New Copper Alloy Valves for Ships

Copper and copper alloys have excellent electrical conductivity, thermal conductivity, anti-magnetic properties, corrosion resistance, and antibacterial properties. They also possess good mechanical properties, including processing, forming, cutting, and sealing. Additionally, copper alloys for ship valves offer economic and practical advantages, making them widely used in ship valves and parts. The key to the application of copper alloy valves on ships lies in their corrosion resistance. Due to the high thermodynamic stability of copper, a cuprous oxide protective film forms on the surface of the copper alloy, with corrosion products often depositing on this film to enhance protection. Seawater and seawater mist can cause severe chemical corrosion of copper alloys. When copper alloys are exposed to seawater or seawater salt spray for a period, the valve seat and valve disc may corrode, leading to leakage. Additionally, marine organisms can also corrode the valve. There are two main causes of valve corrosion and damage: erosion corrosion and galvanic corrosion. High flow rates in the valve body can create turbulence, leading to severe erosion corrosion. The materials used for the valve body, valve seat, valve stem, and pipeline are often different. In seawater, this can lead to severe galvanic corrosion, which accelerates the corrosion of anode components and induces more dangerous forms of damage, such as pitting, crevice corrosion, and stress corrosion. Therefore, selecting the appropriate materials for marine valves and their components is crucial.
 
Considering the characteristics of copper alloys and to meet economic and practical requirements, different types of copper alloys can be selected for manufacturing valves and their components. Table 1 lists the materials selected for some parts of typical copper alloy valves. Currently, the most common copper alloys are cast tin bronze for the valve body, cast aluminum bronze for the valve disc, and aluminum bronze for the valve stem.
 
Table 1 Typical material selection for copper alloy valves 

 

Copper alloys have been widely used in the marine valve industry due to their good physical and processing properties. However, the old standard marine copper alloy valves have poor corrosion resistance and short lifespans, which cannot fully meet the operational requirements of ships. In recent years, with the continuous improvement in ship automation, China has developed and designed many new marine copper alloy valves. These new marine copper alloy valves feature innovations in materials, structures, and processes, meeting the requirements for copper alloy valves in ships. Moreover, many of the newly developed products have significant potential for widespread adoption. In terms of materials, Cu-Ni alloy is widely used in seawater piping systems of ships, including condensers, seawater pipelines, and heat exchangers, due to its excellent seawater corrosion resistance, machinability, and thermal and electrical conductivity. The Luoyang Ship Material Research Institute has developed a new Cu-Ni-Al alloy, building upon the Cu-Ni alloy used as the primary pipeline material. The potential of this new Cu-Ni-Al alloy valve is similar to that of common seawater piping materials like B10, effectively preventing galvanic corrosion. In terms of design, the Luoyang Ship Material Research Institute has strong capabilities in ship material design. Addressing the poor corrosion resistance and short lifespans of traditional copper alloy valves, the institute actively invests in developing and applying new copper alloy valves for ships. The institute's valve technicians use finite element analysis to coordinate engineering concepts in the design and development of new copper alloy valves for ships, achieving CAD/CAPP/CAM integration, and utilizing simulation design and optimization to shorten the design period, improve product quality, and effectively reduce development costs. As shown in Figure 1, the stress analysis of the sea valve is clearly illustrated through simulation analysis. Through parametric design and repeated comparisons, the optimal parameters are determined, significantly shortening the product development cycle and improving product reliability.
 

Figure 1 Stress analysis of sea valves
 
The following is a description of a newly developed copper alloy valve for ships. The newly developed copper alloy low-noise side sea valve for ships, studied by the Luoyang Ship Materials Research Institute, incorporates an internal bypass pressure-equalizing structure, allowing it to bear pressure in both directions and effectively reduce the opening and closing torque. Compared to current sea valves, the opening and closing torque can be reduced by 80%, significantly extending the service life, with an expected service life of 30 years.
 
The flow resistance and noise can be effectively reduced through the optimization of the flow channel design (Figure 2 and Figure 3). The data shows that the flow resistance of the new sea valve is reduced by 18% and the fluid noise is reduced by 7% compared to the previous sea valve. The valve features advanced surface hardening, insulation, and anti-fouling treatments, which significantly increase reliability. Additionally, its miniaturization and lightweight design ensure that the new copper alloy valve fits well in the available installation space.
 

Figure 2 Pressure distribution cloud map in full open state (positive)


Figure 3 Velocity distribution cloud map in full open state (positive)
 

Copper alloys are widely used in the marine valve industry, but there is still a significant gap between the marine copper alloy valves produced in China and those from advanced foreign countries. Specifically, these valves exhibit poor corrosion resistance and a short lifespan, which do not fully meet the operational requirements of ships. Additionally, the manufacturing yield rate of marine copper alloy valves needs improvement. Currently, all maritime powers emphasize the research, development, and application of high-performance copper alloys for ships. They focus on the physical and chemical properties, economic aspects, and compatibility of these alloys, keep abreast of trends in copper alloy development, and strengthen basic research in the field. In response, China should address these issues and enhance technical research on copper alloys, focusing on the following aspects:
Research and development of copper alloy products with long lifespans and excellent corrosion resistance.
Research into cost-effective technologies for copper alloys.
High-strength and advanced welding process technologies for copper alloys.