standards / manuals / guidelines for small hydro development - AHEC

E. GovernorDifferent types of governors are in use in different hydro power stations:o Mechanical governor can be classified as follows• Fly ball type• Accelero technometric typeo Governor employing magnetic amplifier.o Governor employing electro hydraulic amplifier.o The governor may require maintenance because of the following reasons:• Chocking of oil parts and throttles.• Wearing out of throttles due to which oil leakage becomes more andreadjustment of governor becomes essential. In this case governor should beopened and all the throttles etc. Should be cleared. Filters should also becleaned, and after cleaning and reassembly governor parameters andcharacteristics should be readjusted so that there is no hunting of the governor.F. Governing Oil SystemThe oil sump should be well cleaned and filled with filtered oil. The oil samples should begot tested for verification of the desired properties. Regular centrifuging of oil with the helpof De-Laval type oil purifying machine would go a long way in enhancing the life of the oil.In certain cases oil retained its properties even up to 15 to 20 years of continuous use.During annual overhauling OPU sump and pressure accumulator should be completelyemptied and cleaned. The strainers should be inspected and repaired of necessary. The OPUpumps require maintenance when they develop excessive noise or vibration. This may be dueto some worn out bearing of the pump which would be replaced.One more problem which has been faced in different power station is entry of water in thegoverning oil system. From following two sources the water can enter in the governing oilsystem.G. Headeri) From top cover, through oil leakage pumps which caters leakage of servo motor oil.Its sump being located will below the level of servo motors in the top cover may notbe properly sealed, thus providing access to the top cover water which may ultimatelybe pumped in to the OPU sump.ii) In case of Kaplan turbine water may enter into the runner hub through rubber seal ofblades.To eliminate first possibility the oil leakage unit delivery was isolated from the OPUsump and connected to a separate tank.But for the second possibility there is no way except replacing blade seals if excessivewater found in the Governor oil.Daily check of the OPU sump oil sample and test of the same is necessary to keeptrack of such possibilities.In Kaplan turbine the oil header is required to supply governing oil to the runner servomotorand return oil to the OPU sump. Oil header has an oil guide connected with the rotating andAHEC/MNRE/SHP Standards/ E&M Works – Guidelines for Operation and Maintenance of Small Hydropower Station 26