Main ventilation fans are critical equipment on mines and any down time has major consequences to production. Let us consider the process of changing the Non-Drive End (NDE) bearing, as this bearing carries the highest load and thus most likely to fail.
The process is as follows:
1. The Motor needs to be moved thus losing all alignment.
2. The coupling needs to be removed which is normally heat shrunk to the shaft, this makes removal difficult often leading to damage.
3. The brake mechanism needs to be removed. This often leads to potential damage too.
4. The Drive End (DE) bearing needs to be removed and replaced. This is done since it will be damaged during removal.
5. The NDE bearing can now be removed and changed. A difficult job as the shaft cannot be raised since it goes through ducting of the fan. Often the Plummer block needs to be moved towards the DE. This means that all alignment is lost.
6. Once the NDE bearing has been replaced, the reassembly process may begin. This is followed by a lengthy re-alignment.
The above process takes about 24 hours and the cost of two bearing replacement, as well as the possible cost of a coupling. The alignment process can also take many hours.
The SRB bearing can be changed within an hour, with no loss of alignment so the benefit of the conversion to SRB saves 23 hours down time and also the cost of two bearings and possible coupling damage. Another benefit is that the bearing can easily be inspected in situ thus complying with critical equipment inspection.
OE Bearings has converted most of the Main Ventilation fans in the Platinum industry, as well as many in Gold and Coal mining. With over 300 fans running successfully running on SRB, OE Bearings has developed some unique propriety knowledge for example the location of the NDE bearing versus the industry standard of locating the DE bearing.
This break with industry has put us at loggerheads with some fan manufacturers, thus let us clarify the engineering thinking behind this change;
The DE bearing often experiences very light upward radial loads, due to the cantilever of the over hung fan. It should be noted that the SRB minimum load is a third of the typical Plummer Block bearing it replaced.
The NDE bearing is often a larger shaft size, thus this bearing is better equipped to accommodate the Axial and Radial load.
The break with industry standard means the SRB bearing operates at significantly lower temperatures compared to the Plummer Block bearings they replaced.