What’s Old is New Again - A Proven Technology from the Past is the Solution to Recurring Main Guide Bearing Failure

摘要

Frustrated by constant adjustments and premature bearing failure of synthetic/plastic and composite guide bearings, hydro operators are returning to the original main guide bearings first used in 1929 for a solution. Self-lubricating lignum-vitae bearings are proving to be an answer to the challenge of extending bearing life. This paper describes a recent experience to demonstrate the benefits of lignum-vitae self- lubricating main guide bearings to successfully replace synthetic/plastic or composite bearings that have a high failure rate. The paper focuses on problems at the Osage Plant with composite guide bearing materials after an upgrade to existing turbines. This paper will also examine another problem Osage experienced while using synthetic/plastic or composite bearings, involving increased degradation of the bearing sleeve and rapidly precipitous shaft runout causing the unit to trip off after 45 minutes of operation. After detailing efforts to discover the root causes of these problems, this paper discusses how plant management decided to transition back to lignum-vitae, the original main guide bearing. Lignum-vitae has since been used in the unit for three years with no adjustments to date. This paper includes findings of a Norconsult evaluation, along with attendant charts and graphs, as well as a brief discussion of how the unique properties of lignum-vitae wood allow it to withstand the intense forces of extremely turbulent waters significantly better than any synthetic/plastic or composite materials currently used in main guide bearings. Finally, this paper discusses economic, environment and other advantages gained by using lignum-vitae as our predecessors in the hydro industry did before us - proving that everything old is new again.