Result
- Lag time
- 15.3 s
- Internal volume
- 492.5 mL
- Actual flow in the line
- 1.93 L/min
How it is calculated
- Internal volume = π/4 × inside diameter² × length.
- For gas, the standard flow (0 °C, 1.01325 bar a) is converted to actual flow at line pressure and temperature using the ideal gas law.
- Lag time = internal volume ÷ actual flow. Liquids are treated as incompressible.
- Add the volume of filters, valves and conditioning components separately — they also add delay.
How to shorten lag time
- Use the smallest tube inside diameter the flow and pressure drop allow.
- Increase the flow — for example with a fast loop or bypass that returns most of the sample.
- Reduce the pressure in the line: compressed gas moves more slowly for the same standard flow.
- Shorten the route and place the analyser closer to the tap.
Techwin sample line bundles use process tubes of 1/8″–3/4″ or 6–12 mm OD. See analyzer sample lines for heated and inert-coated options.
Frequently asked questions
What is sample line lag time?
Lag time, or transport time, is the time a sample takes to travel from the process tap to the analyser. It equals the internal volume of the line divided by the actual volumetric flow through it.
Why does line pressure increase the lag time of a gas sample?
Gas flow is usually set in standard units. At higher pressure the same standard flow occupies a smaller actual volume, so it moves more slowly through the tube and takes longer to arrive.
How can I reduce analyser lag time?
Use a smaller tube inside diameter, increase the flow with a fast loop or bypass, lower the line pressure, and shorten the route between the tap and the analyser.
Does heating the sample line change the lag time?
Slightly. A hotter gas occupies more volume, so at the same standard flow it moves a little faster. The main purpose of heating is to keep the sample above its dew point, not to change transport time.
Need a sample line built to your numbers?
Send the tube size, length, flow and the temperature the sample must be held at, and our engineers will propose a heated sample line bundle.
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