Flow Meter Selection Guide


General selection

Choosing a flow meter can be considered from five aspects: flow meter performance, fluid characteristics, installation conditions, environmental conditions and economic factors. The five detailed factors are as follows:

1. Instrument performance: flow meter accuracy, repeatability, linearity, range, flow range, signal output characteristics, response time, pressure loss, etc.

2. Fluid characteristics: temperature, pressure, density, viscosity, chemical corrosion, abrasion, scaling, miscibility, phase transition, conductivity, sound velocity, thermal conductivity, specific heat capacity, isentropic index;

3. Installation conditions: pipeline layout direction, flow direction, length of straight pipe section on the upstream and downstream sides of the detected part, pipe diameter, maintenance space, power supply, grounding, auxiliary equipment (filter, deaerator), installation, etc.;

3. Environmental conditions: ambient temperature, humidity, electromagnetic interference, safety, explosion-proof, pipeline vibration, etc.

4. Economic factors: instrument purchase cost, installation cost, operating cost, calibration cost, maintenance cost, instrument service life, spare parts, etc.

Selecting steps

1. Select the available flow meter types according to the types of fluid and five considerations (there should be several types for selection);

2. Collect data and price information of the primary election types to for in-depth analysis and comparison;

3. Using the elimination method to gradually pick up 1 or 2 types, and then make comparative analysis according to the five factors and determine the primary target. 

Matters needing attention

1. Fluid characteristics mainly refer to gas pressure, temperature, density, viscosity, compressibility, etc. Since the volume of gas varies with temperature and pressure, it should be considered whether the temperature / pressure compensation .is equipped.

2. Instrument performance refers to the accuracy, repeatability, linearity, range ratio, pressure loss, initial flow, output signal and response time of the flow meter. When choosing the flow meter, it shall be carefully analyzed and compared with the above indicators, and the instrument shall be selected that can meet the requirements of measuring medium flow.

3. Installation conditions refer to gas flow direction, pipeline direction, upstream and downstream straight pipeline length, pipe diameter, space position and pipe fittings, etc., which will affect the accurate operation, maintenance and service life of the gas flow meter.

4. Economic factors refer to the purchase cost, installation cost, maintenance cost, calibration cost and spare parts, which are also affected by the performance, reliability and life of the gas flow meter.

5. Precision level and function of the instrument should be selected according to the measurement requirements and the use of the occasion. In cases where the accuracy level is selected, such as level 1.0, level 0.5, or higher, for process control, different accuracy levels are selected according to the control requirements. Some just check process flow, without having to do precise control and measurement, lower precision grade, such as 1.5, 2.5, 4.0, can be chosen and even then you can choose cheap plug-in magnetic flow meter for medium velocity measurement.

6. Instrument range and diameter should also be paid attention when choosing a flow meter. When measuring the general medium, the full flow of the electromagnetic flow meter can be in the medium flow rate range of 0.5-12m /s, which has a wider range to choose. The selected instrument specifications (diameter) and process piping size may not the same, it shall consider whether measuring flow range within the scope of the flow velocity, namely when the pipeline flow velocity is low which can not meet the requirement of the flow meter, or under the velocity, the measurement accuracy can't promise, it need to reduce the port size of flow meter, thus improve the pipe flow velocity, so as to get satisfied measurement results.

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