Fundamentals of ex-protection and solutions
For further standardization of explosion protection in the EU and for adaption to a new directive concept, EC Directive 94/9/EC on the "approximation of the laws of the Member States concerning equipment and protective systems intended for use in potentially explosive atmospheres" was enacted in 1994. This was replaced in 2014 by EU Directive 2014/34/EU (ATEX). It regulates the requirements on the properties of explosion-protected equipment and protective systems (e.g., by setting out provisions for conformity assessment, protective levels, certification, manufacture and quality assurance, marking, operating manuals and declarations of conformity) by prescribing the essential health and safety requirements that must be satisfied by manufacturers and importers. The directive thus ensures the free movement of goods within the European Union and must be adopted as it stands into national legislation.
In Germany for instance, this took the form of the Explosion Protection Product Ordinance as the 11th Ordinance of the Equipment and Product Safety Act (11. ProdSV). It applies to all industrial areas at risk of explosion (including mining). The directive applies to equipment, components and protective systems for use in potentially explosive areas. It also applies to safety, control and regulating apparatus used outside the hazardous area if this is necessary with respect to explosion hazards for the safe operation of equipment in the hazardous area. The directive does not refer to established standards, but sets out fundamental safety requirements, which are deemed as binding quality requirements. Protection from other hazards (e.g., electric shock) which may be caused by these devices must also be taken into account.
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1. Physical principles and definitions
2. Legal fundamentals
3. Technical principles
- Technical principles >
- Zone classification >
- Equipment categories and equipment protection level >
- Device groups >
- Ignition temperature and temperature classes >
- Ignition protection types >
- Certification >
4. Installation and operation of electrical equipment in potentially explosive areas
- Installation and operation of electrical equipment in potentially explosive areas >
- Obligations of operating company, installer and manufacturer >
- Classification of the areas and selection of equipment >
- Installation methods >
- Maintenance >
- Installation and operation of electrical equipment in potentially explosive areas >
5. Appendix
These Internet pages were created on the basis of the "Basics of Explosion Protection" brochure from R. STAHL Schaltgeräte GmbH. We would like to thank them for their friendly support.
Ex-protection solutions
The product range of the series includes all familiar function principles, such as throughbeam photoelectric sensors, retro-reflective photoelectric sensors and diffuse reflection sensors with background suppression.
To protect against mechanical damage, the sensors are enclosed in a metal housing. The highest requirements regarding resistance to shock of the housing are thereby safely met. The sensors can be used in potentially explosive areas with these classification requirements (see table).
| Device group | Device category | Equipment protection level | Zone | Subgroup |
| II | 3G | Gc | 2 | IIB |
| II | 3D | Dc | 22 | IIIC |
The ex marking of the devices. The devices also meet the special demands on equipment which work with optical radiation in potentially explosive areas (EN 60079-28).
The sensors of the 92 Ex series are designed as throughbeam photoelectric sensors, retro-reflective photoelectric sensors or diffuse reflection sensors and reliably detect objects at distances from 300 mm to up to 12 m. The intrinsically safe ATEX sensors reliably transmit the switching signals to the VS 403 isolated switching amplifiers with the help of the NAMUR interface. The sensors of this series may be used in zones 1 and 2 in areas where there are potentially explosive gases and dusts.
With the VS 403 isolated switching amplifier, it is possible to realize the intrinsically safe circuit for the sensors of the BR 92. The sensors are supplied with voltage and the switching signals transmitted via the NAMUR interface. Certified in accordance with the latest ATEX directives, the isolated switching amplifier is available with either 24 V voltage supply and relay or transistor output or with 110 to 240 V AC voltage supply and relay output.
For setting up an intrinsically safe circuit, Leuze electronic also offers blue cables with M12 round connectors for connecting sensors and isolated switching amplifiers.
Special accessories for devices in explosion-proof version:
- K-V M12-Ex interlocking guard, 50109217 (prevents unintentional disconnection of plug connections)
- Cable for connecting intrinsically safe sensors
Identification is also a topic in the area of explosion protection.
Systems often have a mixed design, i.e., some sub-areas are subject to explosion hazard, others are not. Available especially for surface-treatment applications (dipping baths, varnishing machines, drying, etc.) as an extension of our RFID devices for Ex Zone 2 (ATEX) is the RFM 32 SL 200 Exn device with long cable (10 m).
The function range corresponds to the RFM 32 SL 200 "standard device" (operating range up to max. 110 mm). Depending on the application, a number of transponders with ATEX approval (Zone 2) are available in addition to our standard range of transponders.
The distance sensors of the ODSL 96B Ex d and ODSL 30/V-30M Ex d series contactlessly detect objects located in the light beam or that move through the light beam and measure the distance to these objects. The sensors have a housing that features pressure-proof encapsulation and can be used in potentially explosive areas with these classification requirements (see table):
| Type | Device group | Device category | Equipment protection level | Zone | Subgroup |
| ODSL 96B Ex d | II | 2G | Gb | 1 | IIB + H2 |
| II | 2D | Db | 21 | ||
| ODSL 30 Ex d | II | 2G | Gb | 1 | IIA |
| II | 2D | Db | 21 |
The ex marking of the devices. The devices also meet the special demands on equipment which work with optical radiation in potentially explosive areas (EN 60079-28).
Measuring light curtain CML 720i Ex
Our measuring light curtains with explosion protection are available standard with a beam spacing of 10 mm and with a measurement field length from 140 to 2860 mm or with a beam spacing of 20 mm and with a measurement field length from 130 to max. 2850 mm. The devices can be used without additional protective measures in potentially explosive areas with these classification requirements (see table)
Safety light curtain MLC 520 Ex
The safety light curtains of the MLC 520 Ex series are optoelectronic protective devices and satisfy these safety requirements:
| MLC 520 Ex | |
| Type in accordance with EN IEC 61496 | 4 |
| Type in accordance with EN IEC 61496 | 4 |
| Performance Level (PL) in accordance with EN ISO 13849-1 | e |
| Safety Integrity Level (SIL) in accordance with IEC 61508 and SILCL in accordance with EN IEC 62061 | 3 |
The devices can be used without additional protective measures in potentially explosive areas with these classification requirements (see table).
| Type | Device group | Device category | Equipment protection level | Zone | Subgroup |
| CML 720i Ex | II | 3G | Gc | 2 | IIB |
| II | 3D | Gc | 22 | IIIB | |
| MLC 520 Ex | II | 3G | Gc | 2 | IIB |
| II | 3D | Gc | 22 | IIIB |