Throttle orifice flowmeter

Duoqin Instrument (Shanghai) Co., Ltd

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Throttle orifice flowmeterTechnical parameters required for selection:

1. Media name

2. Pipe diameter and material

3. Normal working flow, Z-high flow, and Z-low flow

4. Normal work pressure, Z high work pressure

5. Normal operating temperature, Z-high temperature, Z-low temperature

6. Fluid working density or standard condition density

7. Volume percentage of each mixed fluid

Note:Differential pressure throttling orifice flowmeterSpecially designed based on the data reported by the customer, therefore the above parameters are the basis for detailed calculations by the manufacturing plant before production. Without these parameters, it is difficult to produce a machine that meets the user's requirementsDifferential pressure orifice flowmeterThe manufacturer calculates based on the above parametersDifferential pressure orifice flowmeterThe differential pressure value of the sensor (range of the differential pressure transmitter). These tasks are calculated and completed by professional engineers in the manufacturing plant.

Throttle orifice flowmeterPrinciple and structure:

When the fluid filled in the pipeline flows through the throttling device inside the pipeline, the flow velocity will form a local contraction at the throttling point of the throttling device, thereby increasing the flow velocity and reducing the static pressure. As a result, a pressure drop or pressure difference is generated before and after the throttling device. The larger the flow rate of the medium, the greater the pressure difference generated before and after the throttling device. Therefore, the size of the fluid flow can be measured by measuring the pressure difference. This measurement method is based on the laws of energy conservation and flow continuity.

Throttle orifice flowmetercalculation formula

Q=0.003998*a*e*d² * √ △ P / ρ

M = 0.003998 * α * d²* √ △ P * ρ

Please refer to the calculation sheet provided at the time of supply for the meanings and units of each code in the formula.

Throttle orifice flowmeterIntroduction to Structural Form and Application

（1） Orifice plates can be divided into the following structural forms according to their structure and purpose:

(1) Standard orifice plate. (2) Integrated orifice plate. (3) Eccentric orifice plate. (4) The garden lacks perforated plates. (5) Circular orifice plate. (6) Eight slot orifice plate. （7）Flow restriction orifice plate. (8) High pressure lens pad orifice plate.

1. Standard orifice plate.

It has the characteristics of high measurement accuracy, easy installation, wide range of use, and low cost. Widely used for flow measurement of various media. Nominal diameter: DN50—1200mm.

According to the pressure measurement method, it can be divided into corner joint pressure measurement, flange pressure measurement, and radial distance pressure measurement.

According to the connection method, it can be divided into flange connection and direct welding.

The material can be customized according to user requirements to meet the needs of different working conditions.

2. Integrated orifice plate.

Integrated orifice plate is a complete measurement system that combines an orifice plate with temperature or pressure sensors and differential pressure transmitters. It is widely used for precise measurement of fluids and is more suitable for gas trade settlement measurement.Nominal diameter: DN50—1200mm.

3. Eccentric orifice plate.

It has the characteristics of being less prone to blockage and having shorter straight pipes at the front and back. Suitable for measuring gases and liquids containing dust and impurities such as blast furnace gas and coke oven gas.Nominal diameter: DN100—2000, pressure level: 0—PN400Mpa.

3. Eccentric orifice plate.

It has the characteristics of being less prone to blockage and having shorter straight pipes at the front and back. Suitable for measuring gases and liquids containing dust and impurities such as blast furnace gas and coke oven gas.Nominal diameter: DN100—2000, pressure level: 0—PN400Mpa.

3. Eccentric orifice plate.

It has the characteristics of being less prone to blockage and having shorter straight pipes at the front and back. Suitable for measuring gases and liquids containing dust and impurities such as blast furnace gas and coke oven gas.Nominal diameter: DN100—2000, pressure level: 0—PN400Mpa.

4. The garden lacks perforated plates.

The principles of the missing hole plate and the eccentric hole plate are basically similar, both applied to the measurement of stolen media. More suitable for measuring low Reynolds number fluid media, due to its complementarity with orifice plates and nozzles, it is very stable when measuring low Reynolds number media. Nominal diameter: DN100—2000, pressure level: 0—PN400Mpa.

5. Annular orifice plate

The pressure tapping method of the annular pressure tapping orifice plate can truly reflect the pressure difference before and after it. Not easily clogged. It is a high range ratio flowmeter. Nominal diameter: DN50—DN1000, Pressure rating: less than 25MPa

6. Eight slot orifice plate

The pressure measurement of the eight slot orifice plate is stable and suitable for occasions with high measurement accuracy requirements. The specific structure is shown in the following figure.

7. Flow restriction orifice plate

Restricted orifice plates are commonly used for flow control applications. The pressure loss of the system is relatively large. Widely used for measuring various fluids when pressure reduction or flow restriction is required.

8. High pressure lens pad orifice plate

The high-pressure lens orifice plate is used in high-temperature and high-pressure applications and is an ideal instrument to replace other instruments in high-temperature and high-pressure conditions. Produced and tested according to JB/T2776-92 standard, nominal diameter: DN50-DN250mm, pressure rating: PN400MPa

Contact us for detailed information!

4、 install

4.1 Basic Requirements:

4.1.1 For newly installed pipeline systems, the pipelines must be purged before installing throttling devices.

Before installation, carefully check whether the number, tag number, and specifications of the throttling device match the pipeline condition, flow range, and other parameters. The end marked with a "+" near the pressure tap should be connected to the upstream pipe section of the fluid, and the end marked with a "-" should be connected to the downstream pipe section of the fluid.

The centerline of the throttling device should be coaxial with the centerline of the pipeline.

4.2 Requirements for pipelines:

4.2.1 A measuring tube should be installed before and after the throttling device, with at least a straight tube of equal diameter of * D and 5D at the back, to ensure measurement accuracy.

4.2.2 If valves need to be installed before and after the throttling element, select gate valves and fully open them during operation; The regulating valve should be located in the pipeline downstream 5D.

5、 Requirements for differential pressure outlet pipeline:

The inner diameter of the pressure pipeline is related to the length of the pipeline and the degree of contamination of the medium. Usually, an inner diameter of 8-12 is used within 25 metersmmThe pipe. Gas measurement can be appropriately thickened to DN15.

When measuring liquid flow rate, the horizontal section of the pressure pipe should be in the same horizontal plane. If throttling devices are installed on vertical pipelines, a certain distance (perpendicular direction) between the short pressure pipes will affect the zero point of the differential pressure transmitter, which should be corrected through "zero point migration".

5.3 The pressure pipeline should be supported by sturdy brackets, and the two pressure pipelines should be as close to each other as possible and away from heat sources or vibration sources. When measuring water vapor flow, insulation materials should be used to wrap them together. If necessary (such as when the temperature is below 0 ℃), heat tracing pipes should be added to prevent freezing. When measuring dirty flow rate, an isolator or settler should be attached.

5.4 The pressure pipeline must always maintain a single-phase fluid state. When the measured fluid is a gas, the entire pressure pipeline (including the pressure chamber of the differential pressure gauge) is in the gas phase; When the measured fluid is a liquid, the entire pressure pipeline is in liquid phase and there should be no bubbles. For this reason, a drainage valve should be installed at the Z-low point of the pressure pipeline or an exhaust valve should be installed at the Z-high point. Special attention should be paid when installing or repairing differential pressure instruments.

6、 Usage and maintenance

6.1 Precautions for use

6.1.1 For new meters or throttling devices that have been disabled for a period of time and then restarted, the pressure pipeline should be checked for blockages or leaks before use. For liquid media, the pressure pipeline should be filled with clean water or other pressure guiding liquids, and attention should be paid to the discharge of gas mixed in the pipeline. For gas media, attention should be paid to the accumulation of liquid in the discharge pipeline.

6.1.2 Before operation, open the balance valve in the "three valve group", tightly close the valves on the positive and negative pressure pipelines, check and calibrate the zero point of the differential pressure transmitter, and be sure to note that the "zero point" is when the positive and negative pressure chambers are at equal pressure (i.e. the differential pressure is equal to 0). Check and adjust the differential pressure transmitter.

6.1.3 Even if the "balance valve" is fully opened under fluid flow, as long as the pressure valves on the positive and negative pressure pipelines are not tightly closed, the zero point cannot be verified. Because the balance valve itself has resistance, it cannot balance the pressure in the positive and negative pressure chambers, that is, it cannot reach the "zero differential pressure" state.

6.1.4 When measuring the flow rate of dirty fluids, it is necessary to configure a settling device or isolator. Pay attention to the reasonable selection of the inlet, outlet, and discharge positions of the pressure guiding fluid to achieve the purpose of discharge.

When measuring the flow rate of corrosive fluids, it is necessary to choose a suitable isolator, select the appropriate isolation liquid according to the specific gravity of the medium, and pay attention to the reasonable selection of the inlet of the isolation liquid and the measured fluid.

Whether the design parameters of the throttling device match the actual parameters directly affects the measurement accuracy. When the throttling device is put into use, if the measured parameters are within the range of the design parameters, the measurement accuracy generally does not exceed the design calculation accuracy; However, if the measured parameters are far from the design parameter range (assuming that the selection, manufacturing, and installation of the throttling device and differential pressure transmitter meet the requirements), it is possible that the provided design parameters are incorrect, and the design parameters should be changed and the calculations should be redesigned.

6.2 Maintenance precautions：

6.2.1 Daily maintenance work mainly involves removing the scale inside the settler or isolator, regularly draining it from the discharge outlet, and paying attention to safety when removing when the measured medium is high-temperature and high-pressure corrosive or toxic fluid.

6.2.2 The zero point of the differential pressure transmitter may sometimes drift, affecting measurement accuracy (especially when the flow rate is small and the differential pressure is close to the lower limit), and the zero point should be calibrated regularly. Good quality differential pressure transmitters can extend the zero calibration cycle to one year based on experience, while poor quality transmitters may calibrate the zero point every few days. Therefore, we recommend using good quality differential pressure transmitters to reduce daily maintenance workload.

Sample display of the same series:

After sales and warranty

All products supplied by Duoqin Instrument (Shanghai) Co., Ltd.:

All products come with a 2-year warranty;

Provide free consultation, guidance on installation and debugging services;

Negotiate on-site guidance for installation, debugging, and other matters, and only charge reasonable travel expenses;

Large quantities can provide free on-site guidance for installation and debugging;

Service tenet: No matter how long the product is used, as long as you find us, we will solve all problems for you until you are satisfied. We believe that our over 10 years of experience in the flowmeter industry can provide you with satisfactory service.

Duoqin Instrument (Shanghai) Co., Ltd. Main products:Electromagnetic flowmeter, vortex flowmeter, turbine flowmeter, ultrasonic flowmeterVCone flowmeter, metal rotor flowmeter, elliptical gear flowmeterUltrasonic heat and cold meters, as well as (explosion-proof) quantitative control systems and other products,Your needs and satisfaction will always be our pursuit. Please contact us for consultation and purchase