The Bulkscan® LMS511 from SICK Automation uses time-of-flight laser technology to provide non-contact volume flow measurements on conveyor belts. Regardless of the bulk material type and weather or visibility conditions, the multi-echo technology in the Bulkscan sensor allows it to generate reliable volume flow signals using the laser’s time of flight and the conveyor belt speed. This calculates total quantities of mass and flow.

The sensor monitors conveyor belt operation without making belt contact and provides prompt warning of any belt slippage. An integrated bulk materials centre-of-gravity calculator detects uneven loading, preventing excessive belt wear, and an integrated heater ensures safe operation at low ambient temperatures. These, and other benefits, make this scanner ideal for most bulk material types, including uncommon types as is demonstrated in this case study.

LANXESS case study: Steel scrap adds colour to cities

The Inorganic Pigments Business Unit at LANXESS manufacturers over 100 colour shades to dye concrete materials. Concrete is dyed with synthetic iron oxide and chromium oxide pigments which allows for colour in projects like hotel facades or waterside paving stones, for example. 

At its production site in Krefeld-Uerdingen, Germany, LANXESS uses five SICK Bulkscan LMS511 laser volume flowmeters to optimise the processes used for transporting high-quality iron chips. Using an oxidation and chemical precipitation process, colour pigments are obtained from the chips over a period, which are transported to the individual processing stations on conveyor belts while the transformation process occurs. A solution to guarantee the quantity and volume of material transported, as well as provide sensible control of the metering flow over a work day, was needed. 

 These requirements amounted to a non-contact measuring principle, traditionally a challenge for optical devices in the environments in which LANXESS operates. Detecting dark iron chip masses on dark conveyor belts under difficult lighting conditions is one of them.

SICK proposed the Bulkscan® LMS511 – its ultra-fast sampling technology that enables high precision laser measurement in virtually all weather and ambient conditions. Called 5-echo technology, it is suitable for applications needing reliable detection of dynamic objects in changing or unfavourable conditions. This includes applications with poor visibility such as in tunnels or in mines. In addition to maintaining excellent visibility in unfavourable conditions, 5-echo technology ensures maximum accuracy.

 “We have a classic control loop at two locations,” explains Achim Eumes, Process Control Technology Inorganic Pigments, at LANXESS Deutschland GmbH. “Bulkscan supplies us with the current actual value for the quantity being transported on the conveyor belt and set point values are used for control at certain points. The measurement supplies the actual value and the controller then adapts the desired quantity by means of the speed of the first screw conveyor. This results in a constant transport flow.”

The laser scanners are mounted at five locations above the conveyor belt and continuously measure the height profile of the iron scrap passing beneath using laser pulsing. “A notable aspect of this design is the reliable detection of the height profile, even with external interference factors such as dust or bulk material suspended in the air,” explains Xaver Meier, Head Product Management and Applications Engineering Departments, SICK Automation AG. “This is possible due to new signal analysis technologies, which reliably filter out the correct height profile signal from a large number of echoes. The software algorithm determines the correct signal from the various reflected laser pulses and, at the same time, suppresses any haze that might interfere with measurement.”

Fast scanning frequencies, up to 75 Hz, and fast response times are used to achieve maximum resolution for the height profile (and thus high measurement accuracy). They also enable the measurement of conveyor belts at speeds of up to 30 meters per second.

The Bulkscan system offers six individually assignable switching outputs for additional signal processing, such as a warning or impulse output or as continuous outputs for measured value transmission over TCP/IP (Ethernet). Processing and measured value preparation take place directly in the sensor, which also has two inputs. No additional data acquisition system is required.