Last November, a routine maintenance check of a ferry in Walla Walla, Washington, ended in the destruction of an electric drive motor which put the watercraft out of commission for five months and cost $3 million to repair. Washington State Ferries investigators determined that the incident could have been avoided if preventative maintenance and engine repair crews at the Eagle Harbor Maintenance Facility had followed protocol.
"We conducted a thorough and detailed investigation into what happened and why," said David Moseley, Washington State Department of Transportation assistant secretary, ferries division. "Safety is our No. 1 priority at WSF. We need to learn from these mistakes and focus on improving complex maintenance practices."
What caused the problem?
The maintenance crews originally claimed that the incident was caused by dust or paint on the motors, and that they didn't have sufficient time or manpower to do the job properly, reported Kitsap Sun. But the investigation determined that the engine damage was caused by human error. The workers were unfamiliar with the tasks, since they hadn't performed this particular type of work on the motor before, and they didn't have written instructions to follow.
Two separate groups of workers - maintenance and engine crews - did not communicate properly during the maintenance. Each group thought the other had taken steps to contain the current before electrifying part of the propulsion system. When power was sent to one motor so it could be turned during reconditioning, the second motor also received electricity but was locked and unable to rotate, reported Kitsap Sun. The current caused two brush assemblies to overheat and melt connecting metals. As the room heated, a temperature alarm sounded, but workers had to wait 45 minutes for the engine room to cool down and the smoke to clear before entering. Although there was no fire, the engine's motor was severely damaged.
How could it have been prevented?
Officials are now saying that the problem could have been detected immediately, and prevented, if a worker had been present in the engine room and had discontinued the reconditioning process. In the future, the Washington State Ferries plans to give appropriate training before complex maintenance, establish checklists, meet with personnel before working on vital equipment and explore alarms or equipment monitoring technologies.
Unfortunately, routine maintenance incidents like this one are all too common in industrial, plant, mining and other situations. In this case, human error cost millions of dollars and many lost hours of productivity. Companies that depend on complex equipment and mechanical systems may want to consider predictive maintenance practices that allow them to make smarter maintenance decisions and that better inform workers about how systems are operating.