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Adjustment-free turbine sealing at Loch Ness

The 5MW Francis turbine in Foyers Falls Power Station at Loch Ness, Scotland, has successfully relied on James Walker's innovative HydroSele^® for efficient shaft sealing since 1996.
Scottish & Southern Energy's hydro engineer, Douglas Smillie, confirmed that an early version of HydroSele ran adjustment-free for eight years with just 3 litre/hour of controlled water leakage.
Prior to HydroSele, the 305mm diameter turbine shaft was OEM fitted with a pair of internally mounted mechanical seals containing segmented carbon rings, plus an outboard labyrinth.
Sand and peat in Foyers River caused excessive wear to these expensive seals, and scored the shaft at the labyrinth. Water sprayed from the housing towards the generator, which meant that many hours had to be spent every year replacing worn seal components.

Eight-year life for elements
Working at a nett head of 100m, the turbine runs constantly for 48 weeks each year at full load speed of 756rpm, with the overspin limit set at 1100rpm.
   This was an ideal installation for the early HydroSele — as it was not until Foyers' maintenance outage in 2004 that the cartridge was on-site fitted with two new elastomeric sealing elements.
"These elements are still running perfectly four years later, with every indication that they will continue for a long time to come", commented James Walker product manager Tim Smith.
   The innovative feature of HydroSele is the way its sealing elements operate within the fully-split cartridge.
   Two elements work back-to-back with filtered flush water introduced between them. In operation, the elements are pressure balanced and run on a hydrodynamic fluid film that provides high speed capability with a low level of controlled leakage.
   Said Tim Smith: "'The overall benefit for Foyers Falls Power Station is that our fit-and-forget HydroSele has delivered many years of trouble-free sealing.
"This has improved operational output, helped to reduce overall maintenance costs and maximised uptime on this turbine".

08 Aug 08