Selection of Flow Measurement Instruments (Part 2)
Time:2022-11-16 Read:886
Reading guide: With the development of science and technology, new flow-measuring instruments have been rapidly promoted and applied. According to their principles, they can be divided into differential pressure flowmeters, volumetric flowmeters, turbine flowmeters, electromagnetic flowmeters, float flowmeters, vortex flowmeters, ultrasonic flowmeters, and mass flowmeters. Flowmeters with different principles correspond to different media and working conditions. In practice, various factors should be considered in a unified way.

Selection of corrosive, conductive, or solid particle flow measuring instruments

1 Electromagnetic flowmeter

For conductivity greater than 10 μ S/cm liquid or homogeneous liquid-solid two-phase medium flow measurement. It has good corrosion resistance, wears resistance, and no pressure loss. It can measure various media such as strong acids, strong alkalis, salt, ammonia, slurry, pulp, etc.

The installation direction can be vertical, horizontal, or inclined. When installed vertically, the liquid must be from bottom to top. For liquid-solid two-phase media, vertical installation is preferred.

When installed on a horizontal pipe, the pipe section shall be filled with liquid, and the electrodes of the transmitter shall be on the same horizontal plane; The length of the straight pipe section shall not be less than 5~10D at the upstream and 3~5D at the downstream, or there is no requirement (different manufacturers have different requirements).

The transmitter shall not be set in a place where the magnetic field strength is greater than 398A/m.

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Selection of Flow Measuring Instrument for High Viscosity Fluid

1 Volumetric flowmeter

(1) Oval gear flowmeter

  • For clean liquid with high viscosity, a more accurate flow measurement is required. When the equivalent range ratio is less than 10 ∶ 1, an elliptical gear flowmeter can be used.
  • The oval gear flowmeter shall be installed on the horizontal pipe, and the indicating dial surface shall be in the vertical plane; Upstream and downstream block valves and bypass valves shall be set. The upstream shall be equipped with a filter.
  • For microflow, a micro oval gear flowmeter can be selected.
  • When measuring various easily gasified mediums, add a degasser.

(2) Waist flowmeter

  • For clean gas or liquid, especially lubricating oil, flow measurement with high accuracy is optional.
  • The flow meter shall be installed horizontally, with a bypass pipeline and filter at the inlet.

(3) Scraper flowmeter

  • The scraper flowmeter can be used to continuously measure the liquid flow in the closed pipeline, especially for the accurate measurement of various oil products.
  • The scraper flowmeter shall be installed so that the fluid fills the pipeline, and shall be installed horizontally so that the number of the counter is in the vertical direction.
  • When various oil products are measured and required to be accurately measured, a degasser shall be added.

2 Target flowmeter

For liquid flow measurement with high viscosity and a small number of solid particles, when the accuracy is required to be no higher than 1.5 and the range ratio is not greater than 3:1, the target flowmeter can be used.

A target flowmeter is generally installed on a horizontal pipeline. The length of the front straight pipe section is 15-40D, and the length of the rear straight pipe section is 5D.

Supmea Flow Measurement Instruments

Selection of Flow Measuring Instrument for Large-Diameter Pipe

When the pipe diameter is large, the pressure loss has a significant impact on energy consumption. Conventional flowmeters are expensive. When the pressure loss is large, flute-type averaging tubes, plug-in vortex street, plug-in turbine, electromagnetic flowmeter, Venturi tubes, and ultrasonic flowmeter can be selected according to the situation.

1 Flute averaging tube flowmeter

Clean gas, steam, viscosity less than 0.3Pa ˙ For the flow measurement of clean liquid, when the pressure loss is required to be small, the flute-type averaging tube flowmeter can be selected.

The flute-shaped averaging pipe is installed on the horizontal pipe. The length of the straight pipe section is not less than 6~24D at the upstream and 3~4D at the downstream.

Flow Measurement suppliers

Selection of new flow measuring instruments

1 Ultrasonic flowmeter

Ultrasonic flow meters can be used for all fluids that can conduct sound. Except for general media, ultrasonic flow meters can be used for media that work under severe conditions such as strong corrosion, non-conductive, flammable and explosive, radioactive, etc. when contact measurement cannot be used.

2 Mass flow meter

When it is necessary to directly and accurately measure the mass flow of liquid, high-density gas, and slurry, the mass flowmeter can be selected.

The mass flowmeter can provide accurate and reliable mass flow data without being affected by changes in fluid temperature, pressure, density, or viscosity.

The mass flowmeter can be installed in any direction without a straight pipe section.

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Model Selection of Powder and Lump Solid Flow Measuring Instrument

1 Impulse flowmeter

For the flow measurement of free-falling powder particles and lump solids, when it is required to transport materials in a closed manner, the impulse flowmeter should be used; The impulse flowmeter is applicable to all kinds of bulk materials of any particle size, and it can also be accurately measured when there is a lot of dust, but the weight of bulk materials shall not be greater than 5% of the weight of the predetermined punching plate.
The installation of an impulse flowmeter requires that the materials must fall freely and no external force shall act on the measured object. The installation angle of the punching plate and the angle and height between the feed inlet and the punching plate have certain requirements and are related to the selection of the measuring range, which should be calculated before selection.

2 Electronic belt scale

Used for solid flow measurement of belt conveyor, installed on belt conveyor with standard performance. The installation requirements of the weighing frame are strict. The distance between the weighing frame on the belt and the blanking port has an impact on the measurement accuracy, so the installation position should be selected.

3 Weighbridge

Dynamic track scales should be selected for continuous automatic weighing of railway freight cars.