The work of shuttle tanker crews in the Arctic is significantly influenced by environmental conditions and navigators have to deal with phenomena such as icing, reports Riviera.
Exploring in sub-zero temperature
Captain Alexander Andreev has vast experience in Arctic waters and explains the methods used to protect against icing.
A large number of Sovcomflot’s vessels operate on the Northern Sea Route (NSR). Navigating in the Arctic seas is conditioned by several interrelated factors. These include irregular hours of sunlight (polar day, polar night), specific atmospheric circulation, the unevenness of the earth’s surface due to continental and drifting ice, as well as the heat impact of the Atlantic Ocean, the Pacific Ocean, and the water flow from Siberian rivers.
The climate in the Arctic is considered to be harsh and cold, but the temperature can rise sharply due to cyclones. The air in the Arctic Basin is colder than its water. For example, the minimum air temperature in the Siberian basin reaches −50°C. During the polar night, the air temperature drops continuously because there is no light or heat.
Cyclones and anticyclones
During the polar day, large amounts of heat and light are absorbed by the snow and ice. The regions adjacent to the waters of the Atlantic and Pacific Oceans are warmer, and there is more precipitation, while the climate in the inner regions of the NSR is colder and drier.
In winter, cyclones from the Atlantic intensify in the western part of the Arctic. During this time, the air temperature is high, there are strong winds, and the maximum amount of precipitation and cloud cover is observed. Anticyclones occur in the Siberian part of the Arctic. The winds here are insignificant, temperatures are very low, and there is little precipitation. In summer, the air temperature in the Arctic basin is 0–5°С; it is very humid (up to 98%), with frequent fog, sleet and rain, and moderate winds.
Icing is a serious risk for the operation of marine equipment in the Arctic seas. It can occur even during the summer periods and can persist throughout the year. Seafarers working in this region must be prepared to deal with this phenomenon.
The problem of icing
Low temperatures, winds, icing, and snow worsen the conditions for carrying out maintenance, causing breakdowns in equipment and machinery, reducing the work performance quality, and increasing the work execution time. Complications can occur while people move around the vessel, increasing the likelihood of injury.
Snow cover and wind impede the operation of the air intakes and vents on ballast tanks and open drainage systems, which leads to additional loads on the equipment, pipelines and cables.
The structure and properties of metal change significantly upon cooling and the exposure time is important, therefore measures to protect and remove ice should not be postponed.
Measures taken
The first attempts to remove pipelines and cables under the casing were made on Arctic tankers in the Samotlor series.
The catwalk on the cargo deck was raised to over 2 m, and closed pipelines and cable routes were installed on both sides of it, while the pipeline routes were insulated with glass wool. These were the first steps taken to prevent ice formation on ship structures and equipment by heating them and providing adequate covering. Later, the solution to these problems brought about fundamental changes in the layout of ship structures. The calculated operating temperature was used as a basis for determining materials for the manufacture of foundations, fasteners, pipelines, coatings, and gaskets.
An electrical heating system was first implemented on the Vasily Dinkov-class tankers (serving the Varandey project) by covering the equipment with heated covers and is still used on many ships today. This system is low maintenance and relatively reliable, provided that self-regulating heating cables are installed properly.
However, this approach has generally failed to pay off. Due to the vessel’s operation under extreme sea conditions and strong winds, the coating fell into a dilapidated state after just one season of operation. Storm surges were devastating to both the protective covers and the equipment underneath.
Closed Heating system
A ’deck trunk’ closed-heating system was applied on Shturman Albanov-class vessels as part of the Novy Port project. It was fairly simple to stow most of the equipment located on the cargo deck in a room closed off from any outdoor exposure. The main advantage of the closed-heating system is that it helps to protect all the electrical and electronic equipment of the cargo system and facilitates maintenance of the cargo and fire safety systems at low temperatures and in challenging environmental conditions.
The operational experience of the Shturman Albanov vessels showed that maintaining positive temperatures in the trunk had a positive effect on the operation of cargo tank radars, ensured comfortable work when measuring cargo and taking samples, prevented the cargo from freezing and the precipitation of heavy fractions in the cargo lines, and significantly reduced the risk of defrosting trunk systems.
The flaws
The necessary changes to the design will be taken into account for ships of new generations. According to the Mooring Equipment Guidelines, the distance between the winch drum and the hawse should be at least 19 diameters of the drum width in order not to exceed the deflection angle of 1.5° when laying the mooring line. This requirement is not met due to the fact the winches are on the trunk and the intermediate hawse is installed at the edge of the trunk.
There are other flaws in the system that need to be addressed. These include the need for additional heating of the valves in the inert gas system on the open deck, as the valves freeze due to the condensate inside. Some of the pipes of the atmospheric sampling system are also located on the open deck, which leads to freezing due to the condensate inside and prevents taking measurements. In any closed method, there are still points of contact with the environment, and these represent weak points which require increased attention and a combined approach.
Regulatory documents are revised and changed frequently, but it is normal practice for the design of a ship to be completed and for the ship to begin operating simultaneously with the release of new requirements. In such cases, ship navigators have to make structural changes during periods of scheduled repair. At the same time, this allows crews to take part in the process of adjusting the equipment and gaining experience, as well as influencing the process of developing requirements.
Practical conclusions
Lifting equipment, cranes, and monorail hoists located on the open deck must be of Arctic design with appropriate protection for personnel. Therefore, all cranes on ships operating in the Arctic must be equipped with insulated cabins.
Design solutions for mooring areas should minimise the appearance of snow or icing on easily dumped structures in bulwarks and drainage systems. These areas are susceptible to water splashing and intense icing due to their location at the edge of the end structures of the vessel. Solutions for such structures should minimise icing on the outer surface and ensure their structural reliability.
The company continues to collect data on the reliability and efficiency of the use of such systems on ships to further improve and develop safe conditions and methods for conducting ship operations and reducing environmental impact
Did you subscribe to our daily newsletter?
It’s Free! Click here to Subscribe!
Source: Riviera
