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Turbine Manual Bhel

The shaft seals function to seal the interior of the turbine casing from the atmosphere at the front and rear shaft penetrations. The seals use a labyrinth design with seal strips caulked into segmented rings and the rotor to form a path that impedes steam outflow. At the exhaust end, see-through seals are used with opposite facing seal strips caulked into the shaft and casing rings. The seal rings are divided into segments held in position by springs and steam pressure, allowing freedom of movement. Steam spaces within the seals draw off any leakage to the seal header or condenser.

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599 views2 pages

Turbine Manual Bhel

The shaft seals function to seal the interior of the turbine casing from the atmosphere at the front and rear shaft penetrations. The seals use a labyrinth design with seal strips caulked into segmented rings and the rotor to form a path that impedes steam outflow. At the exhaust end, see-through seals are used with opposite facing seal strips caulked into the shaft and casing rings. The seal rings are divided into segments held in position by springs and steam pressure, allowing freedom of movement. Steam spaces within the seals draw off any leakage to the seal header or condenser.

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Steam Turbine

Description IP Turbine
Shaft Seals

Function
The outer seal rings can be removed for inspection
The function of the shaft seals is to seal the interior of the and if necessary seal strips can be replaced during a
turbine casing against the atmosphere at the front (thrust short turbine shut down keeping module in place.
bearing end) and rear shaft penetrations of the IP turbine.
Gap Sealing
The shaft seals are axial-steam-flow non-contacting seals.
Sealing between the rotating and stationary
In the region subject to low relative expansion in the elements of the turbine is achieved by means of seal
vicinity of the combined journal and thrust bearing, the seal strip (9), caulked into seal rings (3; 5) and into the rotor
strips are caulked alternatively into the shaft and into spring- (4) (details A and C).
supported segmented rings in the casing, forming a labyrinth
to impede the outflow of steam. The pressure gradient across the seal is reduced by
conversion of pressure energy into velocity energy
In the region subject to greater relative expansion at the which is then dissipated as turbulence as the steam
exhaust end, see-through seals are used, in which the seal passes through the numerous compartments according
strips are located opposite each other, caulked into the shaft to the labyrinth principle.
and into seal rings centered in the outer casing.

BHEL, Hardwar 6.1-0330-01/1


Seal Rings When the turbine is started from the cold or warm
state, the seal rings naturally heat up faster than the
The seal rings (3), the number of which depends on the mounting rings however.
pressure gradient to be sealed are divided into several
segments as shown in Section BB and mounted in grooves in They can expand freely in the radial direction
the rings such that they are free to move radically. against the centering force of the helical springs (6).

Each segment is held in position against a shoulder by Steam Spaces


helical springs (6) and by the steam pressure above the seal
rings (3). Steam spaces are provided within the shaft seals.
From space ‘P’ leakage is drawn off to the steam seal
This provides the proper clearance for the seal gaps. header.
Should rubbing occur the segments concerned can retreat?
The slight amounts of leakage steam which are still
The heat developed by light rubbing of the thin seal strips able to pass the seal ring are conducted from the
(9) is so slight that it cannot cause deformation of the rotor space ‘R’ into the seal steam condenser.
(4).

BHEL, Hardwar 6.1-0330-01/2

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