Vesconite Bearings is a South African-based, internationally recognised manufacturer of self-lubricating polymer bearings and wear materials for demanding industrial applications. One of the company’s clients is a reputable OEM manufacturer of highly specialised underground mining machines. The OEM needed bushings and sliding pads for its cement shotcreting machine to be deployed in a rugged underground mining environment.
Typically, shotcreting machines are exposed to water, alkaline cement slurry, and aggressive wash-down procedures. Instead of bronze, which is considered the traditional choice, the OEM chose Vesconite Hilube self-lubricating bushings and sliding pads.
The gains have been significant: reduced lubrication-related downtime, which has resulted in assured availability.
By Jimmy Swira
In underground mining environments, mission-critical equipment is subjected to conditions such as contamination, moisture, and dirt ingress. If not prevented, these conditions increase maintenance which results in downtime, with huge implications to the bottom line.
Cement or shotcrete spraying machines used for lining the interior of underground tunnels are not immune to these challenges.
The convenience
There is no doubt the OEM manufacturer’s machines bring great convenience to complex shotcreting tasks.Their roll-over boom movement allows a complete advance to be covered in a single setup, reducing repositioning time.
The inconvenience
Availability is vital for equipment teams operating these machines.
The extreme conditions underground, together with the materials they handle, subject shotcrete spraying machine components to impact, abrasion and corrosion. Particularly problematic are the cement fines, sand, and rock dust present at pivot points and articulation joints. Furthermore, the machines are regularly exposed to water, alkaline cement slurry, and aggressive wash-down procedures.
Inevitably, these conditions accelerate wear and tear, which necessitates the correct choice of wear-resistant bushings and sliding pads – for adequate protection.
subject shotcrete spraying machine components to impact, abrasion and corrosion.
Wide range of wear protection materials
OEMs have a wide choice of wear materials as a result of continuous product R&D.
Common usage of bronze
Bronze is commonly used, but a few years ago one prominent machine OEM in South Africa elected to buck the trend.
The Vesconite Hilube option
From inception, the OEM selected Vesconite bushings and sliding pads at the articulation points on all its new concrete-spraying machines.In addition, Vesconite was to supply spares should they be needed.
Since then, the shotcrete machines have used Vesconite Hilube bushings and sliding pads at various articulation points.The bushings and sliding pads have prevailed in conditions where bronze would have faltered.
Precise planning and meticulous installation
Monique Potgieter, a leading chemical engineer at Vesconite Bearings, attributes the success of Vesconite bushings and sliding wearpads in the machines to precise planning and meticulous implementation in the engineering process.
One of the vital factors was consideration of the extreme temperatures to which the bushings would be exposed underground, Potgieter highlights.
Minimal clearances
Vesconite Bearings could design the bushings with minimal clearances, but still large enough that they fit perfectly when the machines are underground.
“It took some engineering to get that sweet spot where enough clearance was allowed to prevent seizure underground, while still ensuring a snug fit upon assembly,” Potgieter notes.
The next consideration – equally crucial – was the cost.
The design was as cost effective as possible. “Vesconite Bearings went with simple bushings and separate flanges. If Vesconite Bearings had made one-piece flanged bushings, the costs would have been higher since larger, thicker-walled stock material would have been required, resulting in much more waste,” relates Potgieter.
Fully machined items
Vesconite Bearings supplied 10 sets offully machined items for the concrete sprayers. The parts included:
- 152 Vesconite Hilube bushings (6 different designs)
- 180 Vesconite Hilube washers (4 different designs)
- 160 Vesconite Hilube sliding plates (8 different designs)
- 144 Ultrablack plates (6 different designs)
Some sets were for new machines being built, and others for spares kits.Most importantly, Vesconite Bearings suggested that the OEM order one test set first to confirm fitment and identify any changes that might be required.
Significant Benefits
Regular feedback from the client indicates that Vesconite has brought significant benefits, affirms Potgieter particularly from reliability and availability perspectives, in the following areas:
1. Minimal maintenance
Maintenance is minimal, lubrication is optional, and downtime is virtually eliminated.
2. Improved performance in abrasive and wet conditions
Vesconite Hilube is engineered to handle dirty and wet conditions without scoring mating surfaces.
3. No lubrication
Bronze relies on a lubricating film to prevent wear.On the other hand, Vesconite Hilube can operate effectively with no lubrication.This reduces abrasive paste formation, a common failure mechanism in bronze bushings when grease mixes with cement dust.
4. Reduced downtime
Bronze bushings require regular greasing to prevent metal-to-metal contact and to purge contaminants.Where it is carried out, this task increases machine downtime, which affects project completion.In addition, due to access constraints, this task is often neglected or inconsistently performed.This increases the risk of lubrication-related failure.In contrast, Vesconite Hilube’s low coefficient of friction and self-lubricating properties allow it to run dry or with minimal lubrication.This lowers maintenance frequency, reduces unplanned downtime, and improves machine availability.
5. Corrosion and chemical resistance
Bronze is susceptible to corrosion and dezincification in certain chemical environments.This can accelerate wear and lead to premature failure.Vesconite Hilube does not corrode and is resistant to chemicals commonly found in cement and mining environments, resulting in more predictable service life.
6. Superior load handling with reduced shaft wear
Bronze is comparatively rigid and transfers shock directly to the shaft, often causing shaft scoring or ovality.Vesconite Hilube exhibits good compressive strength and elasticity, allowing it to absorb shock loads and vibration generated during concrete spraying and boom articulation.Its ability to conform slightly under load protects shafts and pins, reducing refurbishment costs during overhauls.
7. Lower operating noise and smoother articulation
Polymer bushings such as Vesconite Hilube damp vibration and reduce noise at pivot points.This is a distinct advantage in confined underground tunnels where noise levels are already high.Smoother articulation also improves operator control of the spraying boom during precision concrete application.
8. Overall lifecycle cost savings
While bronze bushings may have a lower initial unit cost in some markets, Vesconite Hilube typically delivers a lower total cost of ownership.Extended service life, reduced lubrication requirements, shaft protection, and lower maintenance effort combine to deliver measurable cost savings over the machine’s operating life.
Clear technical and operational advantages
Fundamentally, the OEM’s experience demonstrates that using Vesconite Hilube in a cement or shotcrete spraying machine offers several clear technical and operational advantages over bronze.
Engineered for Mining, Multiple Applications
Vesconite Bearings’ low-wear, self-lubricating bearing materials were originally developed specifically for use in the ultra-deep gold mines of South Africa.The harsh mining environment, characterised by dirt, grit, moisture, and limited lubrication opportunities, drove the need for a maintenance-friendly alternative to traditional metal bushings.
While the company serves multiple sectors, including rail, agriculture, pumps, and marine, mining remains a core application area because the demanding operational conditions align closely with Vesconite’s performance advantages.
Vesconite Bearings’ bearings and wear parts are used in many underground and open-cast mining operations in a variety of countries.Several OEMs specify Vesconite materials in their equipment, and many mines and mining equipment suppliers supply or use Vesconite.
