ASME PTC 19.10-1981 scan — Flue and Exhaust Gas Analyses

28 10 月, 2026
ASME Standards

💨 ASME PTC 19.10-1981 is Part 10 of the “Instruments and Apparatus” supplements in the ASME Performance Test Codes series. It covers methods of determining the pollutants and gaseous constituents found in the flue and exhaust of stationary combustion sources burning fossil fuel. This Part replaces an older one published in 1968 and was issued in 1981. Analysis of oxygen, carbon dioxide, carbon monoxide, and other constituents in flue gas is the measurement foundation shared by many performance test codes — including boiler efficiency tests (PTC 4) and gas turbine tests (PTC 22) — and is also the direct tool for combustion control, emission monitoring, and evaluation of pollution-abatement equipment.

💡 Flue gas analysis is a classic “composition infers process” measurement: from O₂, CO₂, and CO concentrations you can derive excess air, judge combustion completeness, and assess air infiltration and cold-end corrosion risk — one accurate gas analysis answers several performance questions.

1. Object and Measurement Purposes 📌

Section 2 of the Part lists the typical purposes of flue gas tests on a steam generator and the corresponding probe locations, as summarized in Table 1:

Purpose of Test	Probe Location
Air infiltration	Furnace and boiler outlet
Gas stratification	Furnace, boiler outlet, duct, stack
Air heater leakage	Gas entering and leaving air heater
Unit efficiency	Gas at outlet of unit (see PTC 4.1)
Excess air	Economizer or air heater outlet
Pollution determination	Stack or exhaust duct
Tube wastage from reducing atmosphere	In furnace at wastage area
Scrubber performance	Inlet and outlet of scrubber
Odor control	Outlet of unit
Cold-end corrosion (acid dew point)	Air heater inlet and outlet

⚠️ When the purpose of the tests is compliance with government standards, the testing guidelines published by the federal, state, or local authority must be followed unless a variance is obtained. Compliance and general performance testing have different method requirements.

2. Measurement System Types 🎛️

The Part groups gas-analysis techniques into three general areas:

Extractive: a sample probe draws flue gas through a transport line and conditioning system into analyzers. This is the most widely used approach for stationary sources, but the sampling stage (probe design, transport, condensation, filtration) can introduce errors;
In-situ (spectrometric): no sample conditioning is required — the concentration is determined from the effect on a light (or other energy) source as it passes through the exhaust before impingement on a sensor. Source and sensor are mounted on the stack either across from each other or on one side with a reflector;
Remote: measurements taken at a distance, suited to special applications.

Measurement Type	Sample Conditioning	Advantages	Limitations
Extractive	Required (probe + line + conditioning)	Mature, multi-point sampling, lab analysis possible	Representativeness, condensation/adsorption loss, slow response
In-situ (spectrometric)	None	Fast response, line-average concentration	Dust and window fouling, complex calibration
Remote	Method dependent	Distance and wide-area coverage	Atmospheric and geometric constraints

3. Sampling and Test Preparation 🧪

Section 3 highlights key sampling considerations:

Range matching: the instrumented or manual method should span the entire range of expected concentrations; the highest expected concentration should not exceed the range, and ideally the average lies at 75% of the range;
Multi-point calibration: several calibration points spanning the expected concentration range are the minimum requirement for the analytical system;
Stratification: unless prior experience shows no stratification at the sampling plane, measure the velocity, temperature, and composition profiles across the plane; if stratification is significant, traverse the stack with multi-point sampling or use a multi-hole probe;
Time stability: if stack conditions vary appreciably with time, average the results over a suitable period;
Test plan: prepare a detailed plan before the test, including shakedown of instrumentation and sampling system, calibration procedures and frequency, the number of test runs at each nominally identical condition, and the calculation procedures to convert raw readings.

🚨 Sample representativeness is the largest error source in flue gas analysis: only a very small part of the total flow is analyzed, so the gas must represent the average exhaust. Composition, velocity, and temperature stratification at the sampling plane, poor probe placement, or adsorption losses in the conditioning system produce systematic bias.

4. Manual vs. Instrumental Methods 📊

In an extractive system the first choice is between manual (normally wet chemical) and instrument methods:

Manual methods: simple apparatus, inexpensive — for example the Orsat analyzer for absorption of CO₂, O₂, and CO — but results are delayed and accuracy depends on an experienced technician;
Instrument methods: usually required for extended-period monitoring and real-time feedback; more expensive with relatively complicated sample conditioning and calibration systems, but far more convenient when many readings are needed.

Typical techniques for common constituents include: paramagnetic or electrochemical analyzers for O₂; non-dispersive infrared (NDIR) for CO₂ and CO; chemiluminescence for nitrogen oxides (NOx); and UV or electrochemical methods for SO₂. Specific guidance per constituent is given in Section 4 of the Part.

💡 A common engineering combination: an in-line paramagnetic O₂ analyzer for combustion control, plus wet-chemical or NDIR determination of CO₂/CO during efficiency tests. Let analyzers warm up and drift-stabilize before calibrating, use calibration gases spanning the range, and re-calibrate on schedule.

5. Engineering Practice Essentials 🛠️

🔍 Probe location: prefer planes with stable flow, no swirl, and no obvious stratification; multi-point grids or traverses markedly improve representativeness;
🔧 Conditioning system: flue gas contains moisture and dust; insulate transport lines to prevent condensation dissolving SO₂ and other components; replace desiccant and filter elements regularly;
📊 Coordination with performance tests: in boiler efficiency tests (PTC 4) gas composition and flow are tightly linked — synchronize gas sampling and analysis time windows with power and flow measurements;
📋 Calibration records: retain calibration records, calibration-gas certificates, and raw data so results are traceable and reviewable.

6. Frequently Asked Questions ❓

❓ Q: Why is O₂ concentration used for combustion control rather than measuring excess air directly?
A: Excess air bears a stoichiometric relationship to O₂; measuring O₂ is simple and reliable and lets you derive the excess-air factor. Measuring excess air directly requires simultaneous precise fuel and air flow measurement, which is error-prone and expensive.

❓ Q: Why do in-situ and extractive measurements disagree?
A: In-situ methods give the line-average concentration along the optical path, while extractive methods give local concentrations at the sample point; stratification or uneven moisture in the duct can make the two disagree. Verify the measurement-plane consistency before interpreting the difference.

❓ Q: How should the analyzer range be selected?
A: The highest expected concentration must not exceed the range; the ideal average lies around 75% of the range. An overly wide range degrades low-end resolution; an overly narrow range risks over-ranging the sensor or producing nonlinear readings.

🔍 Q: How do I choose between manual wet-chemical and instrumental methods?
A: For short tests with few constituents and low cost, choose manual methods; for extended continuous monitoring, real-time feedback, or many data points, choose instrumental. Compliance testing may specify the method — satisfy regulatory requirements first.