Brief Analysis of Measurement Principle and Application of Rosemount Mass Flow Meter in Petrochemical Industry

Abstract: The measurement principle and application analysis information of Rosemount mass flow meter in petrochemical industry are provided by excellent flow meter and flow meter manufacturers and quotation manufacturers. Abstract: This paper mainly introduces the working principle of the Rosemount Coriolis force mass flowmeter (CMF) sensor and transmitter, and introduces in detail the mass flow measurement principle and density measurement principle of the flowmeter, the signal characteristics of the transmitter, DSP digital signal processor. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following is a brief analysis of the measurement principle and application of Rosemount mass flowmeters in the petrochemical industry. This paper mainly introduces the working principle of the Rosemount Coriolis mass flowmeter (CMF) sensor and transmitter, and introduces in detail the mass flow measurement principle and density measurement principle of the flowmeter, the signal characteristics of the transmitter, and the DSP digital signal. Processor characteristics and applications. Foreword Rosemount mass flowmeter is widely used in petrochemical and other fields. It is one of the most advanced flow measurement instruments in the world. It is used reliably in the measurement of main products such as ethylene, propylene and main raw materials of light hydrocarbons in our factory, with an accuracy of up to 1.7‰, which improves the accuracy of energy and material flow measurement in our factory, avoids unnecessary losses, and creates considerable economic benefits. Mass flow measurement principle A mass flow meter measurement system consists of a sensor and a transmitter for signal processing. Rosemount mass flow meters are based on Newton's second law: force = mass×Acceleration (F=ma) As shown in Figure 1, when a particle of mass m moves at a velocity V in a pipe that rotates with an angular velocity ω on the P-axis, the particle is subjected to two components of acceleration and its force: (1) method Toward acceleration, that is, centripetal accelerationαr, whose magnitude is equal to 2ωr, towards the P axis; (2) tangential angular velocityαt, the Coriolis acceleration, whose value is equal to 2ωV, the direction is the same asαrVertical. Due to compound motion, at the particleαThe Coriolis force Fc=2ωVm acts in the t direction, and the pipe acts on the particle with an opposite force -Fc=-2ωVm. When the density isρWhen the fluid flows at a constant velocity V in a rotating pipe, any pipe of length Δx will experience a tangential Coriolis force ΔFc: ΔFc=2ωVρIn the formula AΔx(1), A—The flow cross-sectional area of ​​the pipe. Since there is a relation: mq=ρVA so: ΔFc=2ωqmΔx(2) Therefore, mass flow can be measured directly or indirectly by measuring the Coriolis force of the fluid flowing in the rotating tube. Inside the sensor is a U-shaped flow tube (Figure 2). When there is no fluid flowing through the flow tube, the flow tube is driven by an electromagnetic drive coil installed at the end of the flow tube, with an amplitude of less than 1mm and a frequency of about 80Hz. The fluid flows into the flow tube When forced to accept the vertical movement of the flow tube up and down. During the half cycle of the upward vibration of the flow tube, the fluid opposes the upward movement of the tube and exerts a downward force on the flow tube; conversely, the fluid flowing out of the flow tube exerts an upward force on the flow tube against the downward movement of the tube, causing the Its vertical momentum decreases. This causes the flow tube to twist. During the other half cycle of the vibration, the flow tube vibrates downwards, in the opposite direction. This twisting phenomenon is called the Coriolis phenomenon, or the Coriolis force. According to Newton's second law, the distortion of the flow tube is completely proportional to the mass flow through the flow tube. The electromagnetic signal detectors installed on both sides of the flow tube are used to detect the vibration of the flow tube. When no fluid flows through the flow tube, the flow tube is not twisted, and the detection signals of the electromagnetic signal detectors on both sides are in the same phase (Fig. 3); when there is fluid flowing through the flow tube, the flow tube is twisted, resulting in two Each detection signal produces a phase difference, and the magnitude of this phase difference is directly proportional to the mass flow through the flow tube. Since this mass flowmeter mainly relies on the vibration of the flow tube to measure the flow, the vibration of the flow tube and the impulse of the fluid flowing through the pipeline generate the Coriolis force, which causes each flow tube to produce torsion, the amount of torsion and the vibration period. It is proportional to the mass flow rate through the flow tube. Since the twist of one flow tube lags behind the twist of the other tube, the sensor output signal on the mass tube can be compared by the circuit to determine the amount of twist. The delay time between the left and right detection signals is measured by a time difference detector in the circuit. this“Time difference”ΔT is digitally measured, processed, and filtered to reduce noise and improve measurement resolution. The time difference is multiplied by the flow calibration factor to express mass flow. Since temperature affects flow tube rigidity, the amount of distortion produced by Coriolis forces will also be affected by temperature. The measured flow is continuously adjusted by the transmitter, which detects the output of the platinum resistance thermometer sticking to the outer surface of the flow tube at any time. The transmitter uses a three-phase resistance thermometer bridge amplifier circuit to measure the temperature of the sensor, and the output voltage of the amplifier is converted into frequency, which is digitized by the counter and read into the microprocessor. Density Measurement Principle One end of the flow tube is fixed and the other end is free. This structure can be regarded as a weight/spring system composed of a weight suspended on a spring. Once a motion is applied, the weight/spring system will vibrate at its resonant frequency, which is related to the weight's resonant frequency. quality related. The flow tube of the mass flow meter vibrates at its resonant frequency through the driving coil and the feedback circuit. The resonant frequency of the vibrating tube is related to the structure, material and quality of the vibrating tube.

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