7
Photograph 1.--Thrust bearing high pressure lubrication port.
2.3 Thrust Bearing High Pressure Lubrication System
The thrust bearing high pressure lubrication system provides high pressure oil between the thrust
shoes and the runner to provide lubrication on start-up and shut-down of a unit. The oil is
pumped from the bearing oil pot by a high pressure pump, through a manifold to a port machined
in each of the shoes. Photograph 1 shows a typical oil ring on a thrust shoe for a high pressure
lubrication system. The primary use for the high pressure lubrication system is to reduce friction
during start-up and shut down, but it is also a very useful system during alignment. With the
system on, it is possible for a couple of people to rotate a unit by hand or move the rotating
components laterally on the thrust bearing. Both rotation and lateral movement are required
during the alignment process, which will be discussed later in this document.
shoes and the runner to provide lubrication on start-up and shut-down of a unit. The oil is
pumped from the bearing oil pot by a high pressure pump, through a manifold to a port machined
in each of the shoes. Photograph 1 shows a typical oil ring on a thrust shoe for a high pressure
lubrication system. The primary use for the high pressure lubrication system is to reduce friction
during start-up and shut down, but it is also a very useful system during alignment. With the
system on, it is possible for a couple of people to rotate a unit by hand or move the rotating
components laterally on the thrust bearing. Both rotation and lateral movement are required
during the alignment process, which will be discussed later in this document.
2.4 Guide Bearings
Guide bearings support the shaft radially and help hold the shaft in alignment. Ideally, the guide
bearings in a vertical shaft unit should be very lightly loaded. In reality, due to imperfect
alignment, unbalance, hydraulic forces from the turbine, and other factors, the guide bearings can
see significant loads. The designs of guide bearings vary a great deal. The bearing surface is
usually babbitt, but there are older units that use water lubricated lignum vitae, a hardwood, or
high density polyethylene bearings. The bearing may be a sleeve type journal bearing or a
segmented shoe design. The turbine bearing is nearly always a sleeve type journal bearing with a
cast steel shell (figure 9). The axial length of a turbine bearing is usually greater than its
diameter. Turbine bearings are typically lubricated by an auxiliary pump that pumps oil to the
top of the bearing and the oil flows by gravity through the bearing. The turbine bearing may be
held in place in the turbine bearing housing by dowels or with a tapered fit allowing very little or
no adjustment.
bearings in a vertical shaft unit should be very lightly loaded. In reality, due to imperfect
alignment, unbalance, hydraulic forces from the turbine, and other factors, the guide bearings can
see significant loads. The designs of guide bearings vary a great deal. The bearing surface is
usually babbitt, but there are older units that use water lubricated lignum vitae, a hardwood, or
high density polyethylene bearings. The bearing may be a sleeve type journal bearing or a
segmented shoe design. The turbine bearing is nearly always a sleeve type journal bearing with a
cast steel shell (figure 9). The axial length of a turbine bearing is usually greater than its
diameter. Turbine bearings are typically lubricated by an auxiliary pump that pumps oil to the
top of the bearing and the oil flows by gravity through the bearing. The turbine bearing may be
held in place in the turbine bearing housing by dowels or with a tapered fit allowing very little or
no adjustment.
The generator guide bearings may be a sleeve type journal bearing or may be made up of
segmented shoes (figure 10). The axial length of the bearing is usually less than the diameter.
segmented shoes (figure 10). The axial length of the bearing is usually less than the diameter.