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ASME PTC 3.3-1969 (1979) — Test Code for Gaseous Fuels
🔥 ASME PTC 3.3-1969 (1979) is the Performance Test Code (PTC) series standard devoted to gaseous fuels. Its lineage goes back to the 1944 Test Code for Gaseous Fuels; in 1958 PTC Committee No. 3.3 on Fuels was reorganized and directed to revise that 1944 edition, working closely with ASTM Committees D-2 (Petroleum Products and Lubricants) and D-3 (Gaseous Fuels). Approved by the Performance Test Codes Committee on June 14, 1968, and adopted by the ASME Council in September 1968, it was published in 1969 and reaffirmed in 1979. The Code defines sampling, measurement, analysis, and water-vapor determination methods for gaseous fuels, forming the fuel-side foundation of boiler, gas turbine, and industrial furnace performance tests.
💡 PTC 3.3 is deeply interlocked with ASTM standards: it adopts, with minor modifications, ASTM D-1145 (sampling natural gas), D-1265 (sampling LPG), D-1071 (measurement of gaseous fuel samples), and D-1945 (gas chromatography of natural gas).
1. Object and Scope 📌
The object of PTC 3.3 is to provide uniform sampling, measurement, and analysis procedures for gaseous fuels so that results obtained by different test crews and laboratories are comparable. The Code covers:
- Natural gas: the ASTM D-1145-53 standard method of sampling (with minor changes);
- Liquefied petroleum gases (LPG): the ASTM D-1265-55 standard method of sampling;
- Manufactured gas: ASTM D-1247-54, with the apparatus for continuous sampling revised and the former ASTM section 9 replaced by a reference to ASME PTC 27;
- Measurement of gaseous fuel samples: ASTM D-1071-55 (rotary displacement meters omitted and section 24 formula units revised).
⚠️ This Code addresses gaseous fuels for combustion. Sampling and analysis results feed heating-value, density, and combustion-air calculations. For particulate-laden streams, use ASME PTC 27 and PTC 28 — the methods are not interchangeable.
2. Sampling of Gaseous Fuels 🧪
Sampling is the largest single source of error in gaseous-fuel testing. The Code prescribes apparatus and procedures by fuel type: natural gas requires representative sampling from the transmission line while avoiding liquid carryover and composition stratification; LPG must be sampled under pressure with the liquid phase retained so that no phase change alters the composition; manufactured gas uses continuous samplers adapted to the composition swings of gasification.
| Fuel | ASTM Method Referenced | Sampling Key Points | Primary Use |
|---|---|---|---|
| Natural gas | D-1145-53 (modified) | Representative line sampling, avoid condensate | Heating value, custody metering |
| LPG | D-1265-55 | Pressure sampling, keep liquid phase | LPG composition and calorific value |
| Manufactured gas | D-1247-54 (revised) | Continuous sampler, prevent oxygen ingress | Gas-plant production control |
| Sample measurement | D-1071-55 (revised) | Metered flow, volume correction | Flow and heat input calculation |
3. Volumetric Analysis of Fuel Gases 🔬
The Code specifies volumetric-chemical analysis for natural gas constituents. In the classic Orsat-type apparatus, CO₂, unsaturated hydrocarbons, oxygen, and carbon monoxide are absorbed sequentially in different reagents; methane and hydrogen are then determined by explosion or slow combustion, and nitrogen is obtained by difference. The Code also includes ASTM D-1136-53 (volumetric-chemical method for natural gas) and D-1945-64 (gas chromatography), noting that chromatography is preferred when higher accuracy or complete component separation is required.
💡 Field experience: volumetric-chemical analysis gives adequate accuracy for the major constituents (CO₂, O₂, CO) needed in heating-value work, but gas chromatography is the more reliable tool for complex mixtures and C₂⁺ hydrocarbons. The industrial arrival of GC in the 1960s is exactly the backdrop of this revision.
4. Water Vapor and Dew-Point Determination 💧
Water vapor in gaseous fuel affects heating-value calculation, pipeline transmission, and burner operation. The Code provides three moisture methods:
- Dew-point temperature method (ASTM D-1142-63, with section 5c and Tables II and III omitted): water content is derived from the measured dew-point temperature;
- Simplified water dew-point method: a quick field procedure for routine checks;
- Oil dew-point method: determines the dew point of condensed hydrocarbon oil, important for compressed natural gas and LPG vapor.
🚨 The higher the pressure, the higher the dew point. Dew points taken at different pressures must be referenced to a common pressure base before comparison; in the field, keep the pressure gauge and the measuring cavity thermally uniform or readings can drift by several degrees Celsius.
5. Engineering Application of the Code 🛠️
- 🔍 Heating-value computation: combine component analysis (dry/wet basis conversion) to obtain higher and lower heating values, and with density to compute air requirement and flue-gas quantity.
- 🔧 Combustion equipment tests: in boiler (PTC 4) and gas turbine (PTC 22) tests, heat input is established from gas consumption and calorific value, so gas measurement accuracy directly bounds overall efficiency.
- 📊 Custody and acceptance: large gas trades settle by heating value; uniform sampling and analysis are the basis for dispute arbitration.
- 📋 Traceability: the Code requires complete records of sampling location, time, ambient conditions, and method so tests are reproducible.
6. Frequently Asked Questions ❓
❓ Q: How do PTC 3.3, PTC 27, and PTC 28 differ?
A: PTC 3.3 covers composition, heating value, and moisture of gaseous fuels; PTC 27 measures dust concentration in a gas stream; PTC 28 determines the properties of fine particulate matter. All belong to the fuel and emissions test family but measure entirely different quantities — the manufactured-gas continuous-sampling apparatus was referenced to PTC 27 in section 9.
A: PTC 3.3 covers composition, heating value, and moisture of gaseous fuels; PTC 27 measures dust concentration in a gas stream; PTC 28 determines the properties of fine particulate matter. All belong to the fuel and emissions test family but measure entirely different quantities — the manufactured-gas continuous-sampling apparatus was referenced to PTC 27 in section 9.
❓ Q: Why does the Code list both volumetric-chemical and chromatographic analysis?
A: Both analyze natural gas composition. The volumetric-chemical method is the classical reference technique, simple and needing no elaborate calibration; gas chromatography gives higher precision and more complete separation. The Code permits either, depending on purpose and available equipment.
A: Both analyze natural gas composition. The volumetric-chemical method is the classical reference technique, simple and needing no elaborate calibration; gas chromatography gives higher precision and more complete separation. The Code permits either, depending on purpose and available equipment.
❓ Q: How is dew-point temperature converted to water content?
A: With the dew point known at a given pressure, the saturated water-vapor partial pressure can be read from steam tables and converted to water content; humidity charts or vapor-pressure equations are commonly used, always on a consistent pressure base.
A: With the dew point known at a given pressure, the saturated water-vapor partial pressure can be read from steam tables and converted to water content; humidity charts or vapor-pressure equations are commonly used, always on a consistent pressure base.
❓ Q: Is this 1969 edition still usable today?
A: As a reaffirmed historical edition it remains a reference: its sampling principles, dew-point measurement, and gas-analysis logic still underlie modern gaseous-fuel testing (e.g., fuel analysis in PTC 22 tests). For current execution, combine it with the latest ASTM D-series methods.
A: As a reaffirmed historical edition it remains a reference: its sampling principles, dew-point measurement, and gas-analysis logic still underlie modern gaseous-fuel testing (e.g., fuel analysis in PTC 22 tests). For current execution, combine it with the latest ASTM D-series methods.
