Some standard content:
National Metrology Verification Regulation of the People's Republic of China JJG942—2010
Bail Pneumatic Dead Weight Testers2010-05-11Promulgated
Implementation on 2010-11-11
Promulgated by the General Administration of Quality Supervision, Inspection and QuarantineJJG942—2010
Verification Regulation of Ball PneumaticDead Weight Testers
JJG942—2010
Replaces JJG942—1998
This regulation was approved by the General Administration of Quality Supervision, Inspection and Quarantine on May 11, 2010 and came into effect on November 11, 2010.
Responsible unit: National Pressure Metrology Technical Committee Drafting unit: Shanghai Institute of Measurement and Testing Technology Shandong Institute of Metrology Science
Jiangsu Institute of Metrology Science
This regulation is entrusted to the National Pressure Metrology Technical Committee to be responsible for the interpretation of this regulation Drafters of this regulation:
JJG942-2010
Hu Anlun (Shanghai Institute of Measurement and Testing Technology) Ma Dian (Shandong Institute of Metrology Science) Tu Limeng (Shanghai Institute of Measurement and Testing Technology) Zhang Qiang (Jiangsu Institute of Metrology Science)1||tt ||Scope·
References·
Metering performance requirements·
Accuracy level·
Effective area of floating ball
JJG942—2010
Catalog
Quality of special codes and code racks (including floating ball)
Verticality
Discrimination
Influence of air source changes
Periodic change rate of effective area of floating ball
General technical requirements
5.1 Appearance
Special magnetic code and code rack·
Stability of float operation
6 Control of measuring instruments
Verification items
Verification conditions
Verification methods
Processing of verification results
Verification period
Appendix A
Appendix B
Determination method of pressure-flow relationship
Reference value of air buoyancy correction coefficient (β) in major cities in China Reference value of gravity acceleration in major cities in China Appendix C
Appendix D
Appendix E
Appendix F
Float pressure gauge calibration record format
Float pressure gauge calibration certificate, calibration result notification formatFloat pressure gauge usage instructions…
(2)
(3)
(4)
(4)
(5)
(6)
JJG942-2010
Verification procedures for float pressure gauges
This procedure is applicable to the initial verification, subsequent verification and in-use inspection of float pressure gauges with an upper limit of the measuring range of 2kPa to 10MPa.
References
This procedure refers to the following documents:
JJG99--2006 Magnetic code verification procedures
When using this procedure, attention should be paid to using the current valid versions of the above-mentioned references. 3 Overview
The float pressure gauge is mainly composed of a float, a nozzle, a bracket, a special magnetic code, a flow regulator, a gas filter and a base.
The float pressure gauge uses a precision ball placed at the mouth of a cylindrical or conical nozzle. The bracket and the special magnetic code act on the top of the ball. The gas is sprayed to the ball through the flow regulator and the filter. The pressure in the nozzle acts on the lower part of the ball to make the ball float in the nozzle. When the force of the gas on the float is balanced with the gravity of the float, the bracket and the special code, the float pressure gauge can output a stable and accurate pressure. The float pressure gauge is divided into two types according to the flow adjustment method: a manual flow adjustment float pressure gauge and an automatic flow adjustment float pressure gauge. As shown in Figure 1 and Figure 2. 13
Figure 1 Schematic diagram of the structure of the manually adjustable float pressure gauge15
1 Gas source: 2-Gas source switch: 3-Flow meter regulating valve, 4-Flow meter; 5-Level bubble; 6-Special magnetic code, 7-Code rack: 8-Float, 9-Nozzle; 10-Pressure stabilizer; 11-Output switch, 12-Output; 13-Filter; 14 Flow stabilizer, 15-Base, 16-Leveling footJJG942-2010
Figure 2 Schematic diagram of the structure of a flow automatic adjustment float pressure gauge 1-air source, 2-air source switch: 3-level bubble: 4-special code: 5-brick code rack: 6-float; 7-nozzle: 8-pressure stabilizer; 9-output switch; 10-output; 11-leveling foot; 12-flow regulator (automatic); 13-base 4 Measurement performance requirements
4.1 Accuracy grade
The accuracy grade and maximum allowable error of the float pressure gauge shall comply with the provisions of Table 1. Table 1 Accuracy grade and maximum allowable error
Maximum allowable error
Accuracy
Upper limit of measuring range
≤2kPa~25kPabZxz.net
±0.02%FS
±0.05%FS
Effective area of float
Upper limit of measuring range>25kPa~10MPa
When the pressure value is above 10% of the upper limit of the measuring range, it is actual The maximum allowable error of the effective area of the float ball of the float pressure gauge shall comply with the provisions of Table 2. 2
Accuracy grade
JJG942—2010
Table 2 Maximum allowable error of the effective area of the float ball
Maximum allowable error of the effective area of the float ball
4.3 Mass of special code and code frame (including float ball) The maximum allowable error of the mass of the special magnetic code and code frame (including float ball) of the float pressure gauge shall comply with the provisions of Table 3.
Table 3 Maximum allowable error of quality of special code and code frame (including float) Accuracy grade
Verticality
Maximum allowable error of quality of special base code and base code frame (including float) ±0.008%
The deviation of verticality between the center line of the float nozzle and the horizontal plane of the float pressure gauge shall comply with the provisions of Table 4. Table 4 Verticality
Accuracy grade
4.5 Discrimination
Verticality is not greater than
The discrimination of the float pressure gauge shall be less than the code mass value that can produce a pressure equivalent to 10% of the maximum allowable error. 4.6 Influence of air source change
4.6.1 Influence of pressure change
For the automatic flow adjustment float pressure gauge, when the air source pressure changes within the range specified by the manufacturer, the change in the output pressure of the float pressure gauge shall comply with the provisions of Table 5. Table 5 Effect of pressure change
Accuracy level
4.6.2 Effect of flow change
Output pressure change is not greater than
For a manually adjusted float pressure gauge, when the gas source flow changes within the range of 0.5 divisions, the change in output pressure of the float pressure gauge shall comply with the provisions of Table 6. Table 6 Effect of flow change
Accuracy level
Output pressure change is not greater than
4.7 Cyclic change rate of effective area of float
JJG942-—2010
The cyclic change rate of effective area of float refers to the ratio of the difference between the effective area of this and last calibration cycle to the effective area of last calibration cycle.
After calibration, the cyclic change rate of effective area of float pressure gauge shall comply with the provisions of Table 7. Table 7 Periodic change rate of effective area of float
Accuracy grade
5 General technical requirements
The periodic change rate of effective area of float shall not exceed 0.01%/year
0.02%/year
5.1 Appearance
5.1.1 The nameplate of the base of the float pressure gauge shall be marked with the name, model, instrument number, measurement range, accuracy grade, manufacturer name and factory date. 5.1.2 The nozzle and float surface of the float pressure gauge shall be clean and smooth, and shall not have defects such as rust, scars, burrs, etc. that affect the measurement performance.
5.1.3 The base of the float pressure gauge shall have an intact level and horizontal adjustment screw. 5.2 Special code and magnetic code rack
5.2.1 The special code and code rack shall be marked with the instrument number, pressure nominal value and the sequence number of the special magnetic code. 5.2.2 Special codes of the same nominal value should generally have the same shape and size. 5.2.3 If the special code and code frame have adjustment cavities, the adjustment plug shall not be higher than the surface of the special code and code frame. 5.2.4 Special code and code frame should be made of non-magnetic metal materials. 5.3 Stability of floating ball operation
Within the full range of the floating ball pressure gauge, the floating ball should work smoothly and there should be no jumping or jitter that affects the measuring performance.
6 Control of measuring instruments
Control of measuring instruments includes initial calibration, subsequent calibration and inspection during use. 6.1 Calibration items
The calibration items of the floating ball pressure gauge are shown in Table 8. Table 8 Verification items
Verification items
5.1 Appearance
Special magnetic code and code frame
Stability of float working
Effective area of float
Quality of special code and code frame (including float)
First verification
Subsequent verification
Inspection during use
4.4 Verticality
4.5 Discrimination
Verification items
4.6 Influence of air source change
4.7 Periodic change rate of effective area of float
JJG942-2010
Table 8 (continued)
First verification
Subsequent verification
Note: "10" in the table indicates items that should be inspected, and "1" indicates items that may not be inspected.
6.2 Verification conditions
6.2.1 Verification equipment
6.2.1.1 Verification standard instrument
The verification standard instrument for float pressure gauge can be a piston-type large digital pressure gauge and a standard liquid pressure gauge, etc. When selecting a piston pressure gauge as a standard instrument, only measure 1% of the maximum allowable error. The absolute value of the maximum allowable error of the pressure gauge is smaller than the float being tested (vacuum). When inspecting a gas piston pressure gauge during use, the maximum allowable effective area of the piston should be smaller than 1/3 of the absolute value of the maximum allowable error of the float being tested. When selecting other pressure gauges as standards, the range of the standard instrument for the float pressure calibration should be as consistent as possible with the measurement result of the float pressure gauge being tested. If the range of the standard instrument is inconsistent with that of the float pressure gauge being tested, the standard instrument closest to the upper limit of the range of the float pressure gauge being tested should be selected. 6.2.1.2 Ancillary equipment for calibration See Table 9 for the ancillary equipment for calibration. Equipment
Instrument equipment
Standard day
Mass ratio
Standard code
Special level
Oil and gas separator
Note: * is a necessary equipment.
6.2.1.3 Working medium
Comply with the regulations
Comply with the regulations
Technical requirements
Grade requirements of 2000g
Special silicon
Mass weighing
Quantity range is consistent, such as
Noble noble office
Magnetic code rack (including float)
Send code, code rack (including float)
Mass ball quantity
Gram group, mg group
METROLOGY||tt ||CHA value is not less than 50 times the effective area of the piston of the product
The internal cross-sectional area is not less than
The type pressure
Verify the effective area of the float, discrimination, etc.
Verticality verification
When using the liquid medium piston for verification, separate the two different media of liquid and gas
Kang Nian Xiang
The working medium for the verification of the float pressure gauge is clean, dry, oil-free, impurity-free air or nitrogen. 6.2.2 Environmental conditions
The verification of the float pressure gauge is carried out in a constant temperature room with a temperature according to Table 10 and a relative humidity of less than 80%. Before verification, the float pressure gauge must be placed under environmental conditions for more than 2 hours before verification. Good collection store
|Accuracy level
6.2.3 Other conditions
JJG942—2010
Table 10 Ambient temperature
Float effective area calibration
(20+1)℃
(20±2)℃
Ambient temperature
There should be no gas flow and mechanical vibration that may affect the metering performance during calibration. 6.3 Calibration method
6.3.1 Appearance inspection
Inspect by hand and visually according to 5.1.
6.3.2 Check of yard and yard frame
Inspect by hand and visually according to 5.2.
6.3.3 Check of float working stability
When calibrating the float effective area, observe the working stability of the float. 6.3.4Verification of verticality
Verification of other items
(20±2)℃
(20±2)℃
Remove the bracket and the float, place the special level on the upper end face of the nozzle, and adjust the leveling screws on the base of the float pressure gauge so that the bubble of the special level is in the middle. At this time, the level bubble on the base of the float pressure gauge should be in the middle position. Re-place the special level at any position on the upper end face of the nozzle and read the deviation value of the bubble of the special level from the middle position.
6.3.5Verification of effective area of the float
6.3.5.1Verification method
To verify the effective area of the float, use the rated air source pressure. For the manual flow adjustment float pressure gauge, the pressure-flow relationship given in the last calibration certificate should be used in use. For newly manufactured and repaired ones, the pressure-flow relationship should be measured first. The measurement method is shown in Appendix A, and then the effective area of the float is verified according to the new pressure-flow relationship. When the working medium of the standard piston pressure gauge (or piston pressure vacuum gauge) is gas, the output of the float pressure gauge is directly connected to the standard. When the working medium of the standard piston pressure gauge is liquid, the output of the float pressure gauge is connected to the standard through an oil-gas isolator. When the working medium of the standard piston pressure gauge is liquid, the starting balance point should be determined. The starting balance point pressure value is generally 10% to 20% of the upper limit of the measurement range of the float pressure gauge. Add the corresponding number of base weights on the standard piston and the tested float, adjust the gas source pressure of the float pressure gauge to the rated value (for the manually adjusted float pressure gauge, the input flow should also be adjusted according to the pressure-flow relationship given in the original calibration certificate or the newly measured), and raise the standard piston to the working position. When the standard piston cannot be in the working position, if the standard piston rises, add small weights on the standard piston; if the standard piston falls, reduce small weights on the standard piston until the standard piston can remain unchanged in the working position, and it is considered that the initial balance has been reached. After the initial balance, all the weights added to the standard piston and the tested float pressure gauge must remain unchanged as the initial balance mass. When the working medium of the standard piston pressure gauge is gas, the initial balance method may not be used. 6
JJG942—2010
When calibrating the effective area of the float, the pressure should be increased and decreased evenly. The calibration points are generally not less than 5 points, and they should be evenly distributed within the measurement range as much as possible. The calibration method for each point is the same as the method for determining the initial balance. After determining the balance, record the weight added at each calibration point. For those with an initial balance point, the weight added after the initial balance point should be calculated.
When the working medium of the standard piston pressure gauge is liquid, after the calibration of each point, the initial balance point must be re-measured. The difference between the initial balance mass before and after the calibration shall not exceed the small code mass equivalent to 10% of the maximum allowable error of the point, otherwise the calibration shall be repeated.
Calculate the effective area of the float at each calibration point according to formula (1): Aro.i=
Where: Aro.
mriAso
The effective area of the float calculated at the i-th pressure calibration point of the tested float pressure gauge, m; The effective area of the piston of the standard piston pressure gauge, m; After the initial balance point, the code mass increased at the i-th calibration point of the tested float pressure gauge relative to the balance point, kg;
After the initial balance point, the basic code mass increased at the i-th calibration point of the standard piston pressure gauge relative to the balance point, kg.
Note: When the initial balance method is not used, mT. is the mass of all the codes and code racks (including the float) added to the tested float pressure gauge; ms, is the mass of all the codes, pistons and their connecting parts added to the standard piston pressure gauge. When the standard instrument is not a piston pressure gauge, the mass of the code added to the float pressure gauge and the actual pressure value of the standard instrument are recorded at each calibration point.
Calculate the effective area of the float at each calibration point according to formula (2): mT.ixxg
Where: β is the air buoyancy correction coefficient at the calibration site, see Appendix B; g
is the gravity acceleration at the calibration site, m/s2;
mT. is the mass of all the magnetic codes and code racks (including the float) on the tested float pressure gauge at the i-th calibration point, kg;
p:—The actual pressure value of the standard at the ith calibration point, Pa. 6.3.5.2 Calculation of effective area of the float
Calculate the average effective area of the float according to formula (3): Ato
where n is the number of calibrations.
The experimental standard deviation SA of the effective area value is
The limit error of the effective area of the float is
C(ATO.-AT)2
8A=±3SA
JJG942-2010
The maximum allowable error of the effective area of the float pressure gauge shall comply with the provisions of 4.2. 6.3.6 Verification of discrimination
Good with Dongheche
During the verification of the effective area of the float, the measurement is carried out when the upper limit is balanced. When the pressure is balanced, the minimum code mass value that can destroy the balance or cause the pressure value to change when added to the tested float pressure gauge is the discrimination of the float pressure gauge. 6.3.7 Effect of gas source change 6.3.7.1 Effect of pressure change For the automatic flow adjustment float pressure gauge, the operation should be carried out when the upper limit balance is measured during the float effective area verification. Adjust the gas source of the float pressure gauge to the lower limit and observe the change of the standard pressure. 6.3.7.2 Effect of flow change For the manual flow adjustment float pressure gauge, the operation should be carried out when the upper limit balance is measured during the float effective area verification. Adjust the input flow of the float force gauge to make the true change.
6.3.8 Quality inspection of special weights and weight racks (including floats)
The quality inspection of the weight rack (including floats) is carried out by special weights and weight racks.
According to the formula
, calculate the special code and
divisions, depending on the change in pressure of the standard instrument. According to JJG99-2006
, the mass of the code frame (including the float) is:
m-AXATX
Where: ㎡ special medical code, code frame and float mass, kp measured pressure value, Pa,
Amo—effective area of the ball being tested, m
β The buoyancy correction coefficient of the place of use is shown in Appendix Bg The gravity acceleration of the place where the float type meter is used, m6.3.9 Calibration of the periodic change rate of the effective area of the float "Code Calibration Regulations"
ISHING
The periodic change rate of the effective area of the float is mainly to ensure that the net ball or pressure gauge of the corresponding grade can meet the requirements of long-term stability.
SNAMEROLOGT
Calculate the periodic change rate of the effective area of the float according to formula (7): AA
Where: △A is the annual change rate of the effective area of the float, %; A is the effective area of the float last calibrated, m. 6.4 Handling of calibration results
A calibration certificate shall be issued for float pressure gauges that pass the calibration according to the requirements of this regulation: A calibration result notice shall be issued for float pressure gauges that fail the calibration, and the unqualified items shall be indicated. 6.5 Calibration cycle
The calibration cycle of float pressure gauges shall not exceed 1 year, and the last calibration certificate shall be attached when the gauge is sent for inspection.
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