Vesconite solves bronze bearing problem on large double toggle jaw crushers
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A series of double toggle jaw crushers were manufactured for a South African
copper mine. The set of 4 crushers, to be installed 1250 m (4000') below the
surface, were the largest jaw crushers ever manufactured in South Africa. Each crusher weighs approximately 250 tons and needed to be dismantled and moved underground in sections weighing less than 50 tons. |
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Mass of swing stock = 59 tons
Bearing size = 590 x 500 – 760 mm long (23" x 20" – 30")
2 bearings per swing jaw
Oscillation : 4 mm (0.16") @ 170 RPM
Initially the crusher manufacturer had considered bronze bearings for this
application. The bronze bearings were manufactured and installed. However,
during initial 24 hr tests various operational problems were identified. The
bush and the shaft "picked up", the operation was noisy and there was excessive
wear on the bearing.
Regular lubrication was provided to the bronze bearing by a dedicated
lubrication system directly onto the bearing, but because the oscillation was so
slight, the lubrication was not spread sufficiently to cover the bearing
surface, resulting in high wear.
As a candidate to replace the bronze as the bearing on this crusher, Vesconite
was put through a stringent evaluation process. This was necessary as the
operation of the mine was critically dependent on the operation of the crusher,
which in turn was dependent on its Vesconite bearings. Any stoppage of the
crusher meant operation of this expensive plant came to a standstill.
The original grooving design for the bronze bearing was maintained as was the
lubrication specification.
The Vesconite bearings were machined to the standard industrial specifications
for Vesconite of size of interference fit and running clearance.
The bearing was installed by freezing with dry ice for 3-4 hours. This causes
the bearing to shrink and overcomes the interference fit of 1.4 mm (0.06"). The
bearing was then easily installed by sliding into the swing jaw.
The crusher with the Vesconite bearing was tested for 3 weeks. The following
were noted when the shaft was removed for inspection after the test:
- The operation had been quiet
- There was no wear on the bush other than "bedding in" wear
- There was no wear on the shaft
The self-lubricating properties of Vesconite gave a successful operation even though the grease was not being spread across the whole bearing surface.
After more than 9 months of operation in the mine, the Vesconite bearings
were still performing to requirements. Notably, even when steel that was caught
in the ore fed into the crusher and damaged crusher parts, it did not damage the
Vesconite bearing.
In addition to its long wear life performance advantage, the Vesconite bearings
had the following advantages:
- Ease of installation - By freezing Vesconite with dry ice, installation does not require heavy equipment. Even if bearings have to be removed and replaced even on site 1250 m (4101') below the surface.
- Ease of removal (if required) without the need for heavy equipment. Bronze bearings need to be machined out of their housings. Vesconite can be removed by freezing or easy destructive methods.
- Ability to perform even if lubrication is temporarily suspended.
- The slightly larger running clearance and softer material than bronze gives the Vesconite bearing the ability to operate with a slight housing misalignment without the need to line bore the housing.
Vesconite is manufactured and stocked in the large bearing sizes required for the application.
visitors since Jan 18 2005
Updated Nov 14 2005
