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1.2
Overview
The MASTER Series 421 Belt Scale is designed for applications with flat belts, where the belt-load is low.
The dimensions are extracted from the construction of the existing, or to-be built, belt conveyor.
Theory of Operation
The material is carried by the belt and underlying rollers or idler stations. One or more of these idlers are mounted
on the weighframe and are used to weigh the material going across the belt. The material carried on the belt is
weighed and the belt speed is measured. Both values (belt load and belt speed) are calculated in an integration
function. The integrator totals and calculates the mass flow. These values are displayed and transmitted through
outputs or other forms of communication to a control system or network.
For the operation, refer to the manual of the electronics installed.
1.3
Selection Criteria
Load cell capacity is calculated based on the maximum belt load plus the dead load of the weighframe and the
weight of the rollers. Contact Rice Lake Weighing Systems technical support for assistance.
Net load = (conveyor capacity / belt speed) x idler spacing
Gross load = net load + (idler weight + belt weight + mounting hardware)
Examples:
Net load = (20,000 lb (9,072 kg) per minute / 400 ft (122 m) per minute) x 4 ft (1.22 m) spacing
Net load = (50 lb (23 kg) per ft) x 4 ft (1.22 m) spacing
Net load = 200 lb (91 kg)
Gross load = 200 lb (91 kg) + (175 lb (79 kg) idler + 48 lb (22 kg) belt + 24 lb (11 kg) hardware)
Gross load = 447 lb (203 kg)
1.4
Calibration and Test Weight Device
Mounting points can be provided to apply static test weights. Test weights are used to test repeatability and the
state of the belt scale after initial calibration.
To determine absolute accuracy, it is necessary to do a test with material. For this procedure, refer to the manual of
the electronics installed.
2
MASTER Series 421 Belt Scale
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