MEDIDOR DE FLUJO MÁSICO

1. ¿Cómo funciona un medidor de flujo másico?¿Porque los tubos del sensor vibran?¿Cómo detecta la masa este medidor de flujo?¿Cuál es el principio de funcionamiento del medidor ? MEDIDOR DE FLUJO MÁSICO

2. MEDIDOR DE FLUJO MÁSICO • A flowmeter consists of a sensor, a transmitter and, in many cases, peripheral devices to provide monitoring, alarm, and/or control functions. This diagram is a typical example. • Sensors detect flow rate, density and temperature. • Transmitters process signals from the sensor and provide this information as outputs. • Peripherals provide additional functionality, such as batch control and enhanced density functions.

3. MEDIDOR DE FLUJO MÁSICO • Introduction to Coriolis: • Whether for liquid or gases, Micro Motion's Coriolis technology offers many advantages over traditional volumetric technologies. • Multi-variable measurement:     Mass flow rate     Volumetric flow rate     Density     Temperature • High accuracy (+/-0.1%) and repeatability • Easy installation because there are no special mounting, no flow conditioning, and no straight pipe run requirements. • Low maintenance because there are no moving parts, and it's non-intrusive.

4. MEDIDOR DE FLUJO MÁSICO • Tubo de Vibración:El fluido de Proceso que entra al sensor es dividido en dos, la mitad pasa a través de cada tubo. Durante la operación, es energizada una bobina guía. Esta bobina produce una oscilación en los tubos que vibran arriba y hacia abajo en oposición uno del otro. 

5. MEDIDOR DE FLUJO MÁSICO Signal Generation: Magnet and coil assemblies, called pick-offs, are mounted on the flow tubes. Wire coils are mounted on the side legs of one flow tube, and magnets are mounted on the side legs of the opposing flow tube.

6. MEDIDOR DE FLUJO MÁSICO Each coil moves through the uniform magnetic field of the adjacent magnet. The voltage generated from each pickoff coil creates a sine wave. Because the magnets are mounted on one tube, and the coils on the opposing tube, the sine waves generated represent the motion of one tube relative to the other.

7. MEDIDOR DE FLUJO MÁSICO No Flow - Tube Motion: The flow tubes oscillate 180 degrees in opposition to one another; while one tube moves downward, the other tube moves upward and then vice versa.Both pickoffs - the one on the inlet side and the one on the outlet side - generate sine wave current continuously when the tubes are oscillating. When there is no flow, the sine waves are in phase.

8. MEDIDOR DE FLUJO MÁSICO No Flow - No Coriolis Effect: During a no flow condition, there is no Coriolis effect and the sine waves are in phase with each other.

9. MEDIDOR DE FLUJO MÁSICO • Flow - Coriolis Effect:When fluid is moving through the sensor's tubes, Coriolis forces are induced. These forces cause the flow tubes to twist in opposition to each other. When the tube is moving upward during half of its vibration cycle, the fluid flowing into the sensor resists moving upward, by pushing down on the tube.Having the tube's upward momentum as it travels around the bend, the fluid flowing out of the sensor resists having its vertical motion decreased by pushing up on the tube. This causes the tube to twist.

10. MEDIDOR DE FLUJO MÁSICO • Flow - Delta-T: As a result of the twist in the flow tubes, the sine waves generated by the pickoffs are now out of phase because the inlet side is lagging behind the outlet side. • The amount of time difference between the sine waves is measured in microseconds, and is called Delta-T. • Delta-T is directly proportional to the mass flow rate. The greater the Delta-T, the greater the mass flow rate.

11. MEDIDOR DE FLUJO MÁSICO • Flow Calibration Factors: The Flow Calibration Factor consists of 10 characters, including two decimal points. A typical flow calibration factor for a CMF sensor would be: 4.27454.75The value has two components:1. The first five digits (4.2745) are the flow calibration factor. Each sensor has a unique calibration factor. This calibration factor, multiplied by a given Delta-T (measured in micro seconds), yields mass flow rate in grams/sec.Example:   given 5 microsec Delta-T    5 X 4.2745 = 21.3725 grams/sec flowrate 2. The last three digits (4.75) are a temperature coefficient for the sensor tube material. This coefficient compensates for the effect of temperature on tube rigidity. It is expressed in terms of a percent change in rigidity per 100°C. 

12. MEDIDOR DE FLUJO MÁSICO • Flow Calibration: Each transmitter/sensor pair is factory calibrated before shipment. • After process fittings have been attached and the sensor has been hydrostatically tested, it is ready to be calibrated to customer specifications. At this point, the sensor is married with a transmitter, and meter zero and calibration factors are determined. Batches are run at various flow rates to ensure the meter performs within specification. A density calibration is also performed, on air and water. Validation measures include an DeltaV-based calibration program that prevents the calibration procedure from being completed if any data point is out of specification. This process also serves as a functional test of the sensor/transmitter pair.

13. MEDIDOR DE FLUJO MÁSICO • Mass and Frequency Relationship: • The relationship between mass and natural frequency is the basis for density measurement in the Micro Motion flowmeter. To understand this relationship, consider the spring and mass system. As the mass increases, the natural frequency of the system decreases. | Increase the mass |As the mass decreases, the natural frequency of the system increases. | Decrease the mass |

14. MEDIDOR DE FLUJO MÁSICO • Flow tubes also have natural frequency: • In the Micro Motion sensor, the tubes correspond to the spring. The mass of the tubes plus their contents correspond to the mass at the end of the spring. During operation, a drive coil energized by the flow transmitter causes the tubes to oscillate at their natural frequency.  As the mass of the process fluid increases, the natural frequency decreases. | Increase the mass |As the mass of the process fluid decreases, the natural frequency increases. | Decrease the mass |

15. MEDIDOR DE FLUJO MÁSICO • Density and Frequency Relationship:Density is defined as mass per unit volume, or mass divided by volume. The volume of the fluid contained in the flow tubes remains constant, so the only way mass can change is if density also changes. Because of this relationship between mass and density, the natural frequency of the flow tubes indicates not only the mass of the fluid contained, but also the density. • The density of the process fluid can be derived from the frequency of oscillation of the sensor. This frequency signal is taken from the left pickoff (LPO) coil. • | Increase | Decrease | density of process fluid |

16. MEDIDOR DE FLUJO MÁSICO • Tube period:Frequency is measured in cycles per second. Since it is easier to time the cycles than to count them, the Micro Motion transmitter computes density of a process fluid by using tube period, the number of microseconds per cycle. Tube period is inversely related to frequency. • Density is directly related to tube period. • | Increase density || Decrease density