GB/T 6538-2022 PDF in English
GB/T 6538-2022 (GB/T6538-2022, GBT 6538-2022, GBT6538-2022)
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Determination of apparent viscosity of engine oils - Using the cold-cranking simulator
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| GB/T 6538-2010 | English | 559 |
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Determination of apparent viscosity of engine oils using the cold-cranking simulator
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Standards related to (historical): GB/T 6538-2022
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GB/T 6538-2022: PDF in English (GBT 6538-2022) GB/T 6538-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 75.100
CCS E 34
Replacing GB/T 6538-2010
Determination of Apparent Viscosity of Engine Oil – Using
the Cold-Cranking Simulator
ISSUED ON: OCTOBER 12, 2022
IMPLEMENTED ON: OCTOBER 12, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 5
1 Scope ... 6
2 Normative References ... 6
3 Terms and Definitions ... 6
4 Overview of Method ... 7
5 Instrument ... 8
6 Reagents and Materials ... 9
7 Sampling ... 11
8 Calibration ... 12
9 Operation Procedure of Automatic Cold Cranking Simulator (CCS) ... 14
10 Report on Results ... 15
11 Precision and Bias ... 15
Appendix A (Normative) Manual Operation Procedures of Cold Cranking Simulator
(CCS) ... 17
Appendix B (Normative) Special Procedure for the Determination of Highly
Viscoelastic Oils Using a Manual Cold Cranking Simulator (CCS) ... 23
Appendix C (Informative) Calibration Oil Specifications ... 25
Appendix D (Informative) Calibration Flow Chart ... 26
Appendix E (Normative) Special Procedure of Micro Sample Adapter ... 28
Bibliography ... 30
Determination of Apparent Viscosity of Engine Oil – Using
the Cold-Cranking Simulator
CAUTION: Personnel using this Document shall have practical experience working in
formal laboratory. The use of this Document may involve certain hazardous materials,
equipment and operations; and this Document does not point out all possible safety issues.
It is the user's responsibility to take appropriate safety and health measures and ensure
compliance with the conditions stipulated in the relevant national laws and regulations.
1 Scope
This Document specifies a method for the determination of the apparent viscosity of engine oils
using the Cold Cranking Simulator (CCS) method.
This Document is applicable to engine oils whose temperature is -10°C ~ -35°C and whose
apparent viscosity is 900mPa·s ~ 25000mPa·s.
2 Normative References
The provisions in following documents become the essential provisions of this Document
through reference in this Document. For the dated documents, only the versions with the dates
indicated are applicable to this Document; for the undated documents, only the latest version
(including all the amendments) is applicable to this Document.
GB/T 4756 Petroleum Liquids - Manual Sampling
3 Terms and Definitions
For the purposes of this Document, the following terms and definitions apply.
3.1 Newtonian fluid
The fluid whose viscosity does not change with the shear rate.
[SOURCE: GB/T 4016-2019, 2.05.018]
3.2 Non-Newtonian fluid
position close to the inner wall of the stator. Calibrate the rotor speed as a function of apparent
viscosity. Determine the apparent viscosity of the specimen from the calibrated and measured
values of the rotor speed. This Document provides manual and automatic methods for
determining the apparent viscosity of engine oil by a Cold Cranking Simulator (CCS). The main
text applies to the automatic Cold Cranking Simulator (CCS); while the Appendix A applies to
the manual Cold Cranking Simulator (CCS); Appendix B applies to the determination of high
viscoelastic oil.
5 Instrument
5.1 Type of instrument
There are two types of instruments that can be used in this Document. 5.2 and 5.3 give detailed
regulations for automatic Cold Cranking Simulators (CCS); and A.1 gives specific regulations
for manual Cold Cranking Stimulators (CCS).
5.2 Automatic Cold Cranking Simulator (CCS)
The automatic Cold Cranking Simulators (CCS) consists of the following parts:
--- Direct Current (D.C.) motors, capable of driving the rotor (located in the stator);
--- Speed sensor, used to measure the rotor speed;
--- D.C. ammeter and precise current adjustment knob;
--- The stator temperature control system can ensure that the temperature is controlled at
±0.05°C of the set temperature;
--- Circulating refrigerator, used in conjunction with temperature control system;
--- Test sample injector;
--- Computer including computer interface.
5.3 Autosampler
Under the control of a computer, without the intervention of the operator, it is a device that can
continuously measure the test sample for multiple times.
5.4 Calibrated thermocouples
Placed near the inner surface of the stator, used to indicate the test temperature. The temperature
sensor should have good thermal contact with the inner surface of the stator; regularly clean the
inner surface of the stator and replace the heat-conducting medium with high silver content.
5.5 Refrigeration system
5.5.1 The requirements for stators cooled by coolant are as follows.
--- For the stator in contact with the coolant, the temperature of the coolant is kept at least
10°C lower than the test temperature by means of a refrigerator.
--- When the refrigeration temperature is lower than -30℃, a two-stage refrigeration system
may be required.
--- The connecting pipe between the Cold Cranking Simulator (CCS) and the refrigerator
shall be as short as possible (less than 1 m) and have good heat insulation measures.
--- The coolant is absolute ethanol or absolute methanol. If the humidity in the environment
where the coolant is used is high, causing absolute ethanol or absolute methanol to absorb
water, it shall be replaced with new absolute ethanol or absolute methanol to ensure that
the temperature is within a controllable range.
--- If absolute ethanol or absolute methanol leaks from the instrument, the leak shall be dealt
with before continuing the test.
5.5.2 The requirements for stator cooled by thermoelectric refrigeration are as follows:
--- In order to maintain the test specimen temperature, the cooling temperature of water or
other suitable liquid shall be around 5°C;
--- In order to prevent the coolant from freezing and blocking the pipeline of the refrigerator,
the coolant shall contain 10% ethylene glycol or other solutions that meet the
manufacturer's instructions.
5.6 Ultrasonic bath
5.6.1 Optional equipment, the working frequency is 25Hz ~ 60Hz, the typical output power is
no more than 100W, the size is required to accommodate the sample cup, and it has no heating
function. It can be used for heat dissipation and defoaming treatment of viscous samples before
testing.
5.6.2 Ultrasonic baths with operating frequency and output power exceeding the above range
can be used, but the laboratory shall compare the data to ensure that the test results obtained
from these two types of ultrasonic baths are consistent.
6 Reagents and Materials
6.1 Acetone: analytically pure.
Warning: Flammable, harmful to health.
the test, the sample shall not be shaken, otherwise the sample will easily entrain air and lead to
wrong apparent viscosity results.
7.2 For some types of samples, such as viscous lubricating oil that is easy to entrain air or air
bubbles in the sample, an ultrasonic bath with the heating function not turned on (see 5.6) can
be used. Generally, 5 minutes of ultrasonication can effectively defoam.
8 Calibration
8.1 Current check cycle
The motor current shall be measured when starting a new instrument or when changing the
driving parts of the viscosity cell (motor, belt, speed sensor, etc.). Initially the motor current
shall be rechecked every month (see 8.3) until the variation of the motor current is less than
0.005A for several consecutive months, thereafter, check it every three months. Appendix D
gives a flow chart of the calibration process.
8.2 Temperature calibration
8.2.1 Use the Temperature Verification Plug (TVP) to verify that the instrument is able to
accurately calculate the temperature.
8.2.2 Unplug the temperature sensor plug from the rear panel of the instrument, and plug in the
high temperature plug of the temperature calibration plug.
8.2.3 Select the temperature calibration function from the computer software, input the
resistance value of the corresponding temperature calibration plug, and record the displayed
temperature difference.
8.2.4 Repeat the above operation with the second plug.
8.2.5 The recorded temperature difference shall be less than 0.06°C, otherwise contact the
instrument manufacturer for maintenance.
8.3 Calibration and verification of current
8.3.1 Select the option to set the motor current on the computer software, run the calibration oil
with an apparent viscosity of about 3500mPa·s at a temperature of -20°C; and the CL250 meets
the requirements of this Document. This procedure will cool the sample to -20 °C and keep the
temperature constant. If it is recalibration, operate according to 8.3.2. If it is to check the motor
current, operate according to 8.3.3.
8.3.2 After the motor starts for 20 seconds, monitor the motor speed; and adjust the current
adjustment knob to set the speed to 0.240kr/min±0.001kr/min (displayed in "SPEED" on the
computer screen). Complete this procedure within 50s ~ 75s after starting. If it times out, repeat
8.6 Calibration requirements
8.6.1 The regression coefficient automatically calculated by the software is no less than 0.99.
8.6.2 The deviation between the calibration data and the certified apparent viscosity value of
the calibration oil shall not exceed 1.6%, preferably all deviations shall be less than 1%.
8.6.3 If more than 3 pairs of data are discarded due to out-of-tolerance at each test temperature,
re-calibration shall be conducted. If the recalibration is done within 4 working days using a
complete set of calibration oils, the calculated regression coefficients may include test data for
all calibration oils. If only the calibration oil whose data has been discarded is retested, then
two calibration oils with previously retained data shall be added when retesting.
8.6.4 At the test temperature, the calibration data shall be collected in the shortest possible time.
When the time interval between starting and completing a calibration at a certain temperature
exceeds 4 working days, the operator shall retest one or two calibration oils measured earlier
and include the data in the calibration analysis. It is to ensure that the instrument is operating
under the same conditions as when the calibration was started. If the operator regularly adds
calibration data to the confirmed valid calibration data, the 4 working day period no longer
applies.
8.6.5 After deleting the outlier data, the calibration data at each temperature shall contain at
least 10 data points; and the apparent viscosity values shall be uniformly distributed in the used
apparent viscosity range.
9 Operation Procedure of Automatic Cold Cranking
Simulator (CCS)
9.1 Add at least 55 mL of sample to a 60 mL sample cup. For high viscoelastic oil, it can be
operated according to Appendix B. When using micro-sample adapter, the operating procedures
are specified in Appendix E.
NOTE: When using an autosampler, ensure that the size of the sample cup matches the sample tray and
that the sample injection tube does not touch the bottom of the sample cup, preventing aspiration of
sedimented material into the instrument.
9.2 Enter the sample number and test temperature.
9.3 For instruments equipped with an autosampler, repeat procedures in 9.1 and 9.2 until all
sample cups are on the sample tray and all sample information is entered into the computer test
form. It is recommended to add a quality control sample to each set of specimens.
9.4 Follow the instructions of the instrument software to start testing the sample. During the
test, the instrument cools the temperature of the specimen to close to the test temperature, and
keeps the temperature constant for 180s. Then start the motor and record the speed, but only
the average speed of 55s ~ 60s is used to calculate the apparent viscosity.
NOTE: The new specimen will automatically replace the previous specimen, no solvent cleaning is
required. Both temperature and motor operation are computer controlled. The measurement of the motor
speed and the calculation of the apparent viscosity of the specimen are executed and displayed by the
computer.
9.5 If the difference between the test results of the quality control samples and the expected
value exceeds the reproducibility range of this Document, the test results of this group of
samples are suspicious. If two consecutive sets of results are suspicious, recheck the rotor speed
by calibration oil CL250 at -20°C. If the rotor speed exceeds 0.240kr/min±0.005kr/min, find
and solve the cause of the deviation, and recalibrate.
10 Report on Results
Report the apparent viscosity and temperature displayed on the computer monitor.
11 Precision and Bias
11.1 Overview
The precision of this Document is obtained from the statistics of samples with a measurement
temperature of -20°C ~ -35°C and an apparent viscosity of 2700mPa·s ~ 15000mPa·s. Judge
the reliability of the test results (95% confidence level) according to the provisions of 11.2 and
11.3.
NOTE: The precision of this document is obtained through statistical calculation by the CCS-
4/5 instrument with version 4.X or higher software (coolant cooling) and the CCS-2050/2100
instrument equipped with ViscPro CCS software (thermoelectric cooling). The temperature
range of the test sample is -20 ℃ ~ -35 ℃; and the apparent viscosity range is 2700mPa·s ~
15000mPa·s.
11.2 Repeatability (r)
The difference between two consecutive test results obtained by the same operator in the same
laboratory, using the same instrument and the same method to measure the same sample shall
not exceed the repeatability limit specified in Table 2.
11.3 Reproducibility (R)
The difference between two single, independent test results obtained by different operators in
different laboratories, using different instruments and the same method to measure the same
sample separately shall not exceed the reproducibility limits specified in Table 2.
Appendix A
(Normative)
Manual Operation Procedures of Cold Cranking Simulator
(CCS)
A.1 Instrument
A.1.1 Manual Cold Cranking Simulator (CCS) includes the following parts:
--- Direct current (D.C.) motors, capable of driving the rotor (located in the stator);
--- Speed sensor, used to measure the rotor speed;
--- D.C. ammeter and precise current adjustment knob;
--- Stator temperature control system can ensure that the temperature is controlled at
±0.05°C of the set temperature;
--- Circulating refrigerator, used in conjunction with the temperature control system.
A.1.2 Thermocouple: Shall be calibrated and placed near the inner surface of the stator to
indicate the test temperature.
A.1.3 Refrigeration system: Control the coolant temperature so that its temperature is at least
10 °C lower than the test temperature. It is best to cool by mechanical mode; and a dry ice
refrigeration system can also achieve satisfactory results. The connecting pipe between the Cold
Cranking Simulator (CCS) and the refrigerator shall be as short as possible and have good heat
insulation measures. The coolant used in the refrigeration system is absolute methanol or
absolute ethanol.
A.1.4 Temperature sensor: It shall be in good thermal contact with the inner surface of the stator.
Regularly clean the inner surface of the stator and replace the heat-conducting medium with
high silver content. Adjust the temperature of the coolant so that the temperature of the viscosity
cell is at least 10°C lower than the test temperature.
A.1.5 Methanol or ethanol circulator: Optional equipment, only applicable to manual Cold
Cranking Simulator (CCS). The device provides hot methanol or ethanol to the stator for easy
sample replacement and evaporation of cleaning agents.
A.2 Reagents and materials
See Clause 6.
Establish a calibration curve or equation (see Clause 8). Before performing a series of
determinations, at the test temperature, the instrument and calibration shall be thoroughly
checked with at least one calibration oil. When running the sample for inspection (see Appendix
C), if the difference between the displayed motor current and the current determined in A.3.2
is greater than 0.005A, the current value shall be reset. After running for 15s according to A.3.2,
observe and correct the current value. When the difference between the test value of the
calibration oil and the standard value is greater than ±5%, it is necessary to re-test to ensure
that the test result is correct. If the test result of the calibration oil is correct, re-calibrate
according to A.3.3. Perform a comprehensive check of instrument performance at least monthly
by quality control samples or reference samples.
NOTE: During the entire operation of the instrument, keep the cooling pool well stirred; otherwise, there
will be a large temperature difference inside the cooling pool. These temperature differences will affect
the temperature of the sample and reduce the accuracy of the viscosity measurement.
A.4.2 Operation procedure of Cold Cranking Simulator (CCS)
A.4.2.1 Use a dropper to inject the specimen into the oil filling pipe to ensure that the specimen
fills the gap between the rotor and the stator; and a small amount of specimen is covered above
the rotor to completely fill the cup. Turn the rotor by hand to ensure that the surfaces of the
rotor and stator are completely wetted as the specimen flows through. Fill the injection tube
completely and insert a rubber stopper at the end of the tube. For viscoelastic oils, when the
motor is started (see A.4.2.2), the rubber stopper shall be compressed in order to prevent the
sample from pushing the rubber stopper out of the tube and emptying the specimen in the shear
zone of the viscosity cell. If this operation cannot prevent the specimen being emptied from the
viscosity cell, appendix B shall be carried out. See Appendix B for special procedure for high
viscoelastic oils.
NOTE: Some specimens are so viscous at room temperature that they cannot flow into the gap between
the rotor and the stator. Those specimens whose kinematic viscosity exceeds 100mm2/s at room
temperature can be heated (not exceeding 50°C) and then injected into the viscosity cell.
A.4.2.2 Turn on the refrigeration system (A.1.3) and temperature control (A.1.4) switches to
cool the stator. Record how long the coolant runs out (use a stopwatch or other timer that counts
seconds). If the test temperature is as low as -20°C, it shall reach the control temperature within
30s~60s; if the test temperature is as low as -30°C, it shall reach the control temperature within
60s~90s and adjust the instrument test temperature. If the test temperature of -20°C, reach the
test temperature of -30°C within 60s~90s. If these requirements are not met, the coolant shall
be replaced with absolute methanol or absolute ethanol (see 6.2 or 6.3), or the cooling
temperature of absolute methanol or absolute ethanol shall be adjusted. The zero temperature
indication of the temperature indicating instrument and the coolant circulation control system
reaches the test temperature. Adjust the setting button of the instrument used for temperature
indication so that the reading of the instrument is slightly to the left of zero, so that when starting
the motor at the test temperature, there is no need to make too many adjustments.
If the time to reach the control temperature is too slow to meet the above requirements, the
coolant shall be replaced with absolute methanol or absolute ethanol (see 6.2 or 6.3) or reduce
the temperature of absolute methanol or absolute ethanol (see 6.2 or 6.3).
If the time to reach the control temperature is faster than the required time, the temperature of
the coolant absolute methanol or absolute ethanol shall be increased to obtain a more
satisfactory temperature control effect.
A.4.2.3 Turn on the motor 180s±3s after the coolant flows out.
A.4.2.4 Connect the plug of the speed sensor to the interface marked "CAL"; and record the
reading of the speedometer immediately after the motor is turned on. If the tachometer reading
rises and then quickly falls to a position at least 5% below the maximum reading, there may be
residual solvent in the shear zone. Abnormal changes in digital speedometers or deflection of
analog gauge needles can also occur with poor temperature control (watch the thermometer
reading). The most common case is poor contact between the thermocouple and the temperature
measuring hole on the stator. At this time, the operation shall be terminated, the sample shall
be taken out and cleaned according to the procedure in A.4.3; and the new specimen shall be
re-run according to the procedure in A.4.2.
A.4.2.5 Record the speed 60s±5s after the motor is started. In the absence of a digital instrument,
the reading of the analog instrument is estimated to one-tenth of the smallest division. Turn off
the motor and coolant control switches.
A.4.3 Cleaning procedures of Cold Cranking Simulator (CCS)
A.4.3.1 When cleaning, turn on the methanol or ethanol circulator to heat the stator (35 ℃ ~
45 ℃), keep the flow of hot methanol or ethanol until A.4.3.2 is completed, A.4.3.3 is an
alternative method.
A.4.3.2 Clean the rotor/stator block first with petroleum ether and then with acetone (the solvent
is flammable and shall be used with care); and dry the viscosity measuring cell with a vacuum
pump. In the final stage of drying, turn the rotor several times by hand to ensure that the gap
between the rotor and stator is clean and dry.
A.4.3.3 According to the procedures in A.4.2, at least 30mL of the next sample can be used to
wash the original sample in the viscosity cell and fill it up. This method can be used as
alternative method for a solvent cleaning method in A.4.3.1 and A.4.3.2.
A.4.4 Protection measures of Cold Cranking Simulator (CCS)
To prevent damage to the instrument due to accidental starting, keep the last sample in the
instrument after completing all tests. This specimen can also be used as the first specimen to
run after the instrument has been stopped for a period of time, so that the electronic components
and motors in the instrument can be preheated, and the speed sensor of this specimen is not
recorded before testing a new specimen.
Appendix B
(Normative)
Special Procedure for the Determination of Highly
Viscoelastic Oils Using a Manual Cold Cranking Simulator
(CCS)
B.1 The specimens on the Cold Cranking Simulator (CCS) under low temperature conditions
will show different characteristics, which in turn requires corresponding changes in the test
procedures. After the rotor is started, some highly viscoelastic oil will spiral along the direction
of the rotor axis. If the specimen climbs up from the shear zone; the speed of the rotor will
increase significantly. Generally, the test procedure in Clause 8 can be ensured smoothly by
adding a rubber stopper to the sample injection tube (see A.4.2); however, a special test
procedure shall be used for specimens with high viscoelasticity. The test procedures in B.2 to
B.7 can be used for both viscoelastic and non-viscoelastic specimens. In a very short period of
time, B.5 has more complicated operation procedures than A.4.2. Since the calibration curve
will vary slightly, the calibration oil shall be run in the same procedure.
B.2 Use a dropper to add the specimen to the sample injection tube so that it fills the gap
between the rotor and the stator, so that the liquid level is about 1mm above the rotor. When
the specimen overflows from both sides of the rotor, turn the rotor by hand to ensure that the
specimen completely saturates the surface of the rotor and stator.
B.3 Turn on the temperature and coolant control switch to cool the stator. Control the test
temperature to be below -20°C in 30s~60s; control the test temperature to be below -30°C in
60s~90s. Confirm the selected test temperature, start the motor of the Cold Cranking Simulator
(CCS); and run a low viscosity specimen to set the temperature set point of the coolant circulator.
The temperature of the coolant supplied to the viscosity cell shall be about 10°C lower than the
test temperature. There shall be good heat transfer between the temperature probe and the
temperature measuring hole on the stator; the temperature measuring hole shall be cleaned
regularly (see A.1.4).
B.4 Set the zero-adjustment knob at a position slightly lower than the test temperature, so that
when the rotor is started at the test temperature, it is not necessary to adjust the temperature too
much.
B.5 When the test temperature is reached, start the timer (according to the action of the
temperature indicating instrument and the coolant circulator). After the timer is started for
10s±2s, directly add supplementary sample to the viscosity cell to make the viscosity cell
completely full.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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