a vehicle to crash into these pipes, breaking them and releasing the propane that ignited.

2. The diameter of the pipe downstream from an excess flow valve was too narrow, which prevented the valve from functioning properly.
An excess flow valve that was designed to stop the flow of all but an extremely small amount of liquid propane in the event of a severed line did not function because the diameter of the pipe downstream from the valve was too narrow to allow the valve to activate. Post-incident tests of the valve showed that it would have operated as designed if the pipe downstream had been the proper size. A functioning excess flow valve on the liquid line would have greatly reduced the severity of the fire that engulfed the tank. This likely would have prevented the BLEVE.

CONTRIBUTING CAUSE

The State Fire Marshal did not detect deficiencies in the design and installation of the propane storage facility.
Under Iowa law, the State Fire Marshal should have received a plan of the farm's propane system prior to its installation in 1988. The State Fire Marshal had no record of the farm's system, however. Iowa law did not specifically designate which party -- the owner or the installer of a large propane tank facility -- was required to notify the State Fire Marshal. In addition, the State Fire Marshal did not have a program in place to adequately monitor or inspect large propane storage facilities.

As a result, the CSB made the following recommendations:

RECOMMENDATIONS

Herrig Brothers Farm

Install protection (i.e., fencing or barricades) to protect aboveground propane pipes from possible damage from vehicles.
Install properly sized propane outlet piping from excess flow valves.

Iowa State Fire Marshal
Develop a program to ensure implementation of the requirements of the National Fire Protection Association's NFPA 58 Standard for the Storage and Handling of Liquefied Petroleum Gases, as adopted by Iowa law. Ensure that this program includes, at a minimum, the following elements:

Designation by regulation of the party (such as a facility owner or installer) who is responsible for submitting planned construction or modification documents to the State Fire Marshal;

Procedures for approving the plans for new or modified installations;
Procedures governing the issuance and posting of permits authorizing the use of equipment; and
On-site inspections of new, modified, and existing propane and other Liquefied Petroleum Gas storage facilities that are covered by Iowa state law.

Fire Service Institute of Iowa State University
Ensure that fire fighter training materials address proper response procedures for BLEVEs.

National Propane Gas Association (NPGA)

Ensure that fire fighter training materials address proper response procedures for BLEVEs.
Distribute the CSB findings and recommendations in this report to NPGA members.