Some standard content:
Critical flow meter calibration procedure
JJG 620—1994
Critical flow meter calibration procedure
Werifleatian Kegunliou or
Critical flow meter
......
JJG 62U1994
This standard was approved by the National Technical Supervision Bureau on May 9, 1994, and was withdrawn on December 19944! The relevant unit: Ningguo Institute of Metrology Proposal unit: China Institute of Metrology Instrument Factory
The drafting unit of the technical provisions of this regulation is responsible for the drafting process, and the main drafters of this regulation are:
Site supervision: (4 Medical Metrology Institute)
Ten self-he: (Copy list)
Wang Dongwei: (Chinese Institute of Metrology) Drafting person:
Lan Station: North China Oil Pipeline Bureau)
Jian Fangxin: (Liaoning Institute of Metrology and Testing Technology) Zhang Baoguo: (Ningbo Institute of Metrology and Testing Technology) 1260
Technical requirements
Verification parts, procedures and methods
Verification result processing and verification period
Appendix]
Appendix 2|| tt||Appendix 3bzxZ.net
Appendix 4
Appendix 5
Appendix 6
Calculation method of critical pressure ratio and the relationship between critical pressure ratio and previous ratio (A, A,) for different types of gases and low pressure
Calculation method for natural gas C
Flow meter table
Numerical table
Recording type of determination result
Verification procedure for critical flow meter
In the current relevant new manufacture, use and repair to measure the critical flow flow meter of gas flow, the flow meter (hereinafter referred to as flow meter) is composed of a primary and a secondary meter, and the outlet is equipped with a sieve. The flow meter can be calibrated according to this procedure. The secondary meter is used for the calibration of critical flow meter. The secondary aggregation includes the retreat meter and the thermometer or density, as well as the required configuration position elasticity of the measured electrical benefit. 2. The symbol for the completion of the etiquette
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critical flow flow with! In the case of the gas pressure drop in the vehicle, the pressure is the pressure at the gas flow rate. The pressure at the gas flow rate is the pressure at the time of the gas flow. This standard uses the absolute positive pressure test. The positive pressure can be obtained from (1). The gas pressure drop is the pressure at the gas flow rate when the gas flow rate is zero. This regulation only uses absolute stop temperature values. The hysteresis temperature can be avoided by using (2) to obtain the critical flow rate of the nozzle. The shape and shape of the nozzle make the flow under critical conditions. 2.2.4 The Reynolds number of the nozzle is the gas velocity at the nozzle, and the dynamic viscosity of the gas at the boiling state outside the nozzle is calculated. The characteristic length is the throat under the working condition. The throat Reynolds number is determined by formula (3). The key coefficient of the throat Reynolds number is the ratio of the actual flow rate to the ideal flow rate obtained by the same flow condition. It is an absolute parameter. For the nozzle design and installation specified in this regulation, the Reynolds number of the nozzle is the number of the nozzle. [263
2.2.6 Critical flow frequency
The function of gas properties and band conditions, which characterizes the thermodynamic properties of the actual gas flow at the jet and the inhaler
2.2.7 Critical flow coefficient
The relationship between the critical flow function and the critical flow function is C- -+v:
2.2.8 Single ratio
Under a certain sliding force, when the gas mass flow rate through the nozzle is or a maximum value, the algorithm for the ratio of the static pressure at the nozzle head to the sea soil pressure is recorded in Table 1.
2.2.9 Back pressure ratio
The ratio of the boundary flow to the upstream stop pressure of the nozzle is recorded in Table 1.
3 Basic formula
Under the actual boundary flow, although
4m-7(RM)T
, the value can be calculated by any method with proven accuracy. For gas, the value is more difficult to calculate in Table 2. Or expressed by (6):
Hm - A,cx.w(pp
wherein (the calculation is carried out by a method with proven accuracy. For natural gas, the calculation method can be referred to Appendix 3,
2 Technical requirements
+ push-through island
The accuracy of the nozzle flow rate shall be in accordance with the special requirements specified in the technical documents. 5 Requirements before nozzle
5.1 General requirements
5.1.1 When manufacturing nozzles, the selection of H values should be based on the materials used. The main cost is virtual Consider the following aspects: The material must meet the requirements, the smelting system, the pores and inclusions are not suitable for use, the material design and its surface rust treatment are reasonable, so as to ensure that the work is not affected, the core material should have stable thermal conductivity [such as the material is used at different temperatures when the limit diameter is measured], so that the appropriate limit diameter can be obtained.
5.1.2 The nozzle shape, the throat to the conical expansion section should be smooth, and the roughness [composition] should not exceed 15 × [0-\d,
5.1.3 The reverse clamp expansion section of the variable nozzle is not allowed to have convex, non-connected, non-existent, and the straightness is not allowed to be 1: the surface roughness of the expansion section is 105.1.4 The inner surface of the nozzle should be free of dirt
5.2 The requirements for the air throat of the mesh ring nozzle are different. 5.2.1 The ring throat nozzle side
a. The ring throat nozzle end should meet the requirements of Yin]
.3d-2.7
1 National Environmental The mouth
Bei Ping Sheng
An Bei place turns your table machine times, this is more than 15, the four deviations can be greater than (.01:, in the shape of the light equal to 2.. the plan is the population, it nozzle to grams
C. The spray said that the person I "avoids the good is a typical straight shape, which should be extended from the gate to the minimum section (throat) and tangent to the expansion part. In the three tours of the population plane, the shape is not specified, but in each axial position, its diameter is the same! Or large Ding to the expansion part of the shape of the examination. The deviation of the mountain surface between the gate plane and the expansion section of the nozzle should not exceed =0.001z: the radius of the rate of the She Ba shape surface on the plane where the axis of symmetry is located should be 1.·-2.2.1. The expansion section is the lower part of the nozzle that is adjacent to the flared curved surface. It is a 2.5"-6\ head body and has a length of not less than the nozzle diameter. 5.2.2 The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2. The nozzle throat should be consistent with Figure 2.The deviation of the nozzle surface should not exceed 1.001dr. The difference between the diameter of each part in the nozzle and its average value should not be greater than 1.001dr. The throat diameter should be measured on the high plane of the nozzle. At least 4 diameters should be measured at approximately equal angles. The average diameter obtained in this way is used for flow meter. The average diameter of each part in the nozzle should not be less than 0.5 of the average length of the nozzle and the limit nozzle. There should be no defects in the connection between the nozzle and the nozzle. The connection should be smooth. The surface twist should not exceed 1510. The connection between the throat belt and the nozzle expansion section should be smooth. If there are three defective expansion sections, the nozzle is equipped with a flat angle of 3". The length of the nozzle section should not be less than three throat diameters. 6. Common nozzle installation requirements
There are two types: the upstream of the nozzle is the same shape and the upstream of the nozzle is a large space, 6.1 The upstream pipe of the nozzle is a shaped
The nozzle can be installed in a round straight pipe, the actual accuracy should be within 0.02 mm: the nozzle is 11 to 31) of the specification, the inner wall roundness does not exceed 0, and the rough requirement is not too large -: the inner diameter is less than 4eta
(.2 The upstream of the nozzle is a large space
between the center line of the nozzle and the plane of the mouth 5 or less, the upstream is called the spray barrier:, a large space. 6.3 Upstream of the spray zone, no matter what type of spiral installation, there is no vortex. In the upstream pipeline where there is flow, a rectifier should be installed, and the rectifier structure should be installed. The installation position should be greater than S (the distance between the inlet plane and the installation position should be greater than S).>
Characteristics book zero
Figure tour safety I require
Pressure gauge
Here, the rate of the spray zone is within the heart and the danger does not exceed 5
Downstream cold request
Spray out instantly! ! 7.1 When the upstream of the nozzle is a rectangular pipe, the upstream pressure tapping hole is preferably located at a distance of 0.9-1.17 from the nozzle inlet (4 meters) to the cylinder wall. Under the condition that the measured pressure can reach the nozzle end pressure balance, the pressure tapping hole on the pipe wall can also be located upstream or downstream of this position. 7.2 When there is a space upstream, the upstream non-constricted hole should be located at a distance of 10 meters from the nozzle plane and parallel to the nozzle. Under the condition that the measured pressure can reliably obtain the nozzle pressure balance, the pressure tapping hole can also be located upstream or downstream of this position. 7.3 In the case of the above situation, the center of the pressure tapping hole should intersect the center line of the nozzle perpendicularly, and the pressure tapping hole should be a rectangular through hole. Edge roughness, and the radius of the pressure hole should not exceed 1.1 times: when the upper pharyngeal pipe is discharged, the diameter of the hole should be less than (, and less than 12t, the hole should be within a length of 2.5 times the diameter of the hole (see Figure 4).
.4 In order to maintain the critical flow state, the downstream pressure is generally measured. The distance between the wall pressure hole and the center of the nozzle expansion section outlet should be less than 1.5 standard diameter,
c.oer...2m
2 times the
medical 4 The small point of the hole
In some applications, the gas flowing through the nozzle can be directly put into the atmosphere! Know the pressure, do not exist in this high attachment, in order to remove the condensate or other materials that may exist in the duct, it is necessary to equip the necessary equipment, in When measuring flow, the gas shall not flow through this hole: the discharge port shall be located upstream of the nozzle, with a total diameter of 0.01 + 0.02 + 0.12mm. The discharge port shall be located upstream of the nozzle. The discharge port shall be in a plane with a diameter of 0.01 + 0.02mm. The humidity sensor and the temperature sensor shall be installed upstream of the nozzle. One or more temperature measuring holes shall be placed upstream of the nozzle. When the upstream is of suitable size, the temperature measuring hole shall be located 1.82.2° upstream of the nozzle inlet plane. The diameter of the sensor shall be less than 0.04°. It must not be aligned with the pressure measuring hole in the flow direction. If a sensor with a diameter of less than 0.01 + 0.12mm cannot be obtained, the sensor shall be installed in a position that will not affect the measurement. Under the condition that the measurement base can accurately obtain the nozzle temperature, the sensor can also be installed farther upstream. When the difference between the contraction temperature of the flowing gas and the temperature of the solid medium in the pipeline exceeds 5°C, the sensor shall be installed in a position that is less than 0.04°C. Thermal radiation is not recorded by sensitive internal sensors and heat is applied to the end of the channel.
When it is necessary to measure the density of the gas entering the nozzle at 1, the meter should be installed upstream of the nozzle and the pressure gauge should be measured. In order to correctly measure the density change, special attention should be paid to the following points: a. The position of the density meter cannot affect the pressure and the heat of the next degree: 5. If the density meter is installed outside the upstream main channel: the test should be carried out to ensure the heat resistance of the gas recorded in the gas pipe in the detection section. The pressure, temperature and conditions at the density meter should be as close as possible to the nozzle! Conditions to avoid adjustment. If the equipment is to be properly burned, the density can be calculated by the state equation and the avoided density. This mark indicates that the "density meter" should be single-phase (or 1. The test of the steady flow of gas (known center) is carried out. 2. Verification items, items and methods
12 This regulation is mainly for the verification of the nozzle (primary device). The source and density or density release instrument (primary device) should be tested according to the corresponding verification procedures and have a valid verification certificate. The inspection and installation and use of the equipment during use should meet the relevant requirements of Article 6. 13 The inspection methods of this regulation are divided into two methods: the inspection method and the calibration method: 267
"I" Inspection method
14 "The inspection method is a method to inspect the nozzle size according to the requirements of Article 5 to determine its quality. 15 External inspection
Use the inspection method to inspect the nozzle surface (including consulting the technical documents), and its viscosity flow meets the requirements of 5.1.1 and 5.1.4.
16 Person 1 Sin Inspection
16.1, the toilet ring Xi Wei mouth of the La with the shape of the plane of the support through the six months card to carry out the inspection, the beam degree will meet the requirements of 5.2.1h5.3.1,
2 spray end person receiving arrow section of the energy radius, and the use of the three standard measurement machine inspection, using the continuous scanning method, "the diameter is obtained, the curve system round reward deviation, to the number of points not less than 20 points: the number of tearing processing and other use a small line reduction combination, the result is Liu ring The throat of the nozzle should meet the requirements of 5.2.2c and 5.2.21. For the recessed membrane nozzle, the throat should be inspected by a standard machine or a universal microscope. Measure the nozzle diameter at least at four equiangular diameters and take the average value as the throat diameter. For the round nozzle, the diameter of the nozzle should be measured on the plane of the nozzle mouth. At least four equiangular diameters should be measured and take the average value as the throat diameter. In addition Measure the diameter of the nozzle in three different directions and calculate the difference with the diameter of the nozzle. The final length of the nozzle is measured. The result meets the requirements of 5.2.26. 18. Coordinate measurement for initial inspection of nozzle expansion section length, expansion diameter, straightness, etc. The line shall meet the requirements of 5.1.3 and 5.2.1k or 5.2.2F. 10. Surface roughness test The surface index R of the nozzle is generally measured by a surface roughness wheel. The result is that the surface selection of the nozzle meets the requirements of 3.1 and 5.2. The accuracy of the various instruments for testing the nozzle is lower than the required standard. According to the test of Article 14.19, the nozzle meets the requirements of the installation and use of Article 11. The outflow coefficient of the nozzle has been calculated by the formula (N: For each carbon nozzle, the number of "8" in the figure is 4, see Table 2, installation, and w' kry
The coefficient of the nozzle is calculated by 1
3.5 × Nrg.2.4× IU
2.6x Rr2.
G= m=J
The relative difference of the coefficient of the nozzle end is 05%, and the probability of the error is 1268
395%:
(II) Calibration method
22 The method of measuring the gas flow through the nozzle and the efficiency of the nozzle flow system is applicable to the following nozzles: The method cannot be tested according to Articles 11-19 or the test results are not selected. b. The coefficient of the nozzle needs to be accurate to ± .5%. Other more calibrated nozzles || TT || 23 calibrated sources only require valid certificates: its accuracy is better than 1/2 of the accuracy of the nozzle.The sound isolation and its parameters (pressure bar recognition rate measurement instrument installation conditions and flow through the spray gas conditions are higher than the requirements of Article 11
24 is better to calibrate under the nozzle use conditions, otherwise the results under the calibration conditions can only be sufficient for non-European conditions
25 Sedimentation coefficient calculation
According to formula (5), the flow is calculated according to the same
According to me () to calculate the flow
I, 4 flow war standard installation and measured: and T, or the measuring instrument before the nozzle is measured: A, Measure the diameter of the dustpan according to Article 17 in advance, or calculate it according to the air flow table. 26 Calculate the coefficient of the gas mountain and the complexity of the calculation
-a single center calibration 6 times
in the formula.
t. See the appendix.
27 Calculation of the accuracy of the elimination of the vomiting
27.1 Calculation of the test method
or the 21st service E10.5%
27.2 Calculation of the calibration
2F source type accurate change calculation
=-(F+F-3
28.1 ridge method calculation
= +[ . + + +
Extract formula (6) to calculate the flow system
&- bu++ Iei+ P.+Ex. I
In (14), (15)
-± 0.5%
EA,-= 2E- F 1
iI, 2. -n
Other bases are given according to the conditions of use
28.2 standard calculation
According to formula (5) to calculate the flow
8 - t-=[E-
Connect formula (6) to calculate the common flow
2- Fu -1[F? -LFR - bx]
In formula (19), (20), calculate according to formula (13). If the pressure measuring and density measuring instrument used in the room are the only instruments, then in formula (19) and (20), , , and F are zero. IV. Processing of calibration results and calibration cycle
29. A calibration certificate is issued to nozzles that pass the calibration, and a calibration result certificate is issued to nozzles that fail the calibration. A flow meter that passes the calibration is issued a flow meter calibration certificate, and a flow meter calibration result certificate is issued. The format of the calibration certificate is attached. Note 6
3 The verification period of the nozzle (primary instrument) is generally 5 years, indicating that the given period of temperature measuring instruments (secondary instruments) shall be in accordance with the relevant verification regulations.
Appendix 1 Calculation method of the critical pressure ratio and the relationship between the back pressure ratio and the area ratio (1/A,) Calculation method of the critical pressure ratio
The formula for the critical pressure ratio of the spray is:
2 The relationship between the nozzle pressure and the area ratio (A:,) is as follows: When the number of teeth is too large, the nozzle under the above degree, the maximum allowable downstream pressure can be determined according to the following relationship:
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