What technology is the most suitable for my application? Technologies selection guide Please refer to the flowmeter selection guide section for an overview of the technology offered by Polycontrols. Technologies road map Selecting the right flowmeter, and even more importantly, commissioning it correctly, are critical for the proper operation of automation systems. If not selected correctly, not installed correctly or not calibrated adequately, flowmeter may produce huge errors and cause a great deal of trouble. Flowmeter selection guide section presents essential information for selecting the right flowmeter for your application. Up to the 80’s, volumetric flowmeter were largely used in industry. Volumetric instrument allowed basic readings and adjustment. In spite of their fair performance, users had the possibility to estimate is flow consumption by making manual flow correction to evaluate the uncertainty caused by process variations. In the last decade, affordable Vortex and Mass flowmeters’ arrival in the market caused a fundamental change from traditional technologies towards new technologies. These latest generations of instrument met industry requirements, reducing their production cost and eliminating quality problems related to process variability. Nowadays, advantages of the Coriolis mass measurement are only beginning to be acknowledged. These meters are the first commercially viable devices capable of measuring mass flow directly, as opposed to volume flow of liquids and gases. Direct mass measurement was a major advancement for the process industry, which is (or should be) more interested in metering mass than volume to ensure the tightest control. Unlike volume, mass is unaffected by changes in pressure, temperature, viscosity, and density. Although Coriolis meters directly measure mass, they can also perform volume and density measurements.
What gases have special MFC requirements? Many gases used in semi-conductor, analytical and chemistry applications are extremely sensitive to moisture and pressure variations. Subsequent reaction often results in creation of highly corrosive product, particle contamination or phase shift from the gas to liquid. These phenomena obstruct MFC sensors and other components of gas system. Section Gases with special MFC requirements presents some of the most common problems encountered. What should I be aware of if I want to use an existing meter on a new application? Users who want to use a flowmeter on a gas or liquid other than the one it was calibrated for should be aware of three different things: 1) Chemical compatibility with the new gas or liquid. Chemical compatibility of all components and seals must be verified in order to prevent damage or injury resulting from a leak or a contamination. Manufacturer compatibility chart or gas data and chemical resistance chart should be used. 2) Scale shift If a flowmeter is operated with a gas other than the one it was calibrated for, a scale shift will occur as a result of the difference in the physical properties between the two gases. - For a volumetric device, manufacturers can recalculate new conversion factors based on meter’s construction (float shape and specific gravity, tube size, scale). - For a mass flowmeter, this scale shift can be calculated by using the ratio of the molar specific heat of the two gases, or the sensor conversion factor. You will find a conversion example in the section Usage of a MFC/MFM for a different gas than it was calibrated for and appropriate conversion factors are available in the section Gas data and chemical resistance chart 3) Valve capacity/linearity If a valve is used in the flow path, in addition to the previous considerations, the maximum flow allowed by the valve orifice should be estimated. The maximum flow must be superior to the desired flow but should not be grossly oversized. If oversized, the valve will generate oscillations and will not properly control the flow. Comparing valve orifice factor can estimate the maximum flow. Usage of a MFC/MFM for a different gas than it was calibrated for and Gas data and chemical resistance chart sections provide requested information to achieve this estimate. Why should I work with Polycontrols? Flow measurement is critical in ensuring repeatable process results and no technologies are currently able to satisfy all industrial applications conditions. Each instrument has limitations and proper selection requires a good understanding of the process characteristics and variables. In addition of being specialized in selection and distribution of flowmeters since 1982, Polycontrols offers engineering, technical and metrological services related to many types of flow applications. The individual and collective expertise of our flow specialists provides global solutions in a timely manner to all our customers. When working with Polycontrols, you are assured to receive: - Personalized and customer-oriented service |
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