Some standard content:
National Standard of the People's Republic of China
Methods for measurement of capacity of pump
Methods for measurement of capacity of pump Subject content and scope of application
This standard specifies the method for measuring the capacity of pumps. GB/T 3214-91
Replaces GB 321--82
This standard is applicable to the measurement of the capacity of centrifugal pumps, mixed flow pumps, axial flow pumps and vortex pumps. Other pumps can also be used for reference. Cited standards
GB2624
Flow measurement throttling devices Part 1: Throttling devices are standard orifice plates for angle-connected pressure tapping and flange-connected pressure tapping, and standard push nozzles for angle-connected pressure tapping
GB 3216
JJG 198
Test methods for centrifugal pumps, mixed-flow pumps, axial-flow pumps and vortex pumps Verification procedure for turbine flow transmitters
Names, symbols, definitions and units of quantities
The names, symbols, definitions and units of the quantities used in this standard are shown in Tables 1 to 3. Table 1 Name, symbol and unit of quantity
Symbol of quantity
Opening diameter of throttling device
Inner diameter of pipeline
Weir groove width
Weir mouth width
Weir mouth height
Weir head
Displacement between two pipe sections
Approved by the State Administration of Technical Supervision in 1991-0323
Implementation in 1992-01·01
Symbol of quantity
Symbol of quantity
GB T 3214—91
ContinuedTable 1
Distance between the offset position of two pipe sections and the pressure tapping hole or annular chamberMass
Volume of liquid
Average velocity
Free fall acceleration
Absolute average roughness of the inner wall of the pipe
Uncertainty
Standard deviation
Table 2Names, symbols, definitions and units of quantitiesNames of quantities
Mass flow rate
Volume flow rate
Fluid density
Flow coefficient
Definition (or formula)
Mass of liquid passing through per unit time
Volume of liquid passing through per unit time
Mass per unit volume
Difference between two pressure values
Or α=
Cube Meter
Meter per second
Meter per second squared
Depending on the value
Depending on the value
Kilogram per second
Cubic meter per second
Kilogram per cubic meter
Pascal
Symbol of quantity
Name of quantity
Opening area of throttling device
Diameter ratio of throttling device under working condition
(Dynamic) viscosity
Kinematic viscosity
Reynolds number
GB/T3214—91
Continued Table 2
Definition (or formula)
Defined by the following formula: =μ
The speed of a flat plate when it moves parallel to a fixed flat wall in its own plane
The distance from the flat plate to the fixed flat wall. But this distance should be small enough to make the fluid flow between the flat plate and the fixed flat wall laminar
Fluid friction force acting on the unit area of the flat plate during the movement of the flat plate
Table 3 Symbols and lower right corner code meaning
Square meter
Pascal second
Quadratic meter per second
Original value or zero value
Upstream side of the throttle
Downstream side of the throttle
Effective
GB/T3214-91
4 Standard orifice plate, standard nozzle and standard venturi nozzle 4.1 Standard orifice plate, standard nozzle
When using orifice plate and nozzle to measure flow, standard orifice plate and standard nozzle in accordance with GB2624 should be used. 4.1.1 The inner surface of the measuring tube should be clean, free of pits and sediments, and at least within the length range of 10D upstream and 4D downstream of the throttle.
4.1.2 When the temperature of the measured fluid exceeds the normal temperature range, the measuring pipe section and flange shall be insulated at least over the entire required straight pipe section. 4.1.3 Beyond 2D from the throttle, the pipeline between the throttle and the first upstream resistance or spoiler can be composed of one pipe section or several pipe sections.
As long as the misalignment between any two pipe sections does not exceed 0.3%D, there is no additional uncertainty in the flow coefficient. If the misalignment between any two pipe sections exceeds 0.3%D, but the relationship of formula (1) or (2) is satisfied, the uncertainty of the flow coefficient shall be arithmetic added with an additional uncertainty of ±0.2%; if the misalignment is greater than the limit value given by formula (1) or (2), the installation does not meet the requirements of this standard.
20.1+2.3B
The diameter of the downstream straight pipe section shall be within 3' of the average diameter of the upstream straight pipe section at least along the length of 2D along the upstream end face of the throttle.
4.1.4 The pipeline should be provided with exhaust holes, but no fluid should flow through these exhaust holes during the flow measurement process. Exhaust holes shall not be set near the throttling device. If they have to be set near the throttling device, the diameter of these exhaust holes shall be less than 0.08D, and their position shall be more than 0.5D away from the pressure-taking hole on the same side of the throttling device. 4.1.5 The installation position of the throttling device and the pressure-taking ring chamber shall meet the following requirements: a. The throttling device shall be perpendicular to the center line of the pipeline, and its deviation shall be within the range of ±1.0°; b. The throttling device shall be concentric with the pipeline. If a pressure-taking ring is used, it shall be concentric with the pressure-taking ring. The distance ex between the center line of the opening and the center line of the upstream and downstream pipes shall satisfy the relationship of formula (3): 0.0005D
0. 1 + 2.38-
(3)
If ex is in the relationship of formula (4), the uncertainty of the flow coefficient α shall be arithmetically added with an additional uncertainty of ±0.3%. If ex is in the relationship of formula (5), it shall exceed this standard; 0.0005D
0.1+2.3B1
0.1+2.384
c. When a pressure ring is used, the pressure ring shall not protrude into the pipe. (4)
(5)
4.1.6 The clamping method and gasket shall meet the following requirements: a. After the throttling device is installed in the appropriate position, it shall remain stationary. When the throttle is fixed between flanges, it should be able to expand freely due to heat to avoid wrinkling and deformation;
b. When using a gasket, the gasket should not protrude into the pipe at any point. When using an angle connection to take pressure, the pressure tapping hole or pressure tapping groove should not be blocked. The gasket should be as thin as possible and should not be larger than 0.03D in any case; c. When a gasket is used between the throttle and the pressure tapping ring, the gasket should not protrude into the ring chamber. 4.1.7 Uncertainty of standard orifice flow coefficient: Assuming that B, D, Re and k/D are known and have no error, the relative uncertainty of α value is shown in Table 1
0. 6..8≤ 0. 75
GB/T3214-91
Angle connection pressure
Flange pressure
Uncertainty of standard nozzle flow coefficient: Assuming that β, D, Re and k/D are known and have no error, the relative uncertainty of α value is:
When B0.6, it is 0.8%;
When B>0.6, it is (2β -0.4)%.
4.1.8 Pipeline conditions and installation requirements shall comply with the provisions of Chapter 4 of GB2624. It is recommended to use a valve installed on the downstream side of the throttling device to adjust the flow. When the valve on the upstream side of the throttling device is needed to adjust the flow, a rectifier can be used.
4.1.8.1 The rectifier is installed on the straight pipe section between the throttling device and the upstream regulating valve. The length of the straight pipe section between the valve and the rectifier inlet should be at least 20D, and the length between the rectifier outlet and the throttling device should be at least 22D. Moreover, the rectifier is fully effective only when there is a minimum gap around the choke tube of the rectifier so that there is no bypass flow that can hinder the correct function. When using a rectifier that meets the above installation conditions, there is no need to add any additional uncertainty. 4.1.8.2 The standard forms of rectifiers are divided into three types: A, B, and C, as shown in Figure 1. This type of rectifier will cause pressure loss, for type A pv2), type C is approximately 5 (1
rectifier is approximately 5 (一
pv2); type B is approximately 15 (-
pu2).
Type A,Zanker rectifier. It consists of a perforated sheet with circular holes of specified size and a groove formed by a number of flat plates behind it (one groove for each hole). The main dimensions are given in Figure 1. The various plates should have appropriate strength but should not be unnecessary thick.
Type B, Sprenkle rectifier. It consists of three perforated metal plates connected in series, with the spacing between two adjacent plates being one tube diameter. It is best to have a chamfer on the upstream face of the hole, and the total area of the holes on each plate should be greater than 40% of the cross-sectional area of the tube. The ratio of the thickness of the plate to the hole diameter is at least 1.0, and the diameter of the hole should be less than 1/20 of the tube diameter. The three plates should be connected together by rods or bolts, which should be distributed around the inner circumference of the tube and as small as possible as the hole diameter and have the required strength. Type C, tube bundle rectifier. It consists of a number of parallel tubes fixed together and rigidly fixed in the tube. It is important to ensure that the tubes are parallel to each other and therefore parallel to the tube axis. If this requirement is not met, the rectifier itself may cause interference to the flow. There must be at least 19 tubes, the length of which should be greater than or equal to 20d. The tubes should be connected together and the tube bundle and the pipe should be tangent. 207
Drilled plate
Flow square
GB/T3214—91
d/D= 0.139
d/D = 0.141
r/R= 0.56
66°40°
Type A, zanker rectifier
Type B. Sprenkle rectifier
Type C, tube bundle rectifier
Rectifier
Note: To reduce pressure loss, the entrance of the hole can be made into a 45 degree slope. 208
18°30
11°40
d/D=0.110
GB/T3214—91
4.1.9 The estimation method of the uncertainty of flow measurement shall be carried out in accordance with the provisions of Article 4.3 of this standard. 4.2 Standard Venturi nozzle
The standard Venturi nozzle consists of an inlet nozzle part consisting of two arc surfaces, a circular throat and a conical diffuser, as shown in Figure 2.
Short diffuser
Long diffuser
Figure 2 Standard Venturi nozzle with short or long diffuser Standard Venturi nozzles for different pipe diameters have geometrically similar structures. 4.2.1 The size and technical requirements of the inlet nozzle part of the standard Venturi nozzle shall comply with the relevant provisions of Article 3.3.2 of GB2624. 4.2.2 The length of the cylindrical part e from the center of the pressure-taking borehole to the beginning of the conical diffuser is 0.40 to 0.45d. This part of the cylindrical part and the cylindrical throat of the inlet nozzle together determine the total length of the cylindrical throat with a diameter of d. The inner surface processing requirements of this part shall comply with the provisions of Article 3.3.2 of GB2624.
4.2.3 The conical diffuser is directly connected to the cylindrical throat without the need for a circular transition, and its diffusion angle can be up to 30. The length of the diffuser actually has no effect on the flow coefficient, but it has an effect on the residual pressure loss in conjunction with the diffusion angle. 4.2.4 The pressure-taking method only adopts the corner connection pressure-taking method, and the structural form and technical requirements of the pressure-taking device shall comply with the provisions of Article 2.4 of GB2624.
When the pipe diameter D is 0.065~0.500m, the diameter ratio β is 0.32~0.77 and the Reynolds number Re is 1.5×105~2×10, the smooth tube flow coefficient α of the standard Venturi nozzle in the 4.2.5
smooth pipe is listed in Table 5, which lists the relationship between the value of β4 and the flow coefficient α. Table 5 Flow coefficient α value
0. 989 30. 993 3
1.03951.0437
1.095911.10131.1068
1. 061 21. 065 9
1.118 2[1.124 1
1.07061.0754
1.080 4 1.085 1
1.136 31.1425
GB/T 3214—91
4.2.6 The outer surface of the flow section shall be engraved with the symbol (+, -) indicating the installation direction of the standard Venturi nozzle, the manufacturing number, the installation direction, the design dimension value of the pipe inner diameter D and the actual dimension value of the cylindrical throat diameter d. 4.2.7 The pipeline conditions and installation requirements shall comply with the provisions of Article 4.1.8 of this standard. 4.2.8 The inspection method shall be carried out in accordance with the provisions of Chapter 5 of GB2624 standard. 4.2.9 Uncertainty of the flow coefficient of a standard venturi nozzle, when applicable within the limits of 4.2.5, assuming that β is known and has no error, the relative uncertainty of the value of the flow coefficient α is calculated by formula (6): da
4.3 Estimation of uncertainty in flow measurement
±(1.2+1.58)%
（6）
4.3.1 Definition of uncertainty
The uncertainty in measuring flow with a standard orifice plate, standard nozzle and standard venturi nozzle is the estimate of the range of values within which 95% of the measured values fall, i.e., the confidence probability is 95%. The uncertainty in flow measurement can be expressed in absolute or relative terms: for volume flow
flow=Q±Q or
b. for mass flow
flow=Q(1±e),
flow=q± or flow=q(1±e).
In the formula, the uncertainties α and β should have the same dimension as Q and q. When edo
, e is dimensionless.
The flow uncertainty defined in this way is equal to twice the standard deviation in statistical terms. The standard deviation is obtained by synthesizing the uncertainties of the relevant quantities used in calculating the flow (assuming that these uncertainties are relatively small and many of them are independent of each other). Although for a single measuring device and the coefficients used in the measurement, some of these uncertainties may actually be the result of systematic errors (of which only the estimates of their maximum absolute values are known), it is allowed to synthesize them if they are regarded as random errors that conform to the Laplace-Gaussian normal distribution. 4.3.2 Practical calculation method of uncertainty
The actual calculation formula for the uncertainty of flow is as follows: 8Q
Wherein:
±［(
（7）
The uncertainty of the flow coefficient is given in Articles 4.1.7 and 4.2.9 of this standard: the uncertainty of the inner diameter of the pipeline is the maximum value obtained by the provisions given in Article 4.3.2.1 of GB2624 standard; the uncertainty of the throttling device opening diameter is the maximum value obtained by the provisions given in Articles 2.2.2.7 and 3.3.2.5 of GB2624 standard;
The uncertainty of the differential pressure depends on the measurement method; the uncertainty of the density depends on the measurement method. 4.4 Determination of differential pressure
GB/T 3214--91
The differential pressure △P of the standard orifice plate, standard nozzle and standard venturi nozzle can be measured by a differential pressure gauge. The measurement uncertainty of △P (Ap
) is determined according to the differential pressure gauge used. If a liquid column differential pressure gauge is used, the following should be achieved: the inner diameter of the glass tube of the liquid column differential pressure gauge is 6-12mm; a.
b. The air in the pressure conduit and the liquid column differential pressure gauge must be completely discharged; c. The pressure conduit can generally use a connecting pipe with an inner diameter of 6-12mm. The connecting pipe can be made of stainless steel pipe, copper pipe, rubber pipe, transparent plastic pipe, etc. according to different system pressures;
d. The uncertainty of the differential pressure △p measurement of the liquid column differential pressure gauge should be within ±1.0%. 4.5 Calibration of standard orifice plates, standard nozzles and standard venturi nozzles All standard orifice plates, standard nozzles and standard venturi nozzles manufactured in accordance with GB2624 and this standard should be regularly inspected for size or inspected on a device with a higher level of uncertainty. Calibration (generally stipulated as one year). 5 Water weir
5.1 Structure of water weir
The water weir consists of a weir plate and a weir groove.
5.1.1 The structure of the weir plate is shown in Figure 3 and Figure 4 (Figure 4 is a prefabricated structure). 5.1.1.1 The weir mouth is at right angles to the inner side surface, and the lip thickness is 2mm. The burrs should be removed from the 45° inclined surface to the outside. 1.6
Direction of water flow
Figure 3 Cross-section of the weir plate
Water Flow direction
Figure 4 Sectional view of assembled weir
Flow direction
The edge of the weir should be trimmed into a sharp edge and not rounded. The inner side of the weir should be smooth, especially the area from the top to 100mm. 5.1.1.2
The weir should be made of stainless and corrosion-resistant materials. The weir must be installed vertically. The weir should be located in the center of the width of the weir groove and at right angles to the two side walls of the weir groove. 5.1.1.4
5.1.1.5 The weirs of various water weirs are shown in Figure 5. The right angle bisector of the right-angle triangular weir should be vertical, and the right angle tolerance is ±5'. The lower edge of the weir mouth of the full-width weir and the rectangular weir should be horizontal, and the right angle tolerance of the weir mouth is ±5', and the weir mouth width tolerance is ±0.0016.211
Right-angle triangular weir
Full-width weir
GB/T 3214 --91
Figure 5 Weir mouth of water weir
5.1.2 The weir trough consists of an inlet part, a straightening device part and a straightening part. O
Rectangular weir
5.1.2.1 The weir trough (including the supporting plate) should be strong and not easy to deform, and can be made of steel plate or concrete. 5.1.2.2 A straightening device (4 to 5 straightening grids) should be installed upstream of the weir trough to reduce the fluctuation of the water surface. The recommended grid hole size is shown in Figure 6. The width of the rectifying part is equal to the width of the introduction part. Figure 6 Grid hole size
GB/T 3214—91
The bottom and two side surfaces of the weir groove should be flat, and the side surfaces and the bottom surface should be perpendicular. The two side surfaces of the full-width weir groove should be extended outward, as shown in Figure 5. The extended wall should be as flat as the two side surfaces and perpendicular to the edge of the weir mouth. 5.1.2.4
Right angle tolerance ±5'. Ventilation holes should be set on the extended wall. The vents should be close to the weir mouth and below the water head to ensure that the air inside the water head is unobstructed during measurement. The area of the vents is:
Where: hmax
The maximum weir head, that is, the vertical distance from the high water surface of the water flow to the bottom point of the weir mouth (right-angle triangular weir) or the lower edge of the weir mouth (rectangular weir, full-width weir), m.
5.1.2.5 The capacity of the inlet section should be as large as possible. The width and depth of this section should not be less than the width and depth of the downstream of the rectifier. The water pipe should be buried in the water.
5.1.2.6 The length of the weir is shown in Figure 7 and the dimensions are listed in Table 6. Inlet part
Straightening device
Weir slot length
Straightening part
Weir slot length size
Table 6:
Right angle triangular weir
Rectangular weir
Full width weir
>20 hmax
About 2hmax
>（B+hmax）
>(B+2hmax)
>(B+3hmax)Www.bzxZ.net
5.2 Water head measuring device of weir
5.2.1 Water head measuring device is shown in Figure 8. A small hole is provided on the side wall of the weir slot to communicate with another small bucket, and the water level is measured in the bucket. The length of the connecting pipe between the bucket and the weir should be appropriate to ensure convenient and accurate measurement, and the pipe diameter is 10~30mm. 213
GB/T 3214--91
Figure 8 Measurement device
5.2.2 The position of the small hole should be (4-5) hmax from the weir mouth, and the distance from the lower edge of the weir mouth and the bottom of the weir groove should not be less than 50mm. The small hole should not have burrs, and the axis of the small hole should be perpendicular to the wall of the weir groove. 5.3 Method for measuring the water head of the weir
5.3.1 The measurement should be carried out when the water flowing over the weir mouth is not attached to the weir plate. 5.3.2 The height from the weir mouth of the water weir to the water surface of the pool outside the weir mouth shall not be less than 100mm. 5.3.3 The water level can be measured by a hook needle water level gauge or a floating water level gauge (as shown in Figure 9), but the hook needle water level gauge cannot be used when the water level is unstable. When using a hook needle water level gauge, the needle should be sunk into the water first and then lifted up to align with the horizontal plane to eliminate the influence of surface tension. In addition to the water level gauges mentioned above, other water level gauges with water level measurement accuracy not less than these two water level gauges can also be used. Xue scale
Set screw
(a) Hook needle water level gauge
60° needle tip
Horizontal plane
Figure 9 Water level gauge
Vernier scale
Set screw
(b) Float water level gauge
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