5-10% Heavier Than Japanese and South Korean Ships! Why Can't China's Light Ship Weight be Reduced?

Over the past few years, Chinese shipbuilding enterprises, in spite of advantage in technology, won in the market against Japanese and South Korean competitors upon high value-added shipping orders by virtue of low cost. However, since 2017, South Korea has lowered the cost for orders they receive, making China lose the cost competitive edge and even making it the weakness of China. In particular, the light weight of Chinese shipbuilding enterprises, particularly, has become a major weakness.

Reducing the light weight can save 5 billion RMB for Chinese shipbuilding enterprises. Compared with Japanese and South Korean light ship weight, Chinese ones are generally 5% to 10% heavier. Except for some bulk carriers, the weight gap has not been effectively narrowed during recent ten years. In 2017, the light weight of VLCC delivered by Daewoo Shipbuilding & Marine Engineering Co. is about 42.6 thousand tons, while the Chinese one is about 46.1 tons, 3500 tons (8%), heavier than that of Korean ones. Compared with the MR product carrier of Hyundai Mipo Dockyard weighing about 10.4 thousand tons, the ships made by a certain Chinese shipping company weighs about 11.5 thousand tons, 1100 tons (11%) heavier than that of MR product carrier. If the steel plate was priced at 5000 RMB per ton, then the differences in costs of rolled steel for every single ship are respectively 17.5 million RMB and 5.5 million RMB. In 2017, Chinese shipbuilding enterprises consumed over 10 million tons of steel for vessels, accordingly, 5 billion RNB of materials and production cost would be saved if the light weight could be cut down by 5%. However, the total gross profit of Chinese shipbuilding enterprises was far less than 5 billion RMB in 2017.

Continuous improvement of structural optimization is the main reason for Japanese and South Korean low light weight. For example, the reason that light weight becomes a distinct advantage of Daewoo Shipbuilding & Marine Engineering Co. mainly due to the company's unremitting efforts to optimize ship structures (to be standardized and light), which has already become part of its designers' daily work. In 2004, the company put forward a goal of reducing the weight of VLCC by 10% and the number of structural parts by 20%. During this period, it would propose an overall optimization requirement for different types of ships every two years on average with several partial optimization requirements proposed every single year. At the end of 2016, the light weight of VLCC structurally optimized by this company fell 2%, and this ship type has become the standard ship in recent orders received.

The key to reducing light weight lies in the basic design. Taking an oil tanker as an example, the weight of hull structure often accounts for 70-80% of its light weight (up to 90% for VLCC). More than 80% of hull structure optimization is determined at the basic design stage (over 50% at GA/MA/T&S, over 30% at Hull Key Plan stage), less than 10% at the detailed design stage and there is almost no possibility to optimize at the production design stage. Therefore, there will be not more than 1% decrease in light weight no matter how much efforts one make at detailed design stage if the structural optimization was not taken into consideration at the basic design stage. According to an analysis made by a South Korean designer who led the structural optimization of multi-type hulls, with same intensity, 10-20% of hull structures for vessels made by Chinese Shipbuilders can be optimized. Based on the original design drawings, it usually takes 3 to 4 months to optimize the structure for each type of ship.

The optimization of hull structure brings many direct economic benefits to shipbuilding enterprises. First, it saves steel and processing costs while shortening the construction cycle. Second, it saves the expense for the related NDT of structure and quality. Third, standardization and steel utilization rate shall be improved. Fourth, production efficiency per unit can be increased to achieve overall cost reduction and efficiency improvement. Fifth, it strengthens shipyard's ability of designing and coping capacity of being approved.

What are the major obstacles for Chinese shipbuilding enterprises to reduce the light weight? Ensuring structural strength to reduce light weight is not an unconquerable difficulty. It is not that tough to optimize the work as long as Chinese shipbuilding enterprises have willingness, clear targets and experienced designers. There are three main reasons for this long pending problem. First, the basic design capacity is mainly concentrated in the design institutions while other institutions hold insufficient knowledge of the production characteristics of shipbuilding enterprises, causing low motivation for optimization. Second, these shipbuilding enterprises started to develop its basic design capacity and inexperienced at optimizing. Third, too many redundancies are retained in all design processes.

Under the enormous pressure of the rising prices of raw material, reducing light weight is one of the most effective means to decrease cost and increase efficiency with few departments involved, short optimization cycle but notable results. Once the capacity is developed, consistent optimization can be ensured according to the actual production situation of the shipbuilding enterprises so as to further simplify the design and facilitate production.

It is advised that shipbuilding enterprises take advantage of the policy of all-around opening-up in shipping industry and actively carry out international cooperation and enhance their capabilities so as to promote the high-quality development of China's shipping industry from place to place across the board.

Resource: China Ship News

Copywriter: Li Xing