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Recently, the research ship Xiangyanghong 28 successfully passed its sea trial. The propulsion system with fixed pitch propellers was transformed into a propulsion system with adjustable pitch propellers by Nanjing High Accurate Marine Equipment Co., Ltd. (hereinafter referred to as “NGC Marine”), a subsidiary of NGC, which satisfies the low-speed sailing requirements for scientific investigations.

With 74.55 m in length and 10 m in width, the research ship Xiangyanghong 28 was driven by two low-speed diesel engines, which were manufactured in the 1970s. Such engines were connected to the thrust bearing and the fixed pitch propellers with the pneumatic tube clutch. The original shafting vibrated violently in operation, and the torque transmission capacity of the pneumatic tube clutch decreased. Following repeated demonstrations and analysis with the owner and the manufacturer as well as field investigations, NGC Marine determined to reserve the original engines, and replaced the pneumatic tube clutch with a gearbox with a built-in hydraulic clutch and thrust bearing. In addition, a high-elastic shaft coupling was installed between the gearbox and the engine. In order to satisfy low-speed sailing during scientific investigations, the fixed pitch propellers were replaced by adjustable propellers. With the advantages of low cost, high efficiency, and less transformation work, this solution was accepted by the owner and the manufacturer. Meanwhile, NGC Marine designed a new oil distributor for small-sized adjustable propellers, which successfully resolved a series of technical issues existing in space layout and hydraulic oil supplies for pitch adjustment, and passed the strict ex-factory pitch adjustment test.

With many parts remaining unchanged, the propulsion system was transformed in a tight schedule with great difficulty. The transformation even involved complicated and arduous field installation and configuration. NGC Marine not only prepared various solutions for issues that may occur in the process of field installation and configuration, but also instructed the manufacturer to resolve existing problems in a timely manner. During the sea trial, the research ship Xiangyanghong 28 achieved low-speed sailing, while the highest speed remained close to the original speed. Violent vibrations of the original shafting were effectively resolved, and the torsion vibration test was successfully passed. The owner spoke highly of NGC Marine for its technical strength and service quality in the transformation of marine propulsion systems. (By Qian Pengchun)