In recent years, pumps have been used in the various environments, depending on their region and purpose of use.
EBARA employs numerical analysis technology, as well as experimental approaches, for the swift engineering of pump materials in various environments (temperature, salinity level, etc.).
We are also working on the development of coating materials with the aims of preventing corrosion and extending the useful life of the equipment.
We obtain field data by investigating corrosion behavior of the materials for pumps in seawater at a wide range of salinity levels (3.5 to 35 %) and water temperatures (10 to 110 °C).
We also possess extensive knowledge and experience regarding various causes of corrosion, such as the effect of fluid dynamics on seawater corrosion and the impact of galvanic corrosion.
EBARA uses that knowledge to achieve appropriate material engineering and deliver reliable seawater pumps around the world.
Conducting corrosion tests in oceans around the world
EBARA has worked with Tokyo Institute of Technology on the joint development of numerical analysis technologies using the boundary element method and is using those technologies in corrosion-protection design and countermeasures against galvanic corrosion*1.
The improvement of calculator capabilities of recent years has enabled the performance of large-scale analysis, making corrosion-protection design possible for the interior of transfer pumps, which have complex flow routes, and for entire pump stations.
Stainless steel, which has been used to make seawater pumps in recent years, has good corrosion resistance in seawater, but localized corrosion may occur due to certain factors such as changes in the environment.
In particular, crevices such as the contact surfaces of metal plates, e.g., bolted joints, have a higher risk of corrosion, and those areas may corrode more quickly than other areas (crevice corrosion).
For this reason, with the aim of establishing corrosion protection measures through a deep understanding of corrosion mechanisms, EBARA is working with the Tokyo Institute of Technology on the development of technologies for the numerical analysis of crevice corrosion in stainless steel.
Cathodic protection analysis of pump stations using the boundary element method
In-bed heat transfer tubes fitted in internally circulating fluidized-bed boilers enable to control the internal temperature and recover heat efficiently. On the other hand, these heat transfer tubes may be damaged due to high-temperature erosion corrosion.
To protect the heat transfer tubes, their surfaces are modified through thermal spraying of self-fluxing alloy and weld overlay.
EBARA, Hokkaido University, a thermal spray engineering company, and other parties worked together to develop self-fluxing alloy coatings that have a contoured surface.
The developed material has better erosion corrosion resistance than existing coating materials, which extends the useful life of the equipment.
Development of self-fluxing alloy with erosion corrosion resistance for in-bed heat transfer tubes fluidized-bed boilers
*1 Galvanic corrosion:
A phenomenon in which, when two materials with dissimilar corrosion resistance are used in a conductive state in the same water, the material with the lower resistance corrodes in preference to the other material.
*2 Erosion corrosion:
A phenomenon in which erosion and corrosion occur simultaneously, which accelerates the damage more significantly than if either erosion or corrosion were to occur on their own.