How to Prevent Cylinder Cover Cracks in Marine Diesel Engines?
Introduction
For marine diesel engines, the cylinder cover is the most complex part among all components, and it is also one of the parts that bears the highest load. The bottom of the cylinder cover belongs to the combustion chamber, which directly contacts the gas, and also withstands the cyclical action of high temperature and high pressure. Therefore, cylinder cover cracks are one of the most common failures of marine diesel engines. This article will introduce the failure analysis and preventive measures from two aspects.
Failure Analysis of Cylinder Cover of Marine Diesel Engine
- Causes of Cylinder Cover Failure of Marine Diesel Engine The reasons for the failure of the cylinder cover of marine diesel engines are multifaceted, mainly including the following:
- The influence of thermal fatigue. The temperature at the bottom of the cylinder cover is as high as 400°C. The continuous thermal load and additional tensile stress will cause cracks to appear. If the local temperature is much higher than the allowable value and the running time of the diesel engine is prolonged, the additional tensile stress generated will be greater, and it will be easier to produce cracks.
- The influence of mechanical stress. The comprehensive effect of high-frequency alternating mechanical stress caused by explosion pressure and low-frequency alternating thermal stress caused by thermal load can also cause cracks.
- The influence of thermal shock. The continuous start and stop of the diesel engine and the impact temperature wave on the bottom of the cylinder cover make the ductility of the bottom components of the cylinder cover continuously decrease, eventually becoming brittle, and causing brittle fracture at the bottom of the cylinder cover.
- Improper operation of relevant personnel. Improper operation of relevant personnel will cause the parts to overheat, the temperature to be too high, and the mechanical and thermal stresses of the parts to exceed the allowable values, resulting in mechanical fatigue and thermal fatigue of the parts.
- Lack of daily maintenance and upkeep. Daily maintenance and upkeep are one of the important tasks to extend the service life of the machinery.
- Judgment of Cylinder Cover Failure of Marine Diesel Engine Whether the pointer of the cooling water pressure gauge swings, whether the water level in the water tank fluctuates, whether there is air leakage, oil stains, etc., and whether the indicator valve smokes or burns insufficiently can be used to determine whether there are cracks in the cylinder cover.
Preventive Measures for Cylinder Cover Failure
- Improving the Material Used for Cylinder Cover. Improving the material used for the cylinder cover can effectively reduce the occurrence of cracks. If the diameter of the cylinder cover is not more than 400mm, the material can be selected as grey cast iron. If the diameter of the cylinder cover exceeds 400mm, the material can be selected as ductile iron.
- Strengthening the Cooling of the Parts with High Temperature in the Cylinder Cover. A baffle can be added in the cooling water channel of the cylinder cover to increase the speed of water flow, and the guidance can be strengthened according to the needs.
- Reasonable Operation and Maintenance. Relevant personnel should operate the diesel engine according to regulations, and do a good job in daily maintenance and upkeep work to avoid damage to parts due to excessive mechanical or thermal loads caused by poor management.
Conclusion
Cylinder cover cracks of marine diesel engines are a common and serious failure, which will have a huge impact on the normal operation of the ship and the safety of the crew. Therefore, ship management personnel and operators should strengthen the maintenance and upkeep of the cylinder cover, reduce mechanical and thermal loads, and operate reasonably, so as to extend the life of the cylinder cover as much as possible and ensure the safety and normal operation of the ship.
