Page 96 - The Tribology Handbook

Profiled pad thrust bearings AI 6

LUBRICANT FEEDING
Lubricant should be directed to the inner diameter of
the bearing so that it flows radially outward along the oil-
ways. The outlet from the bearing housing should be
arranged to prevent oil starvation at the pads.
At high speed, churning power loss can be very signifi-
cant and can be minimised by sealing at the shaft and
runner periphery to reduce the area of rotating parts in P
contact with lubricant.

Lubricant feed rate
A lubricant temperature rise of 20°C in passing through
the bearing housing is typical. For a feed temperature of
50°C the housiing outlet temperature will then be 70”C,
which is satisfactory for general use with hydrocarbon
lubricants. The flow rate necessary for 20°C temperature
rise may be estimated by
Q= KH,
where K = 0.3 x lQ-’ for Qin m3/s, H in W
or K = 0.3 for Qin gal/min, H in h.p.

BEAR I N G S FOR B I - D I R ECTlO N A L
0 P E RAT1 0 N
For bi-directional operation a tapered region at both
ends of each pad is necessary. In consequence each pad
should be circumferentially longer than the corresponding
uni-directional pad. The ratio (mean circumferential
Bengthlradial vvidth) should be about 1.7 with central
land 20% of length. This results in a reduction of the
number of padls in the ring, i.e. about 3 the number of
pads of the corresponding uni-directional bearing. The
resulting load capacity will be about 65%, and the power
loss about BO”/,, of the corresponding uni-directional
bearing.

PRESSURE
DISTRIBUTION
DISTRIBUTION
W
u,
RUNNER

PROFILE ALONG PAD - BI -DIRECTIONAL

A16.5