Japanese multinational electrical engineering and software company Yokogawa Electric Corporation has developed an explosion-proof version of its TDLS8200 probe type tunable diode laser spectrometer.

Yokogawa announced earlier last month that its TDLS8200 probe was scheduled to be released for sale on July 25 as part of its OpreX Analyzer family.

The TDLS8200 probe is used for accurate heating furnace and boiler combustion control and safety monitoring in the oil and gas, petrochemicals, chemicals, electric power, iron and steel, and ceramics sectors.

The TDLS8200 features low installation cost, high measurement stability, and high reliability, and is able to simultaneously and directly measure concentrations of two gas types – including oxygen and either carbon monoxide or methane – at high speed.

Currently on offer are probes that are capable of measuring temperatures up to 600 ºC and 850 ºC, and the addition of an explosion-proof version makes it possible to facilitate efficient combustion control and safe operation across a broader range of applications.

Development Background
Any excess air that is supplied when controlling combustion in a heating furnace will absorb heat inside the furnace before exiting out of the stack.

In addition to resulting in heat loss, this can generate large volumes of nitrogen oxides and sulfur oxides, a source of air pollution.

On the other hand, if insufficient air is supplied, complete combustion will not occur, resulting in energy loss, the emission of carbon monoxide and black smoke, and residual methane.

Carbon monoxide and methane are flammable gases that can readily form an explosive mixture with air if allowed to accumulate inside a furnace.

As such, oil and gas, petrochemicals, electric power, iron and steel, and ceramics plants need to monitor the concentrations of oxygen and carbon monoxide or methane inside furnaces in order to control and thereby ensure an efficient, environment-friendly, and safe combustion process.

However, the use of digital devices in zones where combustible gases reach concentrations that result in the risk of an explosion is limited by regional laws and regulations as they have the potential to ignite such gases.

Features
The most significant feature of the TDLS8200 is its dual laser light sources and optics, which give it the ability to simultaneously measure oxygen plus either carbon monoxide or methane concentrations for combustion control.

Its direct measurement system relies on the use of lasers, which are easier to maintain than conventional sampling systems and are more robust than catalyst-based sensors.

This ensures stable, simultaneous and lossless measurement.

Also, by adopting a probe design with no sampling device, it is easy to install and replace.

The explosion-proof TDLS8200 that is being released for sale conforms to the International Electrotechnical Commission explosion-proof standards, the FM explosion-proof standards of US and Canada, and the European Union’s ATEX explosion-proof directives.

Notably ATEX directives are the legal requirements for controlling explosive atmospheres and the suitability of equipment and protective systems used in them.

Compliance with these regulations enables the device to be used in zones where combustible gases reach concentrations that result in the risk of an explosion.

Going forward, Yokogawa will work toward acquiring certification for the explosion-proof standards of other regions and countries too.
How it Works
Yokogawa's laser gas analysers use a method called tunable diode laser spectroscopy to detect gas concentrations.

They offer superior real-time performance because they are installed on ducts and do not require a sampling system, so they can measure concentrations directly and at high speed.

They use a spectrum area method that calculates the gas concentration from the area in a light absorption distribution chart, which enables stable concentration measurement even in an environment where the temperature and pressure fluctuates or where other types of gas or large amounts of dust are present.