Reconstruction of seals at steam turbines

At thermal plants the axis - radial seals are permanently replaced with the cell ones, this will enhance the cost-efficiency, reliability and increase the service life as well as reduce the costs of future capital repairs of the turbines.

Over-banding cell seals are widely used in foreign and domestic aviation engine construction since the 70’s. Cells have the form of the alveolus of size 0.9x0.9 mm, are made of foil of 0.05 mm thickness (material - HN78Т and HN80) and are soldered to inserts- blocks, from which the ring is composed for further installation into diaphragm.

Over-banding seal prior to reconstruction	Over-banding seal after reconstruction

At the moment of start-up of rotor the blade comb edge easily cuts the groove in the cells. After the output of the cells the labyrinth effect remains. This technology allows to do with no disassembly the liquid end and costly repairs, associated with emergency shutdown of the turbine.

During replacement of existing seals with the cell ones reduce the radial clearance from 1.5 mm till 0.5 mm. As a result of reconstruction reduces escape through the seals and by 4-6% increases the internal relative efficiency of the turbine.

In 2006 were reconstructed the over-banding seals of the liquid end of turbine and their replacement with then cell ones at 6 turbines (Kazan CHPP-2, CHPP-3, Zainsk Condensation Plant, Nizhnekamsk CHPP, Naberezhnye Chelny CHPP).

The work continues.