ASTM D3700-21 PDF

Overview

ASTM D3700-21 is the standard practice developed by ASTM International for obtaining representative samples of liquefied petroleum gas (LPG) using a floating piston cylinder (FPC). This method is designed to prevent loss of volatile light components, such as methane, ethane, and nitrogen, which may otherwise occur during sampling by alternative practices like ASTM D1265. The standard outlines the necessary equipment, procedures, and safety considerations to ensure sample integrity for accurate testing and analysis. It is widely referenced for sampling LPG, natural gas liquids (NGL), and high vapor pressure liquids in compliance with industry specifications and international standards.

Key Topics

• Floating Piston Cylinder (FPC) Use: The FPC is a specialized high-pressure sample container with a free-floating internal piston, which separates the LPG sample from a pressurizing inert gas, preventing vaporization and preserving the true composition of the sample.
• Representative Sampling: Detailed procedures and equipment recommendations help users obtain and maintain samples that truly represent the source material, especially for determining light hydrocarbon composition with high accuracy.
• Sample Integrity Risks: The standard identifies sources of interference that can compromise samples, including poor sampling location, contamination from lubricants and cylinder surfaces, leaks, improper cleaning, and incorrect handling.
• Safety and Compliance: Users are reminded to adhere to jurisdictional safety requirements, use appropriate pressure vessel certifications, and follow health, safety, and environmental protections.
• Practical Limitations: ASTM D3700-21 is intended for single-phase specification products; its direct use for raw, multi-phase, or contaminated mixtures requires additional precautions. Practice D8009 is referenced for UN Class 3 liquids below 300 kPa at 52°C.
• Purging and Mixing: Emphasizes thorough purging of sampling lines and equipment to avoid contamination, as well as sample mixing to prevent stratification in collected samples.

Applications

• LPG Quality Measurement: Essential for accurately determining composition-including trace light components-in custody transfer, regulatory compliance, and quality assurance of LPG and NGL products.
• Valuation of NGL Mixtures: Enables precise composition analysis, crucial for commercial transactions where product value depends on individual hydrocarbon content.
• Specification Testing: Especially important when product certification or regulatory reporting demands the highest accuracy for volatile component determination, such as in ethane- and propane-rich LPGs.
• Laboratory and On-site Sampling: Used by laboratories, refineries, petrochemical plants, and midstream operators to ensure reliable sample transport and analysis.
• Specialty Sampling Scenarios: Useful in situations where loss of volatile components could bias analytical results, or where regulatory bodies stipulate stringent vapor phase composition limits.

Related Standards

• ASTM D1835: Specification for Liquefied Petroleum (LP) Gases. Defines product requirements referenced by D3700.
• ASTM D1265: Manual sampling of LP gases; suitable for routine specifications but not for highly accurate light component analysis.
• ASTM D8009: Practice for manual piston cylinder sampling of volatile crude oils and liquid petroleum products.
• ASTM D4175: Terminology relating to petroleum products, liquid fuels, and lubricants.
• GPA 2140: Liquefied Petroleum Gas Specifications and Test Methods.
• GPA 2174: Guidance on obtaining liquid hydrocarbon samples for analysis, including NGLs.

Keywords: ASTM D3700, LPG sampling, floating piston cylinder, natural gas liquids, NGL sampling, volatile hydrocarbons, sample integrity, LPG quality, petrochemical standards, gas sampling cylinder.