The Case of the Fire-Breathing Forklift

DN Staff

June 27, 2005

3 Min Read
The Case of the Fire-Breathing Forklift

In a Pennsylvania processing plant, cranes moved hot steel bars from "soaking pits" to rolling mills that turned the big slugs into flat sheets of varying width and thickness. The hot sheets were rolled into 40,000 lbs coils and moved by electric lift trucks with ram-like forks. These fang-like forks gave these trucks the looks of a mythical steel monster.

Standing in a centrally located compartment, the driver controlled this behemoth with one hand on a hydraulically assisted steering tiller, the other on a combined speed-control/lift-control tiller, and a foot on a brake control treadle bar.

Scene of the Crime

Coils were moved between the rolling mills, annealing, or other secondary heat-treatment facilities, and cooling/shipping areas. These loaded ram trucks had to drive over some of the roughest floor surface imaginable. The environment included rutted and broken concrete and hard-packed bumpy dirt. Any relatively smooth concrete flooring was crossed by a web of many flush-mounted, but rough, in-plant railroad tracks.

In daily, multishift use, the trucks received general maintenance by in-plant personnel and major repairs by dealer service personnel. Although carefully driven by an experienced driver, the truck in this case accumulated wounds requiring major repairs only a month before this calamity.

While moving a coil, the truck bumped across some in-plant tracks. The driver heard a hissing noise that quickly turned into a roar of flame that seared his arms, hands, and legs. With his clothes on fire and skin peeling from his burnt hands, the driver climbed over the panels that covered the batteries behind the driver's compartment. He scrambled to the edge and jumped some 5 ft to the floor, breaking both ankles. Fellow workers beat out his flaming clothes, turned fire extinguishers on the truck, and called paramedics.

The Investigation

The driver sued the truck manufacturer and the service company. The manufacturer's attorney retained a fellow consultant and me to try to determine the cause of the fire. The manufacturer furnished electrical schematics, hydraulic installation drawings, structural details, and production photos. The steel company furnished service records.

The plaintiff's expert opined that negligent design resulted in an unsupported hydraulic hose being abraded through its cover and steel braid by a nearby electrical cable. Further, he opined that the contact completed a circuit to the truck frame with a resulting arc that ignited a spray of oil from the pressurized hose; and that the fiery spray went through the motor control area, burned through the compartment covers, and burned the driver.

The theory gave doubt because this truck did not employ a grounded electrical system and a fault path would require a wire of opposite polarity to contact the frame. The cable that allegedly abraded the hose was the common line for the control system. There were no places where the control system "hot" side or even the common lines were grounded to the frame. There was no burn pattern near the alleged breach in the hose.

The Smoking Gun

Records showed that technicians had replaced two hoses from the lift cylinders to a tee fitting mounted to a steel bracket. This tee fitting and its bracket were not bolted to the frame. Circular markings showed where missing nuts and lock-washers had been once installed. Unrestrained, the heavy hoses could move around due to pressure pulsation and truck vibration.

The right-hand hose had rubbed against a sharp edge of the frame, cutting through the hose's elastomer layers and the wire braid reinforcement. It appeared that the resulting spray of pressurized oil went through an opening in the frame section and across the electrical panel which contained high-current motor control electrical contactors. Arcing from the electrically active contactors ignited the spray resulting in an intense flame.

The hoses, tee, and bracket were recently worked on, leading to the conclusion that the technicians didn't tighten the bracket fasteners, or had failed to replace them resulting in the hose breach and subsequent fire. My client, the defendant, settled before trial with favorable terms.

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