Cost savings from rubber torsion bases
LEVERLINK managing director Richard Sharp concludes his two-part feature on the history and use of the rubber torsion spring motor base.
Tensioning device
In the early 1990s, the majority of vibrating screen drives rarely exceeded 30kW. However, once the market demanded larger motor bases for bigger screens and feeders with drives requiring motors 37kW and larger, improved mechanical adjustment was required.
Previously, this was achieved with open type mechanical devices and, while relatively inexpensive, they were prone to seizure and premature failure.
The designs of fully enclosed and lubricated mechanical tensioning devices were then developed.
These had the benefit of being able to purge old grease and lubricants at regular intervals and remain failure-free.
The late 1990s saw a greater emphasis placed on pump and crusher drives ranging up to 630kW.
Many requests from mine sites were based on safety issues, particularly with the larger overhead drives that were all mounted on conventional jacking screws.
Mechanical
In addition, the mechanical problems should not be overlooked.
These are due to design and/or corrosion in most cases.
The results of corrosion can include an inability to make the drive and driven shafts parallel, the inability to face drive and driven pulley and the inability to achieve and maintain the correct drive belt tension as per the belt manufacturer’s specifications.
Cost
In today’s market, labour is the single largest cost.
Almost without exception companies strive for efficiencies and cost reductions.
So, why do some end users continue with archaic technology when there are cost effective designs available that can reduce labour costs by up to 90 per cent?
Motor bases can be rebuilt and refurbished.
This may extend their service life to 30 years or more.
Many mine sites recognise the cost benefits.
Case study
Leverlink had a mining client who accepted as normal practice that it took a full eight hours and four men plus a crane to change out a set of vee-belts on a large pump drive.
All of their pumps were conventionally mounted on jacking bolts.
Leverlink designed a Verti-lift motor base to fit the existing pump base frame, used the existing vee-belts, and recommended a new guard that could be removed by two men without the use of a crane.
Windows were included in the guard at belt mid-span for checking belt tension when checking or re-tensioning.
The initial design included details such as ensuring the drive and drive shafts were parallel and that the drive and driven pulleys were faced.
Unless the motor was removed or perhaps new pulleys fitted, they would remain so at each and every belt change-out.
The cost savings were undeniable. Two men in two hours did what took four men, eight hours plus a crane.
The payback period was well within the client’s financial model.
The client went on to install about 30 additional pump motor bases.