JUMO 902820 PROCESStemp RTD Temperature Probe for Process Technology (Also with ATEX Approval) Ex i Operating Manual - Manual (Page 7)

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It is not mandatory to connect the versions in flameproof enclosure to intrinsically safe circuits, however, it
must always be ensured that the rise in temperature of the thermometer remains limited, as was described in
detail in Section 5.1. and demonstrated by the case studies.
The temperature classes and safety reserves apply equally to both protection types, and the temperature
development in the terminal head (if used with a built-in transmitter) must also be taken into account.
For operation in Zone 0 (G) or 20 (D), type "d" protection “Flameproof enclosure” is by no means sufficient
by itself!
In a potentially explosive atmosphere the terminal head and/or connection terminals must not be opened
when voltage flows if the ignition protection class "intrinsically safe" (Ex "i") is not also applied.
5.4 Use in areas with an explosion hazard caused by dust
Dust explosion protection: safe limitation of energy
Type of protection "protection type intrinsic safety"
For the safe limitation of the energy fed to the sensing element – also in the event of a fault of the supply unit
– using a circuit with "intrinsic safety" protection is highly appropriate. The protection type "protection type
intrinsic safety" means that, in the area with an explosion hazard caused by dust, the only criterion is the
characteristic of safe limitation of electrical variables in the intrinsically safe equipment by means of the
associated intrinsically safe devices. Head-mounted transmitters in Category 1G or 2G are included in the
"Protection through enclosure" type of protection inside the terminal head. The associated intrinsically safe
device, that has to be positioned outside the hazardous area, need not meet the requirements of Category
1D or 2D. The category markings for equipment requirements in areas with an explosion hazard caused by
gas 1G or 2G are therefore sufficient for the intrinsically safe equipment or associated intrinsically safe
devices.
The following temperature values must be taken into account for applications in areas with a dust
explosion hazard:
Applicable to all zones:
The surface temperature of the equipment must not rise to a level that could ignite swirling dust or dust
deposits on the equipment. This is achieved through the following regulations:
No dust deposit
The surface temperature must not exceed
2
/
3
of the ignition temperature (in °C) for the corresponding dust-
air mixture.
With dust deposit
Surfaces on which a dangerous accumulation of smolderable dust cannot be prevented must not have a
temperature that is higher than 75 °C below the smoldering temperature of the dust concerned. If layers
thicker than 5 mm occur, a further reduction of the surface temperature must be applied.
Where a combination of swirling and deposited dust occurs, the lower of the values derived above must be
applied.
Note
In this case, "surface" means the exterior surface of the equipment, see also 60079-14.