08/19/2011 • Machine safety, industrial safety

Extreme switchgear – “tried and tested”

A developer of switchgear for extreme applications and conditions has to be able to simulate these conditions in the laboratory. A look behind the scenes of the steute testing department reveals just what steute switches have to cope with.

Vibrations, moisture, heat, dirt, salt spray, explosive atmospheres, high-pressure cleaning: these are just some of the conditions which switching devices are exposed to in certain contexts, e.g. foodstuffs production or offshore technology. It is also not unusual for these ambient conditions to occur in combination.

In these environments, conventional switching devices would fall far short of achieving the desired service life or providing the required reliability. Using switchgear developed especially for extreme circumstances is therefore the option of choice. The steute business field “Extreme” is dedicated to developing and manufacturing just such devices. The tests performed during the initial development phase, as well as for ongoing product series, are equally extreme.

Impact and shock tests
Switching devices intended for use in explosive areas need to pass an impact test in which a testing mass made of hardened steel is dropped onto the device from a pre-defined height (Fig. 1). This test, in accordance with EN 60079-0, has been passed by the entire steute Ex-range. Impact tests of a different kind are required for emergency-stop devices (Fig. 2). Here the test, in accordance with EN 60947-5-5, reveals whether the emergency-stop device is still able to function correctly even when actuated repeatedly and vigorously.

Yet other tests, in accordance with IEC/ EN 60068-2-27, are performed on switching devices such as the HS Si 4 safety sensor which have to meet particularly high standards regarding shock and vibration resistance.

Resistance to damp, moisture and saltwater
100 litres of jet-propelled water per minute: this is the quantity of water which switching devices have to withstand in order to achieve protection class IP 66 (Fig. 3). Even extremer are the requirements for protection class IP 69 K: here switching devices are exposed to a hot (80°C) water jet at a pressure of 100 bar, proving that they can also withstand cleaning by a high-pressure washer. This is a requirement both in hygienic applications, e.g. foodstuffs production, and dirty applications, e.g. vehicle construction.

The steute switchgear range for offshore applications – including, for example, the position switches in series ES/EM 95 – additionally need to pass periodic salt spray tests. Another testing procedure demands complete immersion in water: mandatory for switchgear hoping to achieve protection class IP 68 (Fig. 4).

Manufacture according to the highest quality criteria
These are just a few examples of the tests which switching devices in the steute business field “Extreme” are subjected to. Of course, “extreme”, i.e. particularly high quality criteria are adhered to not only in the laboratory, but also in the production hall. For example, steute has invested in a new machine which superimposes highly efficient seals on enclosures automatically or semi-automatically. The powder coating machine for metal enclosures on the robust position and foot switches from steute also fulfils the highest standards of surface quality.

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steute Schaltgeräte GmbH & Co. KG

Brückenstr. 91
32584 Löhne

Phone: +49 (0) 5731/ 745- 0
Fax: +49 (0) 5731/ 745- 200