Pressurized Vessels On Vehicles: Part 2 Pressurized Strut Challenges

Subject: Pressurized Vessels on Vehicles - Part 2 Topic: Catastrophic Failure of Pressurized Cylinders During Vehicle Fires Objective: Review real-world incidents of firefighter injuries due to failure of energy-absorbing bumper...


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Case Study Incidents

On Sunday, Nov. 21, 2004, the Windsor Locks, CT, Fire Department responded to a reported car fire. On arrival, the fire was confined to the engine compartment of a late-model Buick automobile. Firefighter Drew Hill was assigned the task of gaining access to the engine compartment by opening the hood at the front latch. He had just released the hood safety latch when one of the hood hinge struts exploded. Because the hood was still closed, the strut was in a horizontal position. When it failed explosively, it blasted straight forward like a missile. The almost 18-inch-long strut unit struck Hill in his upper thigh. It traveled through his bunker pants and pierced completely into his leg. It stopped with one end sticking out of each side of his leg. Hill reacted by reaching down and grabbing the burning hot strut and pulling the whole unit out of his leg.

From the West Coast, the Sacramento Metropolitan Fire District experienced a very similar incident. On Jan. 24, 2005, at approximately 1:28 A.M., a firefighter assigned to Engine 27 suffered a penetrating wound to the left leg during the extinguishment of a vehicle fire.

Engine 27 responded to a reported vehicle fire and arrived to find the engine compartment of a 1999 Pontiac Grand Am partially involved. Engine 27 initiated extinguishment operations by approaching the left front wheel well from a 45-degree angle with a one-inch booster line. The firefighter approached the vehicle in what is widely considered to be a direction of safety. The firefighter completed the initial attack at the wheel-well and then noticed flames through the front grill of the vehicle. The firefighter moved to the right corner of the vehicle and crouched at the corner with his right thigh resting against the headlight, extinguishing the visible fire in through the grill. The firefighter was looking for the latching mechanism when the piston body of the gas-filled hood strut struck him in the leg.

Investigation revealed that the hood strut was in the closed and compressed position in a track created by the inside of the right front quarter panel and the partially open hood. Examination of the original position of the hood strut revealed that the hood strut shaft attachment failed from exposure to heat and expanded driving the solid shaft approximately three inches into the base of the right A pillar. This caused the 14-inch strut casing to be propelled forward, striking the firefighter and penetrating his thigh. The strut casing was found in line with the original position 53 feet away.

The Sacramento Metro firefighter received a penetrating wound to the left medial side of the femur that exited through the back of the leg. He was wearing appropriate protective clothing that included 7.5-ounce-per-square-yard PBI outershell structural pants with seven-ounce-per-square-yard Aralite thermal liner.

Comparison of Incidents

The incidents of hood hinge strut failures being reported all across the country have some common factors. Firefighters must accept the fact that these pressurized struts are becoming more common on late-model vehicles. We must also recognize that because there are no designed or engineered relief valves on these units, they can and will fail any time they are exposed to high heat. This is not limited to vehicle fires. Sacramento Metropolitan Fire District experienced the failure of two pressurized struts on a vehicle parked inside a garage at a structure fire. One of these struts was launched upward and traveled approximately 60 feet. The other strut failed and was found on the driveway.

As firefighters, we must also accept that engine compartment fires present the greatest risk to firefighters regarding the failure of the struts. Remember, when the hood is closed, the strut is compressed and in a horizontal position aimed towards the front of the vehicle.

In the Connecticut incident, Hill was forcing the hood while standing in front of the burning engine compartment.