After entering service, vessels are periodically taken into ship repair docks for scheduled maintenance. In recent years, heightened tensions under the Trump administration towards China’s shipbuilding industry have drawn global attention to the overwhelming presence of Chinese shipyards, which account for roughly 60% of newbuilding output worldwide on a CGT*¹ basis. Less widely recognized, however, is the fact that China also leads the world by a significant margin in the ship repair dock sector.
In this article, we provide an in-depth overview of ship repair docks—the backbone of vessel maintenance—covering the fundamentals, regional characteristics, latest repair market trends, and emerging developments in decarbonization-related retrofits.
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Standard Cargo Ship Equivalent Tonnage
A repair dock is a facility for ship repair and inspection. In particular, a dry dock is a trench that can accommodate a vessel, where the entrance gate is closed and water is drained to fix the vessel, allowing work to be carried out on the hull, including the bottom. It is used for large-scale repairs and modifications.
A repair dock is used not only for general maintenance work, but also for regular surveys and various modification projects. Since it is more economical for a vessel to remain in service for as long as possible unless it suffers critical damage, repairs and modifications are often carried out at the same time as required surveys.
Just as automobiles on public roads are legally required to undergo regular inspections, vessels must also be inspected to ensure that their structure and equipment meet safety and environmental standards. These surveys are generally conducted in accordance with international conventions established by the International Maritime Organization (IMO) and are carried out by the government of the country where the vessel is registered or by a classification society authorized by that government. There are two main types of inspections: a Special Survey, which is conducted every five years, and an Intermediate Survey, which takes place midway through each five-year period.
（Photo: When marine organisms such as barnacles attach to the hull, they increase water resistance, which can lead to reduced speed and decreased fuel efficiency.）
A “retrofit” refers to modification work that adds new technologies or functions to existing equipment and systems. In the shipping industry, a typical example is the installation of equipment on existing vessels to comply with environmental regulations or upgrade performance.
Such modification work may include, for example, converting vessels to operate on alternative fuels such as LNG or methanol, or changing the purpose of a vessel, such as converting an LNG carrier into an FSRU (Floating Storage and Regasification Unit). It also includes the installation of SOx scrubbers and ballast water management systems.
Since the late 2010s, retrofits to comply with environmental regulations have become especially common. The entry into force of the Ballast Water Management Convention in 2017*2 led to the rapid installation of ballast water management systems, while the strengthening of SOx regulations in 2020*3 accelerated the installation of SOx scrubbers.
From around 2019, the sharp increase in installation projects for ballast water management systems (BWMS) and scrubbers prompted new entrants into the ship repair dock sector. At the same time, existing repair docks expanded their capacity and introduced new facilities to accommodate the growing demand.
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An international convention to control and manage vessels’ ballast water and sediments to prevent the cross-border movement of aquatic organisms affecting the marine environment.
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Regulations to limit the sulfur content of marine fuel oil to prevent air pollution caused by sulfur oxides (SOx) generated by combustion on board (engines, generators, etc.). Since 2020, the limit in general sea areas was reduced from 3.5% to 0.5%. By installing SOx scrubbers, ships can use fuel with higher sulfur content by removing SOx from exhaust gases to meet regulatory standards.
Transfer of aquatic organisms via ballast water.
All vessels owned by the MOL Group have been equipped with ballast water treatment systems, and all newly built vessels delivered after that date will be completed with these systems installed. (Source: MOL website)
Although the installation of ballast water management systems has already peaked due to the deadline for retrofitting existing vessels (September 2024), and the installation of SOx scrubbers has also peaked as the price gap between HSFO and LSFO has narrowed, overall demand for vessel repairs continues to increase.
According to Clarksons, repair demand is growing at an average annual rate of 3%, driven by the expansion of the global fleet. In 2025, approximately 11,800 vessels (cargo ships of 2,000 DWT or more, and cruise ships and similar vessels of 2,000 GT or more) were scheduled to undergo special surveys. Considering the age profile of the world fleet, it is expected that over 12,000 vessels per year will be subject to survey in 2026–27, leading to a rush of special surveys at repair docks.
Furthermore, about 70% of the vessels scheduled for survey in 2025 are expected to be 15 years old or older, a clear sign of fleet aging compared to 2016, when the figure was around 45%. Older vessels tend to require longer dock stays than younger vessels. For example, surveys at 15 years of age take about 20% longer on average than those at 10 years. This lengthening of docking periods is one factor driving up demand for repair docks.
Although retrofitting vessels to reduce GHG emissions and advance decarbonization is increasing, it has not yet entered a full-scale phase. These energy-saving technologies include the following types of equipment:
Approximately 540 installations of such equipment were recorded in 2024, and a similar number was expected for 2025. However, this has not resulted in a surge comparable to the rapid spread previously seen with ballast water treatment systems or SOx scrubbers.
Looking ahead, retrofits such as the installation of onboard CO₂ capture systems and conversions to alternative fuels, including LNG and methanol, are expected to increase. However, since the beginning of the 2020s, each of these retrofit types has so far remained at around 50 cases. In addition, as amendments to international conventions for GHG reduction were not adopted at the IMO’s extraordinary session in October 2025, it is considered that the full-scale rollout of decarbonization-related retrofits will take some additional time.
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Currently, almost all vessels in the global fleet have completed installation of ballast water treatment systems, so retrofit work demand has temporarily settled down. With the introduction of the EU Emissions Trading System (EU-ETS) for the maritime sector in 2024, some shipowners are seeking to reduce the need to purchase emission allowances by modifying their vessels—such as replacing bulbous bows and propellers for slow steaming, or installing energy-saving equipment like air lubrication systems and shaft generators.
Going forward, fuel conversion for vessels will be key.
Since most new vessels are still designed for conventional fuels, converting them to alternative fuel vessels requires large-scale work on engines, fuel tanks, piping, systems, and structures. For fuel conversion, it is necessary to secure space for new equipment inside the hull in accordance with classification society rules and the International Code of Safety for Ships Using Gases or Other Low-flashpoint Fuels (IGF Code)*4. So-called “ready” vessels*5 have space secured in advance for future fuel conversion work, but other vessels have existing equipment installed inside, making it a design challenge to secure tank space while minimizing any reduction in cargo capacity.
Fuel conversion retrofits require about two years for the entire project, including design and engineering, feasibility studies, replacement of equipment and systems compatible with new fuels, and sea trials. If fuel conversion retrofits surge in the future, there is a risk of tight supply and demand and soaring costs at repair yards. Repair docks need to establish sufficient capacity, and shipowners and ship management companies need to make advance preparations to ensure they can secure repair docks when needed.
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International regulations to ensure the safety of vessels using low-flashpoint fuels such as LNG, LPG, and methanol. It sets standards for the installation and arrangement of machinery and systems on board to minimize risks to vessels, crew, and the environment.
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Vessels that are designed or modified to allow for future fuel conversion.
For vessels sailing 365 days a year, regular maintenance and repairs are a crucial component in safe operation. As updates to hulls to comply with environmental regulations are also required, it is important to once again recognize the critical role that repair docks play in the trouble-free operation of vessels.
References:
Kaiji Press, Ship Repair Dock Guidebook 2024; Ship Repair Dock Guidebook 2025
Kaiji Press articles: https://www.kaijipress.com/news/shipbuilding/2025/09/195969/
MOL Solutions website: About the Maritime Industry in Turkey -Insights from Eight Years of Experience in Turkey-