Why Hot Spots?
Posted on October 19th, 2020
One of the more common causes of unscheduled downtime and potential ignition sources leading to fires, is the frictional overheating of conveyor idlers / rollers internal bearings, that are in the process of or have failed in service.
The Hot Spots ® ‘predict-to-prevent’ approach to detect failing idler bearings on conveyor systems, increases the reliability and availability of the conveyance system, through the early visual warning of conveyor idlers / rollers surrendering to in service bearing failure.
With these idlers / rollers constantly being in the presence of fuel sources such as layered flammable dusts, accumulated lubricants or accumulations of combustible material (belt fabric, rags, paper, wood), the strict management of the potential heat source is paramount to negate the unintended initiation of fires.
Control measures that are risk ranked are applied in managing this identified hazard, yet recurrently fail, as “hot rollers” are still regular and common place in the industry. The primary control measure used to manage this potential ignition source is regular visual inspections by suitably qualified and competent personnel. The majority of ‘hot rollers” detected during online inspections is either from noise or smell. At these advanced stages of failure, it is not uncommon for the surface temperatures of the idlers / rollers to have exceeded the auto-ignition temperature of many layered dusts found in the Underground Mining environment.
To add further guidance to these requirements, it is also legislated (Australian Coal) that the maximum allowable surface temperatures in an Underground Coal Mine is <150°Celsius, to prevent the auto-ignition of layered coal dust.
You can’t PREVENT what you can’t PREDICT.
With 2 caged roller bearings in each idler in the system, at some time each idler has two opportunities to fail, with no simple inexpensive way to predict single or bulk failures, prior to the dangerous overheating.
Many bearing manufacturers only guarantee 95% of their bearings from early life failure, with many additional factors also influencing the predictive lifetime rating of the idlers.
Without the aid of continual thermal monitoring or imaging, early stage idler / roller bearing failures, are being walked past daily during visual inspections, unknown to the persons completing the inspections.
THE HOT SPOTS® APPROACH
Hot Spots® are intended as a non-reversible, single use, disposable first warning indicator system, to assist in the early visual detection of conveyors rotating mechanical components such as idlers, rollers and pulleys, in the early stages of bearing failure.
With visual inspections being one of the major recognised controls for the detection of overheating, smouldering’s and fires in the mining workplace, Hot Spots® assist those undertaking the inspections discharge their obligations and duties effectively, by recognising an elevated hazard before becoming an unacceptable risk.
The Hot Spots® concept is easily adapted to a mines Safety Health Management Systems as a proactive means of managing the risk of fire and ensuring that current controls in place are effective.
“The concept of Hot Spots® is to give a Simple – Affordable – Functional – Effective resource, in which to assist persons completing inspections and maintenance on conveyor belts, to make consistent and practical decisions, based on a visual repeatable engineered solution”.
Hot Spots® added to the idlers / rollers in areas not accessible during online inspections, allows for effective inspections and maintenance decisions, when access to the idlers is available during maintenance periods.
Hot Spots® give a non-reversible first visual indication of a failing bearing prior to the noise or smoke as the usual tell-tales to a failed bearing. First visual indication at ≥60°C and second final warning at ≥100°C on the double indicator Hot Spots® or single indicator Hot Spots® activating at ≥90°C.
The Hot Spots® predict to prevent approach, allows for a proactive resilient conveyor inspection scheme, adding multiple levels of value to the operations such as –
- Effective compliance to legislation.
- Effective control for annual insurance audits.
- Consistency of inspections and interpretation.
- Reduced unplanned maintenance / repair.
- Effective management of the fire risk.
- Effective maintenance decisions and use of resources.
- Correct idlers identified for replacement during maintenance.
- Reduced belt wear and damage due to seized and worn idlers.
- Non walkside idlers / rollers risk managed for offline inspections.
- Reduced unplanned downtime from.
- Minimal effort – maximum benefit.
Contact Cool Mine on +61 (0) 407 965 043 or +61 (0) 455 069 512