Smell, See, Hear
Current Trends in Gas Measurement Technology
Gas comes from chaos. That is to be taken literally because the word ‘gas’ originates from the Greek/Latin word for dissolution and disarrangement. Those looking for clarity – because many gases are inflammable, poisonous and can asphyxiate – turn to gas measurement technology. There are fixed and portable devices for this that are being constantly developed further.
The applications of gas measurement technology are more than numerous: you can find mobile as well as stationary measurement devices throughout industry, and the chemical industry in particular, in environment and energy commerce, in laboratories and in civil defense through to offshore platforms. A timely warning of dangerous gases is not infrequently a matter of survival and very often necessary to protect the health of employees. National and European limits form the basis for reliable tolerance levels. Gas measurement technology uses sensors, most of which use a catalytic method of operation. There are also sensors made of semiconductors, while other gas measurement technologies use the fact that the thermal conductivity of certain gases is higher than that of the surrounding air. In addition there are, amongst others, infrared and ultrasound gas detectors.
Technology and Handling, Documentation
Even when product life cycles in gas measurement technology are comparatively long, the engineers are simultaneously working on many fronts. Listening to the manufacturers, it becomes clear that both the accuracy and the measurement procedure itself are being developed. This applies to multi-gas systems and multifunctional systems, but also to concepts that affect integration into the whole safety management process: service, documentation and locating portable devices, for example, are important aspects.
There should be as few buttons as possible, because self-explanatory systems not only improve the ease of operation but also reduce the amount of training necessary for employees. The fundamental economic aspect behind this also supports a further trend: the attempt to provide platforms for different tasks that are very similar to one another. In this way a device that is suitable for person-related monitoring should also be able to be used for clearance measurements, for example in the cleaning of containers or for location monitoring.
This has the advantage that a new device with associated training is not necessary for each mode of operation.
Accessories and Networking
The way to attain multiple usage of the core unit is by using attachments, these stretches from pumps and pipes for tanks through to local monitoring devices that network themselves without cables into one safety network. In this way, other areas will be advised if a problem is reported at one location.
Networking permits further adaption. Certain actions can be linked to an alarm – even before the control room is made aware and takes appropriate action – so that, for example, fans can be automatically switched off to prevent spreading the problem or to prevent an explosion.
As far as the heart of the gas measurement device is concerned – the sensors – work is ongoing above all on improving their longevity. Some catalytic EX sensors can be poisoned by certain chemical substances and become increasingly insensitive. Examples of this are sulfur compounds in refineries. Even if sensors come into contact with the substances contained in lubricant sprays or hand creams they can become insensitive. For this reason, research is constantly looking for new compositions that will lead to higher resistance to sensor poisons.
There is a further-reaching development of new measurement processes – for portable as well as stationary devices – and multi-gas systems. The use of tunable lasers – that are already being used, above all, in America – for sensor technology will be a while coming. This technology uses the effect that most substances absorb light, and indeed the light of a particular color.
The manufacturers also consider the further development of optical monitoring technology – such as infrared – to be important. It will become cheaper and can be used for ever more measurement jobs. Amongst the currently most important development areas is the growth of ultrasound technology that is particularly suitable for the very rapid detection of leaks and the smallest cracks in pipes. In contrast to ‘smelling‘ (recalescence, electrochemical, semiconductor) catalytic and ‘seeing‘ optical (infra-red) detection methods, this is a sort of ‘hearing‘ technology using the fact that gases leaking from pipes and joints, produce a hissing noise, just like a leaky gas bottle.
Evaluation of the Data
However, the systematic evaluation of the data gathered from the gas measurement devices, that is also already widespread in the USA, to be an important development. Just detecting and documenting is not enough. Transmitting the data and evaluating it centrally is also important: when has which gas been detected and where? In what concentration? The data, should be so evaluated and projected in the result that one can determine, for example, when training measures are necessary in individual departments in order to avoid a safety problem. On the basis of the data, one can in fact clearly determine whether the individual employees are acting according to the prescribed standards, or whether they are staying too long and hesitating dangerously and against regulations, while the measurement results indicate that other measures are necessary. More important still than the further development of sensor technology is to proactively evaluate the existing data that are currently being discarded.
Locating Portable Devices
In large installations where many portable gas measurement devices are being used, it is important to be able to locate the device of an employee that is sending data, for example so that rescue measures can be taken. The main difficulty here though is the transmission, above all when the signal is affected by concrete, steel and metal.
(Working) Daily Device Tests
The reduction of acceptable limits naturally makes monitoring safer, and the demands on sensors increase accordingly. Technology and standardization become aligned, step by step. The operator must regularly check that the devices are working correctly, even daily – the latter is becoming commonplace in ever more industries. The trade associations and authorities are checking ever more often that this actually happens.
As this is becoming a strong trend generally and Europe-wide, it will be increasingly important for operators to carry out these checks properly and to document them. The documentation must be understandable and practical to fulfill. Test stations should be automatic if possible and test as many devices as possible at the same time. Increasing lack of time in the companies requires quicker software developments. The frequency of the tests also makes them an economic factor: the test gas is not very cheap, in particular when we‘re talking about many hundreds of devices. For this reason, the developers are trying to reduce the test times and the required amount of test gas.
Matthias Erler and Steffen Ebert, Wiley VCH & Co KGaA, G.I.T. Security