Cradle to grave
The proper maintenance of tyres is essential in any mining operation .
Leon Louw
Getting the most from tyres
A
potential safety risk in opencast mines comes in the form of the ultra-large tyres on off-the-road ( OTR ) vehicles . Over the past couple of decades , there have been recorded instances of these tyres catching fire and , in some cases , actually exploding — with potentially serious consequences . However , nitrogen tyre inflation has proven to be very effective at preventing tyre fires and explosions .
NitraLife , established in 1996 , was the first international company to use a membrane separation process to generate high-purity nitrogen for commercial tyre inflation and subsequently also in large OTR mine vehicle tyres .
“ When a tyre is under load on the road , it is continuously flexing . Over time , flexing and the resulting heat lead to the accumulation of tiny rubber ( carbon ) particles and other flammable compounds inside the casing . When a tyre is inflated with compressed air , oxygen is added to this mix . Now , if heat is added by a bad repair or some kind of mechanical failure , the stage is set for a potentially lethal explosion ,” explains Tom Sowry , marketing director of NitraLife .
In an extension of this overheating scenario , on certain mines , nitrogen tyre inflation has been used to protect tyres against lightning strikes . The power of lightning is such that it will earth through the tyre to the ground , and has in the past been the cause of tyre fires . There are instances of mines parking their vehicles with air-inflated tyres in safe areas during lightning storms — an expensive exercise when one considers the cost of downtime .
“ To date , we are not aware of an instance of tyre combustion at any mine using our nitrogen tyre inflation systems ,” says Sowry .
Cost is also another good reason why the mining sector has increasingly adopted nitrogen tyre inflation . Nitrogen permeates through tyre walls about four times more slowly than oxygen , and 117 times more slowly than water vapour . Under the sometimes very harsh conditions under which OTR tyres operate , nitrogen inflation ensures that tyre pressures remain optimal for longer .
“ Tyres at the correct pressure flex less , and are less likely to overheat — a factor that is a major cause of premature tyre failures . Based on many years ’ experience and customer feedback , we conservatively estimate that nitrogen tyre inflation extends OTR tyre life by at least 10 %,” says Sowry .
“ Oxygen and water vapour degrade rubber , gradually weakening tyre casings . By removing those elements , tyres last longer , particularly if they are being used in harsh climatic regions where heat and moisture are prevalent ,” Sowry adds . Oxygen and water vapour also rust the steel rims of OTR vehicles , as tyre beads do not seat well on rust-pitted rims , which leads to consistent pressure loss and the risk of tyres running under-inflated .
Furthermore , for most of their operational time , haul trucks drive on the steep gradients of unsurfaced pit ramps , which places tyres under even greater stress . In these testing conditions , correct tyre inflation is more important than ever .
On remote mines , NitraLife nitrogen generators offer a troublefree solution to removing oxygen and water vapour from inside tyres .
“ The generator is completely pneumatic — requiring no electricity — has no moving parts , and is fed air by a conventional compressor , requiring minimal maintenance .
“ We also customise our membrane generators to suit a mine ’ s specific requirements , and can supply both large and small mining companies , through either a rental or purchase option . Additionally , the portable nitrogen trailer — another innovation we have developed — is perfect for mines in remote sites requiring a mobile nitrogen solution ,” Sowry enthuses .
As an option with a generator , NitraLife offers digital automatic tyre inflation . Manual analogue gauges tend to drift out of calibration as the moving parts inside them age . With automatic digital tyre inflation , the correct tyre pressure is entered into the control panel . The digital inflator monitors the pressure during inflation , automatically shutting the generator off when the pressure is correct .
[ 40 ] MINING MIRROR FEBRUARY 2018