Chlorine gas analyser

Let's consider an extensive group of control and measuring instruments, relevant in industry and household. The focus of our attention is on chlorine (Cl2) gas analysers, in all the variety of models and versions. Let's find out why and where they are used, what principles they work on, what characteristics are important for them. In short, you will get all the information for a balanced and correct choice of this equipment.

The very name ‘chlorine gas analyser’ says that the device is used to determine the concentration of one and quite specific gas. But why do you even need to measure its content in the room air or in the environment? For your own safety.

Why chlorine gas analysers are needed

Chlorine Cl2 is one of the gases most used in industry, particularly in the production of household chemicals or PVC and PVC-based products. And because it is used, it can also leak - an unpleasant and dangerous cost of production.

Yes, chlorine has a distinct, pungent and unpleasant odour. But consider how toxic it is. Its concentration in the air at the level of only 0.0001% is already considered dangerous to the human body and irritates the mucous membranes, and the chlorine content of 0.01% and above - provokes burns of the respiratory tract. Simply put, before you smell this gas, inhaling its vapours, you will be seriously poisoned.

This means that we need devices for analysis, which will timely catch deviation of maximum permissible concentration of such a dangerous substance Cl2 from the norm and warn about it. These are the chlorine gas analysers, which are also:

• continuously, in automatic mode, monitor the Cl2 content in the air of open and closed areas;
• signalling the exceeding of chlorine concentration thresholds by means of audible and/or visual indication;
• convert the readings taken into a DC output current.

Yes, chlorine gas analysers may not perform all of these functions, but only some of them. It depends on their type and design. Because gas analysers can be either stationary and used at the same site or mobile, i.e. portable, usually light and compact. In the first case, the devices are usually powered from the mains, in the second case - from an accumulator or batteries. By the way, how do such meters work?

Operating principle of the chlorine analyser

It is clear that any such device determines the concentration of Cl2 in the air mixture. But how exactly does it do this? It all depends on the type of sensor the chlorine gas analyser is equipped with:

• If infrared, it passes infrared rays through the medium and detects their intensity with a sensor. Each gas absorbs light in its own way, differently. The device analyses the wavelengths at the output and from this determines how much of the hazardous component is in the air.
• If electrochemical, it passes the medium through itself. The Cl2 contained in the air, in the process of electrolysis, starts to produce a direct current. The higher its output value, the higher the concentration the chlorine gas analyser sets.
• If photoionisation (PID), it passes UV light through the working medium, saturating it with photons. The gas analyser then records the content of each volatile compound and extracts Cl2 from them.

Of course, chlorine gas analysers equipped with different sensors differ in sensitivity. Chlorine gas analysers with FID are considered to be the most ‘delicate’: they detect even very small fractions of harmful substances in air mixtures.

By the way, the most modern models of gas meters are also notable for their versatility. There are chlorine gas analysers that, in addition to Cl2 itself, capture propane, methane, petrol vapours, carbon mono- and dioxide and so on - up to 8-10 dangerous components in the air. Yes, they cost the most, but, truth be told, they are not always and everywhere necessary.

Where Cl2 gas analysers are used

The sphere of their application is considered to be any open and closed sites where Cl2 leakage is possible. But this is in general, in theory, but what about in practice? Let's consider the cases more specifically:

• Chlorine gas analysers with infrared (optical) sensors are installed on turbine engines, in the shops of oil refineries and chemical plants, at sewage treatment plants. They are in demand wherever flammable media are handled and there is a risk of explosion due to leakage.
• Chlorine gas analysers equipped with electrochemical sensors are installed in underground gas storages, on oil storage tanks, on chemical tanks. Such devices are relevant when working with large volumes of mixtures (not necessarily air) and it is necessary to constantly monitor the concentration of their toxic components.
• FID chlorine gas analysers, i.e. with photoionisation sensors, are installed in industrial hygiene facilities. They are used for continuous monitoring of the environment in order to preserve its purity.

And all this about stationary chlorine gas analysers! But portable models are also worthy of attention, especially since they are used really widely. They are most often used in wells, cellars, underground structures and any other enclosed spaces where Cl2 can only accumulate.

Lightweight and compact, portable chlorine gas analysers are also in demand in industry, e.g. when making rounds of the factory floor to detect and/or prevent leaks. And universal gas analyser models that also capture CO, CO2, methane can be used in households and homes. 

Trust a name, a manufacturer with a positive reputation and a proven track record in the process control market - a quality chlorine gas analyser will serve you well.

How to choose the right chlorine gas analyser

This is the case when you need a device that will be as functional as possible at the site to be serviced. Just one or several? Where do you plan to use your new chlorine gas analyser? This is the first question that needs to be addressed.

If the meter is expected to be used at the same site all the time, e.g. in a production hall where Cl2 leakage is possible, it is better to buy a stationary model. Its advantages, such as noise-protected housing or stability, will be ideally utilised in such operating conditions.

If you plan to take your chlorine gas analyser with you to the workplace, searching for leaks in basements or, for example, along the entire perimeter of a pipeline, of course you need a portable model. What's more:

• the more compact and lightweight the instrument is, the better - ideally it should fit into a jacket pocket or a handbag;
• waterproof housing will be a definite plus - many air samples are taken at the water's edge, splashes are possible;
• the more sources from which the chlorine gas analyser can be powered (battery, socket, even USB), the more convenient - the more autonomous it will be;
• visibility is always important - if the device records the concentration of several indicators at once, it is necessary that all of them are clearly readable on the display;
• the more diverse the signalling, the better - it is good when the selected model not only shows the current Cl2 content in the air, but also notifies when it changes, including sound.

And, of course, any purchased chlorine gas analyser must comply with ISO quality standards. And remember, it is always a certified instrument, so its manufacturer (distributor, seller) is obliged to provide documents confirming the originality of this particular meter at the customer's request.

When choosing any gas analyser, including chlorine gas analyser, it is better to chase quality than price. After all, this is a device on which the safety of labour and people's lives will depend. Plus, an accurate, functional and usable meter today simply cannot be cheap.

Trust the name, a manufacturer with a positive reputation, which has proved itself in the market - a quality chlorine gas analyser will serve you well.