Accurate Measurements

The rapid development of sensor technology provides cement producers with a range of solutions that optimise performance potential and strengthen market presence. The non-contact volume flow measurement of conveyed materials can help to optimise the material handling process from quarry to final product.

Bulkscan flow measurement technology introduced by Sick Automation several years ago has had its portfolio broadened with the introduction of its Bulkscan low cost LMS111. Both versions provide non-contact maintenance-free measurement of volume flow more accurately than mechanical belt scales. They also minimise errors in mass and volume flow rate calculations.

Monitoring flow in cement plants

Knowing how much raw material is in the yard is a challenge. It is essential that conveyors provide a nonstop flow of raw materials, additives, fuel,
clinker and cement upstream and downstream of the pyroprocess. Mechanical scales measure mass and the volume of material transported is calculated using an average material density. This process is hindered when material density changes or when a conveyor belt is not properly maintained. Material density is used to convert mass from the weigh scales into volume and vice versa. “When the density is incorrect, the volume
and mass calculations are also incorrect,” says Felix Bartknecht of Sick.

The solution
Bulkscan flow measurement technology enables the yard manager to directly measure the contour volume, height and material distribution through the use of Lidar (light detection and ranging) based technology. The sensors can be mounted over conveyor belts, onto cranes and reclaimers.

“Inside the Bulkscan sensor, high-pulse laser beams create a profile of the material on the conveyor which, in combination with belt speed, represents volume flow and calculated mass flow,” says Felix. This measurement principle is based on a laser beam that is deflected internally across a rotating mirror. The sequential order of the laser pulses is synchronised with the rotation frequency of the motor and the desired angular resolution.

Generally, the motor rotation speed is determined by the maximum emitted pulse frequency of the laser source and the desired angular resolution. The laser beams scan the surface area of the material
on the conveyor and send this information to the measurement device, which compares the data with an empty reference conveyor belt.

Bulkscan allows plant operators to directly measure volume flow on conveyor belts, bucket elevators or drag chain conveyors outdoors in harsh conditions as well as inside the cement plant. The scanner can be mounted above the conveyor, measuring volume flow without any material contact, making it virtually maintenance free. The collected data can either inform manual processes, or be fed input to fully-automated systems to drive changes in material flow and composition. When large objects are detected, the plant operator is alerted and an automated stop process is triggered.

Optimising processes
Bulkscan also helps plant operators to optimise conveyor operation and reduce unplanned downtime. The same laser beams used to measure the
bulk flow rate provide information about the exact height and distribution of the bulk material on the conveyor. In addition, the centre of gravity of the load and the distance between the bulk material and the conveyor edge is measured and provided to a closed-loop system to adjust material distribution on the belt. This process automation helps increase belt life and decrease one-sided roller wear and downtime.

Sick Automation
Robert de Scánde, Tel: (010) 060-0550