The author served as the chief engineer of a certain ship in 2019. Before boarding the ship, he went to the company for training and was required to pay more attention to the working conditions of the auxiliary engine intake and exhaust valve drive mechanism and the inventory of spare parts after boarding.
After boarding the ship and taking over the shift, it is required that the three tracks inspect the driving mechanisms of the intake and exhaust valves of the three auxiliary engines and test their overall working conditions. Upon reviewing the maintenance records, it was found that all three auxiliary engines had varying degrees of alloy detachment in the intake and exhaust cam bearings, high exhaust temperature, stuck exhaust valves, deformed top rods, broken air valves, increased particle size in the system lubricating oil, decreased alkalinity, dirty turbocharger, and decreased scavenging efficiency.
The poor working conditions of the auxiliary engine have affected the safety of the ship and increased the workload of the crew. What is the reason for the poor working conditions of the auxiliary engine? Is it due to design reasons, substandard quality of spare parts, or problems with our management.
Don't just focus on treating your headache and foot pain, which wastes a lot of manpower and resources, and ultimately leads to a bit of confusion.
The clue to a complete solution to the problem lies in the dismantling and inspection of the oil head of the three rails, and the adjustment of the valve opening pressure. The auxiliary engine model of this wheel is Man B&W L16/24 , During the 2000 hour inspection and testing of the fuel injector valve opening pressure, it was found that the valve opening pressure of all 6 cylinder fuel heads had dropped to 240-270BAR, and several injector springs had broken. According to the manual, the valve opening pressure of this model was 550BAR, which was lower than 350BAR. Therefore, the valve opening pressure had to be readjusted. Influenced by tradition and experience, the valve opening pressure of this model's fuel injectors was adjusted from 550BAR to 440BAR. After readjusting the valve opening pressure, the test found that many fuel injectors had poor atomization, so they were replaced.
This kind of medical treatment doesn't seem to cure the root cause.
Is it because the quality of the fuel injectors is not up to standard? Why are there so many spare parts for the fuel injectors on board.
After carefully reviewing the manual multiple times, I found the following prompt:
" MAN DIESEL &TURBO----FUEL INJECTION VALVE TO BE CHECKED FOR L27/38, L23/30H, L21/31, L16/24,V28/32S, L28/32DF ,L1624S, L21/31S, L23/30S, L27/38S, L28/32 S-DF, L23/30DF"
In case of new nozzles, there can be a drop in the opening pressure up to 50 bar after a few operating hours .
This pressure drop does not mean any functional deficiency and is characteristic for all fuel injection nozzles.
This made us suddenly realize that it was a ship management issue, ignoring the running in period of the fuel injectors.
According to the instructions, after replacing the fuel injector, be sure to use it for a week and then stop the machine to readjust the opening pressure of the test oil head. This is to ensure good combustion conditions for the auxiliary engine.
After disassembling and inspecting the fuel injectors of the three auxiliary engines, according to the instructions in the manual, the fuel injectors were replaced and the valve opening pressure was readjusted. After running for more than ten hours, they were readjusted again.
After 2000 hours of testing and adjusting the valve opening pressure, the turbine was disassembled, inspected, and cleaned. The auxiliary engine operated at 75% load, and the exhaust temperature decreased from 440 ℃ to 270 ℃. Other fault phenomena also disappeared.
In fact, regardless of the model, whether it is the main engine or the auxiliary engine, the running in period of the fuel injector during use should be given sufficient attention.
The YANMAR 6N18L-V series model has the following description about the fuel injectors:
"Fuel injection valve drawing-out check &adjustment 1500-2000hrs the first time 500-800 hrs "
The UEC-52LA model also has the following description about the fuel injectors:
"The fuel injection valve is an element which governs properness of fuel combustion, in order to maintain satisfactory combustion,it is recommended to perform such inspection and maintenance as fuel injection test.etc.at about first 500 service hours and then,gradually extend the inspection interval according to the inspection results ."
So, when managing the fuel injectors of the main and auxiliary engines, we must follow the instructions in the manual and attach great importance to the running in of the fuel injectors.