Super cement producers care about people, products, and profit. Non-contact level sensors use 3D scanners, laser, or radar technologies to ensure accurate monitoring of product levels. Cement manufacturers find non-contact level sensors attractive for several reasons:
- • Nothing comes in contact with material and there’s no risk of equipment interfering with the process or rogue parts breaking off and getting stuck in equipment or contaminating materials.
• Sensors profile continuous level measurement for optimizing inventory and preventing silos from running empty.
No cement manufacturer wants to risk a bad batch due to missing key materials. Today’s most popular non-contact technologies are laser, radar, and 3D scanners. The sensor best suited to a particular application is determined by several factors, including the material being measured, the amount of dust in the environment, the size of the silo, and the desired inventory accuracy. Communications options for retrieving the required data can also vary, along with the price of the sensor and its mounting, wiring, and installation costs.
3D scanners are generally chosen based on budget, vessel size, desired accuracy, and the need for a 3D visual.
3DLevelScanner sees through silo walls
Cement producers can get the equivalent of X-Ray vision using a 3DLevelScanner. With dust-penetrating technology, using the graphical option, 3D scanners visualize and digitize the topography of bulk material inside a silo. 3D scanner is mounted on top of the silo at an optimal location recommended for superior surface coverage, ensuring the scanner can ‘see’ the utmost material surface.
Techno-Speak
3DLevelScanner sends acoustic pulses that sound like chirping crickets to the material surface in a 15-, 30-, or 70-degree beam angle depending on the model. It then measures and maps the material surface at multiple points to detect uneven topography. Distance is calculated using advanced algorithms that convert the difference between the time the echo was sent and received to a distance. Data is sent via 4-20 mA or RS-485 output to software or, if preferred, an HMI/PLC. The included software records the data and calculates level, volume, and mass, creating an optional 3D visual of bin contents.
Customize results in your bin
The 3DLevelScanner is the only level sensor that measures multiple points on the material surface to account for irregular topography. The scanner provides precise volume measurement within 1 to 3 percent of the total stored volume. For cement plants, it offers the added benefit of detecting cone-up, cone-down, or sidewall buildup.
Scanner data goes to MultiVision Software
MultiVision software creates great reports for scanner data. It easily tackles cement operations with numerous silos or various locations where they want to monitor inventory throughout the operation. A 3D scanner will have a slower update rate and tracking speed versus a laser or radar, with scanners taking a few minutes versus others taking less than a minute.
Avoid installing 3D scanners where there is excessive noise that may interfere with the acoustic technology. They also are not recommended for very narrow bins that have corrugation. If there are excessive internal structures that may interfere with operation, a neck extension or alternative sensor technology will need to be used. Due to its robustness, there is no loop power option.
Continuous non-contact radar zaps a single point
BinMaster’s continuous non-contact radar has become increasingly popular in the cement industry since the recent introduction of 78-80 GHz frequency radar level sensors to the market. Unlike the 26 GHz radar, radars using these higher frequencies are quite reliable in dust. Their principle of operation is the same, but they are less prone to erratic data or lost signals. They have a 4˚ versus 10˚ beam angle for better precision and a substantial 393-foot measuring range. Radar works by emitting an electromagnetic pulse through the antenna where the emitted signal is then reflected off the material and received by the antenna as an echo. The frequency of the received signal is different from the emitting frequency, with the frequency difference being proportional to the distance and the height of the material being measured. The difference is calculated using special algorithms contained in the sensor’s electronics, where the material height is converted and output as a measured value.
Since high-frequency radar works in high-dust environments, it is reliable for measuring inventory and suitable for all kinds of rock, sand, and aggregates, including limestone, silica, sand, clay, alumina, bauxite, gypsum, and fly ash.
The NCR-80 radar can also be used in very tall, narrow silos for single-point level measurement at distances up to almost 400 feet. With its 4˚ beam, it can be used in segmented silos with narrow compartments. It is proven to work in silos with excessive noise from falling materials, extreme dust, or high temperatures. Radar technology is ideal for silos where precise aiming is needed to avoid internal structures, flow streams, or sidewall buildup.
Radars can be mounted over piled material, on dome roofs, or in storage bunkers. In large operations, radar is used over conveyor belts to prevent overloading or detect when belts are running empty.
The potential downside of non-contact radar is that it measures only a single point, as does laser technology. Therefore, it is not the recommended instrument when very precise volume accuracy is needed for inventory management. Since it cannot detect the topography of material such as uneven piling or cone up or down, inventory accuracy will be similar to dropping a tape measure at a single point on the material.
Laser lowdown, keep it clear
Laser is not always ideal for cement because it is best suited for low- or no-dust environments. However, because of its very narrow beam, it is a good option for level control in narrow vessels containing solids. It can also be used for plugged chute detection or restrictive chutes and hoppers where precise targeting is needed.
A laser sensor is mounted on top of the silo using an adjustable 10˚ mounting flange that aim the laser at the desired location, generally toward the output of the cone. During configuration, the minimum and maximum distances are set using 4-20mA inputs configured on the sensor. The sensor sends timed laser pulses to the material surface. The distance to the materials is calculated using complex algorithms that convert the laser pulses to a data output. A compensation for ‘slant range’ is made based upon the angle of the beam to ensure accurate level measurement. Materials that do not flow freely, can be used for monitoring buildup when installed above the monitoring point or directed toward the sidewall.
An adjustable swiveling mounting flange is flexible up to 10˚. This may allow for use of an existing mounting location and eliminate drilling another hole in the silo roof. A laser’s extremely narrow beam can be directed to avoid obstructions that could interfere with sensor operation.
It is easily configured in the field using a USB port, while configuration can be performed without filling or emptying the vessel. Laser has a fast update rate of eight times per second and features integrated dust protection for minimal maintenance.
One size does not fit all
When it comes to non-contact level sensors, one size does not fit all. In fact, many cement operations use a combination of sensors – both continuous and point level – to keep their plants running smoothly. Different size silos, different materials, and different material management objectives will all come into play when selecting the right sensor solution for your operation.
The best option is to contact a BinMaster representative who will walk you through the best solution.
