Posted on Sun, Aug 9th, 2015 in: Technology
On August 7th, 2015, the US Army Corps of Engineers (USACE) approved GGB Bearing
Technology's new HPMB filament wound bearings for use in hydropower turbine wicket gates. This approval is based on simulation testing that was performed by Powertech Labs. Conducted in April 2015 in accordance with USACE specifications, the testing simulated the operating conditions of a wicket gate in a Francis turbine. Test results showed an extremely low stick-slip effect, indicating smooth operation of the regulating mechanism in a turbine, as well as a low wear rate with no visible bearing damage in wet, dry, or edge testing.
According to the test report, "The dynamic and static coefficients of friction were quite close to each other, which indicates a smooth end of stroke direction reversal. The test ran smoothly and quietly and the coefficients of friction remained stable for the duration of the test. Overall the bearing was in excellent condition...[and] the wear rate was exceptionally low."
In addition, HPMB™ offers high load bearing capacity, plus it features excellent resistance to shock and misalignment, and also features dimensional stability in water. Additionally, it's also the best-performing bearing material under conditions that include dithering, which are the high frequency, small angle oscillations present in turbine operation.
HPMB™ features a machinable liner that provides tight dimensional control and class-leading tribological properties for hydropower applications. Post-installation ID machining allows IT7 diametrical tolerance to be achieved with improved concentricity and cylindricity. Liners can be machined with commercially-available inserts.
HPMB™ bearings are available in three configurations: finished by GGB and ready for installation; finished OD and length and ready for end-user ID machining prior to installation; and finished OD and length and ready for end-user ID machining after installation. The last two configurations are valid for refurbishing turbines by OEMs that do not know exact component dimensions and tolerances.
The characteristics of these bearings are the following: machinable inner and outer diameters for superior application precision, circularity and cylindricity tolerances; high precision through easy single point machining of the bearing liner, on-site prior to installation; superior precision achieved with post-installation (inner diameter tolerance IT7 attainable) single point machining of the bearing liner; high load capacity; excellent shock and edge loading capacity; low friction with negligible stick-slip; low wear rate for extended bearing life; excellent corrosion resistance; dimensionally stable, with very low water absorption, low swelling; environmentally-friendly grease-free operation; they are available in ID sizes up to 500 mm and various wall thicknesses.Back to blog page