Explosion protection in plant engineering
Explosive atmospheres can occur in many industrial plants, such as in the chemical, pharmaceutical, food and energy sectors. These usually consist of a mixture of flammable substances such as gases, vapours or dusts and air. As soon as an ignition source is added, there is a risk of explosion. To prevent this, there are strict regulations on explosion protection in plant construction, such as the ATEX directives.
What does ATEX mean?
«ATEX» stands for ATmosphères EXplosibles and comprises two central European directives:
The ATEX directive applies to equipment and protective systems intended for use in potentially explosive atmospheres. The directive defines the basic health and safety requirements and the procedures for assessing conformity. They must be applied before such products can be placed on the market.
Three elements must contribute to an explosion:
- a flammable substance in ignitable quantities (e.g. flammable dust/particles or gases/vapours),
- oxygen (normally in the ambient air),
- an ignition source (e.g. a spark, an electrostatic discharge or naked flames).
Explosion protection has three main objectives:
- prevention of explosive atmospheres,
- avoidance of effective ignition sources,
- limiting the explosion effect if an explosion does occur.
Potentially explosive areas are in any industry or business that manufactures, processes or uses flammable materials. These can be, for example, the following:
- Petrol stations for motor vehicles and aircraft,
- Oil refineries, oil rigs and processing plants thereof,
- Chemical industrial plants, plants for the pharmaceutical industry,
- Printing industry (paper and textiles),
- Surface coating industries and paint shops,
- Biogas and wastewater treatment plants,
- Gas pipelines and distribution centres,
- Grain handling and storage, mills,
- Woodworking areas,
- Grinding work on metal surfaces, especially aluminium dust and particles.
Zone categorisation - Where is there what danger?
Potentially explosive areas are categorised into zones. A basic distinction is made between gases/vapours and dusts:
Plant safety requires the operator to classify the various areas by means of a hazard analysis. He must divide all potentially explosive areas into gas or dust zones and define corresponding protection zones. In these clearly defined zones, special explosion-protected devices must then be used, which must be labelled in accordance with one or more standards.
Ex labelling according to international standards
ATEX: Ex protection for Europe, IECEx: International explosion protection, NEC: Explosion protection for the USA.
The source of the graphics and the copyrights for the extracts "Equipment category and type of explosive atmosphere" and "Ex labelling overview" are held by i.safe MOBILE, www.isafe-mobile.com.
Download the complete overview of the Ex markings as a PDF. The copyright of the complete overview of the Ex markings is also owned by i.safe MOBILE.
Requirements for devices and systems
Only devices that have been tested in accordance with ATEX may be used in potentially explosive atmospheres. In addition to the CE marking, such equipment also bears the Ex symbol and details of the equipment group and category. CE labelling in accordance with ATEX is mandatory. It confirms compliance with the basic safety requirements.
Classification into equipment groups and categories:
- Group I (mining) and Group II (above ground): Important for manufacturers for certification.
- Group II (surface) applies: Category 1G (or 1D) - suitable for Zone 0 or 20, Cat. 2 for Zone 1/21, Cat. 3 for Zone 2/22.
For example, the test number ‘II 2 G/D’ identifies a Group II, Category 2 appliance that is suitable for use in Zone 1 or 2 (gas ‘G’) or Zone 21/22 (dust ‘D’). A device that is to be used in Zone 0, on the other hand, must be at least Category 1. Through this categorisation, the ATEX system ensures that only suitable and certified devices are used in the respective zones.
To summarise, ATEX explosion protection ensures that the correct safety precautions are taken in systems with flammable substances. This includes zoning according to the frequency of explosive atmospheres, the use of tested Ex devices and consistent measures to avoid ignition sources. In this way, people, the environment and machines are protected from explosion hazards in the best possible way.
FAQs
Highly flammable gases and solvent vapours are produced in the chemical industry and refineries. In flour, sugar or spice production, fine particles create dust zones. Airborne flour dust, for example, is highly flammable. Spray and thinner paints contain flammable solvent vapours. Explosive vapours are usually permanently present in paint booths and exhaust air ducts in paint shops. Explosive vapours can occur when refuelling vehicles (petrol, diesel) or in electroplating baths.
Both IECEx and ATEX are based on the same standards (e.g. IEC-EN 60079). ATEX and IECEx are directives or certification systems that define safety requirements for equipment and protective systems for use in potentially explosive atmospheres. While ATEX applies specifically to the European Union, IECEx is internationally recognised and therefore applicable in a wider range of countries and areas such as Australia, New Zealand, parts of Asia and the Far East.
Your partner for components in potentially explosive atmospheres
TRI-MATIC AG can offer a wide range of solutions for potentially explosive atmospheres. These include ball valves and shut-off valves with various connections, manually, pneumatically or electrically actuated. Pressure sensors, pressure switches, pressure gauges, pneumatic valves and maintenance units are also part of our range of ATEX standard products. Contact us at +41 41 780 22 22 or info@tri-matic.ch.
An extract from TRI-MATIC's ATEX programme
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