Technical information

Electrical equipment in hazardous areas

A “hazardous area” is defi ned as an area in which the atmosphere contains, or may contain in suffi cient quantities, fl ammable or explosive gases, dusts or vapours. In such an atmosphere a fi re or explosion is possible when three basic conditions are met. This is often referred to as the “hazardous area” or “combustion” triangle.


In order to protect installations from a potential explosion a method of analysing and classifying a potentially hazardous area is required. The methods used to classify an installation can vary depending upon which part of the world it is located, but generally there are three main types of criteria: classification by Type, Zone and “T” Rating.

Gas Classification

The construction of explosion protected electrical equipment intended for use in potentially flammable atmospheres (hazardous areas) is defined clearly in two separate categories to suit the nature of the hazardous area application. The two categories recognised under both the CENELEC (European) Normatives and the IEC Standards are stated as being equipment groups or apparatus groups, and are defined as follows :-

Apparatus Group I - Electrical equipment for mining applications
Apparatus Group II - Electrical equipment for surface industry hazardous areas, other than mining applications

  • IIA - Propane
  • IIB - Ethylene
  • IIC - Hydrogen and asetylen

(The gases noted in the table are typical gases for each group.)


Every dangerous place has to be classified into one of following three zones considering:

ZONE 0 Zone in which a mixture of explosive gas is always present or for long periods or frequently.
ZONE 1 Zone in which a mixture of explosive gas may be present occasionally during normal plant operation.
ZONE 2 Zone in which a mixture of explosive gas is not normally present, and if it is, only it is for short periods of time.

Zone 0 is the most DANGEROUS zone. It has the highest probability of a flammable atmosphere presence. Equipment for this zone must be very well protected against providing a source of ignition and have legal certification of this protection. Every other area of the plant is considered a SAFE AREA.


Temperature classification

The ignition temperature of a flammable material is critical in determining the acceptability of equipment/instrumentation that operates in hazardous locations as the external surface of the enclosure can act as an ignition source if the surface temperature exceeds the ignition temperature of the flammable material. High surface temperatures can result from normal operation of the equipment; abnormal operation (i.e. overheating); or because of a fault condition.

Equipment destined for installation in hazardous areas is marked with a code representing the maximum external surface temperature. Equipment cannot be used in hazardous areas when the maximum surface temperature is greater than the ignition temperature of the gases/vapors present.

Temperature Classification Maximum Surface Temperature of Apparatus (ºC) Ignition temperature of Gas or Vapour (ºC)
T1 450 > 450
T2 300 > 300
T3 200 > 200
T4 135 > 135
T5 100 > 100
T6 85 > 85



Typical Equipment Marketing

All equipment produced by TEMPA SİSTEM A.Ş. for use in hazardous areas is marked as showed below and includes such information as:


a Name and address of manufacturer
b Series and part number
c Year of manufacture and serial number
d CE Marking and number of notified body responsible for production
e Specific marking of explosive protection
f Certificate number
g Type of explosive atmosphere
G – Gases, vapours or mists
D – Dusts
h Equipment Group and category
i Gas group and T Class
j Ambient Temperature
k Other essential information

Ex-protection groups

To ensure the safe operation of electrical equipment in flammable atmospheres, several design standards have now been introduced. These design standards have to be followed by the manufacturer of apparatus sold for use in a hazardous area and must be certified as meeting the standard appropriate to its use. Equally, the user is responsible for ensuring that only correctly designed equipment is used in the hazardous area. For gas detection equipment, the three most widely used classes of electrical safety design are ‘flameproof’ (sometimes known as ‘explosion-proof’ and with an identification symbol Ex d), ‘intrinsically safe’ with the symbol Ex i and Increased safety (Ex e).

EEx d Protection for equipment containing parts which can ignite an explosive atmosphere and that designed to withstand the pressure developed during an internal explosion and prevent the explosion being transmitted to the atmosphere surrounding the enclosure.


Flameproof Type ‘d’ Equipment which may include arcing and sparking (or incendive) devices and can have explosive mixtures present internally. The enclosure construction is designed to contain an internal explosion and prevent transmission of sufficient energy to cause an explosion external to the equipment. Any joints, covers or openings are constructed with flameproof paths which must be periodically inspected and continuously maintained in order to retain the integrity of the form of explosion protection.

Döküm olan bu panolar, devre kesicili, transformatörlü devrelerde, motor kontrol ve sürücü uygulamalarında kullanılır.

EEx e (Zone 1,2) Increased Safety

EEx e Protection for electrical components that do not spark under normal working conditions but where measures are applied to prevent high temperatures and the occurrence of arcs and sparks internally. Devre kesici, yol verici, gibi ark çıkaran malzemelerde uygulanmaz.Ağırlıklı olarak klemens uygulamalarında bu koruma tipi kullanılır.

Technical Features of our TES Series Ex Terminal Boxes:

· Certified : ATEX II 2 G D EEx e II EEx IIC T6 or T5
· Classification Area(s) : Zone1, Zone 2 ve Zone 21   and Zone 22
· Design Standards : EN 50014, EN 50019, EN 50020
· Certificate Number : Sira 03 ATEX 3386   (Component Box : Sira 03 ATEX 3397U)
· Ingress Protection : IP 66 (Acc. to EN60529)
· Ambient Temperature : -50 ° C to + 55 ° C (for T6 and T5)
· Material : Highly Corrosion Resistant , 1,5 / 2.0 mm   Stainless Steel 316L
· Gasket Material : Foamed-in door sealing gasket   (-80 ° C to + 100 ° C )
· Door Fixings : Hinged removable door with captive   fastening screws
· Gland Plates : 2 mm thick, 0,1,2,3 and 4 gland   plate options