Learning from investigations: Worker injured by pin ejecting under pressure


On 4 July 2019 a Caterpillar 797F haul truck was brought into the workshop at the Ravensworth Open Cut mine to undergo a 40,000-hour programmed component replacement. 4 days later, fitters were working to remove the pins from the lower left-hand suspension link. The fitters managed to successfully remove the rear pin, but the front pin became seized after being partially withdrawn. This created a cavity between the back of the pin and the inner collet approximately 70mm in length. A boilermaker was asked to conduct thermal lancing of the pin, to try to remove it. The boilermaker and spotter erected a scaffold on which to stand while performing the lancing. The boilermaker lanced a hole through the pin and quenched it with water. Quenching the pin causes a reduction in the outside diameter making it easier to remove. The fitters attempted to insert a pry bar through the hole however the hole was not large enough. The boilermaker resumed lancing, enlarging the hole through the pin. He turned off the lance and used a water hose to cool the area behind the pin clevis, helping to cool hoses and transmission components. He then applied water to the front of the pin. Water travelling through the pin contacted hot slag, and rapidly converted into steam. The sudden expansion of steam forcefully ejected the 47kg pin, hitting the boilermaker on his left side. For more information, and to see the full report, visit our website.

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