I. Emergency Response Steps for Diesel Engine Water Ingress
When abnormal conditions are detected in a diesel engine, such as a sudden drop in exhaust temperature or abnormal white smoke emission, immediate action must be taken.
The primary step is to decisively stop the diesel engine and quickly close all possible water source valves, including seawater, freshwater, and fuel line valves, to cut off the water ingress path and prevent further damage.
After stopping the engine, the crankshaft should be turned several revolutions using the turning gear as soon as possible.
This action is crucial. It can expel some of the water that may have entered the cylinders, effectively preventing internal parts from rusting or seizing due to accumulated water, thus creating conditions for subsequent repairs.
Next, a systematic and comprehensive inspection is required to locate the source of water ingress. The inspection should cover several key systems: In the cooling system, carefully check the cylinder liner, cylinder head, and cooler for cracks or leakage points;
In the air intake system, check the air cooler, intake piping, and scavenging air box for signs of water backflow;
In the fuel system, confirm whether water has mixed into the fuel;
In the lubricating oil system, check the oil in the crankcase for signs of emulsification or deterioration.
Based on the determined extent of water ingress, take corresponding corrective measures.
If only a small amount of water has entered, the injectors can be removed, water drained by turning the engine over, and the diesel engine started several times to flush out residual water. Afterwards, the engine oil and oil filter element must be replaced.
In the event of significant water ingress or a severe situation that may have caused a “hydraulic lock” (top cylinder), avoid blind operation, as core components such as the piston, connecting rod, and crankshaft may be damaged. In this case, wait for professional personnel to arrive for disassembly and repair.
After completing the repairs, a trial run must be conducted for verification. First, let the diesel engine run at low speed under no-load conditions for a period, then gradually increase the load.
During this process, closely monitor various operating parameters such as exhaust temperature, cooling water temperature, and oil pressure to ensure all indicators return to normal and the engine runs smoothly before confirming the fault has been completely eliminated.
II. Experience Summary and Preventive Measures
To avoid such faults, daily maintenance work must not be relaxed. Coolant should be regularly checked and replaced to ensure its effectiveness;
At the same time, air, fuel, and lubricating oil filter elements must be replaced strictly according to the schedule, and aging seals should be dealt with promptly to prevent problems before they occur.
Standardized operating habits are the cornerstone of safe operation.
Before starting the diesel engine, be sure to perform warm-up and turning gear checks;
During operation, various instrument parameters must be closely monitored at all times. Once any abnormal signs are detected, investigation should begin immediately to nip the fault in the bud.
Furthermore, emergency drills should be taken seriously.
Regularly simulating the handling procedures for emergencies such as water ingress allows crew members to remain calm when facing sudden faults and to operate skillfully and accurately according to procedures.
From the perspective of equipment design, there is also room for improvement.
For example, high-efficiency water separators or humidity alarm devices can be installed at the air intake. This can provide an early warning when water enters the system, buying valuable time for handling.
In summary, the core principles for dealing with diesel engine water ingress are “quick stop, quick drainage, quick inspection, quick repair”.
However, even more fundamental than emergency response is ensuring “daily maintenance is thorough, operations are strictly standardized, and contingency plans are fully prepared”.
Only in this way can accidents be prevented to the greatest extent, ensuring the continuous, healthy, and reliable operation of the diesel engine, the heart of the ship’s power system.
Introduction
In recent years, with the continuous growth of China’s foreign trade volume, the frequency and duration of sea voyages for ships, the main carriers of cargo, have correspondingly increased.
This places higher demands on the overall performance of the ship, as well as the capabilities of operating personnel in equipment usage, maintenance, fault analysis, and troubleshooting.
Particularly for the diesel engine and its auxiliary systems, which are the core of ship power, the probability and complexity of faults are increasing day by day, and the scope of faults is also widening [1-5]. Therefore, meticulous daily maintenance, timely and effective emergency response, and accurate fault diagnosis and troubleshooting are even more necessary.
This article is based on a fault case encountered by a ship during an actual sea voyage. It details and analyzes the handling process, extracting valuable experiences and lessons learned.
It is hoped that the analysis in this article can enlighten all ship marine engineering operators and managers to carefully inspect every possible fault point when a fault is discovered, conduct comprehensive analysis and consideration, thereby providing useful theoretical references and practical guidance for handling similar faults.
▲Source: Internet, Infringement must be deleted
I. Fault Occurrence and Handling Process
1. First Stage of Fault Occurrence
(1) Fault Phenomena
In mid-July 2019, shortly after a ship sailed through a fishing area, the starboard main propulsion diesel engine (referred to as the starboard main engine) located in the aft engine room began to exhibit abnormal phenomena including speed fluctuations, knocking and detonation sounds within the cylinders, accompanied by white smoke from the exhaust.
The duty officer immediately stopped the engine for inspection and found a large amount of seawater in the fuel lines of this engine.
Given this serious situation, all fuel oil tanks on the ship were immediately inspected.
The inspection results showed that, except for the standby No. 1 and No. 6 fuel oil tanks which were in normal condition, varying amounts of seawater were found in the No. 2, No. 3, No. 4, and No. 5 fuel oil tanks.
During the inspection process, the speed of the No. 2 generator diesel engine (auxiliary engine) in the aft engine room suddenly dropped, followed by an unannounced shutdown, causing a total blackout on the ship (the ship is equipped with 3 auxiliary engines usually used in rotation, requiring only one to meet the ship’s electrical demand).
At the same time, other main engines also successively experienced knocking, unstable speed, and white smoke emission. The duty officer immediately executed the emergency stop procedure and initiated the emergency response plan for handling.
(2) Preliminary Fault Screening
According to the ship’s documentation, the ship has a total of 6 fuel oil tanks, which are interconnected via pipelines allowing fuel transfer between them.
The oil pump is mainly used for transferring and distributing fuel among the fuel oil tanks.
Except for the No. 1 fuel oil tank (located in the lower forward part of the ship) and the No. 6 fuel oil tank (located in the lower aft part of the ship), which serve as reserve tanks, the No. 2 and No. 3 fuel oil tanks (located on the port and starboard sides of the lower forward engine room) serve as daily service tanks supplying fuel to the 2 main engines and 1 auxiliary engine in the forward engine room (as shown in Figure 1);
The No. 4 and No. 5 fuel oil tanks (located on the port and starboard sides of the lower aft engine room) serve as daily service tanks supplying fuel to the 2 main engines and 2 auxiliary engines in the aft engine room.
Figure 1 Distribution diagram of fuel oil tanks and diesel engines in the forward engine room ▲ Source: Internet, infringement must be deleted
During navigation, a ship needs to maintain stable buoyancy and stability. To this end, the ship is equipped with a computer control system that calculates the ship’s status in real time and adjusts the fuel distribution among the six fuel oil tanks by controlling the transfer pump to maintain the ship’s balance and stability.
When troubleshooting, the marine engineering operators first inspected the reserve fuel oil tanks (No. 1 and No. 6) and found no signs of seawater in them, thus ruling out the possibility of water ingress into the reserve fuel oil tanks.
Considering that the starboard main engine in the aft engine room was the first to show abnormalities, it was initially suspected that one of the fuel oil tanks No. 2, No. 3, No. 4, or No. 5 had been damaged.
Subsequently, during the inspection, traces of water flow were observed at the stiffener of the No. 4 fuel oil tank, leading to the preliminary judgment that there was a crack or corrosion perforation on the outer shell plate of the No. 4 fuel oil tank, causing seawater to seep into the tank.
(3) Emergency Response
After the fault occurred, the marine engineering operators immediately carried out emergency response and repairs on the relevant equipment. The main tasks included:
1) Quickly using hand pumps to discharge seawater from the No. 2, No. 3, No. 4, and No. 5 daily service fuel oil tanks;
2) Cleaning the fuel oil coarse filters and fine filters of each main engine and auxiliary engine, simultaneously blowing through the entire fuel oil piping system with compressed air, and then re-supplying oil to the system;
3) During the trial run, the main engine operated basically normally, but the plunger of the high-pressure fuel injection pump of the No. 2 generator seized and could not work properly. Subsequently, the No. 3 generator diesel engine in the aft engine room was started to supply power to the entire ship, and the high-pressure fuel injection pump of the No. 2 generator diesel engine was replaced;
4) After determining the cause of the fault, the sealing operation of the No. 4 fuel oil tank was immediately carried out. Thereafter, the two main engines in the aft engine room were supplied only by the fuel oil from the No. 5 fuel oil tank.
At the same time, isolation measures were taken for the other fuel oil tanks, with the diesel engines near each fuel oil tank using the fuel from their corresponding tanks.
After all equipment resumed normal operation, the duty officers strengthened inspections of the fuel oil tanks, and no further increase in water volume was found in any of the fuel oil tanks.
2. Second Stage of the Fault
After completing the emergency response for the diesel engines, several diesel engines temporarily resumed normal operation, and the duty officers correspondingly increased the frequency and intensity of inspections.
After a period of time, the temperature of the main propulsion shaft bearing rose relatively quickly, but since it had not yet exceeded the allowable upper limit, this phenomenon did not attract sufficient attention.
(1) Fault Phenomena
Approximately 2 hours later, the starboard main engine in the forward engine room also suddenly experienced unstable speed and knocking, accompanied by white smoke from the exhaust.
At the same time, the running No. 2 generator diesel engine suddenly shut down, causing a total loss of power on the ship.
Shortly after the emergency start of the No. 1 generator diesel engine in the forward engine room, it also shut down automatically, while other main engines successively experienced abnormal speed, intermittent stalling, and other problems.
Upon inspection, a large amount of seawater was found in the No. 2, No. 3, and No. 5 fuel oil tanks.
After another round of emergency response and re-supplying oil, the auxiliary engines could start and run normally, but the starboard main engines in both the forward and aft engine rooms could not start, mainly manifested by the inability of the crankshaft to rotate during starting.
(2) Fault Finding
By questioning the compartment duty personnel and marine engineering duty personnel, it was found that the faults occurred each time 10 to 15 minutes after transferring fuel from the reserve fuel oil tanks.
Although no seawater was directly found in the reserve fuel oil tanks, it could be inferred that the reserve fuel oil tanks had damage and water ingress.
Further inspection confirmed damage at the stiffener of the No. 6 fuel oil tank, through which seawater entered.
Furthermore, the starboard main engines in the forward and aft engine rooms could not start, and the crankshaft did not rotate. Since no obvious faults were found in other components and systems of the main engines, the cause of the fault still needed to be sought in the fuel oil system.
Specific inspection findings:
1) Seizure of the high-pressure pump plunger (main cause);
2) Slight sticking of the piston;
3) No display of main engine fuel oil pressure: caused by the seizure of the spring and *** inside the fuel oil transfer pump.
(3) Emergency Response
After the fault was confirmed, the marine engineering operators carried out emergency repairs on the relevant equipment. The main tasks included:
1) Quickly using hand pumps to discharge seawater from the No. 2, No. 3, and No. 5 daily service fuel oil tanks;
2) The marine engineering duty officers cleaned the fuel oil coarse filters and fine filters of each main engine and auxiliary engine, blew through the entire fuel oil piping system with compressed air, and then re-supplied oil to the system;
3) Carried out emergency repairs at sea: replaced the high-pressure pump plungers of the starboard main engines in the forward and aft engine rooms, replaced the fuel oil transfer pumps, replaced the injector needle valves, replaced the high-pressure fuel injection pump of the No. 2 auxiliary engine, and thoroughly cleaned the fuel oil systems of all diesel engines.
After the repair work was completed, the following emergency measures were also taken to ensure the continuous and stable operation of the power plant:
1) After each fuel transfer, first re-discharge any seawater that may have mixed in;
2) Cut off the original fuel oil pipeline of the generator. Connect a hose inserted from the top of the daily service fuel oil tank to ensure the extracted fuel is clean and free of impurities;
3) Keep all 3 generators running continuously to avoid plunger sticking or seizure due to prolonged shutdown.
II. Fault Analysis
Through detailed inspection during the dock period, combined with the entire process from fault occurrence to handling, and the distribution characteristics of the ship’s diesel engines and fuel oil tanks, the root causes of the fault were finally determined as follows:
1) When the ship passed through a fishing area, due to the large number of fishing nets in that sea area, the ship’s propeller became entangled with a fishing net, causing uneven stress on the propeller and unbalanced operation.
At the same time, the load on the main propulsion diesel engine increased suddenly, causing intensified vibration of the entire ship’s main shaft, with the vibration amplitude increasing axially towards the propeller.
The strong vibration was further transmitted to the main bearing, causing increased bearing vibration and rising temperature.
(Figure 2 Schematic diagram of fuel oil tank pipes and sounding rod) ▲ Source: Internet, infringement must be deleted
2) The ship was over 20 years old, belonging to the category of old vessels, and had not undergone extensive maintenance or repair recently.
The continuous abnormal vibration of the main shaft eventually led to fatigue cracking of the weld at the stiffener of the No. 6 fuel oil tank located at the stern.
As shown in Figure 2, after the weld cracked, seawater seeped into the No. 6 fuel oil tank through the crack.
Since the density of seawater is greater than that of fuel oil, the incoming seawater settled and accumulated at the bottom of the tank.
3) As shown in Figure 2, during the design of the ship, in order to maximize the utilization of fuel oil tank capacity, the fuel oil suction pipe was arranged at the middle position of the tank.
Therefore, whether for daily fuel consumption or inter-tank transfer, the seawater at the bottom of the tank would be sucked out first by the oil pipe.
However, the installation position of the sounding rod deviated from the center of the tank, and its bottoming depth did not reach the deepest part of the tank bottom.
This resulted in the inability to detect a small amount of seawater at the bottom of the tank using the sounding rod, even though this seawater could be smoothly drawn out by the fuel oil pipe.
(Figure 3 Schematic Diagram of Fuel Oil Tank Arrangement) ▲Source: Internet, Infringement Must Be Deleted
In the first stage of the fault, as shown in Figure 3, the ship’s computer control system automatically transferred fuel oil from No. 6 reserve fuel oil tank to each daily service fuel oil tank based on floating condition and stability calculations.
However, what was actually pumped during this transfer was seawater that had settled at the bottom of No. 6 tank.
The first tank to receive the transfer was No. 4 daily service fuel oil tank, which consequently mixed with the largest amount of seawater, causing the right main engine fuel system in the after engine room to first experience water ingress failure.
4) Due to the first stage transfer operation, No. 4 fuel oil tank received the largest amount of seawater, while No. 2, No. 3, and No. 5 fuel oil tanks only mixed with a small amount of seawater.
As the diesel engine continues to operate, it continuously draws fuel oil from each daily service tank. Therefore, the small amount of residual seawater in No. 2, No. 3, and No. 5 tanks is difficult to detect with the sounding rod, whereas seawater can be clearly detected in No. 4 tank.
Meanwhile, because the seawater at the bottom of No. 6 reserve fuel oil tank had already been pumped out, the sounding rod also failed to detect any abnormality.
This series of test results led to a misdiagnosis of the fault in the first stage.
5) Based on the misdiagnosis in the first stage, No. 4 fuel oil tank was sealed off and taken out of service. However, the damage and water ingress in No. 6 fuel oil tank did not stop, and seawater continued to seep in.
When the fuel oil transfer operation was carried out again, a large amount of seawater was once again transferred from No. 6 tank into No. 2, No. 3, and No. 5 daily service fuel oil tanks, thereby triggering a more severe second stage fault.
III. Fault Lessons and Recommendations
1. Fault Lessons
Throughout the entire fault handling process, the engine department personnel made significant efforts and implemented multiple countermeasures, basically ensuring the normal navigation of the ship, and the effectiveness is commendable.
However, reviewing the entire process still reveals some issues worthy of deep consideration.
1) Deficiencies in Ship Design
First, the hull structure design is unreasonable.
The root cause of this fault was severe vibration caused by the propeller becoming entangled with fishing nets, leading to cracking of the stiffener welds in No. 6 fuel oil tank and subsequent water ingress.
If the oil tank structure at that location had been integrally cast instead of welded, its vibration resistance and sealing performance would have been significantly improved, making such vibration-induced damage and water ingress faults difficult to occur.
Second, the installation position of the sounding rod is unreasonable.
As shown in Figure 2, because the insertion depths of the sounding rod and the oil outlet pipe in the ship’s fuel oil tank are inconsistent, the seawater at the bottom of No. 6 tank could not be detected by the sounding rod in the early stage of the fault, directly leading to a misjudgment in the fault analysis.
After the fault occurred, the ship modified the sounding rod of the fuel oil tank, moving it to the side of the oil pipe and ensuring consistent bottoming depth to prevent similar problems from recurring.
2) Duty Personnel Lacked Thorough Consideration, Information Reporting Was Inaccurate and Untimely
First, insufficient attention was paid to the signs of abnormally increased diesel engine load and intensified main bearing vibration.
When the ship passed through fishing areas, the main engine load increased noticeably, and the main bearing vibration also intensified. Although the magnitude was not large, the duty personnel simply attributed this to the influence of sea swell and did not realize it might be a precursor to equipment abnormality. Consequently, they failed to report it in time, missing the opportunity for early intervention.
Second, during the analysis and troubleshooting of the fault, there were omissions and delays in reporting critical information.
Post-incident investigation revealed that before the diesel engine fault occurred in the first stage, the transfer oil pump had already been running for some time. However, the engine room operators did not mention this situation promptly in the initial fault investigation report, causing the fault analysis to deviate from the correct direction.
3) Deficiencies in Emergency Response Measures
During the emergency response process after the fault occurred… After the fault occurred, the engine room operators quickly implemented a series of emergency response measures. The overall handling effect was relatively satisfactory, but the following deficiencies were still exposed: First, the severity of seawater corrosiveness was underestimated.
Upon discovering water ingress, priority was given to draining the seawater from the fuel oil tank, without immediately performing fuel oil flushing and blow-out protection on the relevant components of the fuel system.
This allowed the intruding seawater to cause severe corrosion to various components of the fuel system within a short period. Precision components such as the plunger and delivery valve assemblies of the fuel injection pump, the plunger assembly of the injector, and the plunger and spring of the fuel transfer pump were prone to sticking due to corrosion, affecting the normal operation of the system.
Second, the consideration during the fault investigation process was not comprehensive enough.
During the initial investigation phase, the operators inspected No. 1, 2, 3, 5, and 6 fuel oil tanks and observed no obvious water flow. They only found water flowing at the stiffener of No. 4 fuel oil tank and directly concluded that the outer shell plate of No. 4 oil tank had cracks or corrosion perforation leading to water ingress.
This judgment failed to fully incorporate other possible factors. For example, it did not adequately consider the transfer of fuel oil between tanks via the transfer pump, nor did it conduct an in-depth analysis of the root cause of possible cracks or corrosion perforation in the outer shell plate of No. 4 fuel oil tank.
Due to the misjudgment, targeted measures were not taken in time, leading the fault into the second stage, further exacerbating the degree of damage to the diesel engine system.
Based on the above analysis, the following usage and management recommendations are proposed for engine room operation and management personnel:
First, when a fault occurs, emergency handling must be timely and accurate.
For faults with high hazard and severe impact, accurate handling must be given priority; if manpower conditions permit, other faults with relatively minor hazards can also be handled simultaneously or promptly thereafter.
Second, during duty hours, engine room operators must carefully and meticulously inspect and pay attention to every operational detail of equipment and devices, not overlooking any abnormal signs, thereby providing sufficient and reliable basis for subsequent fault analysis and troubleshooting.
Third, when analyzing faults, it is necessary to be comprehensive and meticulous, deeply understand every link in the fault occurrence process, carefully examine all fault symptoms, systematically consider the cause and effect of the fault, thereby accurately judge and locate the root cause of the fault, and take corresponding countermeasures.
Fourth, proactive thinking and active action should be taken.
Once defects or hidden dangers are found in the diesel engine and its auxiliary equipment, proactive intervention should be made to carry out necessary technical improvements and optimizations on the relevant equipment or devices, fundamentally avoiding the recurrence of similar faults.
