Some standard content:
National Metrology Verification Regulation of the People's Republic of China JJG 257-2007
Float Flowmeter
Float Meter
2007 - 08 - 21 Issued
Implementation on 2008 ~ 02 ~ 21
The General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China issued JJG 257—-2007
Verification Regulation
of Float Flowmeter
JJG 257—2007
Replaces JJG257-
—1994
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on August 21, 2007, and came into effect on February 21, 2008.
Responsible unit: National Technical Committee on Flow Capacity Measurement Main drafting unit: China National Institute of Metrology Participating drafting unit: National Water Flow Metering Station of Zhejiang Quality and Technical Supervision and Inspection Institute
Zhejiang Yuyao Yinhuan Flow Meter Co., Ltd. Yuyao Jintai Instrument Co., Ltd.
Shenyang Beixing Flow Meter Factory
Kaifeng Instrument Co., Ltd.
Henan Institute of Metrology
This regulation entrusts the National Technical Committee on Flow Capacity Measurement to interpret this regulation Main drafter:
JJG 257—2007
Xu Yinghua (China National Institute of Metrology) Participating drafters:
Shen Wenxin (Zhejiang Quality and Technical Supervision and Inspection Institute) Miao Yusheng (National Water Large Flow Metering Station) Zhu Jiashun (Zhejiang Yuyao Yinhuan Flow Meter Co., Ltd.) Cui Lishui (China National Institute of Metrology) Zhang Lifeng (Yuyao Jintai Instrument Co., Ltd.) Chen Ping (Shenyang Beixing Flow Meter Co., Ltd.) Li Wenxuan (Kaifeng Instrument Co., Ltd.)
Kong Qingyan (Henan Province Institute of Metrology) 1
Scope·
References
Terms and definitions·
4 Overview·
4.1 Structural type...
4..2 Working principle
5 Metrological performance requirements
5.1 Accuracy grade and maximum allowable error, +
Indication error·
6 General technical requirements.
6.1 Nameplate and logo
Supplementary documents．
Appearance·
6.4 Flow measurement upper limit value system
Flow range of flowmeter
Explosion-proof performance requirements
7 Measuring instrument control
Verification conditions...
Verification items
Verification methods
Arbitration·
Processing of verification results·
7.6 Verification cycle·
Appendix A
Type evaluation
Appendix B
JJG257—2007
Common gas density table under standard conditions
Appendix C Verification certificate and verification result notice (internal) format (1)
1 Scope
JJG 257—2007
Verification Procedure for Float Flowmeter
This procedure applies to the type evaluation, initial verification, subsequent verification and in-use inspection of float flowmeter (hereinafter referred to as flowmeter).
2 References
The following clauses and regulations are included in the regulations and constitute the clauses of this procedure through reference. JB/T6844--1993 Metal tube float flowmeter JB/T9255—1999 Glass rotor flowmeter When using this procedure, attention should be paid to the use of the current valid versions of the above-mentioned references. 3 Terms and Definitions
3.1 Maximum flow-rate The maximum flow rate that a flowmeter can measure. 3.2 Minimum flow-rate The minimum flow rate that a flowmeter can measure. 3.3 Positive-stroke calibration Calibration is performed point by point from the lower flow limit to the upper flow limit of the flowmeter, and the flow is adjusted from a flow less than the calibration point to the calibration point, which is called positive-stroke calibration.
3.4 Negative-stroke calibration Calibration is performed point by point from the upper flow limit to the lower flow limit of the flowmeter, and the flow is adjusted from a flow greater than the calibration point to the calibration point, which is called negative-stroke calibration.
3.5 Index flow-rate
The index flow of the flowmeter is the flow indicated by the working diameter position of the float or the indicator pointer. 3,6 Reference flow under standard conditions Reference flow under standard conditions The state where the fluid temperature is 20℃ and the absolute pressure is 101325Pa is called the standard state, and the flow under this state is defined as the flow under the standard state.
3.7 Scale flow rate scaleflow-rate
The flow rate represented by the scale of the flowmeter, that is, a set of scale marks (a combination of scale lines and numbers) on the transparent cone tube or scale plate of the flowmeter. The scale flow rate of the flowmeter is usually marked on the transparent cone tube or scale plate in the form of flow rate, percentage or millimeter height, and the name, temperature, pressure (density) and measurement unit of the scale medium are marked at a prominent position of the flowmeter.
3.8 Reference error fiducial error
The ratio of the absolute error value to the upper limit value of the flow rate, expressed as a percentage. 1
JJG.257—2007
3.9 Flow measurement upper limit value series to maximum flow-rate The number corresponding to the upper limit flow value of the flow rate. 3.10 Flow area annualspacc
The effective gap cross-sectional area between the inner diameter of the flowmeter cone tube and the working diameter of the float. 3.11 Back differential back deviation
The ratio of the difference between the average values of the actual flow rates obtained by the forward and reverse stroke calibration at the same flow point of the flowmeter to the upper limit of the flow rate, expressed as a percentage.
4 Overview
The flowmeter is mainly used for wave body and gas flow measurement. According to the design principle, the flowmeter always keeps the pressure drop before and after the float unchanged during the measurement process, and changes the flow rate by changing the flow area. Therefore, the flowmeter is also called a constant pressure drop flowmeter, a variable area flowmeter and a rotor flowmeter. 4.1 Structural type
4.1.1 Structural type of glass tube float flowmeter The glass tube float flowmeter (referred to as glass tube flowmeter) is usually composed of a glass cone, a float, a sealing gasket, an upper and lower stopper, a support plate and an upper and lower base. According to the connection method of the pipeline, there are structural types such as flange connection, threaded connection and flexible connection, and some flowmeters are also equipped with a flow regulating valve. Depending on the working medium, flow meters can be divided into common type and corrosion-resistant type. The common flow meter structure is shown in Figure 1. Home
Figure 1 Schematic diagram of glass tube flow meter
1-base: 2-gear; 3-support plate screw; 4-seal: 5-pressure cover; 6-pressure screw: 7-float: 8-cone tube; 9-support plate 4.1.2 Structural type of metal tube float flowmeter Metal tube float flowmeter (referred to as metal tube flowmeter) can be divided into indicating type, electric remote transmission type and other structural types of metal tube flowmeter according to its output type. Metal tube flowmeter consists of two major components: sensor and indicator. Its sensor is divided into common type, sleeve type, corrosion-resistant type and explosion-proof type according to different structures and materials. 4.1.2.1 Indicating metal tube flowmeter
Indicating metal tube flowmeter is usually composed of shell, guide ring, float, guide rod indicator, etc. Its schematic diagram is shown in Figure 2. The indicator is composed of balance mechanism, dial, pointer, etc. 4.1.2.2 Electric remote transmission metal tube flowmeter
Electrical remote transmission metal tube flowmeter is based on the structure of indicating metal tube flowmeter, and adds four-link (or cam) mechanism and converter to its balance mechanism. 4.2 Working Principle
When the fluid flows from bottom to top through the tapered tube, it is throttled by the float, and a differential pressure is generated between the upstream and downstream of the float, and the float rises under the action of this differential pressure. When the combined force of the differential pressure, gravity, buoyancy and viscosity on the float is zero, the float is in a balanced position. Therefore, there is a certain proportional relationship between the fluid flow rate and the rising height of the float, that is, the flow area of the flow meter:
The indicating metal tube flowmeter transmits the displacement of the float through magnetic coupling, and drives the pointer to indicate its flow value through the transmission mechanism.
Figure 2 Metal tube flowmeter point diagram
1-shell; 2-guide ring; 3-float; 4-pipe seat; 5-body flange 6-sealing gasket; 7-upper flange; 8-pipe; 9-indicator The electric remote transmission type metal tube flowmeter transmits the height of the float rise to the four-bar mechanism through the coupling of the magnetic steel. After the adjustment of the four-bar mechanism, the pointer and the connecting rod have a displacement linear with the flow rate, and then the second set of four-bar mechanism drives the core to move relative to the differential transformer. The generated differential potential is converted into a standard electrical signal output by the converter. 5 Measurement performance requirements
5.1 Accuracy level and maximum allowable error
Table 1 shows the accuracy level of the flowmeter. For flowmeters for special purposes, the accuracy level and maximum allowable error can be in accordance with the provisions of the enterprise standard or instruction manual. 3
5.2 Indication error
JJG 257—2007
The indication error of the flowmeter adopts the reference error and shall not exceed the provisions of Table 1. 5.3 Hysteresis
The maximum allowable error of the flowmeter shall not exceed the provisions of Table 1. Table 1 Accuracy grade. Maximum allowable error and hysteresis Accuracy grade
Maximum allowable error (%)
Maximum allowable difference (%)
General technical requirements
6.1 Nameplate and identification
The following should be marked on the obvious part of the flowmeter or on the nameplate: Manufacturer name or manufacturer identification;
- Name, model specification and accuracy grade of the flowmeter; Factory number and manufacturing date of the flowmeter;- Measuring instrument identification and manufacturing license number;- Explosion-proof grade and explosion-proof identification (only for explosion-proof flowmeters). 6.2 Random Documents
The flowmeter shall be accompanied by an instruction manual and a certificate of conformity. The instruction manual shall state the maximum working pressure (nominal pressure), flow range, sensor structure and material, explosion-proof grade, power supply form, output signal (the last three items are requirements for electric remote transmission flowmeters) and other relevant technical indicators. The accuracy grade shall be indicated in the certificate of conformity. 6.3 Appearance
6.3.1 The outer surface, float and guide rod of the flowmeter shall be well processed and have uniform color. There shall be no defects such as burrs, marks, peeling, rust or mildew. The fasteners shall not be loose or fall off. 6.3.2 Requirements for glass tube flowmeters
6.3.2.1 The name of the medium used, the temperature of the scale state, pressure (density) and the scale unit shall be marked on the glass tube or other obvious parts of the flowmeter:
6.3.2.2 The flowmeter indication line shall be uniform in thickness, and the words, numbers and symbols shall be correct, clear and standardized. 6.3.2.3 Transparent materials should be free of defects that would impede accurate readings. 6.3.2.4 The number of scale divisions of the flowmeter should generally be selected from the following series: 1 × 10\, 2 × 10, 5 × 10
Any positive or negative integer or zero.
6.3.2.5 The glass cone can be round, round with ribs, triangular or other shapes. 6.3.2.6 The reading position (working position) of the flowmeter float is shown in Figure 3. Special cases shall be in accordance with the manufacturer's regulations. 6.3.3 Requirements for metal tube flowmeters 6.3.3.1 Power supply JJG 257-2 (M07 220V, 50Hz 12V, 24V, hA or (1-5)VDc c. Electrolyte or (0-10)VD d. Other common national standards. 6.4 Flow measurement numerical system Upper limit of basic flow range of flowmeter Where: A ON, A OFF, SAT, etc. (see manufacturer's manual);
-Flowmeter statistics measurement range upper limit value number system: RNAMETROLOCY
Any positive,
integer
--Generally 1, 1.2
Note: The flow measurement upper limit value refers to the standard [6.5 Flowmeter flow range
The flow range of the flowmeter is generally 10:1 or 5:1. 6.6 Explosion-proof performance requirements
Reading positionwww.bzxz.net
Any value in 8.
The requirements for explosion-proof flowmeters shall comply with the relevant provisions of national explosion-proof standards. 7 Measuring instrument control
Measuring instrument control includes type evaluation, initial verification, subsequent verification and in-use inspection. Type evaluation shall be carried out in accordance with the provisions in Appendix A.
7.1 Verification conditions
7.1.1 Verification environmental conditions
General test atmospheric conditions:
Temperature: (5~-35)℃
Relative humidity: 45%~75%
Atmospheric pressure: (86106)kPa
7.1.2 Verification instruments and equipment
JJG 257—2007
The instruments and equipment used for verification shall comply with the provisions of Table 2. Table 2 Verification Instruments and Equipment
Flow Standard Device
Technical Indicators
The expanded uncertainty of the device
Should be better than 1/2 of the maximum allowable error of the flow meter being testedThermometer
Pressure Gauge
Barometer
Density Meter
First Flow Milliammeter or Digital Display Meter
7.1.3 Requirements for Flow Standard Devices
Graduation value is 0.2℃
7.1.3.1 The flow standard device and its supporting measuring instruments shall have a valid verification certificate, and its technical indicators shall comply with or be better than the relevant provisions in Table 2.
7.1.3.2 When verifying the gas flow meter, the pressure and temperature shall be measured at the flow inlet. 7.1.4 Calibration fluid
7.1.4.1 The calibration fluid (liquid or gas) should be as similar as possible to the medium used by the flowmeter. 7.1.4.2 The calibration fluid should be a single-phase flow and fill the test pipe. Its flow should remain relatively stable and free of vortices. If necessary, a flow regulator should be installed upstream of the flowmeter. 7.1.4.3 When the calibration fluid is a liquid, there should be no bubbles or visible debris in the liquid: 7.1.4.4 The calibration medium should be safe, clean and well-preserved. 7.1.5 Installation requirements
7.1.5.1 During calibration, the flowmeter should be installed according to the use requirements to ensure that the system is leak-free, vibration-free and easy to observe. If the weight of the flowmeter causes excessive stress or the system vibrates, measures should be taken to eliminate its influence. 7.1.5.2 The installation inclination of flow meters with accuracy levels of 1.0 and 1.5 should not exceed 2°, and that of flow meters with accuracy levels of 2.5 and below should not exceed 5". 7.1.5.3 The seal of the upstream pipe of the flow meter shall not protrude into the interior of the pipe. 7.2 Verification items
The first verification of the flow meter, the items for subsequent verification and inspection during use are shown in Table 3. 6
Verification items Date
Random documents
Appearance inspection
Indication error, hysteresis
JJG257—2007
Table 3 List of verification items
First verification
Note: "+" indicates a commissioned inspection item; " indicates an item that may not be inspected. 7.3 Verification method
7.3.1 Random documents
Subsequent verification
Check the random documents of the flow meter, and the results should meet the requirements of 6.2. 7.3.2 Appearance inspection
Use the monthly test method to check the appearance of the flow meter, and the results should meet the requirements of 6.3. 7.3.3 Pre-operation inspection
Install the flow meter on the flow standard device, and the results should meet the requirements of 7.1.5. 7.3.4 Verification flow points
In-use inspection
Within the flow range of the flow meter, generally 5 evenly distributed flow points including the upper and lower flow limits should be selected for verification.
7.3.5 Number of verifications
The number of verifications for each flow point is 2. Metal tube flow meters and glass tube flow meters with guide rods are calibrated in forward and reverse strokes, and the number of verifications for forward and reverse strokes is not less than 2 times. 7.3.6 Indication error and hysteresis verification
7.3.6.1 Verification of indication error
The verification of indication error can be done by volumetric method, weighing method and standard table method. During verification, the flow control valve should be opened slowly to allow the fluid to flow through the flow meter. Verification can be started after the fluid state and the float are stable. When verifying a liquid flow meter, the bubbles in the pipeline and attached to the periphery of the float should be removed before verification. During verification, the flow should be adjusted using the downstream valve of the flow meter as much as possible. In particular, when verifying a gas flow meter or using a volatile liquid as the verification medium, the flow should be adjusted downstream.
（1）Calibration of liquid flowmeter
① Volumetric method
Adjust the flow rate according to the flow device operating procedures, so that the float rises to the predetermined calibration flow rate. After stabilization, operate the commutator to reverse, so that the calibration medium flows into the selected "working volume". When the predetermined time or predetermined volume is reached, the commutator is reversed again, and the liquid volume in the working volume, the medium temperature and the current measurement time are recorded. The single calibration operation is completed. The flow rate av measured by the standard device is calculated according to the following formula: qV=
Where: V—the volume of liquid flowing into the working volume: inflow time.
Convert to the flow rate flowing through the flowmeter:
JJG 257—2007
ga = qv pa
Where: Ps, Pm—the liquid density at the standard device and the flowmeter, respectively. Then convert to the flow rate under the standard state (i.e. the scale state) qNN = m[m(e )
Lp(o= em)
where: —
一is the density of the liquid
sub-material under standard conditions;
一is the filter
at the flowmeter. By formula (1), (2), (3):
免 is the correction coefficient,
② Mass method
Liquid mass method
mass, and medium
where: M-
operation and volume method relative environment and this measurement time,
meaning mass index Indication;
weighing
the density of the liquid in the inclined vessel
correction coefficient, c
where βw—device
density, if the installation
formula: Pa-
same as the volumetric method,
③standard table method
ambient atmospheric density,
replace the material to the standard (scale
after the operation is completed, record the liquid in the measuring container and calculate the flow rate measured by the device
e4tpw(ps -Pa);
No base code, then c length a
CHA network standard
Use standard meter method to calibrate flowmeter
(ps pa):
The flowmeter to be calibrated should generally be of the same type and specification. During calibration, when the flow of the standard flowmeter and the flowmeter to be tested reaches stability, read the indicated flow of the two flowmeters synchronously. If the scale status of the standard and tested flowmeters is the same, the indicated flow of the standard float flowmeter does not need to be corrected and can be used as the actual flow rate of the tested flowmeter under the scale status 9, then
①Other liquid standard flowmeter method
Where: 9v-
qn = qv-k
The volume flow measured by the standard flowmeter.
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