Why Following Correct Torque Procedures is Critical
Torque tools play a key role in ensuring safety and quality in a variety of industries. But these torque tools can only provide this quality when the correct torque procedures are followed. Click on the case studies below to read about what can go wrong when torque procedures aren’t followed correctly in a variety of industries.
Carnival Liberty Engine Room Fire
The US National Transport Safety Board determined that improperly torqued bolts were the likely culprit for an engine fire aboard the Carnival Liberty cruise ship on the 7th of September 2015.
It was established that a fire was caused by a leak from the fuel supply inlet flange on a fuel injection pump. Out of the four bolts used on this flange, investigators found that one had become detached, and another bolt was found loosely attached to the flange. This has caused fuel to spray out of the engine, which then ignited when encountering the hot surfaces of the nearby diesel generator. Both bolts were taken to a laboratory to be examined, and both were confirmed to have no signs of deformation or being stretched.
Within the manual for the engine, a Wartsila 46 diesel engine, there was no specific torque values stated for the bolts in question. Present in the manual was a table labelled “Tightening Torques for Other Screws and Nuts” which did specify a torque value for bolts which the same dimensions and strength class. None of the interviewed crewmembers could say if torque tools were used during the latest maintenance as they were not present at the time.
As a result, the US National Transport Safety Board concluded that the fire was caused by fuel spray, which in turn was likely caused by improper tightening of bolts during the last maintenance.