SY/T 7484-2020 in English

Interpretation of the core content of the standard

This standard specifies the method of measuring the hydrocarbon dew point of pipeline natural gas using a cooling mirror automatic detector, with a measurement accuracy of ±0.5℃. It is applicable to single-phase natural gas, but not to gas containing liquid hydrocarbons.

Technical principles and instrument requirements

Key points of the operation process

1. Sampling requirements: The pipeline temperature must be at least 3°C higher than the estimated hydrocarbon dew point, and the low temperature environment must be heated and kept warm
2. Flow control: Maintain a constant flow of 1-3L/min during formal measurement
3. Repeatability verification: The difference between two consecutive measurements must be ≤2.0°C to be valid

Background of Standard Evolution

Compared with the visual inspection method of GB/T 27895-2011, this standard introduces automated detection technology, reducing the manual judgment error from ±3℃ to ±2℃, and increasing explosion-proof safety requirements to adapt to the actual working conditions of the station.

Implementation Suggestions

• Regularly use propane standard gas (-42.1℃@101.325kPa) for instrument calibration
• For high hydrocarbon dew point samples (＞0℃), the purge flow rate needs to be increased to 5L/min
• Establish a mirror contamination assessment system, and clean the mirror when the repeatability is ＞1.5℃