Conveyors carry material in almost every heavy industry, and the further downstream a product goes, the more the proportioning has to be right. Siemens Milltronics belt scales cover that job across a wide capacity range, in conditions that are usually anything but clean — fertiliser, sand, coal, stone, iron and steel.
What the system is made of
A basic belt scale has three parts: a weighbridge carrying the load cells, an integrator, and a speed sensor.
The load cells measure the weight of material on the scale and send the signal to the integrator. The integrator also receives pulses from the speed sensor — mounted at the tail or under the belt — and uses both to calculate throughput:
weight × speed = throughput
One limitation worth knowing first
Siemens Milltronics belt scales measure material only where it produces a vertical force. Material lands on the belt, travels over the weighbridge and presses on idlers mounted on the load cells; that force is sensed by the strain gauges inside. Excited by the voltage from the integrator, the cells return a signal proportional to the flow. Anything that adds force in another direction — a belt pulling at an angle, a skewed idler — does not measure correctly.
The main Milltronics models
MLC — low capacity
For monitoring products such as animal feed, tobacco, fertiliser or sugar. Compact stainless steel build, easy to install, low cost.
MBS — medium capacity
Suited to sand, minerals and animal feed. Single-module design, so installing, servicing and upgrading are all straightforward. Low cost.
MUS — medium to high capacity
Works with construction materials and minerals. Single-module design again, easy to install and upgrade.
MCS — high capacity
Uses the TASS speed sensor. Same design approach as the models above, with load cells in stainless steel.
MSI and MMI — heavy duty
Widely used across light and heavy industry in harsh conditions — coal, iron and steel, sand. Modular design with two load cells in parallel, which raises both accuracy and load capacity.
Accuracy 0.25% to 0.5%, capacity up to 12,000 tf/h. The MMI is a two-MSI system.
Speed sensors
Siemens offers a range covering the usual requirements:
- Straightforward to install
- High accuracy
- Protection IP65 to IP67
The integrator
The Milltronics integrator processes the load cell and speed signals continuously through the measurement, computing both the instantaneous rate and the accumulated total.
It shows belt speed, weight, rate and the raw values from the cells and speed sensor on an LCD, and provides outputs as analog mA, alarm relays, or pulse output of the running total.
Beyond measurement it handles basic control functions — PID and batch control — and communicates with other controllers over RS-232, PROFIBUS and MODBUS.
Application note
KALA Technical Notes
Model choice on a belt scale follows the conveyor and the material, not the throughput figure alone — belt width, idler spacing and how much straight run there is either side of the weighbridge all constrain what accuracy is achievable. Send us the conveyor details and what you are carrying.
● Belt scales, integrators and speed sensors for conveyor weighing.