prior to full-scale field evaluation. The lubricant demonstrated consistent performance across a range of operating conditions, including high-load and low-speed regimes representative of mixed lubrication. At rotational speeds of 400–800 rpm and applied contact pressures of up to 13 MPa, the fluid maintained a stable hydrodynamic film, effectively preventing surface-to-surface contact and mitigating wear of both bearing pads and runner surfaces. Post-test inspection confirmed the absence of any observable damage or distress on the bearing pad surfaces.
with the primary objectives to evaluate the fluid’s stability, compatibility with equipment components and ensure a safe and reliable operation. The condition of the fluid over an 18-month period was measured periodically courtesy of Vattenfall. Over the trial period, the fluid accumulated 12,998 operating hours with 42 stops. Results are shown in Figure 4.
Figure 3: Combined thrust guide bearing test rig.
Further testing was undertaken to evaluate fluid film strength under increasingly severe loading conditions. Despite the application of loads exceeding standard test parameters, film breakdown could not be induced within the operational limits of the rig, indicating a high level of load-carrying capacity and film robustness.
Figure 4: Fluid Condition Monitoring.
The successful outcome of this controlled equipment testing provided the technical basis for advancing to a full-scale field trial, subsequently conducted at the Porjus Hydropower Centre Foundation in Sweden.
Field trial performance of Hydro T-EL at Porjus, Sweden
The Porjus power station on the Lule älv river in Norrbotten, is owned by Vattenfall. The installation of Hydro T-EL is an extended field demonstration on the Unit 8 turbine which is operated by Porjus Hydropower Centre Foundation, a joint collaboration between ANDRITZ Hydro, GE Renewable Energy and Vattenfall. The U8 turbine is a 10MW Francis Turbine using a tilting pad thrust guide bearing (12 babbit pads), operating at 30 m/s (600rpm) with a mean bearing load of 4MPa. The trial began in January 2024
10 LUBE MAGAZINE NO.193 JUNE 2026
The viscosity of the fluid remained stable throughout the trial period. The water content varied between 500-1200ppm and is likely due to seasonal effects. There was a minor increase in the acid value of the fluid as expected as the fluid ages. Demulsibility and air release times remained unchanged. Finally, the ICP elemental analysis (Figure 5) showed no evidence of corrosion or wear metals, suggesting good equipment compatibility and excellent wear performance.
Interestingly the temperature of the fluid was also measured periodically during the trial and was recorded to be about 10°C lower than the petroleum-based product (ISO-68) that was previously evaluated in the equipment. Comparative analysis of the volumetric heat capacities of Hydro T-EL and
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