New whitepaper evaluates technologies for level and flow control
Different technologies are available for in- or out-feed measurement as well as for inventory control in tanks, silos and vessels. Their suitability depends mainly on material characteristics and accuracy requirements for complying with overall process tolerances. Mettler Toledo has recently published a new white paper that discusses the advantages and disadvantages of weighing, level-sensors and flowmeters.
Conveying, feeding, storing and measuring liquids and solids in a tank or silo is a science. Countless publications and presentations at symposia confirm that. System manufacturers use sophisticated testing laboratories to determine the behavior of materials in situations as close as possible to the process environment in practical trials. The findings are used to develop the ideal materials-handling and storage equipment for individual materials. They are also used to determine the appropriate measurement technology for inventory or flow control.
Weighing is most accurate
Weighing technology is typically the most accurate because it is independent from tank design, material distribution and cavities. The measuring result is not influenced by temperature, dust, foam or waves. Variations of density, viscosity, Reynolds number or Di-Electricity don't matter. Their calibration, including traceability to a national standard, is more accurate than for volumetric or distance measuring technologies.
Level sensors are easiest to integrate
This sensor technology is not part of the tank structure and independent from correct design of piping connections. That makes them easier to install and easier replace for repair. Wrapping them with inflatable balloons protects them from dust and preserves accurate measurement over time. Calibration is possible if it is returned to the factory.
Flowmeters measure in parallel
All flowmeter technologies allow measuring of several material flows in parallel. That can speed up production processes for batching operations. Flowmeters based on Coriolis technology can determine mass and density regardless of material temperature. Their calibration is possible if it is returned to the factory or in using mobile devices.
Each technology can be right and users have to decide case by case what suits best for their needs. They have to analyze characteristics and prices of material as well as process tolerances plus consequences of faulty products. Compliance with standards and frequency of calibration can be important criteria as too. Prices for good quality sensors of either technology hardly matter because their overall cost for purchase, installation and maintenance are similar. A white paper that compares these technologies can be downloaded at: www.mt.com/ind-wib
Source: Control Engineering Europe - All Articles