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11METHOD FOR CALIBRATION OF CAPILLARY GLASS VISCOMETERS AND ASSESSMENT OF MEASUREMENT
UNCERTAINTY
1Sh.M.Masharipov, 2N.B. Atamirzaev, 3M.O. Khaidarova
Candidate of Technical Sciences, Associate Professor of the Department "Metrology, standardization and certification" Tashkent State Technical University named after Islam Karimov 2Doctoral student at the Namangan Institute of Engineering and Technology 3Doctoral student of the Namangan Institute of Engineering and Technology https://doi.org/10.5281/zenodo.10048541
Abstract. The article discusses current issues of creating conditions for improving the quality and competitiveness of domestic products through the development and improvement of calibration systems for measuring instruments, the development of mechanisms for mutually beneficial cooperation in the field of metrology with international and regional metrological organizations.
Keywords: regional metrological organizations, metrology, viscometer.
Testing and calibration laboratories ensuring metrological traceability to the International System of Units (SI) is one of the main technical requirements of the international standard ISO/IEC 17025:2017 "General requirements for the competence of testing and calibration laboratories", which is achieved by promoting the integration of the Republic of Uzbekistan into the international economy and international systems to ensure uniformity of measurements as an equal partner. Today, according to the State Unitary Enterprise "Accreditation Center", there are more than 600 laboratories in the state register, the technical competence of which has been officially confirmed.
Main part
Brief description of the calibration performed:
Calibration is carried out by measuring the flow time using two reference viscometers of the same class, selected depending on the viscometer whose capillary viscometer constant is to be determined.
Area of application/object of calibration:
Capillary viscometer constant
Range:
0,001 - 100 mm2/s2
Calibration process
Calibration setup
Figure 1. Capillary Viscometer Calibration Setup EQUIPMENT USED
Name of device Brand Type Serial number Explanation (period and place of calibiration)
0 75525
73942
0C 88545
75477
0B 94534
94540
1 95031
95032
1C 92315
93086
1B 92979
92960
2 85473 UKAS
Ubbelohde Psl-rheotek 91824 Calibration Certificate (ISO
Viscometer 2C 95628 17025)
95627 02.12.2021
2B 90629
92297
3 95520
95522
3C 94444
94443
3B 72258
93743
4 94428
94433
4C 74071
74067
4B 50875
70449
5 88534
88535
Device name Brand type Serial number Explanation (period and place of calibiration)
Viscometric bath Tamson TV7000 LT 19T024 1 year "UzNIM"
Glass thermometer TOT IMM AMA SR5/5OC 84785 TUBiTAK UME
Glass thermometer TOT IMM AMA GP/105C 83741 TUBiTAK UME
Millikelvin thermometer Anton Paar MKT 50 82779658 1 year "UzNIM"
Digital contact thermometer Tamson E20 41B108 1 year "UzNIM"
Stopwatch STOPWATCH ZSD-808 6079 TUBiTAK UME
Stopwatch Tamson Timer 8-channel 18TT41 TUBiTAK UME
Description of the calibration process
Determination of flow time
Set the temperature-controlled bath that will be used for calibration to the temperature at which the measurement will be made, then to better observe the temperature deviation, place a glass thermometer or digital contact thermometer in the temperature-controlled bath. Setting the temperature in the thermostat bath with instability in maintaining the set value during calibration ± 0.02 °C.
You can select Newtonian fluids in the table below according to your test viscometer
Name of group Liquid standard Flow time
0 between 350 - 450
0 1 between 600 - 800
2 between 1000 - 1500
0 between 180 - 250
between OC-1A 1 between 400 - 600
2 between 800 - 1200
between II-V 1 between 300 - 500
2 between 700 - 1200
It is possible to select the ubbelohde reference viscometers to match the test viscometers. You must use two viscometers that are the same size. Once the viscometer class has been determined, the flow time should be determined using the liquids taken from the table above using a test and reference viscometers.
1. Place the viscometers on the appropriate holders, which may be provided by the manufacturers.
2. The test liquid should be poured into viscometers to the point between the scaled lines.
(MF).
3. Viscometers filled with test liquids should be placed in a bath as shown in Figure 1. Before placing it, check whether the surface is smooth using a water bath (alcohol level). After installation, make sure that the height of the water in the bath is approximately 20 mm above the top liquid of the viscometer.
4. Make sure that the viscometers placed in the bath do not touch each other during the measurement. For this purpose also ensure verticality.
1. Ventilation pipe
2. Capillary tube
3. Filling tube
4. Upper reservoir
5. Synchronization lamp
6. Capillary
7. Pendant level lamp
8. Suspended level
9. Compensation tube
10. Bottom reservoir Ring marks Ml and M2 MF fill out the marks
Figure 2. Viscometer
Ubbelohde
5. Close the viscometer air duct using the device (plug) indicated
In picture labove.
6. Vacuum the liquid in the capillary tube (labeled 2 in Figure 2) of the viscometer from the top, either with an absorber or with a device, and lift it to approximately the top level of the upper liquid pan (labeled 4). Perform this operation very slowly to avoid the formation of air bubbles in the liquid. When the vacuum operation is finished, close the pipe from above using a device (plug).
7. Open the viscometer air duct (top) and wait until the liquid reaches the bottom of the immersion level marked 8 in Figure 2 (~5 minutes).
8. Open the capillary tube (labeled 2 in Figure 2) of the viscometer again and observe the downward movement of the liquid in the capillary tube and start the stopwatch when it reaches the line marked Ml. Stop the stopwatch when the liquid reaches the line marked M2.
9. Save the stopwatch value in the log and repeat the above processes for two viscometers (6, 7, 8, 9) and save 5 flow values. If the flow time is greater than 400s, you can take three measurements. You can omit the first measured flow time and take another measurement.
Formulas and calculations necessary to determine the kinematic viscosity and constant of the Ubbelohde viscometer.
Follow the following processes to calculate kinematic viscosity.
1. Determine the average flow time for each viscometer.
' =11 'i n
2. Find the relative difference between the longest and shortest flow times of each viscometer.
t -1
_ max_mm
s —
t
3. st check the t equation for both two viscometers. If there is no equality, repeat measurement.
f dmi.10- v < 1000mm2 /5
s <\
v [d^2.10-3 v > 1000mm2/ 5
4. The kinematic viscosity values of standard liquids can be determined using standard viscometers. The K0, K1, K2 values are calculated using the formula below using the average flow time (for each liquid we measured).
Y V0 • Y Vi ■ Y V2 •
K0 —— ; K1 — — ; K2 ;
'0 'i '2
5. The given viscometer constants can be used in the expression below and check whether the equation is equal, otherwise the measurement should be repeated using liquids for K1 and K2.
I* - K 2
U-21 < U'
'0 V
if the relative uncertainty of the viscosity U'v values is different, then the average of these values should be taken U'v and written instead.
6. If the calibrated viscometer is in the range of 0 to 1a, we should see if the requirements below are met.
|*0 - *2L15 1*1 - K\ |*0 - *1^15 |*i - K2I K 2 K2 K1 K 2
7. If the requirements are met, the kinetic energy correction must be calculated using the formula below
H — K2' '0 - v0' '02;
*If the value of H is positive, we have to find the adjusted flow time using the formula below and the value of K1 is again calculated using the adjusted flow time.
t = t - At = t —
llkorr 'l AtH 'l
H
vi- 'i
As a result, the test viscometer constant is calculated using the formula below.
|*i + K 21
K =
Model function
sk = skn ■ + sst + ös,nd +
Kinematic viscosity value of calibration fluid
Sk Constant value of the reference viscometer
àSTimer Influence of the chronometer used in the measurement
SSt Effect of expiration time
àSincl Tilt effect
àS3o Effect of temperature changes on measurement
Components of Uncertainty a) Viscometer constant S' 2
Explanations for the uncertainty associated with the reference viscometer
(skn )2 = 1(ukn )2
The calibration U'KN uncertainty of the Ubbelohde reference viscometer was calibrated by
the UKAS Viscosity Laboratory viscometer, where the coverage factor (volume) is k=2 and the confidence level is 95%.
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