Case Study - Mass Flow Meter For Slurry

In industrial production, since material balance, storage, and economic accounting all require mass rather than volume, measurement work often involves converting the measured volumetric flow rate into mass flow rate by multiplying it by the density. For example, in mining production, we often need to calculate the flow rate of mineral slurry. Mineral slurry refers to a two-phase solid-liquid suspension system formed by mixing solid ore particles with water (or liquid). However, because of unstable factors in the slurry, such as air bubbles and concentration changes, the volumetric flow rate is often inaccurate. Therefore, we usually use a mass flowmeter to measure the mass flow rate of the slurry.

As an important tool for fluid flow measurement, mass flowmeters are widely used in various fields. They can accurately measure the mass flow rate of fluids, instead of the traditional volumetric flow rate. Thus, they offer higher accuracy and reliability.

Series Coriolis Mass Flow Meters — **Coriolis Mass Flow Meters for Liquid and Gas**

Customized Case

A customer from Ghana wanted to measure the flow rate of mineral slurry. The customer mentioned that there were no air bubbles in the slurry. The solid concentration (mass fraction) was 36.5%. The solid concentration (volume fraction) was 18.1%. The customer also requested a 415V power supply. Based on the above customer requirements, we customized the following parameters for the customer:

Mass Flowmeter
DN200
Measured Medium: Slurry
Flow Range: 600 t/h
Normal Temperature
Pressure Resistance: 1.6 MPa
Output Signal: 4-20mA
Flange Connection
415V Power Supply
Accuracy: 0.2%
225 OD PN 16 HDPE Pipe

Working Principle

The working principle of the Coriolis mass flowmeter is mainly based on the Coriolis effect. Simply put, this type of flow meter contains a vibrating tube. As fluid flows through this vibrating tube, the Coriolis effect causes a slight “twisting” of the tube. The greater the mass of the fluid flowing through, the more pronounced this twisting becomes. Sensors measure the changes in the tube’s vibration pattern to directly calculate the mass flow rate of the fluid. Its greatest advantage is that it measures the true mass flow rate and is unaffected by changes in fluid density, temperature, or pressure. Whether the liquid is thin or thick, hot or cold, the measurement results remain stable and reliable.

Structural Characteristics Of Mass Flowmeters

Different types of mass flow meters have varying structures, but their core components are generally similar, mainly including the following parts:

The measuring pipe is fundamental; the fluid flows through it. Its design directly determines the accuracy of the measurement. For example, Coriolis flow meters use a curved pipe, and the flow rate is calculated by detecting changes in the pipe’s vibration.
The sensor is responsible for capturing the fluid’s motion and the pipe’s vibration, converting these physical quantities into electrical signals. Coriolis flow meters typically use vibration sensors.
The signal processing unit is essentially the “brain” of the flow meter, which analyzes the signals from the sensor and ultimately outputting accurate mass flow data.
Finally, there is the display and control system. For easy reading of measurement results, flow meters are usually equipped with a display screen or connected to a remote control system for real-time monitoring and management.

Product Features

It can directly measure the mass flow rate of fluids.
High measurement accuracy (measurement accuracy can be guaranteed at 0.1% to 0.5%).
Wide measurement range, which generally ensures a measurable ratio of 10:1 or 20:1 with basic accuracy.
Wide range of applications.
Can measure parameters such as density and temperature of the measured medium online, and derive the concentration of solutes in the solution.
Low installation requirements, no requirements for upstream and downstream straight pipe sections.
Reliable operation and low maintenance rate.

Application Fields

Petroleum, such as crude oil, coal slurry, lubricating oil, and other fuels. High-viscosity materials, such as asphalt, heavy oil, and grease;
Suspended solid particle materials such as cement slurry and lime slurry;
Easily solidified materials such as asphalt;
Accurate measurement of medium and high-pressure gases such as CNG;
Micro-flow measurement in fine chemical and pharmaceutical industries;

Factors Affecting The Measurement Accuracy Of Mass Flow Meters

1. Influence and correction of mechanical vibration

From the working principle of the mass flow meter, we know that it is an instrument that measures based on the principle of vibration, vibrating at its own frequency. External mechanical vibrations will inevitably interfere with the amplitude and frequency of the instrument’s own vibration, affecting measurement accuracy, and in severe cases, even damaging the instrument. To eliminate the influence of mechanical vibration on the accuracy of the instrument, attention should be paid during installation and maintenance.

First, the installation location should be chosen as far as possible in a place without mechanical vibration, away from vibration sources such as pump rooms and generator sets. Secondly, the instrument installation should be standardized, using stress-free installation.

2. Influence and correction of process temperature

Changes in process temperature will cause changes in the volume of the medium, but will not affect the measurement results, because mass is always conserved regardless of temperature changes. However, temperature changes will affect the stiffness and zero-point stability of the measuring tube, thus affecting the measurement accuracy of the mass flow meter.

The effect of temperature on the stiffness of the measuring tube is as follows: when the temperature rises, the material of the measuring tube becomes softer, and vice versa, and the deformation caused by the Coriolis force is also affected. However, the stiffness of the flow tube is repeatable and correctable. Generally, an RTD temperature sensor is installed inside the mass flow meter sensor to measure and compensate for temperature.

However, the effect of temperature changes on zero-point stability will produce non-repeatable additional errors. This is caused by the imbalance of the sensor material and geometry. The zero-point instability of the sensor is due to the large deviation that may occur when the medium temperature is inconsistent with the zero-point adjustment temperature. Its value is expressed as the percentage of flow change when the medium temperature changes by 1°C from the zero-point adjustment temperature. When the process temperature differs significantly from the zero-point temperature, the error will be more significant. Therefore, to reduce the impact of temperature on zero-point stability, the instrument can be zeroed at the process temperature.