Increasing the speed of auxiliary engines on ships can lead to serious financial consequences. Studies show that direct repair costs in the cases examined average around $250,000. These costs include repairs, spare parts, specialized labor, and other support services. Additionally, the economic loss due to engine downtime can exceed repair costs. In the cases studied, repair periods varied from 22 to 90 days, primarily depending on the extent of damage, availability of spare parts, and warranty agreements.
Key Lessons from Claims
In two instances, shutdown signals and high-speed alarms were activated, but existing faults in the mechanical linkage prevented the fuel row from moving to zero. These engines continued to operate until the crew manually stopped the fuel supply. Both incidents caused extensive damage to the engine, including damage to bearings, valve equipment, and crankshaft components. Regular torque checks, inspections of pins and flexible links, and blue powder contact tests could have prevented these faults.
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Importance of Maintenance and Safety Testing
In another case, a new actuator was installed with incorrect rotation settings. Neither service engineers nor the crew verified the rotation direction and safety functions before starting the engine. This led to an immediate speed increase and major damage. The initial theory was that a display arm was stuck, but testing and isolation from the regulator showed no faults. The service provider later admitted that the incorrect actuator setting was the root cause of the issue.
In another case, extensive damage occurred where the resistant gear connected to the flywheel and adjustment wheel. Repairs included opening damaged holes, making large bolts, and reworking the generator. Investigations revealed that damaged speed sensors had contacted the flywheel, causing the loss of the engine speed signal. As a result, the overspeed protection system failed to initiate a shutdown. Additionally, the emergency stop valve malfunctioned due to worn O-rings, preventing control air from moving the fuel row to the zero fuel position.
Ultimately, the crew discovered serious damage to the roto-cap just a few months after a major repair. All cylinder units, rods, and pistons had to be replaced during the 22-day repair period.
The key lesson is to ensure that piston crowns, regulators, actuators, and link kits are compatible with the specific engine model before installation. Comprehensive safety system testing before returning the engine to service is also crucial.
How to Reduce Risks and Costs
After any work on control, fuel, regulator, or actuator, perform a local stop valve function test. Introduce air into the stop cylinder and confirm that the fuel row moves to zero.
If services have been performed, add confirmation of serviced parts as an item on the pre-start checklist. These actions are likely to identify stop signals, but mechanics may not work, and if settings are incorrect from the start, further issues may arise.
Check link integrity: Weekly visual inspections and monthly torque/contact confirmations are recommended. Accompany these inspections with monthly tests where it is observed that the row is pulled to zero.
Document and manage parts: Maintain accurate records (torque values, blue powder photos, rotation alignment images, overspeed test sheets, and hardness/rotation results).
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