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.
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.
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.