Application guide
Analyzer Sample Lines
An analyser is only as accurate as the sample that reaches it. Heated and pre-insulated sample lines carry gas and liquid samples from the process tap to CEMS, process analysers and gas chromatographs while holding them at a controlled temperature, so the sample does not condense, adsorb or thicken on the way. Techwin builds these lines as factory-assembled Traceline bundles.
Why sample lines are heated
Stay above the dew point
If a gas sample cools below its dew point, water condenses in the line. Soluble components dissolve in that water, so the analyser reads less than is really in the process.
Prevent adsorption
Reactive and sticky components — sulphur compounds, mercury, ammonia, some VOCs — can cling to cold or untreated tube walls, delaying and lowering the reading.
Keep liquids flowing
Liquid samples can thicken or freeze in cold weather. Holding the line at temperature keeps viscosity and transport time steady.
Protect people
Insulation and an outer jacket keep the surface of a hot line safe to touch. Techwin bundles keep the outer jacket below 60°C.
Choosing how the line is heated
Electrical heat traced sample lines
The usual choice for analyser shelters, stacks and long runs. Self-regulating cables cover about 40°C, 110°C and 120–150°C maintain ranges; constant-wattage cable maintains up to 200°C; power-limiting circuits run up to 450 m.
SpecificationsSteam traced sample lines
For plants with steam available and high-temperature sampling. Heavy steam traced bundles maintain process temperatures over 204°C without an electrical supply in the field.
SpecificationsPre-insulated sample lines
For short, low-heat-loss runs where the sample only needs protection from the weather, not active heating.
SpecificationsNew to tracing? Read the heat traced tubing buyer guide.
Tube materials and inert surfaces
The tube wall touches every molecule of the sample. For reactive or trace components, the surface matters as much as the temperature.
Stainless steel 316 (seamless or welded)
The standard process tube for most gas and liquid samples.
PTFE, FEP or PFA
Fluoropolymer tubes for corrosive samples and where a non-metallic flow path is preferred.
SilcoTek® SilcoNert® coated
Inert amorphous-silicon coating that stops surface adsorption of sulphur, mercury, ammonia and VOCs — for trace and sub-ppb analysis.
Electropolished 316L
Mirror-smooth interiors (Ra ≤ 0.13 µm) with a chromium-enriched passive layer — and the recommended finish before SilcoTek coating.
What to specify
- Sample dew point and the temperature the analyser needs the sample delivered at
- Components to be measured — and whether any are reactive or prone to adsorption
- Line length from the sample point to the analyser
- Heat source available on site — power or steam
- Hazardous-area classification at the sample point and along the route
- Number and size of tubes (sample, return, calibration gas) and their material
Typical Traceline sample line bundles use one or two process tubes of 1/8″–3/4″ or 6–12 mm OD, fibre-glass or aerogel insulation, and an FR-PVC, TPE, TPU or PA outer jacket.
Where Techwin sample lines are used
- Continuous emissions monitoring systems (CEMS)
- Process analysers
- Gas chromatographs
- Instrument sample lines to flow, pressure and level transmitters
Customers named in the Techwin company profile include analyser and instrumentation companies such as ABB, Yokogawa, Emerson, SICK, Thermo Fisher and Horiba.
Frequently asked questions
What is a heated sample line?
A heated sample line is a tube bundle that carries a gas or liquid sample from the process to an analyser while a heating cable or steam tracer keeps it at a set temperature. Insulation and an outer jacket hold the heat in and protect the line.
Why do CEMS and process analyser sample lines need heating?
Samples carried to CEMS and process analysers are susceptible to condensation, adsorption and changes in viscosity. Keeping the line above the sample dew point stops water condensing and taking soluble components out of the gas, so the analyser measures what is really in the process.
Which tube material should I use for an analyser sample line?
Stainless steel 316 suits most samples. PTFE, FEP or PFA suit corrosive samples. For trace sulphur, mercury, ammonia or VOC analysis, a SilcoTek SilcoNert coated tube stops the sample adsorbing on the tube wall; electropolished 316L gives a very smooth, clean surface and is the recommended base for coating.
How long can a heated sample line be?
It depends on the heating cable. In Techwin bundles, power-limiting cable allows circuits up to 450 m, while constant-wattage and self-regulating cables are used on shorter runs. Long lines also increase transport time, which affects analyser response.
Can heated sample lines be used in hazardous areas?
Yes, when the heating cable is certified for the area. The heating cables used in Techwin electrical traced tubing carry IECEx, ATEX and IEC hazardous-area certification.
Specify a sample line
Send the analyser, sample composition, dew point, line length and area classification, and our engineers will propose a bundle.
Request a quote