In natural gas safety, maintaining an adequate concentration of odorant is a critical control parameter. Odorants such as TBM/mercaptan and THT can be checked rapidly in the field using colorimetric detector tubes based on colour change.
What are TBM and THT?
TBM (tert-butyl mercaptan) and THT (tetrahydrothiophene) are among the odorant compounds used to impart a characteristic odor to natural gas. The measurement result is generally evaluated in ppm or, via suitable conversion, as mass concentration.
Why is a correct sample essential in field measurements?
Cleanliness of the sample line, proper pressure reduction, and sample representativeness form the foundation of the measurement. High-pressure gas must not be applied directly to the detector tube; a safe sampling arrangement must be used.
How is the Kitagawa tube method applied?
The appropriate Kitagawa tube for the target compound is selected, the tube tips are broken open, and the number of sample pump strokes specified by the manufacturer is drawn using the AP-20 pump. The colour change is read from the scale; temperature, pump stroke, or conversion factors are applied if required.
What should be considered when interpreting the results?
Rather than relying on a single measurement, process conditions, injection point, pipeline flow rate, and sampling point should be evaluated collectively. Factors such as tube shelf life, interfering compounds, and adsorption within the sampling line can affect results.
When is a laboratory method required?
For routine field monitoring, the detector tube is a rapid and practical tool. When lower uncertainty, statutory verification, or detailed component-by-component analysis is required, chromatographic or laboratory-based methods must be evaluated separately.
Let us specify your natural gas odorant measurement system
Share your TBM, THT, or mercaptan measurement point and expected range; let us evaluate the appropriate Kitagawa tube, pump, and sampling configuration together.
Frequently Asked Questions
Are TBM and THT the same odorant?
No. They are distinct chemical compounds, and the detector tube appropriate for the target compound must be selected for measurement.
Can the high pressure in the natural gas pipeline be applied directly to the tube?
No. Detector tubes must be used with an appropriate sample pressure and volume. A safe sampling and pressure reduction arrangement is required on pressurised pipelines.
Can the result be converted from ppm to mg/m³?
Conversion can be performed using appropriate temperature, pressure, and molecular weight data. The conditions specified by the standard used for official reporting must be taken as authoritative.
Is calibration required for TBM/THT measurement?
The detector tube system operates according to the manufacturer calibration scale; pump leak tightness and volumetric performance must be verified regularly.
Sources and Technical References
- Komyo Rikagaku Kogyo K.K. – relevant TBM/THT detector tube technical data sheets
- Komyo Rikagaku Kogyo K.K. – AP-20 Gas Aspirating Pump
This content has been prepared for general technical information purposes. In measurement, risk assessment, and regulatory compliance activities, current manufacturer documentation, applicable legislation, and relevant standards must be taken as authoritative.