Variable Area Flow Meter

ATEX

Every operator who wants to measure the temperature of explosive substances with Pt100 resistance thermometers, has already dealt with the subject of “explosion protection” and has come across the term ATEX.
ATEX is an abbreviation of the French term Atmosphères exlosibles (explosive atmospheres).
ATEX is mainly based on 2 directives that are legally binding in the European Union.

• ATEX Directive 2014/34/EU
  This defines the obligations of manufacturers of products for potentially explosive atmospheres.
  Manufacturers must ensure that their devices have the properties required for explosion protection.
  The devices are marked accordingly and a declaration of conformity guarantees the operator in which areas (mining or above ground) and for which type of substances (gas/vapor/dust) the devices may be used.
  Furthermore, the safety level (very high/high/increased) of the devices is specified and how explosive the substance to be measured may be (explosion group/ignition temperature, defined by the maximum surface temperature of the devices). For details, see labeling of the devices.
  Link to Directive 2014/34/EU
  
  
• ATEX Directive 1999/92/EG
  This operating guideline regulates the obligations of the system operator and is intended to protect persons working in a potentially explosive atmosphere.
  The operator must prepare a risk assessment of his system, which includes, for example, the classification of the explosion protection zones and the determination of the relevant substance data for the explosive substances used.
  Main objectives for preventing an explosion:
  • Prevention/reduction of an explosive atmosphere.
    e.g.: use other substances, extraction, protective gas atmosphere
  • Avoidance of ignition sources.
    e.g.: Appliances with a lower surface temperature
  • If an explosion does occur.
    Reduce the impact of the explosion to a level that is as harmless as possible. e.g.: Structural measures such as explosion flaps.
  Link to Directive 1999/92/EG
  
  

Key points

• Legal basis
  Legally binding in the EU through directives: 2014/34/EU for products and 1999/92/EC for explosion protection in the workplace.
• Scope of application
  Legally binding in the EU and the EEA (Norway, Iceland, Liechtenstein).
  Not legally binding in Switzerland, but is often accepted in practice.
  In Turkey, ATEX is required by law, as Turkey has transposed the EU directive into national law.
  In the United Kingdom (UK), ATEX is no longer directly prescribed since Brexit. Instead, there is the British UKCA certificate, which is very similar to ATEX.
  ATEX is still required in other countries if deliveries are to be made back to the EU.
• Standards basis
  Based on European standards (e.g.: EN 60079 series), which are harmonized with IEC standards.
• Certification system
  The devices require an EU type examination certificate (ATEX certificate) and a declaration of conformity from the manufacturer.
  The type examination certificate is issued once by a notified body. A notified body is an organization designated and accredited by the EU that is authorized to carry out the type examination and issue the certificate (e.g. TÜV, Dekra, Bureau Veritas).
  Exception: Category 3 (Zone 2/22): No type examination certificate is required here. Based on internal tests, the manufacturer can issue the declaration of conformity without a type examination.

When will the explosion occur?

An explosion is a sudden and violent release of energy that can be triggered by various physical or chemical processes.
It occurs when a rapid transformation of matter or energy takes place, resulting in a sudden increase in pressure. This usually produces shock waves, heat and sometimes light.
Chemical explosions often result from a rapid reaction of flammable substances with oxygen, such as the detonation of explosives or flammable gases.
An explosion occurs when three conditions are met:

Explosion protection zones acc. ATEX and IECEx

Areas with potentially explosive atmospheres, also known as explosion protection zones, occur wherever flammable substances in the form of gases, vapors, mists or dusts can occur in hazardous concentrations. These play a central role when working with flammable substances.
In order to minimize risks for people, systems and the environment, explosion protection zones are divided into different categories, each of which requires different safety requirements. The classification is based on the probability and duration of the occurrence of a hazardous explosive atmosphere.
This systematic classification is the basis for the selection of suitable protective measures, such as explosion-proof devices and safety-conscious operating procedures, and ensures operational safety in potentially hazardous environments.

Device labeling of devices according to ATEX

Device marking in accordance with ATEX is a crucial prerequisite for the safe use of varable area flowmeters in potentially explosive atmospheres.
ATEX stands for the EU directives that regulate the requirements for devices and protective systems for use in environments with a potential explosion hazard.
The marking provides important information about the suitability of a device for certain zones and substances as well as the protective measures that the device offers.
The marking must be permanently attached to the device.
Manufacturers, operators and maintenance personnel must understand the marking to ensure the correct selection, installation and maintenance ofvarable area flowmeters.
Varable area flowmeters without correct labeling must not be used in potentially explosive atmospheres as they can pose a significant safety risk.
In addition to labeling, regular inspections and maintenance are also required to ensure long-term safety.

Main elements of the device labeling:

• Characteristics of the device
  The marking specifies the areas for which the varable area flowmeters may be used (device group, device category) and how the explosion protection has been designed (explosion protection type).
  Furthermore, the maximum surface temperature of the device is specified (temperature class).
• Property of the explosive product
  The marking specifies how dangerous the product to be measured (explosion group) may be. The system operator must ensure that the ignition temperature of the product is not lower than the maximum surface temperature of the appliance (temperature class).
  The explosion group and temperature class many products can be found at:
  
  • Gases: https://gestis.dguv.de
    
  • Dusts: https://www.dguv.de/ifa/gestis/gestis-staub-ex/index.jsp

Example for the marking of electrical devices according to ATEX:
(The colored background is only for the assignment to the following explanation).