Fact of Life
By
maintaining bearings under ideal (laboratory) operating
conditions, rotating equipment will last five to ten
times longer than without bearing seal purge, and contamination
ingress.
Pumps, motors, pillow blocks, fans, gears and turbines
are dramatically more reliable and productive. Costs
of maintenance and operations go down and productivity
goes up.
Quotation from Marcus Wickert, P.Eng., Engineering Manager,
NTN Bearing Corporation of Canada:
"In my experience, determining the re-lubrication
quantity is difficult for the main reason that we are
typically unsure as to how much lubricant is already
in the bearing and cavity. As disassembling the equipment
to retrieve this information is typically time consuming
and undesirable, it is recommended that some precautions
be taken not to over grease a bearing.
If
safe to do so, bearings should be greased when they
are in operation. If a vent is provided in the housing,
excess grease can escape from the vent and the bearing
will pump excess grease out of the cavity. As stated
above, seals may also allow grease to purge during the
greasing process. Where grease venting is not provided,
the grease fitting is sometimes removed for a short
period to vent the system; however, it is important
that the fitting be returned and that contaminate is
not allowed to enter the cavity during this period.
All too often a bearing is greased only when it starts
to make noise and bearing damage has already occured.
Upon disassembly and bearing replacement, lubrication
problems can be overlooked as the bearing now has a
fresh pack of grease and may appear to have been lubricated
adequately. Alternatively, bearings can be greased so
frequently that they can not expel old grease fast enough
resulting in continuously elevated temperatures and
early bearing failure."
Quotation
from SKF's "A Guide to Better Bearing Lubrication"
Publication No. 114-110 Nov. 1980
"If
one is uncertain about the amount of grease in a bearing,
the safe rule is to add grease slowly as the bearing
operates, until the first sign of grease appears at
either seal. If a pressure fitting is used it should
be removed after greasing as a precaution against retaining
grease pressure. Any outward motion of grease is an
indication of pressure."
Our only comment would be - "Perhaps you should
be using a lube vent block!"
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by: McCoy