Innovative gas analysis even in small process pipelines

Gas analysis plays an important role in industrial processes, especially in sectors where accurate control of gas flows is essential for safety and efficiency. Traditionally, gas analyzers are often associated with large pipes and chimneys, but the technology has evolved significantly in recent years to accommodate smaller process pipelines. An important example of this is the use of Tunable Diode Laser (TDL) analyzers, which are used in many industrial settings for their accuracy and speed.

Get high resolution with Tunable Diode Laser (TDL) analyzers in DN50

When we think of Tunable Diode Laser analyzer (TDL), we usually think of those rugged enclosures mounted on either side of a large chimney, several meters in diameter. On one side a laser source, on the other a detector. This image was true, until Mettler Toledo entered the market just over a decade ago with their "Probe Type" analyzers.

Small, but fine

In the process industry, there are not only chimneys and large pipes of one or two meters. Typical process pipelines have a diameter of 50 to about 300mm (DN50-DN100). With a classic TDL analyzer, this is not feasible. With the updated concept it is. The "Probe Type" analyzers are made so that the laser and detector are in one unit. So you only need one flange connection. The laser beam passes through the probe and is reflected back to the detector through a special reflector (the so-called corner cube). Thus, the laser beam passes through the probe twice making the optical path length (OPL) twice the physical length of the probe.

A practical example

In a process in the metal industry, the oxygen concentration in the gas stream must be measured. Since there is a danger of explosion, the oxygen concentration should be as low as possible (< 1%), usually even close to 0%. It is a safety measurement and therefore the response time of the analyzer is very important and should definitely be less than 5s. The pipe has diameter DN80. The temperature can reach 120°C at a pressure of 4bar (absolute).

None of this is so extreme, but still quite a challenge. An analyzer with wafer cell (a circular flow-through cell) with a diameter of DN80 is the solution here. Under the given process conditions, this setup makes it possible to measure oxygen concentration with a resolution of better than 0.2% and with a response time of less than 2s.

Smaller conduit, yet larger OPL

For applications in smaller pipes such as DN50 where a higher resolution (> 0.1%) is required, Mettler Toledo has come up with a unique concept. With the so-called MR2 or MR3 (MR stands for MultiReflector) you increase the OPL two to three times. Recall that the laser beam is reflected which doubles the OPL. The MR2 makes the OPL four times larger than the pipe diameter. With MR3 it is even six times. 

This makes Mettler Toledo the "Technology Leader" for TDL analyzers with the GPro500.

Discover the full blog post with more information on Small Pipe Installation. >>