The anchor is mainly composed of an anchor claw, an anchor crown and an anchor handle, wherein the anchor handle is connected with an anchor chain through a shackle, and is connected with the anchor crown and the anchor claw through a pin shaft, and can rotate relatively within a limited range; The top of the fluke is designed with an acute angle to improve the soil biting performance of the fluke.
In navigation technology, there are many mature technologies and skills about anchor operation. However, in the design and inspection of ships, there are still doubts about the technical requirements of anchors in the industry, and a systematic analysis is needed.
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Application of anchor in ship code
The iron ship stop is connected to the ship with a chain, which can throw the anchor to the bottom of the water to stop the ship. The technical requirements for anchors in the ship code are aimed at mooring equipment temporarily moored in ports or sheltered areas due to waiting for berthing, tides and other reasons. Although anchors have many uses in ship operations and engineering operations, unconventional uses do not fall within the scope of the Code.
Figure 1 Anchorage Structure
1. shackles; ; 2. Handle/lever handle; 3. trematode; ; 4.pin Crownpin； 5. Crown board 6. Anchor chain.
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Number of anchors that the ship should be equipped with.
The ship anchor usually mentioned in the industry refers to the bow anchor in the ship specification. According to the classification standard of steel seagoing vessels of China Classification Society, the number of bow anchors is based on the number of outfitting pieces calculated in the standard, and it can be seen from the table that the number n of outfitting pieces is calculated according to the following formula:
Among them:
δ —— model displacement under load line in summer, t;
B-ship width, m;
H—— Effective height from the load waterline to the top of the highest cabin in summer, m; For the lowest floor height, hi is measured from the center line of the upper deck, or from the lowest line of the upper deck and its extension line parallel to the raised deck when the upper deck is discontinuous.
Table 1 equipment
Table 2 Configuration Table of Anchors and Mooring Equipment
for instance
Taking an international container ship of 1500TEU, which is suitable for 20 18 specifications, as an example, it is known that △ is 32844.6t, B is 25.30m, and the calculation process of H and A is as follows:
Table 3 Calculation process of outfitting number
Therefore, as can be seen from Table 2, there should be two bow anchors.
_ Weight of anchor
Table 2 above defines the mass of each bow anchor.
Note that the specification stipulates that the mass of each bow anchor can differ from the mass of the anchors listed in Table 2 above by -7% to +7%, but the total mass of the bow anchor should not be less than the sum of the mass of the listed anchors. The mass of anchor head of common rodless anchorage, including tip and rotating shaft, should not be less than 60% of the total mass of anchorage.
Bow anchors with rods can be used, but their mass should not be less than 80% of the mass of rodless anchors specified in Table 2 above. When the large grip anchor is used as the bow anchor, the mass of each anchor can be 75% of the mass of the common rodless bow anchor specified in Table 2 above.
When the super-large grab anchor is used as the bow anchor, the mass of each anchor can be 50% of that of the common rodless bow anchor specified in Table 2. For details, please refer to the provisions in Chapter 10 of CCS Material and Welding Code.
Similarly, taking 1500TEU container ship as an example, according to the number of outfitting pieces n, the mass of a single bow anchor should be 6900kg, but the mass difference of each anchor can be in the range of -7% to +7%, provided that the total mass cannot be less than 2X6900kg.
_ Do ships need to be equipped with anchors?
Ships built in different periods have different requirements for standby anchors, which cannot be generalized.
For a long time, the number of anchors is as required in the above-mentioned 2, and even according to the calculation, the number of the first anchor should be more than 2. The specification clearly stipulates that the third anchor, towing line and mooring line are not conditions for ship classification, but only guiding requirements.
Whether it is an international sailing ship, a domestic sailing ship or an inland river ship, this requirement is similar. In this case, providing a third backup anchor is voluntary.
However, starting from the specification of 20 18, the specification no longer has the above statement; Even in the code of 202 1, when the outfitting quantity is more than 205, the number of forecastle anchors is 3, that is, the third anchor-standby anchor is a necessary equipment.
Combined with the specification: "The bow anchor should be connected with its anchor chain, arranged on the ship and ready for use. The total length of anchor chain should be distributed as evenly as possible ",so it is far-fetched to require the connection between backup anchor and anchor chain; Spare anchors should also be equipped with evenly distributed anchor chains, so the length and storage of anchor chains may be problematic.
In the practice of navigation, even if the spare anchor is provided voluntarily, it is not necessary to be connected with the anchor chain and equipped with the anchor chain. This part of the research is not carried out here, but before the revision of the specification, anchors should be equipped according to the number required by the specification.
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Countermeasures for anchor loss on board
Because the ship will drift to a certain extent under the action of wind and waves in the process of anchoring, with the constant tension of the anchor chain, the anchor will get deeper and deeper at the bottom of the sea, sometimes it will get stuck in the gap of the reef, and there are also anchor walking phenomena caused by bad sea conditions such as typhoon and tsunami. In short, there are many reasons, including external environment, lack of good rowing skills, insufficient risk assessment, operational errors, improper maintenance, design defects and so on.
These phenomena lead to the following possibilities: (1) When the ship anchors, the anchor machine does not have enough tension to pull the anchor out of the seabed, and the ship has to abandon the anchor at this time; Sometimes in the process of anchoring, the anchor will be lost because of the break of the anchor chain or shackle.
Of course, there are also some other special circumstances, such as the ship being forced to abandon the anchor and anchor chain together with the chain abandonment device. According to statistics, every year about one ship in 100 may break down.
Figure 2 Mooring state
The loss of anchor and anchor chain will lead to collision and grounding accidents of ships and cause other damage to ships.
In case of similar anchor abandonment, from the perspective of ship safety and insurance, the shipowner must apply to the classification society for inspection and issue a certificate of status to ensure the seaworthiness and effective insurance of the ship. Before this, the ship needs to take the following measures:
Fig. 3 schematic diagram of anchor stress during anchoring.
1, risk assessment;
2. Make an emergency plan; Including duty, duty, etc. ;
3. Strengthen duty;
4, spare parts procurement plan;
5. Notify the dock and port authorities;
6. When necessary, arrange tugboat escort when entering and leaving the port;
7. Check the working condition of another anchor, anchor chain and its accessories to ensure normal work.
8. Locate abandoned objects and sunken ships that affect navigation and anchoring on the chart and report to the competent navigation unit, or even salvage them.
_ Is the inspection due to lack of anchor a statutory project or a class project?
For international seagoing ships, SOLAII- 1 Chapter 3-8 clearly stipulates that the corresponding requirements of competent authorities or recognized organizations should be met.
Therefore, most flag countries usually classify anchor-related content as class items. Accordingly, in the case of lack of anchor, the classification society usually gives entry and exit conditions and requires the ship to be restored within a limited time.
However, the current exception is that the Marshall government clearly stipulates that the technical matters of anchors are related to the construction of safety certificates. Accordingly, in the absence of anchors, classification societies usually give classification conditions and issue short-term structural safety certificates, requiring repairs within a limited time.
There are some technical requirements for domestic seagoing ships registered in China and Technical Regulations for Statutory Construction and Inspection of seagoing ships, but the main meaning is "consistent with the approved drawings"; There is no relevant provision in the Technical Specification for Construction and Inspection of Inland River Ships and Seagoing Ships in China (20 1 1).
However, domestic, domestic and ship legal safety and environmental protection record books contain anchors, so when the above five situations occur, they should be treated as legal temporary inspections.