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D2713-24 – Standard Test Method Technical Guide
📐 Principle and Scope of the Valve Freeze Method
ASTM D2713-24, officially designated as the “Standard Test Method for Dryness of Propane (Valve Freeze Method),” provides a functional procedure for assessing the dryness of propane products. The scope of this test method specifically covers products that do not contain antifreeze agents, such as commercial propane and special duty propane as defined in Specification D1835. The values stated in SI units are regarded as the standard.
This international standard was developed in accordance with internationally recognized principles on standardization established by the World Trade Organization Technical Barriers to Trade (TBT) Committee. As stated in the standard, it is the responsibility of the user to establish appropriate safety, health, and environmental practices prior to use.
🎯 Scope Reminder: This test method is intended for propane without antifreeze agents. The presence of such agents constitutes a major interference (see Section 6.1).
⚙️ Test Procedure and Equipment Setup
The core of the test is the Propane Water Test Valve (Section 7.1), a specially constructed and calibrated valve manufactured solely for this test. A liquid-phase sample of the product to be tested is flowed through this valve to cool the valve body. According to the summary in Section 4, after cooling, the test valve is partially closed to a small, preset flow rate and the time required for the valve to freeze—due to water dissolved in the sample—is recorded.
Higher dissolved water concentrations will result in shorter freeze-off times. The average observed time for several successive observations is recorded as the observed valve freeze time.
| 🟦 Term (Section 3.2) | 📏 Definition per D2713-24 | 🎯 Units / Detail |
|---|---|---|
| Freeze-off time | The time, in seconds, for a propane water test valve to freeze under the conditions of this test method. | Seconds (s). Key measured property. |
| Propane water test valve | A specific valve designed and manufactured for performing in this test method. | Specialized, calibrated apparatus. |
| Valve freeze | An adjective relating to the procedure for determining the dryness of propane. | Defines the test condition. |
⚠️ Critical Interference Alert: Antifreeze agents will interfere with this test method and can indicate that the product is drier than it really is. This test method is a functional test relating water concentration to product behavior in pressure-reducing systems.
📊 Key Measured Properties and Interferences
This test is a functional test in which the water concentration in the product is related to product behavior characteristics in a pressure-reducing system. Experience has demonstrated that excessive water content (dissolved water) will cause freeze-up difficulties in pressure reducing systems (Section 5.1). The freeze-off time serves as the primary measurable indicator of this behavior.
If the tester wishes to assess materials containing antifreeze, the relative freeze-off times of such materials can indicate a tendency to cause freezing in regulators, although the absolute dryness measurement is compromised.
| 📐 Factor | ⚡ Effect on Freeze-Off Time | 🟦 Practical Significance |
|---|---|---|
| High Dissolved Water Content | Shorter freeze-off times | Indicates high risk of freeze-up in pressure reducing systems. |
| Low Dissolved Water Content | Longer freeze-off times | Indicates a dry product suitable for standard use. |
| Presence of Antifreeze Agents | Artificially prolonged (false negative) | Interferes with direct measurement; product appears drier than actual. |
❓ Frequently Asked Questions
🔍 What does ASTM D2713-24 measure?
It measures the dryness of propane products (free of antifreeze agents) using the Valve Freeze Method. The result is an observed valve freeze-off time expressed in seconds.
💡 How does dissolved water affect the test results?
Higher concentrations of dissolved water in the propane sample will result in shorter freeze-off times. The average observed time for successive observations is recorded as the observed valve freeze time.
⚡ Can this test be used on propane containing antifreeze?
The scope of the standard explicitly states it covers products that do not contain antifreeze agents. Antifreeze agents interfere, making the product appear drier than it really is (Section 6.1).
📌 What is the significance of the freeze-off time value?
The freeze-off time relates the water concentration in the product to its behavior in pressure-re