1. Vortex Flowmeter

The vortex flowmeter is based on the principle of Karman vortex, and the velocity of the medium is proportional to the vortex frequency. A vortex flowmeter is widely used and is not affected by the pressure, temperature, density, and composition of the fluid. The split structure can be selected for a high-temperature medium. The vortex flowmeter is directly installed on the pipeline. Compared with the pressure measurement method of impulse pipe, it reduces the risk of leakage and does not require heat tracing. It is very convenient to install and maintain.

Vortex flowmeter has certain requirements on the flow rate of the medium. If the flow rate of the medium is too low, the vortex generator cannot generate a vortex, which will lead to the inability to measure. Under the premise of meeting the pressure loss requirements, the flow rate of the medium can be increased by reducing the diameter. Some manufacturers can provide products with internal diameter reduction for selection, avoiding the trouble of pipe diameter reduction. In addition, the vortex flowmeter has dual sensor products for users to choose from.

During the installation of the vortex flowmeter, a certain number of straight pipe sections at the front and back are required to ensure a good vortex signal. At the same time, it is necessary to keep away from vibration and electromagnetic interference, especially for small diameter measurements. In ethylene glycol plants, the vortex flowmeter is widely used for DMO, DMC, methanol, medium and low-pressure steam, and other media.

2. Target Flowmeter

A target flowmeter is also a kind of velocity flowmeter. As an industrial flow measurement, it has the advantages of a wide application range, large range ratio, high sensitivity, fast response, simple maintenance, etc. Its working principle is that when the medium flows, the flowing particles impact the target, and the target is forced to act on the target rod, causing it to produce small bending deformation. This deformation is sensed by the varistor strain gauge, and the force is converted into an electrical signal proportional to the square of the flow velocity through the strain gauge bridge.

For a small-diameter pipeline, a pipeline installation mode can be selected; For a large-diameter pipeline, a plug-in installation mode can be selected. An online plug-in target flowmeter can also be selected, which can realize the installation, disassembly, commissioning, and maintenance of the flowmeter without stopping production and flow.

In the ethylene glycol unit, the target flowmeter is mainly used to measure the flow with high viscosity, low flow rate, and low Reynolds number. For DMO, EG, and other high-viscosity media, the application effect is very good. However, compared with the vortex flowmeter, the price is higher.

3. Mass Flow Meter

The mass flowmeter can directly measure the mass flow of the medium according to the Coriolis principle and is not affected by the physical parameters such as the density and viscosity of the fluid and the state parameters such as temperature and pressure. The mass flowmeter has a good application effect, high accuracy, and convenient installation and maintenance for high-viscosity glycol medium, incoming and outgoing material metering, and other working conditions in the unit.

4. Comparison of target type flow meters, vortex flow meters, and mass flowmeters

For DMO, DMC, ethylene glycol, and other media in ethylene glycol unit, target flowmeter, vortex flowmeter, and mass flowmeter have their applicability and many application achievements. Considering the price, it is also a domestic brand. The price of the target flowmeter and mass flowmeter is relatively high, while the price of the vortex flowmeter is relatively low. Therefore, a vortex flowmeter can be preferred. In the distillation unit, the flow rate of some mediums is small and the flow rate is low, and the vortex flowmeter cannot meet the minimum flow rate requirements. Therefore, it is necessary to consider reducing the diameter to improve the flow rate of the medium in the flowmeter.

For the flow measurement of the return pipeline at the pump outlet, the pipeline vibration is large. The installation position of the flowmeter should be as far away from the vibration source as possible, and support should be added on the front and rear pipelines of the flowmeter to reduce the impact of vibration on the measurement accuracy. Because the target flowmeter and mass flowmeter have the advantages of high accuracy and good stability in measuring the flow of the high-viscosity medium, they are widely used in the flow measurement of DMO and ethylene glycol.