preface
The main engine of the ship is the power core of the ship, and the good operation of the main engine is the key to ensure the safety of navigation. Since April 7, the Maritime Safety Administration of the Ministry of Transport has carried out a nationwide special action to prevent the failure of ship mechanical and electrical equipment, reduce the risk of ship mechanical and electrical equipment failure, and prevent and curb the occurrence of water traffic accidents. The following introduces a typical case of the increase in the starting air consumption of the main engine due to the oil leakage of the main engine fuel injection control unit, which leads to the loss of control of the ship, hoping to attract the attention of relevant shipping companies and ships and strengthen self-inspection and self-correction.
Case Introduction
In July 2024, on the way to unberth at the wharf, the pressure of the main engine starting air cylinder was insufficient, resulting in the failure of the main engine to start and the ship lost power. After receiving the report from the ship, the maritime department immediately launched an emergency response, organized traffic on the spot, dispatched a nearby tugboat to assist the ship in stabilizing its position, and coordinated anchoring in temporary waters. Subsequently, the PSCO boarded the ship for inspection.
Fault cause analysis and solution countermeasures
After PSCO boarded the ship, it immediately learned from the ship the reason for the loss of control of the main engine (the main engine model: Wartsila 5RT-flex 50-D). The ship said that due to the frequent use of the car by the pilot when leaving the berth, the main engine started and stopped many times, and the pressure of the main starting air cylinder dropped rapidly, which eventually led to the insufficient pressure of the main starting air cylinder and the failure of the main engine starting. Subsequently, PSCO checked the ship's clock record and found that the ship's main engine started and stopped 4 times in the past 20 minutes (see Figure 1 below).
Fig.1 The clock of the ship is recorded
The main engine can only start and stop 4 times in 20 minutes, which obviously cannot meet the needs of frequent speed regulation and reversal in the narrow waterway of the Yangtze River. Referring to the IACS (International Association of Classification Societies) Unified Interpretation (File No. UI M M61.1.5) and the requirements of Chapter 9.5.1.6 of Chapter 3 of the Code for the Classification of Steel Seagoing Vessels of China Classification Society, if the main engine is started by compressed air, at least two starting air cylinders with basically the same capacity and can be used separately should be provided. Its total capacity should be not less than 12 times continuously from the chiller for each reversible host without supplemental inflation, and the test should be carried out alternately in reversing; For each non-commutating main machine, it can start from the chiller no less than 6 times in a row. Therefore, the ship's argument that the pressure of the main engine air cylinder was insufficient due to the frequent use of the vehicle was obviously untenable and was not accepted by the PSCO. Subsequently, the ship's second briefing pointed out that the starting air consumption was likely to be due to the ship's use of light fuel oil, insufficient viscosity, and difficulty in establishing oil pressure. PSCO consulted the relevant information of the same type of main engine, and the use of light fuel oil for this type of main engine does not necessarily lead to difficulties in establishing oil pressure, and the ship should consider the safe operation of the main engine before selecting light or heavy fuel oil.
To find out the root cause, PSCO went on to inspect the main engine starting air cylinders and air compressors. The inspection found that the air compressor was running normally, and there were no other obvious problems with the air cylinder except for a slight leakage of the residual valve. When further checking the main engine, it was found that after the first start failure, the main engine control system automatically entered the "heavy start program" program, and the system automatically extended the starting time, increased the air intake and oil supply, and finally started successfully. The compressed air consumed in the "restart" mode is much higher than the compressed air consumed in normal starting, resulting in more compressed air being consumed each time the main engine is started. After further analysis, PSCO preliminarily judged that the reasons for the difficulty in starting the main engine may be the insufficient starting oil supply, the leakage of the main engine fuel injection system, and the long time to establish the common rail fuel pressure, resulting in the difficulty of starting and the increase in starting air consumption. In this context, PSCO requests that the shipowner contact the classification society and the main engine supplier for assistance.
Under the guidance of the main engine supplier, the ship dismantled the main engine fuel common rail high-pressure oil pipe and fuel injection control unit (ICU). During the disassembly, it was found that there were leaks in many places such as the No.2 to No.5 main engine fuel injection control unit, fuel common rail safety valve, fuel supply pump, etc., due to wear and deformation, which also confirmed PSCO's preliminary judgment on the root cause of the failure.
Fig.2 NO.5 fuel injection control unit of the ship's main engine
Fig.3 Wear details of the ship's old high-pressure oil pipe joints
Fig.4. Replacing the fuel injection control valve
The ship replaced the two fuel injection control valves (ICV) and fuel common rail safety valves of the NO.5 and NO.3 fuel injection control units. After the replacement, the main engine was started test, and the main engine was reversed and started alternately 12 times within 5 minutes, and the main engine started normally. Subsequently, PSCO boarded the ship to verify the main engine starting test, and required the captain and classification society to provide safety statements and emergency measures, and allowed the ship to sail after implementing the self-inspection before the ship sails and the safety measures for the ship's navigation in and out of the river.
Figure 5 Classification society statement
Security management recommendations
(1) Strengthen emergency response. In the event of a failure of mechanical and electrical equipment, the ship should be operated at the residual speed of the ship according to the on-site navigation conditions and the lack of speed preservation ability after the ship is out of control, and if necessary, the double anchor should be used to control the ship's position, and the ship should be reported to the surrounding ships through VHF and other communication methods in a timely manner, and the surrounding ships should be reminded to take avoidance measures, and at the same time, the nearest tugboat should be contacted as soon as possible to assist in stabilizing the ship's position.
(2) Implement entity responsibility. Ship management companies and ships should implement the main responsibility for production safety, ensure that the ship's key equipment and technical systems are effectively maintained and maintained, and strengthen the inspection of wear, looseness and deformation of moving parts. Strictly implement the self-inspection before the ship sails, strengthen the effectiveness test of key equipment, and eliminate the hidden dangers in the bud.
(3) Face up to the root causes. For ships whose fault causes cannot be identified, engineers from professional institutions such as equipment manufacturers should be invited to board the ship for testing, and the causes of the fault should be eliminated in time to completely eliminate potential safety hazards.
(4) Strengthen supervision and inspection. The maritime safety administration should strengthen the prior supervision of ships entering the river, urge the ships to strictly implement the self-inspection before sailing, and carry out emergency drills to prevent the loss of control of ships before entering the river. Combined with the requirements of the special action to prevent the failure of mechanical and electrical equipment, key mechanical and electrical equipment such as the main stage, steering gear, generator and windlasse are regarded as mandatory items, and the technical status of the equipment and the emergency operation ability of the crew are strictly checked, so as to prevent and resolve the risk of losing control of ships entering the river.
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