For the use of flow meters, because the installer does not know much about the meter, it is often thought that the flow rate can be measured by simply installing a flow meter on the process piping. Because the installer does not understand the complexity of the flow meter application. The NONCON Instrument recommends that the instrument personnel should meet with the installer at this time to gain an in-depth understanding of the following issues.

1.Should understand the flow state of the fluid

The flow state of the fluid directly affects the flow velocity distribution because the flow measurement is related to the flow velocity distribution. Fluid flow conditions include laminar, transitional, and turbulent flow. For example, differential pressure flow meters are limited to stable turbulence, and thermal flow meters only require fluid flow to be laminar. If you do not understand the flow state of the fluid, it is impossible to determine what flow measurement method to use. Therefore, before deciding which flow meter to use, you must first calculate the Reynolds number of the fluid, that is, the Reynolds number when the minimum flow rate is accurately measured.

2.Should understand the nature of the fluid

The properties of fluids include physical properties such as temperature, pressure, density, and viscosity; as well as chemical properties such as medium composition, toxic and harmful, and corrosive. Because each type of flow meter has a defined property for the fluid medium it is measuring, it is necessary to understand the fluid properties before selecting the flow meter. If the temperature of the medium to be measured is high, only the throttling device can be selected for measurement. Only volumetric flowmeters can be selected for high viscosity media, and electromagnetic flow meters can be considered for conductive fluids.

3.Should understand the scope of flow measurement and related issues

Some installers only provide an approximate flow measurement range, but can not provide accurate maximum flow, of course, can be determined by experience, such as the production design capacity, the operating data of the number of pumps to estimate. It is best not to use the diameter of the process pipe to estimate the flow, because sometimes the pipe diameter of the process is too large. The author has experienced the data provided by the process to calculate the opening size of the orifice plate, the inner diameter of the pipe of 150mm, the diameter of the opening of the orifice plate is only about 30mm, obviously the process pipe diameter is selected mostly, and it is possible that the process is considered in the future. Development needs. Fortunately, the current differential pressure transmitter and flow totalizer have a large adjustable range, and it is convenient to reset the adjustment if the range is not correct.

Before deciding to use the flowmeter, you should also understand the pipeline construction drawings of the process. When selecting the installation position of the flowmeter on the map, try to avoid and keep away from the valve, elbow, tee, and reducer to meet the flowmeter. , the requirements of the downstream straight pipe section. In the production of the throttling device, some instrument factories also supply the front and rear straight pipe sections of the throttling device installation pipeline, which not only ensures the measurement accuracy but also facilitates the user. Whether the relevant manufacturers supply this way is necessary to understand and implement the flow meter manufacturer.