ICE NAVIGATION THESE THINGS ARE WORTH PAYING ATTENTION TO

Affected by the cold wave weather in winter, the low temperature in many places in China may be rare in the same period in history, the sea ice in the Yellow Bohai Sea has developed from the early glacial period to severe ice conditions, the color of sea ice has changed from dark gray to white or grayish-white, the ice floe fault is decreasing, the thickness of the ice layer is obviously increasing, and the area is gradually expanding, which has had a serious impact on the navigation safety of ships. At that time, the ice conditions affecting our country’s Yellow Bohai Sea in the early stage will become more and more serious, which is bound to have a more serious impact on the navigation safety of ships. Therefore, ships sailing in such ice areas in winter must pay close attention to the following special matters.

1. Usually, how long will the ice situation in our country’s Yellow Bohai Sea last?

According to the long-term observation of our country’s State Oceanic Administration, the sea ice in the Yellow Bohai Sea is a one-year ice, and the development process of sea ice can be divided into three stages, namely the initial ice period, the freezing period, and the final ice age.

(1) First glacial period: refers to the period from the first ice day to the freezing day, which is the process of continuous growth of sea ice. The first ice day in Liaodong Bay and the northern Yellow Sea is as early as early November and as late as the end of November. Bohai Bay is as early as early December, as late as late December, and Laizhou Bay is as early as early to late December, and as late as mid-January.

(2) Freezing period: refers to the freezing date to the thawing date. During this period, the ice situation was serious, and the ice density was greater than 70%. Therefore, the freezing day is usually called the severe ice age, the freezing period of Liaodong Bay is about 2 and a half months, generally from late December to early March, Bohai Bay is about 1 and a half months, generally from early January to mid-February, Laizhou Bay is about one month, generally from mid-January to early February.

(3) Final glacial period: refers to the thaw day to the end of the ice day, during which the sea ice continues to melt as the temperature rises and the sea temperature rises. The melting period is much shorter than the growth period. The end of ice in Liaodong Bay and the northern part of the Yellow Sea is as early as mid-March and at the end of March at the latest. Bohai Bay is from the end of February to the end of March at the earliest, from the end of mid to the beginning of March at the latest, and the earliest in Laizhou Bay is late January and as late as mid-March.

According to the analysis of the ice trend forecast of the Bohai Sea and the northern Yellow Sea from November 2020 to March 2021 released by the National Oceanic Forecast Observatory, the first ice period: Liaodong Bay will appear from the end of November to the beginning of December 2020; The northern part of the Yellow Sea will have initial ice from early to mid-December 2020; Bohai Bay and Laizhou Bay will have initial ice in late December 2020. Severe glacial period: Severe glaciation in Liaodong Bay and the northern Yellow Sea will occur from late January to mid-February 2021; Severe glaciation in Bohai Bay and Laizhou Bay will occur in late January to early February 2021. Final ice age: Liaodong Bay and the northern Yellow Sea will end in mid-March 2021; Bohai Bay and Laizhou Bay will end in late February 2021.

2. How is the ice area reinforcement level of a ship defined?

The ship’s ice area enhancement classification mark can be found in the ship’s Certificate of Classification.

Taking the CCS classification specification for steel seafarers as an example, in the classification symbol and additional marks of the ship, the special performance additional mark of the ship is displayed in the “E” part, indicating that the ship has a special performance design in the structure, and the corresponding additional mark can be awarded separately.

Among them, the additional marks for ice navigation are Ice class B1*, Ice class B1, Ice class B2, Ice class B3, and Ice class B, which correspond to the IA Supper, IA, IB, IC of the Finnish-Swedish ice class rules respectively. The PC1-PC7 additional mark is used as the classification standard for ships sailing in the polar region.

For example: ★ CSA General Dry Cargo Ship; Grab(20); PSPC(B.D); Ice Class B; Loading Computer(S,I,G,D) ； FTP； BWMP

3. How to classify sea ice types and thicknesses?

The International Meteorological Organization (WMO) defines sea ice types and ice density, among other things:

Ice types: It can be roughly divided into six categories, namely new ice, early ice, current ice, old ice, ice shelf and fixed ice. The corresponding thickness ranges from a few centimeters to 3 meters and above.

Ice: refers to the degree of sea ice present in a body of water, usually expressed by one or more ice types and their thickness, ice density, and ice floe scale.

Ice density: refers to the proportion of ice floes covered on the sea surface within the field of view, measured by the ten method, and the ice density can be divided into eight levels. The ice density is used to indicate how difficult it is for a ship to navigate in the ice area.

Ice field: refers to any type of ice in a body of water, including open water, with a relatively consistent mix and distribution of ice conditions.

4. What is the impact of sea ice in the Yellow Bohai Sea on ship navigation?

The National Marine Environment Forecasting Center has previously issued a sea ice warning, with an ice floe range of 37 nautical miles in Liaodong Bay, 16 nautical miles in the northern Yellow Sea, 14 nautical miles in Bohai Bay, and 22 nautical miles in Laizhou Bay on January 9. At the same time, it is expected that the ice conditions in the Bohai Sea and northern Yellow Sea will be close to normal in mid-January 2021. The maximum ice floe range in Liaodong Bay is 50-60 nautical miles, with a general ice thickness of 10-20 cm and a maximum ice thickness of 30 cm; The maximum ice floe range in Bohai Bay is 10-20 nautical miles, with a general ice thickness of 5-15 cm and a maximum ice thickness of 20 cm. The maximum ice floe range in Laizhou Bay is 15-25 nautical miles, with a general ice thickness of 5-15 cm and a maximum ice thickness of 20 cm. The maximum ice floe range in the northern Yellow Sea is 15-25 nautical miles, with a general ice thickness of 10-20 cm and a maximum ice thickness of 25 cm. According to the optical satellite remote sensing detection of the National Satellite Marine Application Center, as of 10 o’clock on January 10, 2021, the total sea ice area in the Yellow Bohai Sea area has reached 20,765 square kilometers.

The ice-breaking performance of a ship is related to factors such as ship type, hull structure, main engine power, and cargo status. When the ice thickness reaches more than 20 cm and the density reaches more than 5/10, the normal navigation of ordinary ships will be hindered. Combined with the current ice area in our country’s Yellow Bohai Sea region, the ice superposition in some areas has reached about one meter thick, without the assistance of port tugs, ordinary ships cannot sail according to the predetermined course, and the sea ice tide will drive the ship to drift downstream of the tide, with obstacles to navigation, and even the risk of being caught in the ice area.

5. Can you sail safely with an icebreaker tug?

During the freezing period of the port, the port will generally arrange high-horsepower tugboats to break the ice in the waters near the port and open up an ice channel for the smooth passage of ships entering and leaving the port. In order to reduce the damage to the hull caused by large ice floes, the tugboat is in front, and the ship behind follows the fish in turn. This operation can greatly mitigate the impact of ice floes on ship navigation, but there are still several risks:

(1) Because the size of the tug is much smaller than that of the large ship, the channel out of the tug is narrow, and the sea ice will still cause damage to the paint and steel plates of the hull.

(2) The distance between ships is not easy to control (usually 2-3 times the captain), if the distance between the ships in formation is too close, it is very likely that the icebreaker in front of the ice will not move the thick ice, the speed will drop sharply, or even stop, while the ship behind is still sailing in the ice-water mixing area, and it is too late to reverse, which is very easy to cause “rear-end collision” accidents at sea, or even serial rear-end collisions.

(3) The activity distance of port tugs is limited, generally limited to 5-10 nautical miles from the port breakwater or pilot station, and the distance from the open sea at the ice and water interface to the pilot station or tugboat assembly point is still unreachable for most ships.

(4) If the ice floe coincides with a high tide, the channel just opened by the icebreaker in front of the tug will be merged by the tide in a short period of time, and the broken ice will be superimposed on the original ice, resulting in thicker ice and greater impact on the navigation safety of ships behind.

6. What are the precautions for anchoring in the ice area?

We have to emphasize that it is very dangerous for ships to anchor in ice zones, and the risk point is not how high the technical requirements for anchoring are, but that anchoring in ice zones is very easy to cause anchor loss accidents. Let’s take dense ice with a thickness of 30 centimeters as an example, when a 1 nautical mile square ice block appears around the ship, the ice floe can weigh nearly one million tons. Ships anchor near tidal ports, anchor is the norm, so we recommend trying not to anchor in ice areas, and try to use the method of preparing vehicles in ice-free areas instead of anchoring in ice areas.

If you must anchor in the ice area, as shown in the figure below, similar to Figure 1, the ice loose or sparse area can still be anchored, the chain should be short rather than long, and some data have a quantitative standard of twice the water depth, which is also somewhat absolute. The significance of the short chain is that after walking the anchor, it can quickly lift the anchor, adjust the position of the ship with the car, and prevent the gradually thickening ice from freezing the anchor and not being able to twist it. If there is an anchor, do not easily put a long chain or throw a double anchor to prevent the ship from anchoring, once the ice thickens or the ice floes accumulate on the hull, it is very easy to cause the chain to break and lose the anchor.

If the thickness of the following figure 2 reaches more than 30 cm of dense ice, ice collection or even full ice, it is recommended that the ship does not need to anchor, due to the thick ice barrier, even adjacent ships will not have dynamic collisions.

Anchoring in the ice area, with the increasing thickness of the ice, the ship will basically be trapped in the ice area, and the volume of water will increase in the physical process of freezing, which will seriously squeeze the hull. We have encountered in practice that after the ship is caught in the ice area, not only the paint on the outer hull plate falls off, but the steel plate is partially deformed, and even the ribs of the cargo hold are deformed.

7、Can reverse be used in the ice area?

It is also common for ships to navigate in icy areas and damage to the propeller after hitting the ice floe. In the process of moving forward, the propeller discharges the flow backwards, generally pushing the broken ice floes away. But when reversing, the discharge flow forward, it is likely to suck the broken ice floes near the stern to the propeller, and then hit the paddles, which is why many captains do not need to reverse easily in the ice area.

The ship speed is very slow or even completely stopped, and the ice floes that are crushed during the ship moving forward will quickly backfill and gather around the hull.

It is strictly forbidden for ships to use reversing in the ice area, which is too absolute. Under normal circumstances, when a fully loaded ship is submerged in the water or ice surface for more than 2 meters, it will generally not break the blades if the propeller is submerged in more than 2 meters below the water surface or ice surface before reversing. Even if it is an unloaded ship, adjust the ballast water in the bow and stern pointed cabins to sink as much as possible, and can also cooperate with the operation of breaking through the ice floes after entering the car at a slow speed, and then reversing.

8. What is the operation of reversing and driving ice at the wharf?

If the port pool of the port freezes, it will bring great inconvenience to the normal berthing of the ship, and in the process of the ship gradually berthing to the dock, the squeezed ice floes will finally accumulate between the inner end of the hull and the dock, resulting in the ship not being able to lean on the dock cushion, which is not a problem for the safety of the ship and the dock itself, but the increased gear distance has caused great safety hazards to the personnel and the ship with cables and cargo operations. Therefore, some port pilots will adopt the operation of reversing the stern as close to the berth as possible, swinging the bow outward, braking the tail inverted cable, and then driving the reverse operation, trying to use the reverse to push the ice floes between the hull and the dock with the forward flowing water.

It has to be said that this method has a certain effect, but the risk is very high. First, the reversing ice floe hits the paddles as mentioned earlier. In addition, if you force reverse for a long time, the tail reversing cable is very easy to break, causing injury or collision. In addition, the ice floes are lined up and have a process of quantitative change to qualitative change, which may not be pushed at first, and when it moves, the ice floes will float away all of a sudden, and the ship will quickly contact the dock, causing contact accidents. It is recommended that the captain should not easily agree to the pilot’s operation, and use the port tug to clean the ice floes on the dock side in advance before berthing operations.

9. The temperature in the cabin is high, does the ice area still need to be anti-freeze?

When a ship sails in an icy or low-temperature area, in addition to the conventional equipment and facilities on the deck and living area, the engine room must also be frost-proof. The engineer should adjust the number of ventilation fans in the engine room, pump room, and servo room to reduce the flow of outdoor air into the cabin, maintain a suitable temperature, and ensure that all equipment is available at any time.

1. Ice floes may block the submarine door, so clean and maintain the idle submarine door in time to prevent pipeline blockage, and if necessary, open the steam heating pipeline of the submarine door to heat the submarine door.

2. The heating and accompanying heating pipelines of the fuel tank, fuel sedimentation cabinet/daily cabinet, overflow cabinet and related fuel pipelines and filters should be kept unobstructed to prevent the increase of fuel viscosity caused by low temperature, and the fuel filter should be cleaned in time to prevent pipeline blockage.

3. The electrical control box of the steering machine room may produce condensation due to low temperature, in order to prevent low insulation, the box door can be opened if necessary, ventilated, and the electrical control box can be kept dry.

4. The hydraulic oil pump on the deck of the rudder engine room should be kept running at a low speed, and the hydraulic oil tank should be turned on to maintain normal temperature. The servo hydraulic oil pump maintains continuous operation.

5. The external pipeline of the ballast water treatment system may also be frozen, and the relevant pipeline should be completely disabled before entering the alpine area, especially the ballast water sampling pipeline.

10. What are the special tips for oil-chemical ships?

1. All steam lines on the tanker must be completely disabled to ensure that there is no condensation in the steam lines on deck and in the pumping room. The cabin sweeping pump system must be completely disabled and the cylinder must be kept warm throughout the unloading operation.

2. After the loading and unloading of the oil tanker oil pipeline is completed, the main pipeline should be disabled in time to prevent pipeline blockage; The sampling pipe/drain pipe of the oil tanker inert system and other operating equipment is disabled to prevent the inert system pipeline connection flange and sampling pipe from freezing and blocking.

3. Before entering the cold area, check the heating coil of the deck water seal to ensure that it is in normal condition, turn on the heating of the deck water seal while enabling the inert gas system, and keep it continuously heated throughout the unloading operation.

4. The fresh water flushing and sampling pipeline of the oil discharge monitoring system of the oil tanker pump room is fully discarded, and the automatic unloading system of the pump room is recommended to add insulation layer, and fully disable to avoid ice jams.