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Ex Basics

Product catalog summary

General Information
An explosive atmosphere is a mixture of air with combustible gases, vapors, mist, or dust that can ignite and cause explosions. These atmospheres are prevalent in industries such as chemical, petrochemical, food, and mining. Global standards, including IEC and ATEX regulations in the EU, aim to prevent explosions through specific safety measures.

Explosion
An explosion is a rapid oxidation or decomposition reaction resulting in a sudden increase in temperature and pressure. It requires three elements: combustible material, oxygen, and an ignition source, which can include hot surfaces, electrical sparks, and open flames.

Explosion Protection Measures (IEC Standard)
Protection measures are divided into primary (preventing explosive atmospheres) and secondary (preventing ignition). Equipment is categorized into Group I (mining) and Group II (other areas), with further subdivisions based on safety levels. Standards like IEC/EN 60079 outline protection principles for electrical equipment in explosive environments.

Zone Classification
Explosive atmospheres are classified into zones based on the likelihood of occurrence. For gases and vapors, zones range from 0 (permanent presence) to 2 (infrequent presence). For dust, zones range from 20 to 22. Equipment is categorized accordingly to ensure appropriate safety measures.

Temperature Classes
Electrical equipment is classified into temperature classes based on maximum surface temperatures to prevent ignition. Classes range from T1 (450°C) to T6 (85°C). Dust requires detailed evaluation, with ignition temperatures ranging from 240°C to 500°C.

Types of Protection
Protection types prevent contact between ignition sources and explosive atmospheres or contain explosions within equipment. Various types are defined in IEC/EN standards, ensuring equivalent safety across different protection methods.

Types of Protection in Gas Atmosphere
"Increased safety" (Ex-e) involves preventing high temperatures and sparks in electrical equipment. Applications include terminal and junction boxes.

Types of Protection:

Intrinsic Safety (-i): Ensures low energy in circuits to prevent ignitable sparks or temperatures. Subdivided into ia, ib, and ic categories based on safety levels and applicable zones.
Oil Immersion (-o): Immerses electrical equipment in oil to prevent contact with explosive atmospheres. Used in switching devices and transformers.
Flameproof Enclosure (-d): Contains components that could ignite an explosive atmosphere within a pressure-resistant enclosure. Common in motors and switching devices.
Moulded Encapsulation (-m): Encapsulates equipment in a moulding compound to prevent contact with explosive atmospheres. Subdivided into ma, mb, and mc categories.
Pressurized Enclosures (-p): Maintains overpressure to prevent explosive atmosphere ingress. Used in switch cabinets and control systems.
Type -n Protection: Applies to 3G category equipment, aiming to prevent ignition under normal and certain abnormal conditions. Includes non-sparking, sparking, and energy-limited types.

Protection in Combustible Dust Atmosphere:

Protection by Enclosures (tD): Prevents dust ingress with a minimum protection of IP 6x.
Moulded Encapsulation (mD): Uses encapsulation to prevent explosive atmosphere contact.
Intrinsic Safety (iD): Maintains low energy in circuits to prevent ignition.
Pressure Proof Enclosure (pD): Uses overpressure to prevent explosive atmosphere ingress.

Labeling:
Explosion-protected equipment must be labeled according to EN 60079-0 and EN 61241-0 standards, indicating manufacturer, type designation, CE conformity, test authority, application area, protection types, and temperature class.

Permits/Approvals:

Certification of Production Sites: Confirms technical safety during production.
EC Type Examination Certificate: Ensures compliance with ATEX and IEC regulations.
Declaration of Conformity: Manufacturer's assurance of compliance with legal conditions.
Additional Approvals: Required in some countries outside the EC, such as Russia and Kazakhstan.

Explosion Protection in North America (NEC Standard)

Introduction
While global principles of explosion protection are consistent, North America has developed unique techniques and systems for electrical devices and equipment that differ from IEC directives. Key differences include the classification of explosion-prone areas, design, equipment, and installation of electrical plants.

Classification of Explosion Endangered Areas
In the USA, areas are classified according to NEC 500 and NEC 505, and in Canada according to section 18 of the CEC. There are three main categories: Class I (gases, vapours, mist), Class II (dust), and Class III (fibres and fluffs). These are further divided into Division 1 and Division 2 based on the frequency and duration of exposure. The USA and Canada also use the IEC classification system for Class I, allowing for optimal technical and economic choices. Explosive gases in Class I are subdivided into gas groups A, B, C, and D, while combustible dust in Class II is divided into groups E, F, and G.

Design Regulations
North America has various standards for designing and testing explosion-protected electrical plants and equipment. In the USA, standards are set by Underwriters Laboratories Inc. (UL) and Factory Mutual Research Corporation (FM), while in Canada, the Canadian Standards Association (CSA) sets the standards.

Protection Types of Enclosures
Protection types in North America are defined by NEMA 250, which considers additional ambient influences compared to IEC 60529. A comparison table provides guidance on equivalent protection types between NEMA and IEC.

Certification and Identification
Electrical devices in explosion-prone areas in the USA and Canada generally require approval unless they are designed to be non-ignitable. Approval is granted by nationally authorized test bodies such as UL, FM, and CSA. Equipment identification must include explosion protection data.

Correct Selection and Configuration of Ex Equipment

Junction Boxes (Ex-e, Ex-i)
Terminal boxes must protect against corrosion and chemicals, with materials like stainless steel, polyester, aluminium, and polyamide preferred. Enclosures must meet impact resistance and temperature conditions, and avoid electrostatic charges. Only Ex certified components are allowed for Ex-e enclosures, and specific limits apply to the number and size of terminals based on spacing and heat generation.

Flameproof Enclosures (Ex-d)
Flameproof enclosures are used to contain ignitable equipment, ensuring that any explosion is contained and cooled to prevent ignition of the external atmosphere. The gap dimensions between enclosure parts are critical to prevent flame propagation, with specific requirements for different explosion sub-groups (IIA, IIB, IIC).

Connection of Conductors in Ex-d Area
There are three methods for connecting conductors in the Ex-d area: direct connection using Ex-d cable glands, Ex-d enclosures combined with Ex-e connection boxes, and cable connections that prevent flame propagation between Ex-d and Ex-e areas.

Local Control Stations
Local control stations are used in various industries, including chemical, petrochemical, and offshore technologies. They are based on Ex-approved enclosure systems and can include command, signaling, and display units, as well as fieldbus interfacing modules.

Terminology and Standards
The document provides definitions and explanations for various terms related to explosion protection, such as ambient temperature, ATEX directives, CE mark, and device categories. It also covers concepts like dust explosion, flameproof enclosures, and intrinsic safety.

Explosion Protection Measures
Primary and secondary explosion protection measures are outlined, focusing on preventing the creation and ignition of explosive atmospheres. The document also discusses the importance of explosion protection documents and measures.

Equipment and Safety Standards
Details on equipment identification, protection levels, and safety standards are provided, including IP protection, maximum operating temperature, and minimum ignition energy. The document emphasizes the importance of adhering to these standards to ensure safety in explosive environments.

Division of Devices and Protection Systems: Devices, protection systems, or components used in explosive atmospheres are categorized based on their maximum surface temperature. The maximum permissible surface temperature is determined by deducting a safety factor from the lowest ignition temperature of the dust.

Type of Protection: Enclosures provide protection against access to dangerous parts, ingress of solid foreign bodies, and water, verified by standardized tests (EN 60529). Special measures prevent ignition of the surrounding atmosphere.

Zone Classification - Dust Zones: Explosive areas are divided into zones based on the frequency and duration of explosive dust/air mixtures. Zone 20 is for permanent or frequent explosive atmospheres, Zone 21 for occasional occurrences, and Zone 22 for rare or short-term occurrences.

Appendix / Tables:

Table 1: Lists electrical protection types for gas-explosive areas according to IEC/EN 60079.
Table 2: Lists electrical protection types for dust-explosive areas according to IEC/EN 61241.
Table 3: Assigns equipment categories to zones based on the presence of gases, vapors, mists, or dust.
Table 4: Details temperature classes and permissible surface temperatures for electrical equipment.
Table 5: Provides ignition temperatures, temperature classes, and explosion groups for various gases and vapors.
Table 6: Lists limit temperatures for dust, including ignition temperatures for settled and swirled conditions.
Table 7: Compares protection types between USA (NEMA) and Europe (IEC).
Table 8: Specifies protective earthing conductor dimensions according to EN 60439-1.
Table 9: Details short-circuit resistance of mounting rails according to EN 60947-7-2.

Catalog excerpts

A Phoenix Mecano Company

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General information 3.) Explosion protection measures (IEC standard) 5 3.3.1) Types of protection in gas atmosphere 13 3.3.2) Types of protection in combustible 6.) Explosion protection in North America 7.) Correct selection and configuration of 7.3) Local Control Stations 40 The brochure has been carefully compiled in accordance with the current version of standards and directives. The current version of the individual technical and legal regulations is binding. Mistakes and printing errors do not imply any claim for damages. All rights, especially the right of copying, distribu- tion and translation,...

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Ex Basics - Explosion Protection Basics 1. General information An explosive atmosphere is a mixture composed of air and combustible gases, vapours, mist or dust under atmospheric conditions, which, once ignited, allows the combustion process to spread and include the entire mixture. In the field of the chemical and petro-chemical industry, explosive atmospheres are frequently encountered as a result of technical processing sequences. However, processes in the food industry, in mills and silos generate combustible dust, leading to a combustible atmosphere in conjunction with oxygen. Methane gas...

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2. Explosion An explosion is an oxidation or decomposition reaction in conjunction with a sudden rise in temperature, pressure or both simultaneously (definition acc. to EN 1127-1). This generates a sudden expansion of the gas volume and the release of large quantities of energy in a small space. The simultaneous existence of three factors is the prerequisite for an explosion to occur: - combustible material - oxygen - ignition source Prerequisite for the mixture to ignite and the subsequent explosion is a sufficient quantity of all three factors. Combustible substances are gases, fluids or solids...

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Explosion protection measures 3. Explosion protection measures (IEC standard) This term encompasses all protection measures and regulations relevant for the construction, production and installation of electrical / electronic devices in explosion endangered areas. In general, there are two types: - Primary explosion protection: Measures to prevent the creation of an explosive atmosphere - Secondary explosion protection: Measures to prevent the ignition of an explosive atmosphere Knowing that an explosive atmosphere is generated in many processes, manufacturers of electrical equipment have to...

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Explosion protection measures Devices to be used in other areas that could be endangered by an explosive atmosphere. Device group II Devices to be used in the other areas that might be endangered by an explosive atmosphere. Subdivision into categories: 1G (zone 0) Devices of Group II are subdivided into three categories (1-3) reflecting different safety levels. The required protection measures must be adapted to the individually required safety level: Category 1: Devices and systems are distinguished by a "very high degree" of safety Category 2: Devices and systems offer a "high degree" of safety...

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Zone classification Measures for dust explosion protection are listed in IEC/EN 60079 and IEC/EN 61241.. Electrical equipment for areas subject to combustible dust EN 3.1 Zone classification Explosion endangered atmospheres are subdivided into zones reflecting the probability of their occurrence. In accordance with the Ex regulations, the zones are defined as follows: I Gases and vapours (EN / IEC 60079-10): Zone 0: Area subject to permanent, long-period or frequent presence of a dangerous explosive gas atmosphere. Typically, these conditions are found inside containers, pipework, apparatus and...

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Zone classification II Areas subject to combustible dust (EN 61241-14) Zone 20: Area subject to constant, long-period or frequent explosive atmosphere consisting of dust/air mixtures. Zone 21: Area in which an explosive atmosphere consisting of a dust/air mixture can be occasionally expected. Zone 22: Area not susceptible to an explosive atmosphere caused by swirled up dust. Its occurrence, if at all, will in all probability be infrequent and short-period. Electrical equipment is subdivided into 3 categories 1, 2, 3 in accordance with its permitted use within the zones. Identification Use in...

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Zone classification Identification Use in zone of the units according to categories combustible material Combustible dust Areas subject to permanent, long-period or frequent presence of an explosive atmosphere Combustible dust Area in which a dangerous explosive dust atmosphere can be occasionally expected during regular operation. This includes the close vicinity to zone 20 as well as close areas around filling and discharging devices. Combustible dust Areas infrequently subject to an explosive atmosphere and, if at all, only shortperiod. Ignitability and the ability of an ignition flashback...

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Temperature classes 3.2 Temperature classes The subdivision of the different gases and vapours according to minimum ignition energies into explosion or gas groups is insufficient to adequately describe gases and vapours with regard to their explosive properties. On the one hand, gas can be brought to explosion by exceeding the ignition energy, but, on the other hand, can also be caused by high temperature, e.g. a hot surface. This ignition temperature, however, is generally not connected to the ignition energy, in other words, a gas with a low ignition energy must not necessarily explode at a...

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Temperature classes The surface temperature of equipment results from the ambient temperature and its intrinsic heat generated by the power dissipation of the electrical devices accommodated in the enclosure. Combustible dust requires a considerably more detailed evaluation of the characteristic technical safety values. 1. Dust mixtures having a particle size of up to 400 µm are ignitable 2. Dust atmospheres are ignitable in concentrations of 60 g/m³ and 2 kg/m³ 3. The ignition temperatures of combustible dust mixtures range between 240°C and 500 °C; depending on the type, for foodstuff and feedstuff...

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Ex Basics

Ex Basics

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