Anyone who has taken one of my HAZMAT or Process Safety training courses has heard about and seen video of the Atlas Foundry LPG BLEVE that occurred back in 2007. But in a recent process safety course, several students (volunteer FF’s outside of their full time job at this PSM facility) debated on the facts of the incident, of which neither was even close to being factual. So as we approach the 10-year anniversary of this fatal accident and BLEVE I thought it would be a good idea to set the record straight with what actually happened and how it happened. And yes, this was another HAZMAT UNLOADING incident gone bad…
Without a doubt, the best factual description of this incident comes from a “safety briefing” provided to the Tacoma City Council by Rich Hildreth, MEP. I have used some of Mr. Hildreth’s materials below in this posting, but I have scrubbed names and revised some other aspects of his briefing. It is advised that you visit his Blog at the link above and read his entire report.
Not only is this incident a case study on BLEVEs, it is also a case study on one of my “pet peeves” – PROPER UNLOADING/LOADING of Hazardous Materials. Many may not know that this fatal accident was caused by UNTRAINED PERSONNEL making IMPROPER REPAIRS to the UNLOADING HOSE which failed, leading to a Catastrophic and fatal “Loss of Primary Containment” (LOPC) event. Video #1 below, shows us the moment the hose fails and how quickly the LPG forms the flammable vapor cloud:
This event began with the delivery of propane by a 64-year-old experienced propane delivery driver. He was in the process of transferring 11,000 gallons of liquid propane to two 30,000 gallon stationary bulk storage tanks. Both stationary tanks were connected together by liquid and vapor transfer lines designed to allow transfer between tanks and/or simultaneous filling. Upon the tanker truck’s arrival at the facility, it was discovered by the driver that fittings on the liquid delivery line had separated from the hose and would require repair prior to offloading of the propane. These repairs were attempted by the driver and three (3) Atlas Foundry workers, none of whom had specific training for repairs of high-pressure lines. Repairs were made using items found on site including several hose clamps and pins not rated for use on high-pressure equipment. It should also be noted that the repaired hose was never pressure tested after the repairs. These improper repairs failed following activation of the Power Take Off (PTO) unit used to pressurize the transfer from the truck to the tank assembly. The security camera video clearly showed the driver hooking up this repaired hose to the truck, activating the PTO and walking towards the stationary tanks to open the Globe valves on the tank intake manifold. The truck was quickly surrounded with a cloud of propane vapors. These vapors found their way into the foundry and 34 seconds later were ignited by an electric arc furnace inside the foundry causing the initial fire and flash type explosion.
Adding to the series of events that led to this event was the failure of an internal Excess-Flow valve on the tanker truck. This valve located inside the MC331 tanker was designed to monitor actual flow rate against a preset safe flow rate. As designed, in the event of a rupture or pipe break, the valve should have closed without human interaction within 20 seconds. An additional safety device, a thermally activated valve rated at 250°F also should have closed, shutting off the fuel supply from the fire. These failures allowed fuel to feed the fire resulting in a BLEVE approximately seven (7) minutes later.
The initial flash type explosion seriously injured the driver; however, he was able to stumble almost 200’ to a perimeter fence and was taken to a hospital. Unfortunately, as a result of serious internal injuries and burns, he died four days later.
Breakdown of the Video
WARNING! Graphic Language in the video, control your volume!
At approximately the 30 second mark of the video, emergency vehicle sirens can be heard responding (This would be approximately 3 minutes after the initial explosion) and even from this location, an estimated 2000 feet northwest of the event, the roar of the fire itself can be heard. It should be noted that at the 1:27 mark in the video Emergency Response Vehicles can be seen in the background establishing a perimeter (this engine would be blocking traffic on South Tacoma Way south east of the fire). At the 2:08 mark small explosions believed to be the tires on the truck can be heard exploding. At the 4:15 mark the BLEVE occurs. It was this explosion that tossed one of the truck axles onto the elevated freeway overpass (Hwy 16). This overpass is almost 150 feet in elevation above the valley floor and almost 1000 feet away from the explosion. That overpass would be immediately to the right of the view shown in the video. Other debris landed on Interstate 5 seen in the background. The video below is from a DOT traffic camera and these roadways and the impacts can be seen. Also, debris from this explosion destroyed a Tacoma City Light substation located 500 feet away knocking power out to over 13,000 customers.
Because of plant layout, visual assessment of the scene was difficult; however, by rotating an elevated closed circuit camera operated by WSDOT located on the Highway 16 overpass the command staff were able to gain visual observation of the stationary tanks and scene. They could visually see flames erupting from the pressure relief valves located atop each tank and what appeared to be an active fire beneath the tanks fueled by a ruptured natural gas line. As Puget Sound Energy worked to shut off flow to the ruptured line, firefighters positioned three trucks with remote controlled water cannons within 150 feet of the fire and directed streams of water to cool the tanks to avoid additional BLEVE’s. Care was taken to use indirect water spray to allow the fire from the relief valves to continue to burn as this was safely allowing pressure to reduce while burning off the vapor. An additional reason to use indirect water spray is that icing could occur around the valves and safety devices, causing additional hazards or failures. To keep tanks of this size cool a minimum of 512 gallons per minute are needed based on the formula 5 x Sq. Root of the Capacity in US Gallons (Emergency Response Guide, 2012, p. 367). By the conclusion of this operation over 4 million gallons of water were needed to cool these stationary tanks. After Puget Sound Energy was able to cap off the ruptured natural gas line, firefighters extinguished the ground fire but allowed the venting propane tanks to continue to burn off vapor. The tanks were then flooded with inert gas and removed for disposal. Firefighters remained on scene for 24 hours to ensure all hotspots were extinguished. Washington State Department of Transportation inspectors examined the freeway overpass for any potential damage and Highway 16 was reopened about 11 hours after the initial explosion. On Sunday morning investigators from the Tacoma Fire Department, Washington State Labor and Industries and the Washington State Patrol then went to work to assess the series of events that contributed to this event.
In investigating the series of events that resulted in the fire and explosions at the foundry Tacoma Fire, OSHA and independent investigators looked over evidence including security camera documentation, fittings, and the remnants of the tanker truck. Based on these investigations, it can be safely assumed the series of events being reported resulted in the BLEVE and the death of the tanker truck driver.
It should be pointed out that propane gas is approximately 1.5 times denser than air. As a result, propane vapor clouds will stay relatively close to the ground and sink into open ditches, sewers and other low spots. It is considered highly flammable with a burning temperature of over 940°F. At an ambient temperature of 60°F, liquid propane has a density of approximately 4.2 pounds per gallon. As Propane’s boiling point is just over -43°F at atmospheric pressure and this boiling point increases as pressure rises, liquid propane must be stored in pressurized containers or tanks to maintain liquid form. When a pressurized propane tank is exposed to fire such as was seen in this incident, the liquid propane is heated above its boiling point causing the propane to convert from liquid to gaseous form causing an increase in pressure. Additionally, as propane is heated, the liquid expands at a rate of 1.5% per 10°F of temperature rise.
In transferring liquid propane, the transfer is accomplished with the use of two separate pressure rated hoses; the first for delivery of the liquid propane and the second to allow vapors to return to the truck. Each hose MUST be rated at a minimum of 1,700 PSI with fittings designed for both the pressure and to resist any corrosive or erosive impacts of movement of pressurized material. Additionally, multiple safety features including automatic shut-off valves are used in hopes of preventing this type of event.
When the improperly repaired hose connection failed, it enveloped the truck in a white cloud of propane gas. This cloud stayed relatively close to the ground and followed a drainage gutter approximately 75 feet and made its way inside the building. It is believed this cloud was ignited by an Electric Arc furnace located inside resulting in the initial explosion. There were two minor explosions followed by the BLEVE approximately 7 minutes into the event.
Case Forensics also investigated the cause of the BLEVE and noted in their report that the recovered globe valves on the stationary tanks were in the closed position which prevented propane from these tanks to add more fuel to the fire. The position of the thermally activated valve on the truck was also in the closed position; however based on the video footage and other indications it appears the BLEVE triggered the closure of the valve post incident. In the Case report it was noted that there were several design flaws in the valve in question. These flaws included the nylon plunger that was triggered by the fusible link, lacked sufficient force to push the release lever while under pressure. The CASE report concluded” an appropriate safety factor was not incorporated in the selection of an emergency safety device on an internal valve. A redesign of the valve further decreased the likelihood that the safety device could function to prevent a catastrophic event, such as a BLEVE from occurring.”
The Washington State Labor and Industries (e.g. WA-OSHA) issued a citation to Atlas Castings and Technology citing three (3) serious violations of workplace safety and health regulations (Labor and Industries, 2008). A fourth violation, not having a remote shutoff valve on the stationary tanks was not considered to be a factor in this incident nor did it contribute to the explosion. The four violations are listed below.
- Not properly training employees on the repair and maintenance of pressurized LP-gas systems.
- Using hose connections that were not rated for LP-gas service and would not withstand the pressure.
- Not testing the repaired hose after assembly to ensure it was free from leaks under normal use.
- Not having a shutoff valve with means of remote control to protect against uncontrolled discharge of LP gas from piping close to the point where the piping and hose connected.
Atlas Castings & Technology is appealing the citations making the following comments on each citation:
- The first concludes that Atlas failed to train two employees on the repair and maintenance of the propane system. The foundry contends these were not the employees’ duties, and that they would not have tried to fix the system had they not been urged and directed to do so by he truck driver.
- A second citation faults Atlas for using hose couplings that would not withstand the minimum pressure required. Atlas says the agency did not conduct performance testing to validate this opinion, and the use of the couplings was the responsibility of the truck driver.
- A third citation blames the foundry for not testing the hose after the attempted repairs, but Atlas states that its employees did not place the hose into use before the tests could occur, because that was the truck driver’s responsibility.
- The final citation finds Atlas responsible for not providing a backflow-prevention device closer to the site where the delivery hose was connected. However, the foundry stated, the evidence “shows that the system did have a backflow device in place. The backflow device was installed along with the original system in the early 1950s, at which time it was in full compliance with the then current codes and no upgrades have since been required.”
It is the foundry’s position that the driver was in violation of both Federal and State regulations when he failed to red tag the delivery hose and immediately take it out of service. It should be pointed out that the Department of Labor and Industries investigation was limited to Atlas Castings itself and that the Department does not have jurisdiction over the truck or the driver.
The family of truck driver filed a lawsuit against Atlas in February, contending his was an unlawful death. An attorney for the family told The Seattle Times that the Dept. of Labor & Industries investigation supports their allegation that Atlas workers failed to follow safety regulations prior to the accident, which require them to reattach a delivery hose to transfer the propane from the truck to a storage tank. “Atlas cut so many corners … They used parts sitting around the yard and just threw this thing together,” said attorney James McCormack told the newspaper.
Atlas has countersued the truck driver’s estate; IXL Transportation Services, which had the driver under contract; Engineered Controls International Inc., the manufacturer of the emergency shut-off valve on the propane tanker (MC331); and Pro-Techs Inc., a company that modified the valve — all because of “excessive damages to (Atlas Castings’) property and equipment.”
The foundry says IXL Transportation Services is responsible for ensuring that its trailers are properly inspected, maintained, and equipped and that all safety equipment operates correctly.
In addition, forensic consultants hired by Atlas have concluded that federally mandated safety devices on the tanker truck’s liquid-propane delivery valve, manufactured by Engineered Controls International failed to operate and close the valve, which caused the release of liquid propane gas that led to the fire and explosion. The forensic investigation also concluded that alterations to the delivery valve and safety devices by Pro-Techs Inc. were at least partly responsible for the failure of the valve to close.
Another great surce used in this posting is http://www.historylink.org/File/8612
EXCELLENT post accident photos: http://www.kevinfreitas.net/blog/photos-atlas-foundry-explosion-fire-aftermath/