E-Zine October 2006
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Variation in certain characteristics of Coriolis mass flowmeters has allowed this technology to be applied to many processes. The following sections define flowmeter design categories and how they fit the needs of their intended applications.
Liquid Coriolis Mass Flowmeters
Most Coriolis mass flowmeters measure liquid flows, however some designs were developed specifically and exclusively for gas flow measurement.
Gas Coriolis Mass Flowmeters
Although the majority of Coriolis mass flowmeters were designed to measure liquid flow, many were found to measure the mass flow of gases with acceptable accuracy. Applying Coriolis mass flowmeters to gas flows eliminates the need for pressure and temperature instrumentation that is used to compensate flowmeters that measure volume, velocity or inferentially. By measuring mass directly and eliminating the additional measurements, the installation is more straightforward and can be more economical.
High Pressure Coriolis Mass Flowmeters
High pressure Coriolis mass flowmeters include flowmeters that can measure fluids at pressures over 125 bar. The flow tubes in these flowmeters usually have thicker walls, so they may not perform as well as Coriolis mass flowmeters designed for lower pressures.
High Temperature Coriolis Mass Flowmeters
Most Coriolis mass flowmeters are limited to approximately temperatures of approximately 200°C. High temperature Coriolis mass flowmeters are capable of measuring over 225°C. These flowmeters are often used in high temperature heating systems.
Metal (other than 316SS) Coriolis Mass Flowmeters
Due to the cost and general applicability of 316SS, most Coriolis mass flowmeters were designed and are constructed of 316SS wetted parts. However, to increase the applicability of the technology, Coriolis mass flowmeters can be constructed using other metals. Note that some Coriolis mass flowmeters have seals that are constructed from non-metallic materials. Therefore, the availability of a Coriolis mass flowmeter made of materials other than 316SS does not necessarily imply that the seals are (or can be) constructed of a material that is compatible with the process.
Plastic/Polymer Coriolis Mass Flowmeters
Most Coriolis mass flowmeters are metal however, Coriolis mass flowmeters constructed of plastics and polymers are available. These flowmeters are used for low flows of high purity fluids.
Sanitary Coriolis Mass Flowmeters
Sanitary Coriolis mass flowmeters are designed and fabricated with materials and finishes that allow application to the food and pharmaceutical industries where they may be cleaned and/or steamed in place. In addition, they can usually be oriented to be self-filling and self-draining for easier cleaning.
Single Path Coriolis Mass Flowmeters
Single path Coriolis mass flowmeters do not split the flow so as allow the fluid to take multiple paths through the flowmeter. This feature is important in applications where it is desirable to ensure that the path through the flowmeter is free of trapped material, such as in applications where the process fluid can "freeze", or solidify.
Straight Path Coriolis Mass Flowmeters
Straight path Coriolis mass flowmeters exhibit the benefits of single path flowmeters and are obstructionless. Their geometry generally reduces the pressure drop at a given operating condition and allows them to be installed in orientations that self-drain and self-fill.
Excerpted from The Consumer Guide to Coriolis Mass Flowmeters