A level measurement device is not a suitable option to detect a powdery substance as it tends to have different composition, which can be either dense or light and fluffy. The characteristics of the material kept in the vessel can differ owing to various factors such as particulate size and moisture content. In chemical processing plants, various types of material can be kept in the same tank. Hence, it is important to install a point level device that operates in different types of materials.
Point Level Sensor
A point level sensor is an advanced device that alerts personnel when the material in a bin reaches a desired level. In other words, it indicates when the vessel is full or empty. The vibrating level sensor or vibrating rod is a piezoelectric device that can be utilized for point level detection in hoppers, silos and bins filled with dry solid materials or powders. The vibrating rod is capable of detecting very light and fluffy materials, such as flakes and powders, and can also detect heavier and denser materials of larger particle size.
Vibrating Rods: Functional and Reliable
Vibrating rods are reliable and high performance devices because the sensitivity is found at the sensor’s tip. The material that clings to the wall of the vessel does not affect the operation of a vibrating rod. Since the vibrating rod is a piezoelectric device, it can be employed to handle complex applications associated with variations in temperature, humidity, material density, or dielectric constant. In chemical processing applications, the materials tend to be rough. In such cases, a vibrating rod made of stainless steel should be selected. Unlike a tuning fork that includes two probes where material is bridged inbetween and give out a false signal, a vibrating rod has a single rod element that stops material from bridging.
A tuning fork can cause bridging even in simple alarm applications where the pressure from material heaped over the device can compress the material in between the two probes. When the level of the material falls below the level where the tuning fork is fitted, the fork will still show a "full" status, since the material lodged inbetween the probes does not drop away and continues to reduce the vibration. Such false signals can interfere with a production process.
This problem can be overcome by using a single rod with a sword-shaped design. This rod is suitable for use in powders because it has sharp edges, which prompt material to flow around the rod and prevent the material from sticking to it. The performance of a vibrating rod is further enhanced when there is minimum surface area for the material to cling to.
This sword-shaped design with sharp edges ensures material flows freely around the rod.
Benefits of Sword-Shaped Rod
The range of vibrating rods available from BinMaster is designed to identify the level of powders materials in silos, tanks and bins. The rod can detect extremely light powdered materials. The unique design of the rod eliminates false alerts and all components are made of stainless steel construction. The device is ideal for low, mid and high level indication.
The sensitivity is located at the tip of the rod which is an important feature of the device. When the active rod is not covered with material, it vibrates. When it is covered with material, the vibration reduces and an electronic circuit makes the relay to switch and gives out an alert that the device is covered with material. Similarly, when the rod is uncovered, the vibration starts again and the relay will switch back to indicate that the level of the material is below the device.
With recent advancements in product design, the majority of vibrating rods do not require calibration and can be easily modified to the required sensitivity level. Moreover, dust does not affect the performance of the rod and thus false alarms can be eliminated. For critical applications, certain models of vibrating rods provide a fail-safe alert that informs when power supply to the device is interrupted. Vibrating level sensors provide better flexibility and can be used as a low, mid, or high level alert installed on the wall of the vessel. They can also be placed in the bottom cone of a tank to detect when the tank is nearly empty, or on top of the tank as a high level detector.
This information has been sourced, reviewed and adapted from materials provided by BinMaster.
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