Explosion Proof Nameplate T-Code and EPLs

How to read an explosion-proof nameplate

A hazardous-location nameplate has to be read as a complete marking. “Explosion-proof,” an IP rating or a Zone number alone does not establish suitability.

For Zone-marked equipment, check:

1. Canadian approval;
2. type of protection;
3. gas or dust group;
4. temperature marking;
5. Equipment Protection Level (EPL);
6. ambient range and special conditions; and
7. the exact catalogue number and options covered by the certification record.

EPL: Equipment Protection Level

EPL expresses the protection level assigned to equipment for an explosive atmosphere.

Gas Zone	EPL normally associated with the Zone
Zone 0	Ga
Zone 1	Ga or Gb
Zone 2	Ga, Gb or Gc

Dust Zone	EPL normally associated with the Zone
Zone 20	Da
Zone 21	Da or Db
Zone 22	Da, Db or Dc

The EPL cannot be checked in isolation. The permitted protection type, group, temperature and any restrictions in the marking or certificate still apply. Division-marked equipment follows the CEC permissions for Division equipment and does not necessarily carry an EPL.

Temperature markings

For gas Zones 0, 1 and 2, Rule 18-054 compares the equipment's maximum surface temperature rating with the minimum ignition temperature documented for the location. For dust Zones 20, 21 and 22, it compares the marked maximum external surface temperature with the lower applicable dust-cloud or dust-layer ignition temperature.

T-code	Maximum temperature
T1	450 °C
T2	300 °C
T3	200 °C
T4	135 °C
T5	100 °C
T6	85 °C

A higher T-number represents a lower maximum temperature. Do not choose a T-code from an industry example; compare the exact marking with the authenticated classification data and the product's rated ambient conditions.

Rule 18-054 also contains default and special temperature provisions. The project professional should apply the Rule to the actual marking rather than assuming an unmarked product is acceptable.

Gas and dust groups

Gas groups under Rule 18-050 include:

Group	Examples named by the CEC
IIA	propane, gasoline, natural gas, ammonia
IIB	ethylene, butadiene, hydrogen sulphide, propylene oxide
IIC	acetylene, hydrogen, carbon disulphide

IIC equipment may be used where IIB or IIA equipment is required. IIB equipment may be used where IIA equipment is required, subject to the rest of the marking.

Dust groups are:

Group	Atmosphere
IIIA	combustible flyings
IIIB	combustible dust other than metal dust
IIIC	combustible metal dust

When comparing Division and Zone groups, use CEC Table 18A and the documented substance. Division Group B does not translate to a single Zone group for every substance.

Example marking

A marking such as Ex db IIB T4 Gb indicates:

• an Ex “db” type of protection;
• gas Group IIB;
• a T4 maximum temperature rating; and
• EPL Gb.

It may be a candidate for a Zone 1 or Zone 2 location, but the Canadian certification mark, ambient range, special conditions, installation instructions and exact certification record still decide whether that model fits the application.

What to request from your supplier

Ask the supplier for the certification record from an accredited Canadian certification body and confirm that the exact catalogue number and options appear in its scope. IECEx documentation can provide useful international product information, but IECEx alone does not cover Canadian approval.

Send LEDEX the complete classification and proposed catalogue number. We will provide available model-specific records and IES files for the project review.