Transcript Slide 1

SEVERE OIL LEAKAGE THROUGH
BEARING PADESTAL
33MW TG. UNIT-1. BORL, BINA
PROJECT
OIL GUARD RING ASSEMBLY
DESCRIPTION
 During
steam
rolling
and
synchronization of U#1 from 22.07.10 to
29.07.10,
severe oil leakage was
observed from rear brg pedestal end
(TE).
The leakage started when turbine
reached at full speed i.e 5000 rpm and
gradually increased. The pedestal end
from where oil was leaking out is located
very close to turbine exhaust casing.
 During
that
time
U#2
pedestal box up work was in progress.
It was seen that with rotor in position,
the oil guard ring was coming in direct
contact with the oil deflector collar of
the
rotor.
As per drg there should be an axial
clearance of 4.0 mm clearance between
rotor and oil guard ring. It was suspected
that
similar condition must be existing in
Unit-1
also.
ACTION TAKEN
 Pedestal was opened for inspection.
Severe rubbing marks on the oil guard ring
was observed.
The oil guard ring was machined on the
face. One of the brass sealing fins had to
be sacrificed in order to obtain adequate
clearance .
 The component was assembled and
4.0mm clearance was ensured. The oil
leakage problem was resolved.
ANALYSIS
The turbine was assembled and tested
at Hyderabad works with all the
components supplied to site.
 During erection, TG axis and pedestal
locations were finalized as per drg.
All clearances of turbine internals were
rechecked and recorded during box up
except this reading.
OIL GUARD RING ASSLY WITH ROTOR
The turbine rotor expands by about
4 mm at coupling end.
During the course of its expansion it
came in direct contact with the oil
guard as there was insufficient
clearance between them.
This caused axial rubbing of the
component and also leakage of oil.
REMARKS
 The oil guard is assembled in the
final stage of erection during box up
of pedestal.
 Though
this
an
important
component, normally it does not
receive proper attention which lead to
such mistakes.
 Assembly of oil guard ring should be
paid special attention in view of the
rotor expansion issue involved with it.