He Baoxin

The "two-in-one" new process and new model of conventional sea trial and gas sea trial of dual-fueled ships promoted by China State Shipbuilding Corporation Limited (CSSC) was successively implemented on 29 ships of 9 types in 6 shipyards in 2022. The results show that the average sea trial period of a single ship was shortened by 6 days, and the cumulative cost saving was more than 40 million yuan.

According to estimates, after the full implementation, the "twoin-one" sea trial is expected to save more than 200 million yuan costs of CSSC shipbuilding enterprises, which will provide strong support for the improvement in quality, speed and efficiency of CSSC shipbuilding and offshore engineering enterprises.

The sea trial of dual-fueled ships used to include two stages:conventional sea trial and gas sea trial.The conventional sea trial is designed for the ship to complete all sea trial items powered by fuel oil after dock mooring test ends; the gas sea trial is navigation test with natural gas and other clean energy as the main fuel after the conventional sea trial to check the safety, operability and reliability of the equipment and system associated with the fuel gas.

In recent years, orders for dualfueled ships such as LNG handheld by CSSC enterprises have increased significantly, and some of them have entered the new field of dual-fueled shipbuilding. If the dual-fueled ship sea trial was still implemented in two stages, not only the cycle would be long, the cost high, but also the organization difficulty and safety risk would increase.

In order to solve this problem,CSSC Hudong Zhonghua Shipbuilding and CSSC Huangpu Wenchong Shipbuilding have begun to explore the"two-in-one" new model originated in China.

Meantime, CSSC requires that the “Office for Promoting the Establishment of Modern Shipbuilding Model” (CSSC Modeling Office) focus on the exploration, practice, application and verification of the "two-inone" new process and new model of conventional sea trial and gas sea trial,so as to form norms and standards as soon as possible, and implement the promotion.

First of all, the CSSC Modeling Office incorporated the promotion of the "two-in-one" new model in Hudong Zhonghua and Huangpu Wenchong into the annual key work,summarized the successful experience,and avoided possible "detours" and repeated R&D investment into the enterprise in the later stage.

Secondly, it led the inauguration of a special research group comprising of shipyard designers, architects and managers and CSSC No.11 Institute process and technical personnel, went deep into the shipyard front to carry out investigation and extensively listen to opinions and proposals of the shipyards, owners and ship surveyors, developed the Guidelines for Conventional Sea Trial and Gas Sea Trial Two-in-One for Dual-Fueled Ships, which was released after review of CSSC modeling experts.

In view of the difficulties and key problems tha came up in the "two-inone" sea trial, the Guidelines defines the management responsibilities of the trial relevant departments,and implements unified command throughout the whole process from preparation to completion and delivery,to ensure the safety under control after LNG embarks.

Meanwhile, it clarifies the coordination content with the ship owner, ship surveyor and other relevant parties, the conditions to be achieved before the sea trial, was well as work content and specific requirements for technology, mooring test, fuel preparation and other aspects. It defines contents and items to be carried out om all links during the navigation test, including sea trial conditioins confirmation, passage voyage, sea trial anchorage, deepwater test area,return voyage, shipyard wharf, engine disasembly, sea trial end. It states the main safety risk control points of the three stages from the start of sea trial to the departure of the ship for delivery,for example, from the LNG ship return starts to before unmooring for sea trial,sea trial start to navigation test end and docking, defection correction to ship delivery departure. It describes the test and work contents of three main systems -- dual-fueled ship main engine, generator and combination boiler -- gas mode mooring test during the sea trial.

In 2022, CSSC Modeling Office intended to hvae promoted the application of the "two-in-one" sea trial new model in no less than five ships, but due to good organization,CSSC related companies made positive response, 29 ships of 9 hull forms have so far realized the "two-in-one" sea trial, and aaprt from Hudong Zhonghua and Huangpu Wenchong, Jiangnan Shipbuilding, Shanghai Waigaoqiao Shipbuilding, Wuchang Shipbuilding,Guangzhou Shipyard International have realized the application of the model.

In terms of effect, taking the 23000 TEU dual-fueled container ship as an example, after the implementation of the"two-in-one" sea trial, the trial cycle was shortened from the original average of 15 days (7 days for conventional sea trial + 8 days for gas sea trial) to 9 days, saving 400 tons of diesel, 220 tons of fuel, and about 2 million yuan direct cost of tug pilot and test labor.Especially practice has proved that the"two-in-one" trial new process and new model has been highly recognized by ship owners, ship surveyors and service providers, and has further enhanced the cooperation and friendship with all parties.

In view of the growing demand for dual-fueled ships in the global newbuilding market, the practice and application prospect of the "two-inone" sea trial new process and new model of dual-fueled ships will become even broader in the future. Under the leadership of CSSC, the CSSC Modeling Office will continue to summarize,optimize and improve the "two-in-one"sea trial new process and new model,strive to form a national standard at an early date, and make new contributions to the transformation and upgrading and improvement in quality, speed and efficiency of China's shipbuilding industry.