Many companies in the sector process flammable materials in the form of gases, liquids or dusts, and consequently they must comply with special regulations. These include the obligation to use so-called Atex-certified components and devices, which prevent the ignition of explosive atmospheres or at least reduce the effects of an explosion to a sufficiently safe level. In addition to the Atex directive, which is valid throughout Europe, the “Betriebssicherheitsverordnung” (Industrial Safety Regulation) and the “Gefahrstoffverordnung” (Ordinance on Hazardous Substances) are authoritative for companies in Germany.
In an ideal situation, even the development of an explosive atmosphere can be avoided, for example by thinning a flammable liquid or reducing the amount of oxygen in the air (primary explosion protection). However, in many cases this is either impossible or only possible with a great amount of effort and expense. At the very least, it must be ensured that there is no source of ignition close by (secondary explosion protection). This can be achieved through the use of special devices with ignition protection types Ex e and Ex i. However, there is only a limited choice of devices and components with these approvals. In addition, not all of these devices and components are suitable for every application.
To enable the processing industry to remain flexible with regard to the design of its equipment despite these problems, Rose Systemtechnik developed the pressure-tight encapsulated (flameproof) series of Ex d enclosures (tertiary explosion protection). With their help, even components without Atex certification can be used in critical
environments.
Different versions and sizes
The main task of Ex d enclosures is to prevent an internal explosion from spreading. For this reason, the ignition gap is designed so that when sparks, flames or hot gases leave the enclosure, they are cooled to such a degree that they cannot ignite the explosive atmosphere in the surrounding area. Rose offers its Ex d series enclosures in several different sizes and in versions made of copper-free aluminium or stainless steel. They are approved for use in explosive gas (IIB, IIC) or dust (IIIC) atmospheres and certified according to Atex, IECEx and EAC.
In addition to the four standard versions, the Porta Westfalica specialists also supply enclosures with customer-specific modifications or carry out surface improvements such as lacquering or fitting inspection windows. The manufacture of special enclosures and the complete machining of the products are likewise included in Rose’s services.
Tests in the in-house laboratory
Rose regularly carries out strict quality and load tests in its own laboratory, in order to ensure the Atex conformity of the Ex d enclosures. These tests take place in the temperature range for which the enclosures were designed.
For example, the self-heating test determines the maximum surface temperature and the programme also includes reference pressure, overpressure and spark transmittance tests. During the reference pressure tests, gas is introduced into the enclosure and then ignited. The spark permeability tests are conducted in a similar way: a gaseous mixture is introduced and subsequently ignited while the enclosure is in an explosive environment. The Atex requirements are not met if the ignition is transmitted to the external atmosphere. The spreading of the ignition spark depends on many conditions: apart from the ambient temperature, the geometry of the enclosure and the installed components also play a role.
Ex d enclosures for a refinery
However, Rose’s Ex d enclosures not only comply with the Atex directive – they also provide IP 66 protection (DIN EN 60529), which means that they are dustproof and protected against the ingress of water. Various other aluminium, stainless steel and polyester models, too, number among the explosion-protected enclosure systems.
Their great sturdiness is the reason for their use in many demanding applications. For example, Rose supplies explosion-protected enclosures in the ProtEx series to a refinery. They are shipped complete with the essential electronics and used as control stations for the compressors during petrol production. The plant is directly next to the sea, so that corrosion resistance of the enclosures was an important condition. In order to meet these high standards, Rose opted for a stainless steel enclosure and 1.4404 material alloy. The stipulated temperature resistance of -20 to +42 °C was not a problem, as the enclosures are suitable for use within a much wider range from -55 to +135 °C.
In addition to this, the order also required the enclosures to be machined, for instance with various cutouts in the cover for installing switches and indicator lights as well as on the underside for fitting cable glands. Another service offered by Rose is the complete mounting of the DIN rail and its electronic components plus the necessary screwing systems.
Suchwort: cppPC218rose
Ask the expert: Individual solutions
What distinguishes Rose
from other manufacturers
of enclosures?
We don’t just manufacture enclosures – we offer our customers complete solutions from a single source. This includes the individual design and machining of each enclosure as well as the installation of standard components and special electronics. Despite the high level of customisation, we can also manufacture these solutions with certification for hazardous areas.
The subject of explosion protection is relatively complex,
of course. Are your customers familiar with all the aspects that need to be considered?
We often experience a degree of uncertainty in this respect. This is why, if our customers ask, we guide them through the certification process or offer them completely certified devices. It’s a service many customers are happy to take advantage of.
Mathias Ohsiek is the manager in charge of explosion-protected enclosures at Rose SystemtechnikPicture: Rose
