SH/T 0090-1991 Engine coolant freezing point determination method

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Card type: Test method

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

• Standard number: SH/T 0090-91 (the year number in the source is 91, the file name is marked as 1991)
• Chinese name: Engine coolant freezing point determination method
• English name: not provided in the available source
• Replacement relationship: not provided in the available source
• Other: the source marks "(200(! year confirmation)", suspected to be "2000 year confirmation", requires confirmation against the source standard (source-text extraction)
• Reference adoption: ASTM D1177-88 "Engine coolant freezing point determination method" (see additional notes)

2. Scope of application and non-applicability

• This standard specifies the method for determining the freezing point of engine coolant under test conditions.
• This standard applies to engine coolant and its concentrated liquid.
• Not applicable: not provided in the available source.

3. Method principle

Take a test sample of 75～100 mL, inject it into a cooling tube with a stirring device, cool the sample with a refrigerant or other method, record the temperature of the sample every minute, and draw a time-temperature curve. The projection point on the vertical axis of the intersection of the cooling curve and the crystallization curve is the freezing point of the sample. If the sample exhibits supercooling, then the highest temperature reached when the temperature rises after supercooling is the freezing point of the sample. (Chapter 4)

4. Reagents and materials (purity / preparation)

• 5.2.1 Industrial ethanol.
• 5.2.2 Solid carbon dioxide or other refrigerant.
• Purity requirements: not provided in the available source.
• Preparation: not provided in the available source.

5. Instruments and equipment

• 5.1.1 Freezing point tester: see Figure 1, consisting of the following parts.
  • 5.1.1.1 Cooling bath: a silver-plated vacuum flask with a volume of 2 L, height about 220 mm, diameter about 125 mm, with glass wool or metal mesh at the bottom.
  • 5.1.1.2 Cooling tube: dimensions see Figure 2 (the source says "Figure 20", requires confirmation against the source standard (source-text extraction)).
  • 5.1.1.3 Stirring device: a spiral stirrer made of stainless steel wire with a diameter of 1.6 mm wound into five turns, the outer diameter of the coil is (20±2) mm, length about 40～50 mm; one end of the stirrer is fixed on a device driven by a small motor, and through the drive of the motor, the coil performs linear reciprocating motion. The length of the stirrer is adjustable; during stirring, the upper part of the coil does not emerge above the sample liquid level, and the lower part just reaches the bottom of the cooling tube.
  • 5.1.1.4 Iron stand: used to fix the complete set of equipment.
• 5.1.2 Thermometer: one set of two, one is −37～2 ℃; the other is −54～−15 ℃, both with a scale division of 0.2 ℃, and their technical conditions are given in Appendix A.
• 5.1.3 Stopwatch or other timer.

6. Recommended operating conditions

• Stirring speed: 60～80 times per minute (7.2).
• Sample cooling rate: controlled within 1 ℃/min (the source says "19C/min", requires confirmation against the source standard (source-text extraction)) (7.3).
• Cooling bath dry ice layer thickness: at least 13 mm (the source says "13r nme", requires confirmation against the source standard (source-text extraction)) (6.3, 7.3).
• Thermometer insertion depth: the bottom of the mercury bulb is about 60 mm from the bottom of the cooling tube (6.1).
• Sample pre-cooling: first pre-cool the sample to 8 ℃ above the expected freezing point (the source says "80C", requires confirmation against the source standard (source-text extraction)) (6.2).
• Recording frequency near the freezing point: record the temperature once every 15 s (7.4).
• Time to continue observing and recording after crystallization: at least 10 min (7.5).

7. Sampling and sample preparation

• 6.2 Sample preparation: for the concentrated liquid, dilute the sample to the specified concentration as required. The dilution method is carried out according to SH/T 0065, and then the freezing point is measured. If the sample is a diluted liquid product, it is not diluted further and can be directly measured.
• If the sample appears as two phases, generally it is not necessary to separate them, because the precipitate may be an added preservative, and removing it may affect the determination result.
• To shorten the experiment time, first pre-cool the sample to 8 ℃ above the expected freezing point (the source says "80C", requires confirmation against the source standard (source-text extraction)), and then carry out the experiment.
• 7.1 Measure 75～100 mL of the pre-cooled sample, temporarily remove the stopper of the cooling tube, and inject the sample into the cooling tube (the sample may also be injected into the cooling tube for direct pre-cooling, and then the test is carried out).

8. Analysis steps

• 6.1 Assemble and adjust the instrument. Before loading the sample, assemble the instrument as shown in Figure 1. The insertion depth of the thermometer is such that the bottom of the mercury bulb is about 60 mm from the bottom of the cooling tube, and the stirrer is placed around it in the middle. After the instrument is assembled, turn on the power and check whether all parts operate normally. If not, adjust them.
• 6.3 Pour industrial ethanol into the cooling bath; its liquid level should be appropriate, so that when the cooling tube is placed in, it neither overflows nor fails to be high enough to be above the sample liquid level in the cooling tube. Add solid carbon dioxide to the cooling bath; the amount added each time must not be too much, otherwise the industrial ethanol is likely to overflow. As solid carbon dioxide is continuously added and continuously melts, the refrigerant temperature drops rapidly; when a certain amount of solid carbon dioxide has been added, the melting rate slows noticeably, and a dry ice layer forms on the surface of the industrial ethanol, with a thickness of at least 13 mm (the source says "13r nme", requires confirmation against the source standard (source-text extraction)).
• 7.1 Measure 75～100 mL of the pre-cooled sample, temporarily remove the stopper of the cooling tube, and inject the sample into the cooling tube (the sample may also be injected into the cooling tube for direct pre-cooling, and then the test is carried out).
• 7.2 Start the stirring device and adjust the speed to 60～80 times per minute. Then start the test, observe and record the temperature of the sample every minute. Note: one complete up-and-down cycle of the stirrer counts as one time.
• 7.3 During the test, continuously add solid carbon dioxide to the cooling bath to maintain a dry ice layer at least 13 mm thick, and control the sample cooling rate within 1 ℃/min (the source says "19C/min", requires confirmation against the source standard (source-text extraction)).
• 7.4 When the sample temperature approaches the expected freezing point, record the temperature once every 15 s. When the sample temperature reaches 0.5～1 ℃ above the expected freezing point, crystallization should be induced to prevent supercooling. The method is to place another small test tube containing the same sample in the cooling bath; because the small test tube is single-walled, the cooling rate is very fast, and it crystallizes before the sample in the cooling tube freezes. Use a small spoon to take a small piece of crystal and put it into the cooling tube, and the sample will crystallize quickly.
• 7.5 After crystallization appears in the sample (that is, when the sample temperature stabilizes at a certain point or, after supercooling, the temperature rises back to the highest temperature), it is still necessary to continue observing and recording the sample temperature for at least 10 min. Note: if the sample exhibits supercooling, the supercooling temperature should be controlled to the smallest possible extent. If the supercooling temperature exceeds 1 ℃ (the source says "1T", requires confirmation against the source standard (source-text extraction)), then this test is invalid.
• 7.6 Draw a time-temperature curve on rectangular coordinate paper.
• 7.7 On the time-temperature curve, find the steeper part of the curve (that is, the cooling curve) and the gentler part (that is, the crystallization curve). The projection point on the vertical axis of the intersection of the cooling curve and the crystallization curve is the freezing point of the sample. As shown in Figure 3(a). If the sample exhibits supercooling, then the highest temperature reached when the sample temperature rises rapidly after supercooling is the freezing point of the sample, as shown in Figure 3(b).

9. Qualitative and quantitative determination and calculation formula

• Definition of freezing point (Chapter 3): in the absence of supercooling, the temperature at which the coolant begins to crystallize; or in the presence of supercooling, the highest temperature reached when the coolant rapidly rises after initially forming crystals.
• Result determination (7.7): the projection point on the vertical axis of the intersection of the cooling curve and the crystallization curve is the freezing point; if supercooling occurs, then the highest temperature reached when the temperature rises after supercooling is the freezing point.
• Calculation formula: not provided in the available source.

10. Precision

• 8.1 Repeatability: the difference between two results of repeated determinations by the same operator and their arithmetic mean shall not be greater than 0.3 ℃ (the source says "0.39C", requires confirmation against the source standard (source-text extraction)).
• 8.2 Reproducibility: the difference between the determination results submitted by different laboratories and their arithmetic mean shall not be greater than 0.6 ℃ (the source says "0.69 C", requires confirmation against the source standard (source-text extraction)).

11. Report

• Take the arithmetic mean of the two results of repeated determinations as the determination result. The result is accurate to 0.1 ℃ (the source says "0.19C", requires confirmation against the source standard (source-text extraction)).

12. Referenced documents

• SH/T 0065 Sampling of engine coolant or rust inhibitor test samples and preparation of their aqueous solutions
• ASTM D1177-88 "Engine coolant freezing point determination method" (reference adoption, see additional notes)
• Appendix A Technical conditions for freezing point thermometers (supplementary document)

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 Q&A reference