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Custom Made: Custom bearings may be the solution to difficult applications |
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Written by Stephen Thompson
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 Have
you ever been in a situation where you knew exactly what bearing you
needed for a troublesome application only to be told that a specific
design or feature was no longer available? Or maybe you’ve changed the
way some of your equipment is loaded and now a shorter bearing life is
driving your maintenance expenses through the roof. Perhaps you’re
discovering that the latest catalogue designs don’t perform as well as
what was previously available and there doesn’t seem to be an
alternative.
These are some of the reasons why there is a growing demand for custom bearings today.
Digging deep
For an example of a custom bearing application, Edmonton-based QA Bearing Technologies Ltd.
assisted a customer that had large pumps removing ground water from a
number of their mine locations. The problem was that as the volume of
water and the depth of the mines increased, they began to experience
reduced life in the fixed bearing location of the pump housing. They
believed if they could separate the thrust load from the existing
spherical bearing, by mating it up with an independent thrust bearing
in the same housing, they could solve their growing maintenance
problem. However, they were having trouble finding a catalogue bearing
with (1) the capacity required within the space available and (2) an
alignment feature to accept the possible shaft and housing alignment
issues.
QA Bearing was contacted by a local bearing distributor, and through
them, they had a number of discussions with the mine engineers to
clearly define the application and the issues. A solution involving
ideas from a number of sources emerged.
By modifying existing equipment (using current inventory) and designing
a custom thrust bearing, all their objectives were realized. The mine
would modify the shaft and produce a special mounting sleeve to accept
both the existing spherical roller bearing and the shaft race of a
custom cylindrical roller thrust bearing. The custom thrust bearing
would have the alignment feature in the housing race and dimensions to
fit within their existing housing with only slight modifications.
During the exchange of design ideas, it was determined that a special
flange should be added to one of the self-aligning housing race
components to assist in holding everything in position during the
horizontal installation. This is the type of value-added feature often
offered at no added expense.
The initial prototype operated for a number of months before suffering
a failure, so the bearing was returned to QA Bearing’s engineering
department for inspection. A complete analysis determined the thrust
bearing had been starved of lubrication. After presenting this to the
customer, they decided to add grease ports to the housing so the thrust
bearing would be assured fresh grease rather than the overflow from the
radial spherical bearing’s grease. Since then, the performance of the
pumps has returned to their initial, acceptable levels.
Cost considerations
It is always prudent to investigate the use of any standard catalogue
product before considering a custom bearing as standard bearings are
more economical and inventory is usually available. Sometimes standard
product can be modified or combined with an additional custom component
to solve smaller problems, such as installation, packaging or
field-retrofit situations.
However, when major dimensional, material or geometric issues are
involved, a completely new bearing needs to be designed and
manufactured. The higher price of low to medium-quantity custom
bearings will require justification from existing high maintenance
costs, downtime expenses or when a priority design project cannot move
forward without finding a solution for a bearing requirement.
Although custom bearings have been around for some time, they have
traditionally required higher production requirements before the
popular bearing manufacturers would consider the expense of designing
and manufacturing them. Tooling charges alone often prohibited requests
for smaller quantities.
Today, however, with 3D modeling design programs and numerically
controlled machining centres, customized bearings can be provided in
low to medium volumes with local engineering support. This is good news
for those who deal with bearings in difficult applications and are
looking for something outside of the normal bearing product lines.
Stephen Thompson, P.Eng., is the vice-president of engineering and
sales with QA Bearing Technologies Ltd., based in Edmonton. For more
information, visit www.qabearing.com.
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