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How to properly install and select the orifice flowmeter
Jan 03, 2019

How to properly install and select the orifice flowmeter

The orifice flow meter is a differential pressure sensing element that measures flow. It can be used to measure, accumulate and control the instantaneous flow and cumulative flow of liquids, vapors and gases with differential pressure transmitters as well as real-world, recording, integrated and regulating instruments. Orifice flowmeter is currently the most widely used in domestic natural gas flow measurement system. Its main advantages are simple structure, easy to copy, relatively stable and reliable performance, low price and no need for real-flow calibration, installation can be used, and the maintenance cost is low. In addition, it has a wide range of applications, including all single-phase fluids (liquid, gas, steam), partial mixed-phase flow, general production process diameter, working state (temperature, pressure) can be applied; and detection components and display instruments can be Separate production, and professional scale production, thereby reducing product prices, is more conducive to the popularity and application of orifice flowmeters.

How to properly install and select the orifice flowmeter

      The throttling device has the advantages of simple structure, convenient installation, reliable use, low price, convenient maintenance and wide selection range (the measuring diameter of the standard section device can be from 50mm to 1200mm, and the diameter of the non-standard throttling device can be as small as 6mm, Up to 3000mm; measuring temperature up to 555 °C; withstand voltage up to 42MPa), and standard throttling device also has the advantages of no need for separate calibration, is the most widely used and most mature product in flow meter, so it is widely used Power, chemical, metallurgy, petroleum, textile, military and other fields.

How to properly install and select the orifice flowmeter

       The throttling device is composed of a throttle piece, a pressure taking device (including a pressure tap, a pressure pipe and a valve, etc.) and a matching flange, and sometimes includes a front and a rear straight pipe section conforming to the standard. Standard throttling devices are available in standard orifices, standard nozzles, and standard venturis. The standard orifice plate is connected by angle (corner chamber or borehole) with pressure, flange pressure and radial pressure; standard nozzles are divided into nozzles and long diameter nozzles; standard venturi tubes are divided into venturis according to the form. Nozzles, venturi tubes (rough cast or machined or coiled). The non-standard throttling device has a small diameter orifice plate, a 1/4 circular orifice plate, a circular orifice plate, a circular orifice plate, an eccentric orifice plate, a double orifice plate, a built-in orifice plate, a tapered inlet orifice plate and the like. Other forms of throttling devices include pitot tube, velocity tube, wedge, cone, and the like.

How to properly install and select the orifice flowmeter

     When using a standard throttling device, the nature and state of the fluid must meet the following conditions:

        (1) The fluid must be filled with pipes and throttling devices and flow continuously through the pipe;

        (2) The fluid flow does not change or change very slowly over time;

       (3) no intersection occurs when the fluid flows through the throttle;

       (4) The fluid must be Newtonian fluid, ie physically and thermodynamically homogeneous, single-phase, or can be considered single-phase, including mixed gases, solutions and dispersive particles less than o. 1 m colloid. Solid particles having a uniform dispersion of not more than 2% (mass component) in the gas, or bubbles having a uniform dispersion of not more than 5% (volume component) in the liquid may also be regarded as a single-phase fluid, but the density thereof shall be an average density.

      (5) Before the fluid flows through the throttle, the flow is a swirl-free flow parallel to the axis of the pipe.

How to properly install and select the orifice flowmeter

        Standard throttling devices are not suitable for flow measurement of moving and critical flows. The throttling device artificially causes throttling in the pipe through which the medium flows. When the measured medium flows through the throttling device, a partial contraction occurs, the stream is concentrated, the flow rate is increased, and the static pressure is lowered, so that the flow is upstream and downstream. A static pressure difference is generated on both sides. This static pressure difference has a certain function relationship with the flow rate. The larger the flow rate, the larger the static pressure difference generated. Therefore, the flow rate can be measured by measuring the differential pressure.

       The orifice flowmeter is different from other flowmeters in that the orifice flowmeter is based on the parameter design drawings and is finally processed. It is only necessary to select the orifice material according to the measurement medium.