Automation in Explosive Areas | First part

Automation systems in hazardous and explosive areas require special products and engineering. The applications to be made in such regions are specified with relevant directives and standards. In the light of these standards and regulations, the dangers of automation systems are eliminated.

The explosion is the release reaction of the high energy that flammable substances perform together with oxygen suddenly. Flammable materials can be in the form of gas, vapor, smoke or dust.

An explosion can occur when all 3 conditions below are at the same time.

• Explosive substance (in sufficient quantity and concentration)
• Oxygen (from the air)
• Ignition source

One of the biggest industrial disasters in modern history took place at the Imperial Sugar factory in 2008. The reason for the explosion was powdered sugar that formed in the packaging area.

An important parameter in safety-related observations is the flash point. The flash point determines the lowest temperature for explosives. External ignition may explode the vapor formed on the liquids (at normal air pressure). If the flash point is above the actual temperature, the explosion may not occur. The flash point may fall down if different liquids mix. In order to create an explosive atmosphere, the concentration of the explosive substance must be within the desired range. If there is too high concentration (rich mixture) or too low concentration (lean mixture) then the explosion may not occur; no permanent reaction or explosion reaction occurs. The mixture reacts only between the lower and upper limits.

EXPLOSION LIMITS DEPEND ON THE AMOUNT OF OXYGEN IN THE AIR FROM THE PRESSURE OF THE ENVIRONMENT.

Physical Basics and Definitions

1-Do not create an environment for potential explosion (Priority protection)

• Avoid flammable materials
• Make it stagnant (add nitrogen, carbon dioxide, etc.)
• Limit concentration by natural or technical ventilation

2-Protect from ignition effect

• Separate potentially explosive zones as dangerous zones

3-Limit the explosion effect (Structural protection)

• Use pressure-tight or shock-resistant construction
• Pressure relief or balancing equipment
• Suppression of explosion using extinguishing equipment

Automation Systems in Hazardous Areas

Europe ATEX (Atmosphère explosible)

Many guidelines and directives have been prepared worldwide and on a regional basis.

Harmonization and unification of national rules and directives have been implemented in Europe since 2001.

WAGO EX modules have been developed for automation applications in explosive areas. It provides flexibility, space saving and economy in applications.

Directive 94/9 / EG (ATEX 95) Manufacturer Directives

• Determining the basics
• Security requirements
• Conformity assessment procedure
• Grouping and categorizing devices
• CE marking
• Directions for use

Directive 99/92 / EG (ATEX 137) Workspace Directives

• Explosion risk assessment
• Classification of the regions
• documentation
• Work safety
• Employee training information classification

International

On a global basis, efforts are made to find a single guide and guideline for explosion protection.

International IECEx (International Electronical Commission)

• Implementation of European EN standards
• Accepted in Australia and China

USA NFPA 70 NEC (National Electrical Code)

• Articles defined in 500 and 505
• Partially similar to IEC

Kanada CEC (Canadian Electrical Code)

• Defined in Chapter 18 and Annex J
• Partially similar to IEC

Ignition Protection Types

The types of fire protection for electrical devices in hazardous areas for gas-based explosions are described in the image below.

Types of ignition protection for electrical devices

Ignition protection types for electrical devices in areas with flammable dust are as follows.

Ignition protection in areas with flammable dust

Increased Security | IEC 60079-7

Basic Principle

Safety is created by creating boxes to prevent the formation of electric arc or spark by preventing overheating.
level is increased, and sources that can create sparks inside the normal device are destroyed.

Main Application

Terminals and junction boxes, control boxes must be Ex materials for assembly. Squirrel cage motors, lighting fixtures.

Flameproof enclosure | IEC 60079-1

Basic Principle

Preventing the flame from leaking out

Main application

Indicators, control systems, motors, transformers, heating devices, lighting fixtures

Pressurized Housing | IEC 60079-2

The Basic Principle

Keeping excess pressure in a container

Main application

• Electric panels and control cabinets
• Large engines and analysis devices

Subcategories

px = Zone 1, 2 is also used.
py = Zone 1, 2 is also used.
pz = used in Zone 2

Internal Security | IEC 60079-11

The Basic Principle

Only parts with increased internal safety are used in explosive areas. If an electrical circuit or device has internal safety, it does not generate sparks and emit heat. It does not create an ignition effect in explosive areas.

Main application

• Measurement and control technology
• Field equipment, sensors, actuators

Subcategory

ia = Zone 0, 1, 2 is used.
ib = Zone 1, 2 is used.
ic = Zone 2 is used

WAGO is EX-i approved for applications in explosive areas and does not require any barrier barrier system, gas and pipeline applications. offers compact and cost-oriented solutions.

Oil immersion | IEC 60079-6

Basic Principle

Electrical equipment or parts are immersed in protection fluid. The aim is to prevent the spark from spreading out.

Main Application

Transformers, resistors.

Powder Filling | IEC 60079-5

Basic Principle

• The box of the electrical equipment is filled with dust. Thus the firing effect is suppressed.
• The spark formed on the surface is not carried inside or the ignition effect caused by overheating is prevented.

Main Application

Sensors, electronic ballasts, transmitter

Coating | IEC 60079-18

Basic Principle

The ignition effect of the parts placed in metal casting is prevented.

Subcategory

ma = Zone 0, 1, 2 is used
mb = Zone 1, 2 is used

Ignition Protection Type | IEC 60079-15

Basic Principle

Electrical components do not create ignition effects. (under normal working conditions or defined working conditions)

Main Application

All equipment used in Zone 2

Subcategories

nA = Spark-free equipment
nC = equipment and components
nR = Gas tight housing
nL = Energy limited equipment

Optical propagation | IEC 60079-28

Basic Principle

Optical diffusion preventing devices.

Main Application

Fiber cable

Subcategory

Ex op is = safe optical emission (natural)
Ex op pr = Protected type optical radiation
Ex op sh = Locked protection