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| perforated plateThere are several methods for measuring the flow rate of media through pipelines, but the most widely used and common one is the differential pressure flowmeter. It consists of a throttling device and a differential pressure gauge, or a throttling device and a differential pressure transmitter together with a secondary gauge. The use of throttling devices has a long history and has been standardized both internationally and domestically. The throttling device is a primary component in differential pressure measurement, which is used by people to create a pressure difference in the fluid inside the pipeline. By using a pressure conduit to transmit the pressure difference generated before and after the throttling device to a differential pressure transmitter, and then inputting it into a secondary instrument, the instantaneous or cumulative flow rate of the fluid in the pipeline is displayed. The flow rate can also be adjusted using regulating instruments. The throttling device has a simple structure, accurate measurement, reliable use, and is easy to maintain and repair. |
| Corner joint chamber pressure standard orifice plate (nozzle) - French ring hole (spray) |
 Model: JD-LG Applicable pressure: Pn0.01～Pn2.5Mpa
Applicable pipe diameter: DN40～DN600
Usage and characteristics: Used for flow measurement, control, and regulation of gases, liquids, and vapors. It has the characteristics of high measurement accuracy, low cost, simple installation, and easy maintenance. |
| Corner joint chamber pressure standard orifice plate (nozzle) - French ring hole (spray) |
 Model: JD-LG Applicable pressure: Pn2.5～Pn6.3Mpa
Applicable pipe diameter: DN40～DN600
Purpose and characteristics: Used for flow measurement, control, and regulation of gases, liquids, and vapors at higher working pressures. It has the characteristics of high measurement accuracy, long service life, and easy installation and maintenance. |
| Corner joint pressure standard orifice plate (nozzle) - French hole (spray) |
 Model: JD-LG Applicable pressure: Pn6.3～Pn10Mpa
Applicable pipe diameter: DN40～DN500
Usage and characteristics: Used for flow measurement, control, and regulation of gases, liquids, and vapors under high pressure. It has the characteristics of high measurement accuracy, easy installation and maintenance. |
| Corner joint pressure standard orifice plate (nozzle) - ring hole (spray) |
 Model: JD-LG Applicable pressure: Pn2.5～Pn32.0Mpa
Applicable pipe diameter: DN15～DN500
Usage and characteristics: Used for flow measurement, control, and regulation of liquids, steam, and heating network pipelines under high temperature and pressure. It has the characteristics of impact resistance, low deformation of orifice plates or nozzles, high measurement accuracy, good sealing performance, and long service life. |
| Corner joint drilling pressure standard orifice plate |
 model: JD-LG
Applicable pressure: Pn0.01～Pn2.5Mpa
Applicable pipe diameter: DN400～DN2000
Purpose and characteristics: Suitable for flow measurement, control, and regulation of large diameters of gases, liquids, and other media. It has the characteristics of high measurement accuracy, easy installation and use, and low cost. |
| Corner joint drilling pressure standard orifice plate |
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 model: JD-LG
Applicable pressure: Pn2.5～Pn10.0Mpa
Applicable pipe diameter: DN400～DN1000
Usage and characteristics: Suitable for flow measurement, control, and regulation of large diameters of gases, liquids, and other media under high temperature and pressure. It has the characteristics of high measurement accuracy, easy installation and use, and low cost.
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![特点]() purpose |
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| The LG/FB standard annular orifice plate and flange orifice plate throttling device are scale-free flow measurement devices that are used in conjunction with pneumatic, electric differential pressure transmitters or double bellows differential pressure transmitters. In the metallurgical, chemical, petroleum, and power industry systems, the pressure difference generated by the continuous measurement of liquid, gas, and steam flowing through an orifice plate with a medium temperature of ≤ 400 ℃ is converted into a proportional output signal by a transmitter. Then, a secondary instrument or regulator is used to record, indicate, or adjust the measured flow rate. |
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![特点]() Working principle |
| The throttling device is a man-made device that causes throttling in the pipeline where the medium flows (as shown in Figure 1). After the measured medium flows through the throttling device, it causes a local contraction, concentration of the flow beam, increase in flow velocity, and decrease in static pressure, resulting in a static pressure difference between the upstream and downstream sides of the orifice plate. There is a certain functional relationship between the static pressure difference and the flow rate. The larger the flow rate, the greater the static pressure difference generated. Therefore, by measuring the differential pressure, the flow rate can be measured. |
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![特点]() structure |
| The structure of the throttling device is shown in Figures 2 and 3: |
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![特点]() Structural characteristics |
1. Ring chamber pressure standard orifice plate:
It belongs to the standard orifice plate. Due to the implementation of ring chamber pressure measurement, measurement accuracy has been improved and the minimum length of straight pipe segments required for installation has been shortened, making it widely applicable in various departments.
2. Standard orifice plate for pressure measurement of corner joint drilling:
It belongs to the standard orifice plate. When the pipe diameter is above 400 millimeters, this form is often used. The pressure measurement methods include drilling holes separately on the flange, using circular pressure equalization rings, or using square pressure equalization rings. The orifice plate can be in the form of a handle hole or a non-standard circular hole plate.
3. Flange pressure gauge standard orifice plate:
It belongs to the standard orifice plate. Regardless of the diameter of the pipeline, the centers of the upstream and downstream pressure tapping holes are located at 1 hour (25.5mm) each from the end faces on both sides of the orifice plate. This form is commonly used in refining systems.
4. Radial distance pressure standard orifice plate:
It belongs to the standard orifice plate. The pressure measurement method is pipeline pressure measurement. The center of the upstream pressure tapping hole is located at twice the inner diameter of the pipeline in front of the orifice plate. The center of the downstream pressure tapping hole is located at a distance of half the inner diameter of the pipe from the rear end face of the orifice plate.
5. Small caliber orifice plate:
Belongs to non-standard orifice plate. Used for measuring fluids within a diameter of 10mm to 50mm.
6. Double orifice plate:
It is composed of two standard orifice plates installed at a certain distance from each other in a straight pipe. In terms of the direction of the flow, the front orifice is referred to as the auxiliary orifice plate, while the rear orifice plate is referred to as the main orifice plate. The cross-sectional ratio m1 of the auxiliary orifice plate is greater than the cross-sectional ratio m of the main orifice plate. Two orifice plates form a nozzle with a liquid wall. It is used for flow measurement of low Reynolds number fluids or high viscosity fluids.
7. Circular perforated plate:
It belongs to non-standard orifice plates and is suitable for measuring the flow rate of fluids that are dirty, have air bubbles, or contain solid particles. Its measurement accuracy is relatively low.
8. Conical inlet orifice plate:
Belongs to non-standard orifice plate. The angle between the circular cone and the centerline is 45 °. This conical inlet orifice plate is suitable for applications with low Reynolds numbers, but the pipe size must not be less than 25 millimeters.
9. Others. |
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![特点]() characteristic |
1) Standard orifice plate - characterized by high measurement accuracy, easy installation, wide range of use, and low cost. Widely used for flow measurement of various media.
2) Standard nozzle - characterized by high temperature and pressure resistance, impact resistance, long service life, large measurement range, and high measurement accuracy. Suitable for measuring high temperature and high pressure steam flow in power plants, heating network pipelines, and fluid flow with high flow rates. There are two forms: A: ISA1932 nozzle (standard nozzle) B: long neck nozzle.
3) Classic Venturi nozzle - characterized by low pressure loss, high measurement accuracy, short front and rear straight pipe length, and long service life.
4) Wing wind measurement device - characterized by low pressure loss, short front and rear straight pipes, and stable measurement.
5) Double Venturi tube - characterized by low pressure loss and stable measurement, suitable for measuring air volume in circular or rectangular pipelines. Specification: DN80-4000mm (or length x width).
6) Circular orifice plate, circular orifice plate, eccentric orifice plate - have the characteristics of being less prone to blockage and having shorter front and rear straight pipes. Suitable for measuring gases and liquids containing powder and impurities such as blast furnace gas and coke oven coal.
7) Double orifice plate 1/4 circular nozzle - widely used for flow measurement of various liquids and gases with low flow rates under low Reynolds number conditions.
8) Anuba flowmeter - characterized by low pressure loss and easy installation. Suitable for flow measurement of circular and rectangular pipelines.
9) Limiting orifice plate - has the characteristics of limiting current and reducing pressure. Suitable for limiting flow or reducing pressure.
10) Single and double chamber balanced containers - suitable for liquid level and steam drum water level. |
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![特点]() model selection |
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*Refers to materials such as flange pipes, and throttling components made of stainless steel.
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| 2) Circular orifice plate, circular orifice plate, eccentric orifice plate |
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| *The material of the flange pipeline, etc., and the material of the throttling element is stainless steel. |
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| 3) Single and double chamber balanced containers |
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| *The material of the flange pipeline, etc., and the material of the throttling element is stainless steel. |
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![特点]() technical specifications |
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Serial Number
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name
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model
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Nominal diameter Dg (mm)
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Nominal pressure Pg (kg/c) ![法兰式孔板流量计]() ) |
notes
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1
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Pressure measurement of corner joint chamber
standard orifice plate
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LGK-H-10
LGK-H-25
LGK-H-64
LGK-H-100
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50-400
50-400
50-400
50-400
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10
25
64
100
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1. According to user needs, our company can provide the following flange standards
(1) Ministry of Chemical Industry Standard HG5010-5016-58
(2) Standard JB78-82-59 of the First Machine Department
(3) Standard of the Ministry of Water and Electricity
(4) Process according to user drawings.
2. The orifice plate material is generally stainless steel. |
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2
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Separate drilling and pressure measurement for corner joints
standard orifice plate
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LGK-E-6
LGK-E-10
LGK-E-16
LGK-E-25
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400-2000
400-2000
400-2000
400-2000
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6
10
16
25
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3
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flange taps
standard orifice plate
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LGK-F-10
LGK-F-25
LGK-F-64
LGK-F-100
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50-750
50-750
50-750
50-750
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10
25
64
100
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4
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Radial pressure measurement
standard orifice plate
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LGK-J-6
LGK-J-25
LGK-J-64
LGK-J-100
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50-2000
50-2000
50-1000
50-600
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6
25
64
100
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5
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Small caliber orifice plate
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LGX-25
LGX-64
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10-50
10-50
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25
64
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6
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Circular perforated plate
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LGQ-6
LGQ-16
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50-2000
50-1600
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6
16
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| When our company supplies complete sets, they include orifice plates, ring chambers, flanges, and fastening bolts. Users can also order orifice plates or orifice ring chambers separately. If the user provides their own flange, they need to inform our company of the standard and size of the flange provided. |
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![特点]() attachment |
（1） Condenser
To avoid the influence of high-temperature media on the differential pressure gauge, a condenser needs to be installed in the pressure pipeline when measuring steam and water with a temperature greater than 70 ℃. The function of the condenser is to condense the measured vapor in the pressure tube and maintain a constant height of the condensed liquid level in the positive and negative pressure tubes. |
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Condenser specifications
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model
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Work pressure Kg/c ![法兰式孔板流量计]()
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FL-64
FL-100
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64
100
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（2） Isolator
For high viscosity, corrosive, and easily precipitated solid liquids and corrosive gases, isolators should be used to prevent direct contact between the measured fluid and the differential pressure gauge or transmitter, in order to avoid damage to the differential pressure gauge (or transmitter). |
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model
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Work pressure Kg/c ![法兰式孔板流量计]()
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notes
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FG-64A
FG-100B
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64
100
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The specific gravity of the tested medium is less than that of the isolation liquid
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FG-64A
FG-100B
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64
100
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The specific gravity of the tested medium is greater than that of the isolation liquid
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（3） Settling device
For various tested gases, a settling device should be installed at the lowest point of the pressure pipe to collect and regularly discharge dirt and accumulated water in the pressure pipe. |
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Settler specifications
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model
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Work pressure Kg/c ![法兰式孔板流量计]()
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CJQ-64
CJQ-100
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64
100
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（4） Gas collector
When the measured fluid is a liquid, a gas collector should be installed at the highest point of the pressure pipe to collect and regularly discharge the gas in the signal pipeline. When the installation position of the differential pressure gauge or differential pressure transmitter is higher than the main pipeline, a gas collector should be installed even more. |
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Specification of gas collector
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model
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Work pressure Kg/c ![法兰式孔板流量计]()
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JQQ-64
JQQ-100
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64
100
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![特点]() install |
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（1） Basic requirements for installation:
1. Before installation, the orifice plate should be checked to ensure that the throttle device number and size meet the requirements of the pipeline installation position.
2. When installing a new piping system, the installation of orifice plates must be carried out after flushing and sweeping the pipes.
3. Pay attention to the installation direction of the orifice plate, where the "+" sign should face the flow beam.
4. The center of the orifice plate should coincide with the centerline of the pipeline, and the concentricity error should not exceed a value of 0.015 (1/β -1).
5. When installing the orifice plate in the pipeline, it should be ensured that its end face is perpendicular to the pipeline axis and the perpendicularity error should not exceed ± 1 °.
6. The sealing gasket used for clamping the orifice plate (including between the ring chamber and the flange, and between the ring chamber and the orifice plate) shall not protrude into the inner wall of the pipeline after clamping.
7. The installation of the orifice plate must be tight and no leakage is allowed. Therefore, installation work must be carried out before pipeline pressure testing.
8. The pressure conduit should be laid vertically or obliquely, with an inclination of not less than 1:12. The inclination of fluids with higher viscosity should be increased. When the transmission distance of the differential pressure signal is greater than 3 meters, the pressure pipe should be inclined in sections, and gas collectors and settling devices should be installed at the highest and lowest points respectively.
9. In order to avoid distortion of differential pressure signal transmission, positive and negative pressure pipes should be laid as close as possible, and anti freezing measures should also be taken in cold areas. Electric heating or steam insulation can be used, but it is necessary to prevent the measured medium from overheating and vaporizing, and to prevent false differential pressure caused by gas generation in the pressure tube.
10. When the orifice plate is installed on the vertical main pipeline, the position of the pressure tapping port can be arbitrarily selected on the plane of the pressure tapping device. The orifice plate is installed in a horizontal or inclined main pipeline, and the pressure port position is shown in Figure 4.
11. The pressure conduit shall be made of materials that are resistant to pressure and corrosion according to the properties of the tested medium. Its inner diameter shall not be less than 6 millimeters, and its length shall preferably be within 16 meters. Table 2 specifies the inner diameter and length of the pressure tube for different media, which can be used as a reference for selection. |
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Table 2 Inner diameter and length of pressure conduit (mm)
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Length of pressure conduit
Inner diameter of pressure conduit
measured media
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>16,000
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16,000～45,000
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45000～9,0000
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Length of pressure conduit
Inner diameter of pressure conduit
measured media
Water, water vapor, dry gas
wet gas
Low and medium viscosity oil products
Dirty liquid or gas
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7-9
13
13
25
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10
13
19
25
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13
13
25
38
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| 12. The upstream and downstream sides of the throttling device must ensure a certain length of straight pipe section, as specified in Table 3. |
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β
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The form of local resistance element on the upstream side of the throttling element and the minimum length of the straight pipe section l1
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Downstream side of throttle component
Minimum straight pipe length
Degree l2 (left side)
Some local resistance
Form of Document |
![法兰式孔板流量计]() |
| A 90 ° elbow or a tee with only one branch pipe flowing. |
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![法兰式孔板流量计]() |
| There are multiple 90 ° elbows in the same plane. |
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![法兰式孔板流量计]() |
Space bends (how many in different planes)
A 90 ° bend. |
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![法兰式孔板流量计]() |
| Reducing tube (large to small, 2D → D, length ≥ 3D, small to large 1/2D → D, length ≥ 1 1/2) D. |
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![法兰式孔板流量计]() |
| Fully open the stop valve |
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![法兰式孔板流量计]() |
| Fully open gate valve |
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1
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2
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3
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4
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5
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6
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7
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8
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≤0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
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10(6)
10(6)
10(6)
12(6)
14(7)
14(7)
14(7)
16(8)
18(9)
22(11)
28(14)
36(18)
49(32)
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14(7)
14(7)
16(8)
16(8)
18(9)
18(9)
20(10)
22(11)
26(13)
23(16)
36(18)
42(21)
50(25)
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34(17)
34(17)
34(17)
36(18)
36(18)
36(19)
40(20)
44(22)
48(24)
54(27)
62(31)
70(35)
80(40)
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16(8)
16(8)
16(8)
16(8)
16(8)
18(9)
20(10)
20(10)
22(11)
24(12)
26(13)
28(14)
30(15)
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18(9)
18(6)
18(9)
18(9)
20(10)
20(10)
22(11)
24(12)
26(13)
28(14)
32(16)
36(18)
44(22)
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12(6)
12(6)
12(6)
12(6)
12(6)
12(6)
12(6)
14(7)
14(7)
16(8)
20(10)
24(12)
30(15)
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4(2)
4(2)
5(2.5)
5(2.5)
6(3)
6(3)
6(3)
6(3)
7(3.5)
7(3.5)
7(3.5)
8(4)
8(4)
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pourThis table is applicable to various throttling components specified in this standard;
② The numbers listed in this table are multiples of the inner diameter "D" of the pipeline;
③ The numbers outside the parentheses in this table represent the values of "zero additional limit relative error"; The number in parentheses is the value of 'additional limit relative error ± 0.5%'. |
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（2） Installation method
The correct installation of the throttling device directly affects the measurement accuracy. Here are several installation examples for reference.
1. The installation of annular orifice plates (Pg10, Pg25) is shown in Figure 5. The specification of the pressure pipe is seamless steel pipe with a diameter of 20 × 6.
2. The installation of the double orifice plate is shown in Figure 6, and the specification of the pressure pipe is a seamless steel pipe with a diameter of 20 × 6. |
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3. The installation of the pressure standard orifice plate for corner joint drilling is shown in Figure 7, and the specification of the pressure pipe is a seamless steel pipe with a diameter of φ 20 × 6.
（3） Connection between throttling device and differential pressure gauge
1. Measure liquid flow rate
(1) Instrument installation location: |
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It is recommended to install a throttling device underneath the instrument to prevent gas in the liquid from entering the pressure pipe and the instrument, as shown in Figure 8 (a).
If the instrument has to be installed above the throttling device, in order to reduce the entry of gas from the liquid into the conduit and instrument, a U-shaped bend should be installed between the throttling device and the pressure pipe, and the lower end of the bend should be at least 0.7 meters lower than the centerline of the conveying pipeline, as shown in Figure (b).
(2) Take pressure
On horizontal or inclined process pipelines, if the pressure tap is opened above the throttling device, gas will accumulate in the pressure pipe; If opened below the throttling device, it will cause sediment to fall into the pressure pipe. Therefore, the pressure pipe should be led out horizontally from both ends of the horizontal centerline of the throttling device section or from both ends of the horizontal centerline downwards at an angle less than 45 degrees.
2. Measure steam flow rate
(1) In order to avoid the influence of high temperature steam, two condensers located at the same height must be installed on the pressure pipeline between the instrument and the throttling device, and the condenser, pressure pipe, and high and low pressure chambers must be filled with condensed water to avoid adverse effects of high temperature on the instrument.
(2) It is best to install the instrument below the throttling device to prevent gas from entering the pressure pipe and instrument. The condenser should be installed near the throttling device during the day, as shown in Figure 9 (a).
(3) If the instrument has to be installed below the throttling device, the condenser should be installed higher than the instrument, as shown in Figure 9 (b). |
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3. Measure gas flow rate
(1) Instrument installation location:
The instrument should be installed above the throttling device to allow the condensate generated in the pressure pipe to flow back into the delivery pipeline. As shown in Figure 10 (a).
If the instrument has to be installed below the throttling device, in order to reduce the condensation of water in the pressure pipe, the pressure pipe leading out from the throttling device should be equipped with a U-shaped pipeline, and the upper end should be at least 0.7 meters higher than the centerline of the conveying pipeline. As shown in Figure 10 (b). |
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(2) Position of pressure pipe opening
On horizontal or inclined conveying pipelines, in order to prevent condensate from entering the pressure pipe, the pressure pipe should be led out from the upper half of the throttling device section.
(3) If the gas contains dirt and dust, a cross joint should be installed at the bend of the pressure pipe for cleaning and blowing.
4. Measure corrosive liquids or gases
When measuring liquids or gases that have corrosive effects on instruments, an isolator must be installed between the instrument and the throttling device. Isolation liquid should be injected into both the isolator and the subsequent conduit. The liquid level of the isolation liquid in the isolator should be equal to ensure that the measured medium does not enter the high and low pressure chambers of the instrument.
(1) When the weight of the tested medium is less than that of the isolation liquid, the FG-64A isolator is installed as shown in Figure 11 (a).
(2) When the weight of the tested medium is greater than that of the isolation liquid, install the FG-64B isolator as shown in Figure 11 (b). |
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（4） Installation requirements
The installation and application of the throttling device are related to the following pipe sections and fittings: the first and second resistance pieces on the upstream side of the throttling element, the first resistance piece on the right side below the throttling element, the pipe section between the second resistance piece upstream and the first resistance piece downstream of the throttling element, and the differential pressure signal pipeline. |
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![特点]() use and maintenance |
1. Correction in use
In practical work, process conditions may sometimes change, which can cause errors in measurement results, so necessary corrections may need to be made at times.
2. When there is a change in pressure and temperature:
The changes in pressure and temperature will affect the changes in the density of the medium. The following formula must be used for correction:
G2=G1![法兰式孔板流量计]()
Q2=Q1![法兰式孔板流量计]()
G1- Reading flow rate
G2- Actual Traffic
Q1- Reading flow rate
Q2- Actual Traffic
R1- Design weight of the tested medium
R2- actual weight of the tested medium
3. Maintenance:
The throttling device, pressure guiding system, and front and rear pipelines should be inspected at least once a year to remove dirt, replace scrapped components, and ensure their normal operation. |
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