checkweigh

Checkweighing is the independent verification of material weight at the point of sale or transfer, performed by a neutral third party to settle disputes over tonnage and thus payment. In mining and extraction, it sits between the producer and buyer as a critical control: the mining company declares a load's weight, but the buyer (or the buyer's representative) uses a certified weighbridge to confirm it before accepting and paying for the shipment.

The practice emerged because disputes over ore tonnage directly affect miner wages and company revenue. A checkweigher, historically an employee of the mining union or a hired independent inspector, stands at the weighbridge with authority to record the true weight. The result becomes the basis for payment calculations. Without this check, sellers have incentive to overstate tonnage and buyers have incentive to understate it; checkweighing removes that asymmetry by introducing a documented, third-party measurement that both parties accept in advance.

Modern checkweighing uses certified dial or digital weighbridges, typically Class III or higher under weights and measures standards, capable of handling loaded haul trucks or rail cars ranging from 20 to 150 tonnes. The weighbridge is calibrated at intervals specified by local metrology authorities (often annually). The checkweigher records the gross weight of the laden vehicle, the tare (empty weight), and calculates net ore weight. Paper tickets or digital records are issued to both seller and buyer simultaneously to prevent later dispute.

Variants exist by context: some operations use portable scales at the pit mouth for real-time checking; others employ checkweighers at railheads or ports where final shipments leave. The role is most common in alluvial mining, hard rock mining, and coal extraction, where wage systems historically tied payment directly to tonnage removed or where buyers purchase by the tonne and guard against short-changing. The term checkweigher can refer both to the person performing the check and to the organization (often a union-appointed inspector in older operations, or a commercial third-party service today).

Disputes still arise: over scale calibration, over whether wet ore should be dried before weighing, over the inclusion or exclusion of packaging. Regulatory bodies in mining regions often mandate that checkweighers be licensed and that scales be publicly accessible so both parties witness the weighing. In some jurisdictions, checkweighing is a legal requirement for certain commodities, particularly where workers' wages depend on tonnage.