If the mechanical and electrical equipment (main propulsion device, main power supply, emergency power supply, boiler, steering device) fails in the process of entering and leaving the port and waterway with heavy water traffic, the ship will lose its ability to maneuver, and it is very easy to cause dangerous accidents.
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, focusing on reducing the risk of ship mechanical and electrical equipment failure, and focusing on preventing and curbing water traffic accidents.
Some of the cases in the special action are representative and worthy of our reference. Below, Xiaobian introduces a recent case of insufficient supply of cooling seawater causing the main engine to cool fresh water and automatically stop at high temperature, and the analysis of the case exposes the lack of maintenance and low business level of the crew, hoping to arouse the vigilance and attention of shipping companies and ships, draw inferences from one another, and strengthen self-correction.
Case Description
The Jianghai direct container ship K sailed from Pudong on April 28, 2024, and sailed to Baoshan North Channel 69# at 0450 hours on the 28th, when the cooling seawater pressure of the main engine was too low, resulting in the temperature of the cooled fresh water being too high, the main engine automatically stopped, and the ship took the initiative to report to the VTS, and then went to the anchorage with the assistance of the tugboat to find the cause of the failure. On the 29th, in accordance with the requirements of the "Notice of the Maritime Safety Administration of the Ministry of Transport on Carrying out Special Actions to Prevent Failure of Ship Mechanical and Electrical Equipment", the security personnel carried out a special inspection on the ship to prevent the failure of ship mechanical and electrical equipment in combination with the FSC inspection.
Case review and analysis
After boarding, the ship described that at 0430 hours on the 28th, the main engine cooled seawater pressure low alarm, only 0.07MPa, the seawater cooling system of the ship is an open system, which is directly completed by the main engine with seawater pump on a daily basis. After the failure occurs, the big pipe wheel immediately starts the emergency seawater pump. The cooling seawater pressure rises to 0.14MPa, then check the seawater cooling system of the host, open the small valve at the outlet end of the seawater pump with the machine to exhaust, discharge a small amount of air, check the seabed door breathable valve, in the open state, at this time the host is running normally, stop the emergency seawater pump at 0435, the seawater pressure is 0.1MPa, the temperature of the cooling fresh water is normal, at 0440, it is found that the seawater pressure drops again, and the emergency seawater pump is turned on again, the seawater pressure is still too low, the engine room reports to the bridge that the host is faulty and requires the speed to be reduced, and the small valve at the outlet end of the seawater pump is checked again and tries to discharge the air, the seawater pressure is still too low。 At 0450, the temperature of the freshwater cooled by the main engine has reached 95 °C, and the main engine automatically stops due to the high temperature of the fresh water. At 0540 hours, with the assistance of the tugboat, the ship broke down at the anchorage to find the cause of the failure.
After anchoring, the ship's engine room personnel carried out troubleshooting, disassembled the outlet valve of the seawater pump with the machine, and found that the internal valve core was lost, and there was a large amount of foreign matter such as sediment in the valve body, and the ship determined that the cause of the failure was that the outlet valve of the seawater pump with the machine was blocked, resulting in low seawater pressure, and explained that the pressure was still not available after starting the emergency seawater pump again after the fault occurred because the outlet valve core of the seawater pump with the machine was lost, and the pressure head of the emergency seawater pump was bypassed from the side of the seawater pump. The ship cleaned up the sediment and foreign matter in the outlet valve, and the valve core of the outlet valve of the seawater pump with the machine was lost by closing the inlet valve of the seawater pump with the machine, and only operated the emergency seawater pump separately for cooling, and then reported to the competent authority that the cause of the fault had been found and eliminated.
The security personnel carried out a detailed investigation on the seawater cooling system of the main engine, which was provided with a seawater pump to cool the seawater during normal operation, and the emergency seawater pump was connected in parallel in the cooling seawater pipeline for emergency backup. At the beginning of the inspection, the chief engineer also said that both subsea doors were in use, but when the security personnel asked for on-site confirmation, it was found that only the low subsea door was open, and the high subsea gate gate valve was closed. When the chief engineer was asked whether the submarine door filter had been inspected and cleaned, the chief engineer told him that he was afraid that the submarine door gate valve was not closed tightly, so he did not dare to open the submarine door filter.
If it is found that the foreign body of the outlet valve of the seawater pump is blocked, it must be caused by the blockage or damage of the seawater door filter, and only the outlet valve of the seawater pump can not solve the fundamental problem, the first task is to check the blockage of the seabed door filter and clean it, and the emergency seawater pump is only used as an emergency. and identify the root cause of low seawater pressure to ensure that the seawater cooling system is functioning properly.
Fault correction and thinking
After the inspection, the ship focused on rectification, actively contacted the management company, and the crew dismantled the high and low submarine door filters under the guidance of the shore base, and found that the blockage was quite serious, and at the same time checked the submarine door ventilation pipe and found that the ventilation pipe was blocked. Subsequently, the crew cleaned the filter, blew through the ventilation pipe of the submarine door, repaired the outlet valve of the seawater pump, and repeatedly carried out operation tests, and the pressure was normal. Therefore, it was found that the root cause of this failure was the reduction of the seawater circulation area due to the blockage of the submarine door filter, and the blockage of the ventilation pipe, which caused the seawater pump to fail to start normally.
The main reason for the failure in this case was that the crew did not do basic maintenance, did not regularly disassemble and clean the submarine door filter, and did not regularly check and blow through the submarine door ventilation pipe. The foreign matter in the outlet valve of the seawater pump is actually flowing in through the submarine door filter, and the failure will not occur if regular maintenance is carried out. On the other hand, the crew lacks the awareness of switching submarine doors and is not familiar with the operation of switching submarine doors.
Security management recommendations
This is the third case in the jurisdiction of Baoshan Maritime Safety Bureau recently due to the lack of maintenance of the cooling system and the blockage of submarine door filters, coolers and other equipment, resulting in high temperature of cooling water, and finally leading to the failure of the mechanical and electrical equipment of the main engine automatic parking ship, which is worthy of everyone's vigilance.
Summer is approaching, when due to the increase in the environment and sea temperature, the cooling system requirements will be more stringent, Xiaobian suggests that all shipping companies, ships, and crews pay attention to and strengthen the regular cleaning of the submarine door and the normal maintenance of the ship's cooling system to ensure the cooling effect of the main and auxiliary power units and the safe navigation of the ship.
Source: Baoshan Maritime
Picks:
Today's Notices and Warnings
Li Xiaopeng presided over the ministerial meeting
Haiqing role model丨2023-2024 "Top Ten Outstanding Youths" of the maritime system directly under Ren Min
Case study (11) - the failure of the solenoid valve causes the abnormal shutdown of the main engine
Media Spotlight丨Maritime News Quick Facts, Issue 93