What’s a Hazardous Area and where to find Ex equipment
Equipment Protection Level (EPL)
What’s a Hazardous Area and where to find Ex equipment
A hazardous area is the area in which a dangerous explosive atmosphere can occur, is present or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of electrical apparatus.
A dangerous explosive atmosphere is a dangerous mixture with air as the oxidizing agent under atmospheric conditions.
Ex equipment can be found at any industry or operation that manufacures, processes or uses material that may flammable.
Examples listed below:
Gas:
-
Petrochemical industries
-
Chemical industries
-
Offshore Oil& Gas
-
Energy production and distribution
-
Nuclear
-
Fireworks
-
Fuel station
Dust:
-
Food industries (candy, sugar, spice, starch)
-
Grain industrie
-
Tabacco
-
Wood
-
Paper
-
Rubber
-
Textiles
-
Pharmaceuticals
-
Fossil fuel power generation
-
Metals
What can create an explosion:
To understand how an explosion can occur we first explain to get a fire. For a fire to be able to burn it needs to have three things present simultaneously: Fuel, Ignition, and Oxygen. Take away any one of these and you cannot have a fire. In fire safety this idea is known as the ‘Fire Triangle’, and is commonly used to help avoid fires.
- Flammable substance in ignitable quantities
- Oxygen
- Ignition source
To understand a combustible dust explosion though, two more elements need to be added to the fire triangle to create the ‘Dust Explosion Pentagon’. The two new elements are Confinement and Dispersion. These elements are created when the fuel, in this case combustible dust, is spread out as a dust cloud within a closed area, such as a factory or warehouse. Much like with the fire triangle, taking away even one of these elements can remove the risk of a dust explosion; however the risk for a fire can still be present.
Gas & Dust zones definition
| Zone | Present | Frequency (hours per year) |
|---|---|---|
| 0 / 20 | continuously for a long period, or frequently under normal condition | > 1000 |
| 1 / 21 | occasionally under normal conditions | 10 - 1000 |
| 2 / 22 | rarely or very short time under normal conditions | 1 - 10 |
Equipment Protection Level (EPL)
Equipment protection level describes the level of protection a device provides. It’s based on assessing both the probability of a flammable atmosphere, and the risk of an ignition source forming on the device. devices for use in explosive atmospheres that contain flammable gases (G) or dusts (D), are classified into three protection levels:
- Ga or Da: “Very High” protection level, for zones 0 and 20
- Gb or Db: “High” protection level, for zones 1 and 21
- Gc or Dc: “Normal” protection level, for zones 2 and 22
The EPL is an IEC designation which is like the ATEX Category & Zones.
Equipment needs to be assigned to groups and categories in line witrh the regulation specified by the ATEX standard and intended use application.
Type of protection
| Ex Code | Type of Protection | Symbol of each level of Protection |
EPL | Description |
|---|---|---|---|---|
| d | Frameproof enclosures | “da” | Ga or Ma | Enclosure can withstand an internal explosion and prevent the transmission of an explosion to the surrounding atmosphere. |
| “db” | Gb or Mb | |||
| “dc” | Gc | |||
| e | Increased safety | “eb” | Gb or Mb | Increased Safety by design to prevent excessive temperatures and the occurrence of arcs and sparks. |
| “ec” ** | Gc | |||
| i | Intrinsic safety | “ia” | Ga or Ma | Protection based on the restriction of electrical energy, within equipment exposed to the explosive atmosphere, to a level below that which can cause ignition by either sparking or heating effects. |
| “ib” | Gb or Mb | |||
| “ic” | Gc | |||
| m | Encapsulation | “ma” | Equipment enclosed in potting compound to keep the potentially explosive atmosphere away from the source of ignition. | |
| “mb” | ||||
| “mc” | ||||
| q | Powder filled | “q” | Quenching of the flame | |
| op | Optical Radiation | “op is” | Inherently safe, protected by shutdown | |
| t | Dust-tight enclosure | “ta” | Dust ignition protection by enclosure | |
| “tb” | ||||
| “tc” |
Equipment group and category
GAS
Group I
Equipment of Group I is intended for use in mines susceptible to firedamp. a typical gas is Methane.
Group II
Equipment of Group II is intended for use in areas with an explosive gas atmosphere other than mines susceptible to firedamp.
Equipment of Group II is subdivided according to the nature of the explosive gas atmosphere for which it is intended.
Group II subdivisions:
- IIA, a typical gas is propane;
- IIB, a typical gas is ethylene;
- IIC, typical gases are hydrogen and acetylene.
DUST
Group III
Equipment of Group III is intended for use in areas with an explosive dust atmosphere other than mines susceptible to firedamp.
Equipment of Group III is subdivided according to the nature of the explosive dust atmosphere for which it is intended.
Group III subdivisions:
- IIIA: combustible flyings;
- IIIB: non-conductive dust;
- IIIC: conductive dust.
Ex marking
The marking according to this standard is to be supplemented by the marking according to Directive 2014/34/EU European marking examples
|
Directive Part
|
Standard Part
|
Equipment example
|
|---|---|---|
|
I M2
|
Ex db I Mb
|
Mining equipment
Type of Protection flameproof enclosure “d” |
|
II 2G
|
Ex eb IIB T4 Gb
|
Gas explosion protected equipment
Type of Protection increased safety “e” |
|
II 1D
|
Ex ma IIIC 120°C Da
|
Dust explosion protected equipment,
Type of Protection encapsulation “m” |
Ignition Temperature Classes
| T-Class | Self ignition temp. of the gas/vapor |
|---|---|
| T6 | ≤ 85°C |
| T5 | ≤ 100°C |
| T4 | ≤ 135°C |
| T3 | ≤ 200°C |
| T2 | ≤ 300°C |
| T1 | ≤ 450°C |