After a first analysis, ABS Costa Rica detected failures originated in the high-speed bevel gear-pair, probably due to wear, which is common in 90° or bevel right angle catalog gearboxes as the ones initially installed, and proposed their replacement by new gearboxes custom designed and manufactured by its brand MGS based on the technical specifications of the Instituto Costarricense de Electricidad (ICE) with the following criteria and objectives:
Standardize the gearboxes so that they can be installed in two types of cooling tower cells (Miravalles I and Miravalles II cells) and can be interchangeable between the different towers of the plant. This has a positive impact on maintenance cost savings, as it eliminates the duplication of spare parts, reduces inventory, and allows a more efficient assessment of overall performance.
Increase the Service Factor of the new gearboxes. ABS Costa Rica designed and manufactured four custom-made gearboxes, through its brand MGS Gears, with the highest manufacturing quality criteria. A case-hardened and tempered steel alloy was used for the bevel gears to achieve high wear resistance and very high gearing precision, which is essential for reliable operation at 1750 rpm. In addition, its geometry was considerably improved by using a globally recognized manufacturing profile that contributes to standardization and ensures component quality. Stronger, closer to the theoretical and ideal rolling tooth shape, and much smoother and more efficient.
To improve the reliability and maintenance of the equipment, it was also decided to incorporate monitoring sensors to remotely control its condition about the temperatures of all its bearings to analyze vibrations, oil level, and a series of other conditioning factors that allow establishing complete and real-time control of the condition of the gearbox and all its components. In addition, to achieve greater efficiency in the reception and sharing of data, the monitoring was integrated with the SCADA (Supervisory Control and Data Acquisition) system, which is currently used by ICE to receive and manage all the information generated in the process for supervision, quality control, data storage, etc.
Currently, the custom-made MGS gearboxes are installed and fully operational at the Miravalles geothermal power plant.