质量流量计工作原理和安装、投用、基本维护.ppt

* * * * 12/17/96 7 Operating the RFT9739, Version 3 (= Transparency 117) * * * * * * * 12/13/96 31 Intro-1 (= Transparency 19) We need to know temperature to compensate for its affect on the elasticity and rigidity of the metal flow tubes, which determine how the tubes responds specifically to flow and density. We’ll discuss that again later. The temperature indicated by the RTD also represents the temperature of the process with considerable accuracy. In current Micro Motion sensor design, the RTD temperature is equivalent to a thermowell sensor in terms of indicating process temperature. * * 12/13/96 16 Intro-1 (= Transparency 9) Other factors besides temperature and pressure come into play when using most volumetric flow measurement technologies. These factors don’t affect Coriolis. Perhaps the best way to get at this is to ask the question first: Is volumetric measurement affected by other factors? If there’s no response, just give the answer, as shown on the transparency. If the audience has some knowledge, make a quick list. There’s no need to discuss flow regime or Reynolds numbers. One important point is that Coriolis measures mass directly. Until relatively recently, this technology wasn’t available. If you wanted to measure mass using a volumetric method, how would you do it? The answer involves density, which leads to the next topic. * 12/13/96 15 Intro-1 (= Transparency 8) Perhaps better question: Why measure volume? The volume of a fluid (and its density) varies with its temperature (and pressure). What about mass? If you are paying by the gallon, do you want to buy the 834 pounds at 200 degrees or at 60 degrees? * 12/13/96 23 Introduction and Theory, Part II (= Transparency 39) Correct installation is extremely important. Remember that the sensor will perform accurately if: the flow tubes are free to oscillate at their natural frequency when filled with process fluid, and the signal generated by the sensor is not interrupted or distorted. Recommended