GB/T 9171-1988 Determination of Borderline Pumping Temperature of Engine Oils

AI-translated method card — human verification pending. This is not an official translation of the standard. Unclear source values remain unverified; check the original standard and product certificate before use.

Card type: Test method

1. Method number / full name / English name / replacement relationship

• Standard number: GB 9171-88
• Chinese name: Determination of Borderline Pumping Temperature of Engine Oils
• English name: Engine oil — Determination of borderline pumping temperature
• Replacement relationship: not provided in the available source (the additional notes only state "equivalent adoption of ASTM D3829—79", and do not mention replacement of an old standard)
• Adoption relationship: equivalent adoption of the American Society for Testing and Materials standard ASTM D3829—79 "Standard Method for Predicting the Borderline Pumping Temperature of Engine Oils"
• Approval/implementation: approved by China Petrochemical Corporation 1988-04-22, implemented on 1989-04-01
• UDC number: UDC 621.892 : 536.5

2. Applicable scope and non-applicability

• Applicable to predicting the borderline pumping temperature of engine oils within the range of 0 ~ —40℃.
• Definition of borderline pumping temperature: the lowest temperature at which oil can be supplied continuously and adequately to the inlet of an engine oil pump.
• If only intended to satisfy certain specification or classification requirements, it is sufficient to determine only that the borderline pumping temperature is below a specified temperature (1.2).
• Non-applicable scope: not provided in the available source.

3. Method principle

1.1 The sample is cooled within 10h at a non-linear programmed cooling rate from 80℃ to the test-required temperature, and held at constant temperature for 16h. Then, on a rotational viscometer, a specified torque is gradually applied, the rotational speed is observed and measured, and the yield stress and apparent viscosity at that temperature are calculated. From the results obtained at three or more test temperatures, the borderline pumping temperature of the sample is determined.

4. Reagents and materials (purity / preparation)

• Calibration oil (4): a Newtonian oil with a low cloud point, with a viscosity at —20℃ of about 30 Pa·s, used to calibrate the viscometer constant of the viscometer unit.
• 2.5 calibration oil: a Newtonian fluid, with a viscosity at —20℃ of about 30 Pa·s, used to determine the range of the relationship curve between the apparent viscosity and speed of this instrument.
• Coolant (3.4): methanol or anhydrous ethanol; when using methanol, attention must be paid to the sealing of the entire circulation system, and anti-poisoning and anti-flammability measures must be observed.
• Rinsing solvent (7.4.3): petroleum ether, acetone.
• Weights: 2–3g weights (7.1.4), 10g, 30g, 40g, 50g and larger weights (7.2.4–7.2.7), 150g weights (6.2.6, 7.3).
• Fine cotton thread: radius 0.05mm (3.1), length 700mm (7.1.4).
• Purity requirements: not provided in the available source (reagent purity grades are not marked).

5. Instruments and equipment

• 3.1 Small rotational viscometer: composed of one or more viscometer units, each unit containing a calibrated rotor-stator component, with all units placed together in a temperature-controllable aluminum block. Standard dimensions:
  • Rotor diameter 17.0mm
  • Rotor length 20.0mm
  • Stator cup inner diameter 19.0mm
  • Shaft radius 3.18mm
  • Radius of the fine cotton thread 0.05mm
• 3.2 Calibrated thermometer: a thermometer with 80℃ graduations and a range of —36~30℃, with a scale division value of 0.2℃, used to measure the temperature of the aluminum block; other temperature-measuring instruments of equivalent accuracy may also be used.
• 3.3 Cooling equipment: cools to the predetermined test temperature under a controlled non-linear rate, with a temperature control range of —40~80℃.
• 3.4 Circulation system: supplies a suitable liquid coolant to the aluminum block.
• Others: pulley, copper block (with two marking rods standing upright), vacuum pump, transparent outer cover (lid), chart recorder (6.4, optional).

6. Recommended operating conditions

• Cooling program (7.1.7): the aluminum block heating rate is about 3℃/min, heated to 80±3℃ (the source text says "803C", requires confirmation against the source standard (source-text extraction)), automatically held at constant temperature for 2h, then automatically switched to the cooling program to carry out 10h non-linear cooling.
• Constant temperature: after cooling to the test-required temperature, hold at constant temperature for 16h (1.1, 7.1.8).
• Temperature calibration (6.1): each position of the temperature selector switch should be calibrated before use; the 0℃ position should reach temperature equilibrium within 30min, and when it deviates by 0±0.5℃, adjust it to 0±0.5℃ using the adjusting screw at the bottom of the instrument; calibrate the temperatures of the 5~—35℃ positions according to 6.1.1~6.1.2, to an accuracy of ±0.5℃.
• Viscometer constant calibration (6.2): carried out at —20℃; when the temperature drops to —20±0.2℃, hold at constant temperature for at least 1h; hang a 150g weight to measure the rotor rotational speed.
• Cooling rate check (6.4): during the 10h cooling period, the reset knob automatically turns one full turn counterclockwise per hour; during the final 6h constant-temperature period, the reset knob should no longer turn.
• Cooling temperature-time table for cooling to —20℃ over 10h (6.4):

7. Sampling and sample preparation

• 5 Sample: a representative sample free of suspended solids and water must be used. If the sample temperature in the container is below the indoor dew point temperature, it should be allowed to rise to room temperature before opening the container to take the sample.
• 7.1.1 If the viscometer unit is clean and at room temperature, take out 9 rotors.
• 7.1.2 Inject 10mL sample into each stator cup.
• 7.1.3 Place the rotor into the original stator cup according to the matching number, and install the upper center pin according to the matching number.

8. Analytical procedure

8.1 Preparation of sample and viscometer unit (7.1)

• 7.1.4 Starting from the first unit on the left, tie one end loop of the 700mm long fine cotton thread to the crossbar at the top of the rotor shaft, wind the long thread around the shaft, install the pulley so that the fine cotton thread hangs in the pulley groove, and hang a 2~3g weight in the loop at the hanging end of the fine cotton thread to straighten it. Turn the rotor shaft by hand, winding the thread around the rotor shaft one loop at a time without overlapping, leaving about 200mm of the tail of the fine cotton thread; when the red-marked end of the crossarm at the upper part of the rotor shaft rotates to the rear of the viscometer, bring the 200mm tail of the fine cotton thread upward over the bearing frame and place it behind that stator cup. Install the other viscometer units in sequence.
• 7.1.5 Cover the transparent outer cover lid to minimize frost formed on cold metal parts exposed to air (the extracted wording is garbled, requires confirmation against the source standard (source-text extraction)).
• 7.1.6 Set the temperature selector switch to the temperature position required by the test, turn the reset knob clockwise to the extreme position; turn the heating knob counterclockwise to the vertically upward position; set the power switch to the heating/cooling (HEAT/COOL) position, the indicator light turns on, and record the time.
• 7.1.7 According to Section 6, carry out the cooling program of heating, constant temperature, and cooling.
• 7.1.8 At the end of the constant-temperature cooling 16h, record the thermometer reading, remove the transparent cover lid of the viscometer unit, and note the calibration value for the temperature reading; at this time, even if the predetermined temperature is not precisely reached, no further adjustment of the temperature control is made, and the yield stress and apparent viscosity at that temperature are determined according to 7.2 and 7.3.

8.2 Determination of yield stress (7.2)

• 7.2.1 Starting from the viscometer unit on the left side of the instrument, test each viscometer unit in sequence.
• 7.2.2 Place the pulley directly in front of the unit to be tested, so that the pulley groove is in line with the rotor shaft, and let the fine cotton thread pass over the pulley and hang down to the front of the instrument; during measurement, ensure that the weights are away from the edge of the instrument.
• 7.2.3 Remove the fine cotton thread from the upper bearing bracket and place it on the pulley very carefully, without pulling the rotor shaft, so that the stator cup is not disturbed. Place the copper block with two upright marking rods in front of the viscometer unit and align it, so that timing is facilitated when the red-marked rotor shaft crossarm passes in front of the viscometer unit.
• 7.2.4 Carefully hang a 10g weight on the end of the fine cotton thread. If the amount of rotation within 15s is less than 10° (equivalent to a pulley peripheral rotation of 0.5mm), it is judged that no rotation is visible. Add another 10g weight, and so on.
• 7.2.5 If rotation occurs when a 30g weight is added, then the yield stress at that test temperature is lower than the critical yield stress, and then proceed according to 7.3.
• 7.2.6 If no rotation occurs when a 30g weight is added, and rotation occurs only when a 40g weight is added, then this yield stress may be called the critical yield stress, and then proceed according to 7.3.
• 7.2.7 If rotation occurs only when a 50g weight or a larger weight is added, record the mass of the weight at which no rotation occurs, and then proceed according to 7.3.

8.3 Determination of apparent viscosity (7.3)

• Hang a 150g weight on the loop of the fine cotton thread; when obvious rotation is observed, start timing from the moment the red end of the crossarm on the rotor shaft passes the alignment marker, and measure the time for three rotations. Unless the time for the first half rotation after timing starts exceeds 1min, in which case only record the time for one rotation.

8.4 Remaining units and cleaning (7.4)

• 7.4 Repeat 7.2~7.3 for each of the remaining viscometer units, with the test sequence from left to right.
• 7.4.1 After all units have been tested, turn the heating knob to the upward position so that the aluminum block is in the heating state, and heat the sample to room temperature or slightly higher.
• 7.4.2 Remove the upper shaft pin of the rotor, carefully take out the rotor, and if necessary also remove the bearing bracket.
• 7.4.3 Use a vacuum pump to extract the sample from the stator cup, rinse the stator cup at least twice with petroleum ether, then rinse twice with acetone, extract the rinsing solvent, and allow the acetone to evaporate dry.
• 7.4.4 Rinse the rotor in the same way.

8.5 Determination of borderline pumping temperature (7.5, 7.6)

• 7.5 First determine the temperatures at which the critical yield stress and the critical viscosity occur, and take the higher of the two as the borderline pumping temperature. For a sample, an abnormal situation may be observed in which its critical yield stress occurs at two different temperatures; to confirm that a higher BPT does not exist, the yield stress of the sample must be measured at a temperature 12±2℃ higher than the predicted BPT and at a temperature 7±2℃ higher than the predicted BPT. If the above two temperatures have already been measured in the test to determine yield stress, they need not be repeated.
• 7.6 If it is desired to determine that BPT is below a specified temperature, first measure the apparent viscosity and yield stress at that temperature; if both are below the specified borderline pumping temperature limit values, then measure the yield stress at temperatures 7±2℃ and 12±2℃ higher than the specified temperature.

9. Qualitative and Quantitative and Calculation Formulas

9.1 Definitions and Basic Formulas (Chapter 2)

• 2.1 Dynamic viscosity: a measure of the internal friction of a liquid when it flows under shear stress, and its value is the ratio of the shear stress applied to the flowing liquid to the shear rate; the legal unit of measurement is Pa·s, and cP is customarily used. 1cP = 10⁻³Pa·s = 1 mPa·s.
• Newtonian oil or liquid: an oil or liquid that exhibits constant viscosity at all shear rates or shear stresses as long as the temperature is constant.
• Non-Newtonian oil or liquid: an oil or liquid whose viscosity changes with changes in shear stress or shear rate.
• Apparent viscosity: the viscosity measured using this method.
• 2.7 Shear rate: the velocity gradient of liquid flow. For Newtonian liquids, in a concentric cylinder rotational viscometer, the shear rate is measured at the outer surface of the inner cylinder, ignoring any boundary effects. The rotor surface shear rate Gs (s⁻¹) is calculated according to formula (1) (the original formula source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction)).
  • For the specific dimensions specified in 3.1.1, the rotor surface shear rate Gs (s⁻¹) is calculated according to formula (2) (the original formula source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction)).
• 2.8 Shear stress: the force per unit area that drives liquid flow; the area refers to the shear surface, and the rotor surface of the rotational viscometer used in this method is the area subjected to shear.
  • The torque applied to the rotor Ts (N·m) is calculated according to formula (3): Ts = 9.81M(Ro + Rr) × 10⁻⁶ (the original source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction))
    • Where: M—— the applied mass, g; Ro—— the radius of the shaft, mm; Rr—— the radius of the fine cotton thread, mm.
  • The shear stress applied to the rotor surface Ss (Pa) is calculated according to formula (4) (the original formula source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction))
    • Where: rotor height, mm (the original symbol is missing, requires confirmation against the source standard (source-text extraction)).
  • For the specific dimensions specified in 3.1.1, the torque applied to the rotor T (N·m) is calculated according to formula (5): T = 31.7M × 10⁻⁶ (the original "10-8", requires confirmation against the source standard (source-text extraction))
  • The shear stress applied to the rotor surface Ss (Pa) is calculated according to formula (6): Ss = 3.5M
• 2.9 Yield stress: the shear stress required for a liquid to just begin to flow; for all Newtonian liquids and some non-Newtonian liquids, the yield stress is equal to zero. Some engine oils have a yield stress, which is a function of low-temperature cooling rate, constant-temperature time, and temperature.
• 2.10 Critical yield stress: the maximum yield stress that allows lubricating oil to flow to the inlet of an automobile engine screen. At higher yield stresses, air may be drawn into the oil pump, and due to oil pump cavitation, suitable oil pressure cannot be maintained.
• 2.11 Critical viscosity: at a certain shear rate, the maximum viscosity allowed for oil to flow smoothly to an automobile engine oil pump. Above this viscosity, the flow of oil to the oil screen or oil inlet pipe is restricted, thereby resulting in failure to maintain the required oil pressure.
• 2.12 Borderline pumping temperature: the highest temperature at which critical yield stress or critical viscosity occurs, and whichever temperature it is, the higher temperature is taken.

9.2 Viscometer Constant (6.2.8)

• The viscometer constant C (Pa/B) of each viscometer unit is calculated according to formula (8) (the original formula (7) source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction)):
  • When using the 150g weight for measurement: η₇₀ = C · tsr (the original is written as "70=C•tsr", requires confirmation against the source standard (source-text extraction))
  • Where: η—— the viscosity of the calibration oil at —20℃, Pa·s; tsr—— the time required for the rotor to make three revolutions, s.

9.3 Yield Stress Calculation and "Vapor-Lock Type" BPT (8.1)

• 8.1.1 If rotation is observed when the 30g weight is added, the yield stress will be less than 105 Pa, and for this method this yield stress can be determined to be zero.
• 8.1.2 If rotation begins only when a weight greater than 30g is added, the shear stress of the maximum mass that does not cause rotation should be calculated according to formula (7) in clause 2.8 (the original "formula (7)", requires confirmation against the source standard (source-text extraction)); the calculated shear stress is called the yield stress.
• 8.1.3 The BPT at which the oil pump fails to pump due to "vapor lock" occurs at the 105 Pa critical yield stress (equivalent to the 30g weight). A curve of yield stress versus temperature may be plotted, and after repeating Chapter 7 at different temperatures, the temperature at 105 Pa may be obtained by extrapolation or interpolation.
• 8.1.4 Rounding the temperature corresponding to a yield stress of 105 Pa to the nearest 0.5℃ gives the "vapor-lock type" borderline pumping temperature (BPT).

9.4 Viscosity Calculation and "Flow-Limited Type" BPT (8.2)

• 8.2.1 The apparent viscosity η (Pa·s) of the sample at each temperature is calculated according to formula (9) (the original formula source-text extraction is incomplete, requires confirmation against the source standard (source-text extraction)):
  • Where: M—— the applied weight mass, g; tsr—— the time for the rotor to make three revolutions, s; C—— the viscometer constant of that viscometer unit, Pa/B.
• 8.2.2 From the graph of apparent viscosity versus temperature, interpolation may be used to obtain the temperature at which the apparent viscosity is 30 Pa·s. This temperature is the BPT at which pumping fails due to "flow limitation". Extrapolation must not be used to obtain data; if necessary, repeat the procedure of Chapter 7 at another temperature.
• 8.3 From the two temperatures determined in 8.1.4 and 8.2.2, select the higher temperature, round it to the nearest 0.5℃, and use it as the borderline pumping temperature (BPT).

10. Precision

The reliability of test results is judged by the following provisions (95% confidence level).

• 9.1 Repeatability: the difference between two results obtained by repeated measurement by the same operator shall not be greater than 1.3℃.
• 9.2 Reproducibility: the difference between two results submitted by two different laboratories shall not be greater than 3.2℃.
• Note: The precision of this method was obtained by statistical testing of results from tests of 13 representative commercial samples in different laboratories; the borderline pumping temperatures BPT of these 13 samples are in the range —14.5~—36℃ (the original "-14.5~ 36C", requires confirmation against the source standard (source-text extraction)).

11. Report

• 10.1 Report the arithmetic mean of the borderline pumping temperatures (BPT) from two repeated determinations carried out according to clauses 8.1~8.3 as the borderline pumping temperature (BPT) of the sample, ℃.
• 10.2 If necessary, it is also permissible to report only that the borderline pumping temperature is below a specified temperature.

12. Referenced Documents

• ASTM D3829—79 "Standard Method for Predicting the Borderline Pumping Temperature of Engine Oils" (equivalent adoption).
• Other referenced documents: not provided in the available source.

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Reference Q&A