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D1827-92 – Standard Test Method Technical Guide
📐 Scope and Definitions
This test method is applicable to electrical insulating liquids with a viscosity of 216 cSt or less at 100°C. It is designed to determine the gas content of such liquids, specifically nonacidic gases that are unreactive with strong caustic solutions, using displacement with carbon dioxide.
Note that the method has a bias for samples containing gases other than oxygen and nitrogen in atmospheric ratios due to differential solubility effects. Gases reactive with KOH, such as carbon dioxide, are not measured. Unsaturated hydrocarbons like acetylene may react slightly with KOH, leading to underestimation of total gas present.
Gas content is defined in two ways:
- Gas content by volume: The volume of gas contained in a given volume of liquid, expressed as a percentage at standard atmospheric conditions of 760 mm Hg pressure and 0°C temperature.
- Gas content by weight: The weight of gas contained in a given weight of liquid, expressed in parts per million.
⚙️ Test Procedure and Apparatus
The test method consists essentially of purging dissolved gases from a small liquid test specimen with pure carbon dioxide gas. The dissolved gases are carried into a graduated buret, specifically a precision nitrometer, filled with a potassium hydroxide solution for precise measurement. The carbon dioxide is completely absorbed by the potassium hydroxide, and the volume of other gases is measured.
Key apparatus includes:
- A precision nitrometer (azotometer) with a calibrated capacity of 1.5 mL, calibrated in 0.01-mL divisions.
- Individual calibration correction tables that provide the correct volume for each 0.01-mL point on the scale when using a 40 % aqueous potassium hydroxide solution.
The test requires care in manipulation and trained, careful personnel to ensure accurate results.
📊 Key Measured Properties and Significance
Electrical insulating liquids, in many applications such as capacitors and certain types of cable, require low gas content. This test is used as a factory control test and as a control and functional test in installation and maintenance work by utilities.
| 🟦 Parameter | 📏 Specification |
|---|---|
| Liquid Viscosity | ≤ 216 cSt at 100°C |
| Gas Content by Volume | Percentage at 760 mm Hg, 0°C |
| Gas Content by Weight | Parts per million (ppm) |
| Apparatus Capacity | 1.5 mL, 0.01-mL divisions |
⚠️ Mercury Warning: Mercury, used in this test, is hazardous and corrosive. Refer to the MSDS and EPA guidelines for safe handling. State laws may prohibit sale of mercury-containing products.
💡 Tip: The test has a bias for gases other than oxygen and nitrogen in atmospheric ratios due to differential solubility. Gases reactive with KOH, like CO₂, are not measured. Ensure trained personnel handle the apparatus for accurate results.
❓ Frequently Asked Questions
🔍 What gases are determined by this test method? Any nonacidic gases that are nonreactive with a strong caustic solution, such as oxygen and nitrogen, can be determined.
💡 Why is carbon dioxide used in the procedure? CO₂ is used to purge dissolved gases from the sample and is then absorbed by KOH solution, allowing measurement of residual gases.
⚡ What is the viscosity requirement for the insulating liquid? The liquid must have a viscosity of 216 cSt or less at 100°C.
📌 How is gas content by volume defined? It is defined as the volume of gas contained in a given volume of liquid, expressed as a percentage at 760 mm Hg pressure and 0°C temperature.