Wear limit of Marine anchor chain
1. Service life of Marine anchor chain wear
Generally with the ship scrap, every six months a security check. If serious damage is found, the Marine will order replacement. But the chances of that happening are zero.
Marine anchor chains are not based on age, but wear and tear. Every time when repairing the ship to measure, wear and tear exceed the limit to change.
No, usually wear is serious need to replace, otherwise the accident is their own!
2. Length of Marine anchor chain wear
Depending on the actual situation, from a few tens of meters to two or three hundred meters. Under normal circumstances, 4-7 times of the water depth is appropriate for the ship's anchor chain length, and the anchorage in strong wind and waves or poor bottom quality should be appropriately extended. Can be according to the following formula: 4D+145M two chain length. D is water depth.
3, Marine anchor chain wear reasons for job-hopping
In the process of anchorage or anchor lifting, the ship's anchor chain ring often jumps out of the sprocket chain groove and loses control, which is often called "job-hopping". If the job-hopping is serious, it will threaten the safety of the ship.
One of the reasons for chain hopping is the torus rotation, that is, sailors often say that the ship's anchor chain has "strong", serious when the ship's anchor chain in the chain cabin is twisted. The ship's anchor chain job-hopping only occurs in the process of anchoring and will not job-hopping in the process of anchoring. The solution is to pour out the anchor chain and trim it at a fixed time (at least once a year and around May is preferred):
The second reason is that sprocket grinding cut "mostly cast iron sprocket) and caused by the chain ring and sprocket ring groove shape displacement, due to excessive wear of sprocket, in throwing, anchor will cause ship anchor chain job-hopping. In the past, the way to solve the problem of how many anchors and anchor chains ships are equipped with is to replace the new sprocket during the planned repair or shutdown, which not only costs a lot, but also increases the repair period of the ship.
After carefully analyzing the stress of the sprocket and calculating the allowable stress of various materials, the original geometric shape of the sprocket is restored by surfacing on the premise of ensuring the strength (the cast iron sprocket needs to be first soldered on the worn surface with a small current of nickel electrode and then surfacing with ordinary electrode). Good results have been achieved. The first sprocket repaired by surfacing welding has been in use for 6 years, and there is no sign of waist loss or shedding in the surfacing place.
4. Evaluation of Marine anchor chain wear
Marine anchor chain is located in the Marine corrosion environment for a long time, and it is bound to be corroded and worn under the combined action of wind, wave, current and floating body movement on the sea surface, and the accumulated damage will affect the safety of mooring system. Therefore, it is necessary to conduct a reliable assessment of the damage of Marine anchor chain in the whole life period.
Under the combined action of Marine environment dynamic elements and platform movement, the analysis method of the internal response of each node contact surface and chain link structure of Marine anchor chain in the whole domain is presented, and the engineering numerical model of long-term dynamic response is established.
Based on the results of numerical simulation, the influence law and coupling mechanism of corrosion on the contact surface of Marine anchor chain joints and friction between chain rings are studied, and an engineering evaluation model of cumulative corrosion and wear coupling damage on the contact surface of Marine anchor chain joints is established.
Finally, it provides a basis for the evaluation of local strength and cumulative damage of Marine anchor chain in the whole life.
