WILLIAM S. CHAMBERS, (Member, STLE)
ANDREW M. MIKULA, (Member, STLE)
Kingsbury, Inc.
10385 Drummond Road
Philadelphia, PA 19154
This paper presents operating temperatures for a 2756 mm
(108.5") 10-shoe thrust bearing installed in a vertical turbine generator
in a pumped storage application. The rated output of the
generator is 350 MW at a rotational speed of 257 RPM. Temperature
data will be presented for shaft speeds up to 257 RPM
and loads that ranged from 8.00 to 11.12 MN (1.8 to 2 ½ million
pounds) thrust.
The data presented demonstrates the relative effect that the hydrostatic
lift has on bearing operating temperatures. Some conclusions
are drawn based upon the effect that the hydrostatic lift has
on bearing operating temperatures.
Introduction
Fluid film thrust bearings are at risk unless a full hydrodynamic
oil film is developed and maintained. This bearing
risk condition occurs at starting, stopping and reversing, or
whenever the operating speed falls below a certain minimum.
When this occurs, full hydrodynamic lubrication is
replaced by boundary lubrication, which leads to wear of
the bearing babbitt face. One solution to this problem has
been the introduction of high pressure oil between the bearing
surfaces to establish a hydrostatic lift (high pressure lift).
This paper describes the in-service data collection for a
large pivoted shoe or pad vertical thrust bearing equipped
with a hydrostatic lift. This particular thrust bearing arrangement
is used in each of the six identical pump turbine
generators installed at the world's largest pumped storage
hydroelectric facility located in Bath County, Virginia. These
units are nominally rated at 350 MW generating and 400 MW
pumping. Each unit operates at 257 rpm and the dead weight
on the thrust bearing is approximately 816000 Kg (1.8 x
106 lbs).
In-service data collection was instituted after several minor
wipes of certain thrust bearings had occurred during the commissioning of these units. Investigations resulted in
the identification of two problem areas. The first was the
discovery of leaks in some of the high pressure lift systems
between the check valve and thrust shoes. These leaks prevented
the development of hydrodynamic pressure in these
shoes and resulted in a corresponding loss of load capacity.
The second area identified was a temperature imbalance
between the oil bath and feed tube supply systems resulting
in thrust shoe radial distortions. The bearings were supplied
with an ISO VG 68 lubricant.
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