Fault phenomenon: A certain ship discovered that the stern shaft water seal failed during navigation, and a large amount of seawater leaked into the engine room.

Cause search: After the crew stopped for inspection and maintenance, it was found that impurities were attached to the contact position between the stern shaft and the sealing ring, causing seal failure.

The stern seal type: Water Lubricated Stern Tube Seal (EVK 610), water-lubricated SELON COMPAC stern bearing system.

The main materials include: Casing: CAC 406, Mating Ring: CAC 302, Seal Ring: Rubber NBR

This vessel had operated for only a little over 3000 hours since launching. A vessel of the same model with a water-lubricated stern shaft experienced the same leakage after its main engine had run for more than 9000 hours. This fault is closely related to the waters in which the vessel operates. Vessels sailing in heavily silt-laden or turbid waters require particular attention to stern shaft seal condition. If signs of increasing seal leakage appear, dismantle and inspect the seal early to avoid an unexpected incident that leaves little room for response.

Pay attention to the following matters in daily management:

1. During daily inspection and inspection, slight leakage of the stern shaft is allowed. Once a change in leakage is found, attention must be paid.

2. The garbage attached to the stern shaft found during ship disassembly and inspection belongs to the sediment category and should be brought in from outside. Since this form of tailshaft cooling water is an open system, impurity residues are more likely to occur in some shallow water areas, muddy water areas and intersection areas between seawater and fresh water, especially when entering inland river basins, which is unavoidable. Engine management personnel are required to dismantle and inspect the stern shaft sealing ring in advance based on the actual situation of the ship.

3. Carefully study the stern seal disassembly and inspection process and its precautions in advance: Clean the contact surface during disassembly and inspection, add butter to facilitate assembly, and avoid damage to the seal ring contact surface. The HALF block cleans the boss and maintains a tight fit with the sealing ring pressing surface. Before assembly, carefully inspect the lips of the sealing surface to avoid damage. Do not apply butter between the HALF block and the sealing surface during assembly.

4. A small amount of leakage is beneficial to the lubrication and cooling of the seal, but the daily leakage 100L-200 continues to leak into the engine room. The condition of the sealing ring needs to be checked in time. If the sealing ring is damaged, the sealing ring needs to be replaced. The installation of the spare sealing ring on the stern shaft requires professional manufacturers to bond it, so the use of the spare sealing ring needs to be cautious.

Source: Sailor M Crew

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