NB/SH/T 0906-2015 Determination of thermal stability of engine oils — Heat tube test method

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Card type: Test method

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

• Standard number: NB/SH/T 0906—2015
• Chinese title: Determination of thermal stability of engine oils — Heat tube test method
• English title: Determination of high temperature deposits of engine oils by hot tube test
• Replacement relationship: first publication; not provided in the available source whether it replaces other standards.
• Adoption relationship: adopted by the redrafting method with modifications from the relevant content of the Japan Petroleum Institute JPI-5S-55-99 "Engine Oils — Determination of High-Temperature Deposits (Heat Tube Test Method)".
• Main technical differences from JPI-5S-55-99: in accordance with the drafting conventions of our country's standards, the relevant content of Chapter 2 "Normative References" and Chapter 7 "Reagents and Materials" has been added.
• Publication/implementation: published on 2015-10-27, implemented on 2016-03-01.
• Custodianship: Subcommittee on Petroleum Fuels and Lubricants of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC280/SC1).
• Drafting organization: Sinopec Lubricant Co., Ltd. Shanghai R&D Center.
• Main drafters: Zheng Jinhua, Qin Zhenqing, Wang Xiaoyun.

2. Scope of application and non-applicability

• This standard specifies the test procedure for determining the thermal stability performance of engine oils using a heat tube tester or other equivalent equipment.
• It is applicable to the determination of the thermal stability performance of engine oils (such as marine engine oils, gasoline engine oils, diesel engine oils and two-stroke engine oils).
• Evaluation is carried out by method A (heat tube color rating standard) or method B (deposit mass).
• Non-applicable scope: not provided in the available source.

3. Method principle

• Inject the test oil into a high-temperature heat tube, insert it vertically into the heating furnace, then introduce compressed air from the bottom of the heat tube, with a compressed air flow rate of 10.0 cm²/min, an oil injection rate of 0.31 cm³/h, and a test duration of 16 h; during the test, the test oil will form a lacquer film on the inner wall of the glass heat tube.
• After the test is completed, rinse the test heat tube with petroleum ether; after drying, rate the lacquer film of the test heat tube using the color rating standard, and report the result to 0.5 grade. Alternatively, weigh the lacquer film in the heat tube or the deposits in the heat tube after the test is completed.

4. Reagents and materials (purity / preparation)

• 7.1 Water: shall meet the requirements for grade three water in GB/T 6682—2008.
• 7.2 n-Heptane: chemically pure.
• 7.3 Cleaning solvent: petroleum ether, 60 ℃~90 ℃. Note: volatile solvent, keep away from ignition sources.
• 7.4 Hydrochloric acid: analytically pure, mass fraction about 36%, prepared into dilute hydrochloric acid with a mass fraction of 5%.

5. Apparatus and equipment

• 6.1 Test heat tube: made of heat-resistant glass into the shape shown in Figure 2; the edge A shall be appropriately rounded during fabrication to prevent cutting the O-type ring; performance shall meet the requirements of HG/T 3115 or the special heat tube of Komatsu Engineering Company. Figure 2 labels: inner diameter 2±0.1 (the unit in the original text is millimeter, source-text extraction doubtful point requires confirmation against the source standard), inner diameter 4±0.2, total length 385±0.5.
• 6.2 Heating furnace: used to heat the test heat tube, composed of a metal bath, insulation layer, thermometer and heater.
  • 6.2.1 Metal bath: a metal block with a diameter of 90 mm, whose function is to minimize temperature changes and prevent temperature variations during the test; the hole for placing the test heat tube, six holes for placing heaters and 2 holes for placing thermal sensors all pass through the metal bath.
  • 6.2.2 Insulation layer: tightly surrounds the metal bath to prevent outward thermal radiation from the metal bath; the bottom and top of the insulation layer are composed of an air layer of 13 mm and an insulation material of 20 mm, and the surroundings are composed of an air layer of 5 mm and an insulation material of 30 mm.
  • 6.2.3 Thermometer: sheathed thermocouple (nickel-chromium alloy-nickel-aluminum alloy); if other types of thermocouples are used, they are required to have resistance under high-temperature oxygen conditions and, at around 300 ℃, to be comparable to the sheathed thermocouple in temperature sensitivity and temperature-sensing accuracy; when a temperature controller is used together with this type of thermocouple, adopting a proportional-integral-derivative (PID) type temperature control mode can achieve more precise temperature control.
  • 6.2.4 Heater: the output power of each heater shall be not less than 60 W; the relative positional distribution of the six heaters, the test heat tube and the thermometer is shown in Figure 3.
• 6.3 Oil injection unit: within 16 h of the test, it can push 6 syringes at a rate of 0.31 cm³/h±0.01 cm³/h to inject the test oil into the test heat tube, as shown in Figure 4. Note: the circular groove used to fix the syringes is made of transparent plastic, and the cylindrical groove is engraved with horizontal scale lines for the test oil amount.
• 6.4 Test oil container (syringe): volume 5 cm³, can hold 0 cm³–5 cm³ of test oil. Note: the piston diameter of this syringe is designed to be 12.1 mm–12.4 mm.
• 6.5 Compressed air supply unit: compressed air of 200 kPa–400 kPa provided by an air compressor is adjusted by a pressure reducing valve to a pressure of 30 kPa–45 kPa; it is evenly distributed to 6 plastic tubes through a gas distributor; the air flow rate in each plastic tube shall be adjusted to 10 cm³/min±0.5 cm³/min, and can be adjusted with a precise flow control valve to allow the compressed air to enter the acrylic component.
• 6.6 Acrylic resin component: shall have a T-type passage structure, made of transparent non-oil-soluble plastic, so as to observe the flow of oil in the passage; the air connection tube and the oil tube are respectively connected to the joints at the bottom and side of the acrylic resin component; the test heat tube used for testing is fixed and connected at the top of the acrylic resin component with a O-type rubber ring, and is fixed at the bottom of the acrylic resin component with a butterfly valve nut to prevent leakage of air and oil.
• 6.7 Connection tubes: the lines used to provide air and test oil, namely the air connection tube and the oil tube, shall be flexible and transparent (inner diameter 4 mm), and shall be made of materials insoluble in oil and petroleum ether.
• 6.8 Oven: after the test is completed, the test heat tube cleaned with petroleum ether is dried in an oven; an explosion-proof oven is recommended.

6. Recommended operating conditions

• Air flow rate: 10.0 cm²/min (4.1); in the test procedure it is 10 cm³/min±0.5 cm³/min (6.5, 9.1.3, 9.1.9).
• Oil injection rate: 0.31 cm³/h (4.1); oil injection unit rate 0.31 cm³/h±0.01 cm³/h (6.3).
• Test duration: 16 h (4.1, 6.3, 9.4.1).
• Test temperature (5.1): gasoline engine oil 280 ℃~310 ℃; diesel engine oil, two-stroke engine oil and marine engine oil 280 ℃~320 ℃; two-stroke engine oil 260 ℃~290 ℃; marine engine oil 300 ℃~330 ℃ (in the original text, this paragraph source-text extraction is misaligned, and the correspondence between temperature and oil type requires confirmation against the source standard (source-text extraction)).
• Heating furnace temperature adjustment: 8.1.2 set to 290 ℃; after 8.1.3 stabilizes, the temperature shall be within 290 ℃±1 ℃; 8.1.4 measure the temperature again at 310 ℃; 8.1.5 for other test temperatures, measure the temperature in the same manner according to product specifications or agreement requirements.
• Temperature fluctuation: the test officially begins when the test temperature is reached and the temperature fluctuation is within ±1 ℃ (9.3.4).
• Air pressure: adjust the pressure reducing valve to 30 kPa~45 kPa (9.1.1).

7. Sampling and sample preparation

• 9.2.1 Connect to the syringe and draw in 6 cm³ of test oil; note that bubbles must not appear in the oil tube and syringe.
• 9.2.2 Plug the end of the oil tube to prevent leakage of the drawn oil.
• 9.2.3 Fix the syringe on the oil injection unit using the concave groove.
• 9.2.4 Fix the oil injection unit on the instrument; wind the steel wire rope on the oil injection unit around the grooves at both ends of the hoist drum and secure it with screws.
• 9.2.5 Remove the stopper from the end of the oil tube, and connect the oil tube to the oil inlet on the side of the acrylic resin component.
• 9.2.6 Check and confirm whether the amount of oil in the syringe meets the volume scale line on the concave groove.
• Other sampling requirements: not provided in the available source.

8. Analysis procedure

• 8.1 Adjustment of heating furnace temperature
  • 8.1.1 Check the through hole in the heating furnace where the test heat tube is placed to ensure that the test heat tube can be easily inserted and pass through the interior of the heating furnace; if it cannot be easily inserted, some oil deposits or adhesions may be attached to the inner wall of the heating furnace, and a steel rod or similar tool may be used to clean it; the diameter of the steel rod or similar tool shall not exceed 4.2 mm.
  • 8.1.2 Turn on the main switch and the heating switch, and set the temperature setter to 290 ℃.
  • 8.1.3 After 2 h, after confirming that the heating furnace temperature is stable, insert the thermometer into the hole where the test heat tube is placed (about 145 mm from the top of the heating furnace); it shall be ensured that the temperature is within 290 ℃±1 ℃. Note: the thermometer shall be a calibrated thermometer.
  • 8.1.4 In the same manner as above, measure the temperature again at a temperature of 310 ℃.
  • 8.1.5 If the heat tube test is carried out at other temperatures (temperatures required by product specifications or agreements), then it shall be carried out at its test temperature in the same manner as above.
• 8.2 Cleaning the test heat tube
  • 8.2.1 After cleaning the test heat pipe with n-heptane, immerse the test heat pipe in dilute hydrochloric acid, then rinse with water; if dilute hydrochloric acid is not available, ultrasonic cleaning should be used in another solvent 5 min.
  • 8.2.2 Place the test tube in an oven at 105 ℃ and dry it at 1 h.
  • 8.2.3 If method B is used for evaluation, the test tube should be placed in a desiccator to cool for 30 min, then weighed, and the weighing should be accurate to 0.1 mg.
  • 8.2.4 If the test heat pipe is not to be used immediately, the test heat pipe should be stored in a desiccator.
• 9.1 Pipeline installation
  • 9.1.1 Use a pressure reducing valve to adjust the air pressure to 30 kPa~45 kPa.
  • 9.1.2 Connect the air connection pipe to the outlet of the flow control valve, and connect it to the air flow meter; the flow meter may be a film flow meter or a float flow meter. Note: The flow meter must be calibrated before use.
  • 9.1.3 Use the flow regulating valve to adjust the air flow in the tubes respectively to 10 cm³/min±0.5 cm³/min.
  • 9.1.4 Place the acrylic resin component in the designated position.
  • 9.1.5 Place the test heat pipe on top of the acrylic resin component, then secure it with wing nuts.
  • 9.1.6 Connect the air connection pipe to the air inlet interface below the acrylic resin component.
  • 9.1.7 Connect the flow meter and the test heat pipe, then close the oil circuit inlet pipe on the acrylic resin component.
  • 9.1.8 Check the airtightness of the pipeline connections.
  • 9.1.9 Check and respectively adjust the air flow in the six test heat pipes so that all reach 10 cm³/min±0.5 cm³/min. Note: The air flow should be readjusted before each test.
• 9.3 Test
  • 9.3.1 Turn on the main switch, start switch, and motor switch of the instrument; set the heater switch to the “check” position; before the test, 1.5 h the test motor should be turned on; during the test, the oil may fail to be supplied uniformly by the oil supply unit at the initial stage of the test due to gear operation problems.
  • 9.3.2 Deliver the test oil to the junction of the T-type passage by adjusting the rotary screw below the syringe piston.
  • 9.3.3 Set the temperature on the temperature control device to the test temperature (the temperature required by the product specification or agreement); when the test oil reaches the top of the test heat pipe, set the heating switch to the “normal” position.
  • 9.3.4 When the temperature reaches the test temperature and the temperature fluctuation is within ±1 ℃, the test officially begins. Note: If the temperature or air flow fluctuates greatly, please install the side panels around the instrument.
  • 9.3.5 During the test, check whether the test oil is normally supplied by the syringe, whether there is oil leakage at the O-shaped ring interface, or whether there is oil leakage at other connections, and ensure that during this process the air and oil pipelines of the instrument are unobstructed and not blocked.
• 9.4 End of test
  • 9.4.1 End the test after 16 h of testing.
  • 9.4.2 Turn off the motor switch and the main switch.
  • 9.4.3 Disconnect the connection on the valve side; disconnect the acrylic resin component; loosen the wing nuts on the acrylic resin component, then quickly remove the test heat pipe.
  • 9.4.4 Close the pressure reducing valve and stop the air supply; plug the end of the oil pipe with a stopper to prevent oil leakage.
• 9.5 Post-test treatment
  • 9.5.1 After the test heat pipe has cooled for about 5 min, clean it with petroleum ether until the cleaning solvent becomes colorless. Note: If some test heat pipes are blocked, the test needs to be redone, because blocked heat pipes may affect the test results of other heat pipes, and all the remaining samples need to be redone.
  • 9.5.2 Place the test heat pipe in an oven at 105 ℃ to dry off the solvent. Warning: The use of an explosion-proof oven is recommended.
  • 9.5.3 If method A is used for the test, compare the test heat pipe with the heat pipe color rating standard, and the rating precision shall be at 0.5 grade.
  • 9.5.4 If method B is used for evaluation of the test results, place the test heat pipe in a desiccator to cool for 30 min, then weigh it, and the weighing precision shall be within 0.1 mg.

9. Qualitative and quantitative determination and calculation formulas

• 10.1 Method A: Compare the tested heat pipe with the heat pipe color rating standard; the comparison area should be within the range of 30 mm from the center of the paint film on the test heat pipe.
• 10.2 Method B: Calculate the weight gain of the test heat pipe according to formula (1) (W), mg:
  • W = W₂ − W₁ ……………………………………（1）
  • Where: W₁ — mass of the test heat pipe before the test, in milligrams (mg); W₂ — mass of the test heat pipe after the test, in milligrams (mg). (In the original source-text extraction, the symbols and subscripts are misaligned; requires confirmation against the source standard (source-text extraction))
• 11.1 Report the color rating and test temperature of the results; the color rating shall be accurate to 0.5 grade, and the test temperature shall be accurate to 1 ℃.
• 11.2 Report the weight gain of the test heat pipe and the test temperature; the test temperature shall be accurate to 1 ℃.

10. Precision

• When the heat pipe rating exceeds 7.0 grade, judge the reliability of the test results according to the following provisions (confidence level of 95%). The precision of method B has not been determined (the original text states “precision not determined for the method”; source-text extraction doubtful point requires confirmation against the source standard).
• 12.1 Repeatability: The difference between two consecutive test results obtained by the same operator, in the same laboratory, using the same instrument, on the same sample shall not exceed 1.0 grade.
• 12.2 Reproducibility: The difference between two single, independent test results obtained by different operators, in different laboratories, using different instruments, according to the same method, on the same sample shall not exceed 2.0 grade.

11. Report

• 11.1 Report the color rating and test temperature of the results; the color rating shall be accurate to 0.5 grade, and the test temperature shall be accurate to 1 ℃.
• 11.2 Report the weight gain of the test heat pipe and the test temperature; the test temperature shall be accurate to 1 ℃.
• Other reporting requirements: not provided in the available source.

12. Normative references

• GB/T 6682—2008 Water specifications and test methods for analytical laboratory use
• HG/T 3115 Properties of borosilicate glass 3.3
• GB/T 1.1—2009 (mentioned in the foreword, as the basis for drafting the standard)

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 for questions and answers