SH/T 0304-1999 Test method for corrosive sulfur in electrical insulating oil

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Card type: Test method

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

• Standard number: SH/T 0304-1999
• Chinese title: Test method for corrosive sulfur in electrical insulating oil
• English title: Electrical insulating oils-Detection of corrosive sulfur
• Replacement relationship: replaces SH/T 0304-1992; equivalent adoption of ISO 5662:1997 (eqv ISO 5662:1997)
• Adoption relationship note: This standard equivalently adopts the international standard ISO 5662:1997 "Test method for corrosive sulfur in electrical insulating oil", and revises SH/T 0304-1992.
• Main differences from ISO 5662:1997: the referenced standards are different. ISO 5662:1997 references ISO 2160:1985 "Test method for copper strip corrosion of petroleum products" and ISO 3696:1987 "Detailed specification and test methods for water for analytical laboratory use"; this standard references GB/T 5096 "Test method for copper strip corrosion of petroleum products" and GB/T 6682 "Specifications and test methods for water for analytical laboratory use".
• Main revisions to SH/T 0304-1992:
  1. The polishing materials are different. The original standard used 63μm silicon carbide paper or cloth and 90μm silicon carbide powder; this standard uses 65μm silicon carbide paper or cloth and 105μm silicon carbide powder.
  2. Added 2,2,4- trimethylpentane as a cleaning solvent, and added specification requirements for distilled water.
  3. The drying method for the test strip is different. The original standard specified that the test strip could be tested after drying in an oven for a few minutes; this standard specifies that the test strip is dried in a hot air stream for at most 5min or in an oven for less than 3min.
  4. This standard has undergone editorial modifications.
• Publication/implementation: approved by the State Bureau of Petroleum and Chemical Industry 1999-12-08, implemented on 2000-05-01.
• Responsible/ drafting: proposed by China Petrochemical Corporation; under the jurisdiction of the Petrochemical Research Institute of China Petrochemical Corporation; drafting organization: Shanghai Refinery of Shanghai Gaoqiao Petrochemical Company; main drafters: Lu Lihua, Li Jing. First published in 1992.

2. Scope of application and non-applicability

• This standard specifies the test method for corrosive sulfur in electrical insulating oil refined from petroleum.
• This standard applies to electrical insulating oil.
• Not applicable: not provided in the available source.

3. Method principle

In the absence of air, a polished pure copper strip and oil are contacted at the test temperature of 140℃. At the end of the test, the color change of the copper strip is examined and evaluated on the basis of comparison with Table 1.

4. Reagents and materials (purity / preparation)

• Analytical reagent grade reagents are used in the analysis.
• 5.1 Cleaning solvent: 2,2,4- trimethylpentane, purity not less than 99.75%. Note: Other sulfur-free volatile hydrocarbon solvents that, using method GB/T 5096, do not discolor the copper strip when tested at 50℃ for 3h may also be used.
• 5.2 Acetone.
• 5.3 Diethyl ether.
• 5.4 Nitrogen: purity not less than 99.9%.
• 5.5 Distilled water: meets the grade 3 water requirements in GB/T 6682.
• 5.6 Sodium phosphate: prepared as 50g/L sodium phosphate solution.
• 4.2 Materials:
  • 4.2.1 Electrolytic copper strip: purity 99.9%, thickness 0.125～0.250mm.
  • 4.2.2 Polishing materials: including 65μm silicon carbide paper or cloth, 105μm silicon carbide powder and pharmaceutical absorbent cotton.

5. Apparatus and equipment

• 4.1.1 Forced-air oven or oil bath: capable of heating and controlled at 140℃±2℃. Note: A circulating forced-air oven is preferred.
• 4.1.2 Bottle: 250mL, made of chemically resistant glass, narrow-mouth, with a ground-glass stopper, and with a volume of 270～280mL when completely filled to the stopper. Note: This volume is required to provide sufficient thermal expansion space for the oil sample; borosilicate glass bottles can meet this requirement.
• 4.1.3 Oven: controlled at a temperature of 105℃±2℃.
• 4.1.4 Tweezers: stainless steel, flat tip.

6. Recommended operating conditions

• Test temperature: 140℃±2℃.
• Heating time: 19h.
• Nitrogen purge time: 2min.
• Test strip drying in hot air stream: at most 5min; oven drying: less than 3min.
• Observation of copper test strip: hold the copper test strip so that light is reflected from the copper test strip at an angle of about 45°.

7. Sampling and test specimen preparation

• 7.1 The sample does not need to be filtered before the test.
• Quickly place the prepared copper test strip into a clean bottle containing 250mL of sample, stand the bent copper test strip upright on the bottom of the bottle so that the horizontal surface of the copper test strip does not contact the bottom of the bottle, and lubricate the ground-glass stopper with a small amount of sample.
• Through a glass tube connected to the pressure reducing valve or needle valve of a nitrogen cylinder, blow nitrogen into the sample in the bottle and form bubbles (if a rubber tube is used for connection, the rubber tube must be sulfur-free). Pass nitrogen for 2min, then quickly place the stopper loosely on the bottle mouth.
• Copper test strip preparation (6.2): Cut a copper test strip of 6mm×25mm (see Note 1) from the copper strip, and use 65μm silicon carbide paper to grind away surface defects. After this treatment, the copper test strip may be stored in cleaning solvent for later use. When used, take the copper test strip out of the cleaning solvent, hold it between fingers protected with ashless filter paper, moisten absorbent cotton with 1 drops of cleaning solvent, pick up 105μm of silicon carbide powder from a glass plate and rub the copper test strip to perform the final polishing. Wipe the copper test strip with a clean cotton ball to remove all metal powder and grinding debris from the surface; when rubbing the copper strip, proceed along the long axis until a new cotton ball shows no dirty marks. Thereafter, handle it only with stainless steel tweezers and do not touch it with fingers. Bend the clean copper test strip into a V shape, with each side length 12.5mm and an included angle of 60°. Then wash separately with acetone, distilled water, acetone and diethyl ether, dry the copper test strip in a hot air stream for at most 5min. Then immediately carry out the test as described in 7.1 (see Note 2 and Note 3).
  • Note 1: A more convenient method is to use a larger copper strip, and after final polishing according to the above procedure, cut it into small copper test strips of the required size before use.
  • Note 2: The cleaning method is according to GB/T 5096.
  • Note 3: The copper test strip may be dried in an oven (less than 3min), but if so, it is necessary to check whether the copper test strip has rust before use.
• Bottle cleaning (6.1): The bottle should be cleaned by chemical methods. First use detergent to wash off oil contamination in the bottle, then wash with sodium phosphate solution, rinse with tap water, then rinse with distilled water, and finally dry in an oven.

8. Analysis procedure

• 7.1 The sample does not need to be filtered before the test. Quickly place the prepared copper test strip into a clean bottle containing 250mL of sample, stand the bent copper test strip upright on the bottom of the bottle so that the horizontal surface of the copper test strip does not contact the bottom of the bottle, and lubricate the ground-glass stopper with a small amount of sample. Through a glass tube connected to the pressure reducing valve or needle valve of a nitrogen cylinder, blow nitrogen into the sample in the bottle and form bubbles (if a rubber tube is used for connection, the rubber tube must be sulfur-free). Pass nitrogen for 2min, then quickly place the stopper loosely on the bottle mouth.
• 7.2 Place the stoppered bottle into a forced-air oven controlled at 140℃±2℃; if oil bath heating is used, immerse the bottle in the oil bath up to the neck. When the sample in the bottle approaches 140℃, tighten the stopper, heat at 140℃±2℃ for 19h, then remove the bottle, allow the sample in the bottle to cool to room temperature, carefully take out the copper test strip and rinse with cleaning solvent to remove all oil sample. Stand the copper test strip on a piece of filter paper, allow the cleaning solvent to evaporate, then observe the test strip as described in 7.3; when handling the test strip, only use tweezers to pick up the copper test strip.
• 7.3 Observation of copper test strip: hold the copper test strip so that light is reflected from the copper test strip at an angle of about 45°.

9. Qualitative and quantitative determination and calculation formula

• According to Table 1, classify the sample as corrosive or non-corrosive.

Table 1 Classification of results

Note: The non-corrosive descriptions above are equivalent to grades 1, 2, 3 in GB/T 5096, and the corrosive description is equivalent to grade 4 in GB/T 5096.

• Calculation formula: not provided in the available source.

10. Precision

Not provided in the available source.

11. Report

According to Table 1, report the test result as corrosive or non-corrosive, and indicate that the test was conducted in accordance with this standard.

12. Referenced documents

• GB/T 5096 Test method for copper strip corrosion of petroleum products
• GB/T 6682 Specifications and test methods for water for analytical laboratory use
• The provisions included in the following standards constitute part of this standard through reference. Unless otherwise expressly specified in the standard, the following referenced standards shall all be currently valid standards.

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