Bulk materials refer to granular or powder media types that are handled and processed in large quantities and stored in vessels, like silos.
Level measurement and monitoring for bulk materials is used in many applications and is a crucial part of many processes.
Some examples industries include:
While the terms "level monitoring" and "level measurement" are often used interchangeably, there are subtle differences in their meaning.
There is a variety of level instrumentation technology that can be used for bulk materials. When working with bulk materials, it's essential to consider factors such as material characteristics, vessel geometry, temperature, and environmental conditions to choose the most suitable level measurement technology for the application.
Many bulk level applications employ a switch or switches installed within the vessel. The challenge with measuring level from the “top” is that many technologies require a reflective surface to operate. The other problem is that, unlike liquids, bulk materials flowing into a container do not create a flat surface.
Depending on where the materials are being inserted into the vessel, there will be a “cone” of extra material above what could be called the “main surface” of the bulk material. Trying to ascertain the level of an uneven surface, using a single point of reference, does not provide an accurate picture of the volume of material in the vessel.
Some level technologies that are sometimes used for “top down” level detection are ultrasonic, guided wave radar, and capacitance. However, these technologies are more commonly used with liquid level applications and not bulk material.
Not all level applications for bulk materials require level measurement. Some simply require level monitoring and control. If measurement is not required, simple level switches offer a much more economical option than level measurement instrumentation. They all operate by mechanical means. Common level switch technology for bulk materials include:
Float/Tilt Level switches are commonly used in simple liquid level applications. There are also tilt switches built for bulk materials, which KOBOLD offers.
NAS Bulk Material Level Float SwitchDiaphragm Bulk Material Level Switches are triggered when the material level exerts enough pressure on a membrane. KOBOLD Bulk Material Diaphragm Level Switches include:
NMF Diaphragm Level Switch for Bulk MediaRotary Paddle Level Switches employ a rotating paddle that constantly revolves in a circular manner. When the level reaches a certain point, the media exerts enough pressure to stop the paddle’s rotation, and this triggers a switch. KOBOLD offers a superior solution to comparable models because of the ability to customize the paddle shape to best fit the material and application. It is designed to counteract the motor burnout prominent in other options in the market.
NIR-9 Rotary Paddle Bulk Material Level SwitchVibrating rod level switches consist of a vibrating probe and an electronic switch. When the probe vibration is damped by contact with rising media, the resulting change in resonant frequency is converted to a switching signal.
NVI Vibrating Level Switch for Bulk MediaThe sensor of a capacitive level switch along with the wall of the tank is a capacitor. The dielectric constant of this capacitor is the air when the material doesn’t reach the sensor. When the product covers the sensor, an electronic circuit detects this change in the dielectric constant and activates an output relay.
NSC Capacitive Level SwitchA pendulum bulk level switch consists of two parts: the aluminum connection housing with the microswitch, and the connection terminals and the pendulum rod with the measuring cone. They are installed vertically on the side of the holding vessel. When the vessel is filled with bulk solids, the rising level causes the measuring cone of the level monitor to swing to the side. This movement is directly transferred from the pendulum rod to a microswitch.
PLS Pendulum Level Monitor for Bulk SolidsMeasuring and monitoring bulk material level presents several challenges due to the diverse nature of these materials and the unique environments in which they are often stored and processed. Choosing the best bulk material level instrumentation is dictated by the specific challenges found in the application. Some of the key challenges in level measurement for bulk materials include:
The accuracy required for bulk level applications depends on the specific application and the components of its processes. Here are some considerations when picking a bulk material level instrument in the light of both accuracy and application components:
KOBOLD offers many different bulk material level monitoring and measuring solutions. For free advice about what the best option is for your application and your budget, please speak with one of our experts at 412-788-2830 or info@koboldusa.com.
KOBOLD USA is a subsidiary of KOBOLD Messring GmbH, a world-leading instrumentation engineering business founded in Germany in 1980 by Klaus J. Kobold. With patented technology and superior service, the company quickly established itself as one of the global leaders in sensor and control systems with high quality products. The KOBOLD brand name became synonymous with superior quality and technological advancement in instrumentation engineering.