Novel possibilities in explosion protection

[ptb] When electrical devices are operated in explosive areas, then it is particularly important to be careful. After all, even a small spark can lead to a catastrophe. To avoid having this happen, such devices must either be elaborately enclosed or it is ensured that no ignitable sparks are generated. The latter protective concept is called "intrinsic safety". So far, intrinsically safe devices have been unable to transform scarcely more than 2 watts active power. With the aid of the newly developed DART technology, it is possible to raise the upper limit of the active power transformation up to 50 watts. This now allows, compared with previous solutions, completely new intrinsically safe areas to be developed or also considerably more electrical devices to be operated intrinsically safe. The DART concept is the result of an AiF research project which is funded by the Bundesministerium für Wirtschaft und Arbeit (Federal Ministry of Economics and Labour). Hereby, the Physikalisch-Technische Bundesanstalt (PTB), as leading research centre, works together very closely with six German industrial firms - the committee conducting the project. From 21 - 25 April, at the Hannover Fair - INTERKAMA, the mode of operation of DART in connection with industrial applications will be convincingly presented (hall 7, stand E 14).

An intrinsically safe electrical device offers many advantages: Among other things, it is possible to save money in production, because no extensive encapsulations or similar protective devices are necessary. Furthermore, it is also possible, during running operation, to carry out such work as refitting, expansion or maintenance without a hot work permit. And also the connection and installation technologies are simpler. However, due to the upper limit of the admissible effective power, this type of ignition protection has up to now mainly been used in measurement and control technology - for instance, for the energy supply of sensors or actors. With the aid of the distinctly higher capacity DART technology, the advantages of intrinsic safety can be assigned to a considerably larger palette of applications. Thus, for example, also industrial PCs, LED illumination systems, sensors with high power requirement, magnetic control elements, magnetic valves or heating installations can now be constructed intrinsically safe.

DART stands for "Dynamic Arc Recognition and Termination". It operates like an emergency switch: It recognises a failure forming (for instance, the electric circuit opening) via the change in current connected with it and switches off the supply immediately. Thereby, the ignition-relevant energy is effectively restricted within a few microseconds and thus the generation of an ignitable spark is prevented. In the case of such a quickly reacting system, also the operating time in the line exerts an influence. Depending on the length of the line as well as the type of application (field bus or high-power application), the maximum admissible effective power for the instrinsic safety type of ignition protection can be raised to 8 watts, and up to 50 watts.

Furthermore, the PTB presents at the fair a survey of its tasks involving the approval of explosion-protected drive systems. The PTB is held in high esteem internationally in this field, not least because it actively participates in national and international standards institutions, on the basis of its own fundamental research.

The INTERKAMA in the Internet
http://www.interkama.de

Contacts at the PTB
DART: Dr. Udo Gerlach, Working Group 3.62 Explosion-protected Field Bus and Supply Systems,
Tel. +49 531 592 3620, E-mail: udo.gerlach@ptb.de

Approval tasks of the PTB: Dr. Christian Lehrmann, Working Group 3.72, Explosion-protected Electrical Drive Systems,
Tel. +49 531 592 3533, E-mail: christian.lehrmann@ptb.de

exhibit description (as *.pdf-Datei)
DART, A New Dimension In Intrinsic Safety