The leading ignition protection type is critical for the electrical connection of a pressure sensor with explosion protection. It generally does not necessarily must be the main one with the stricter requirements. This applies, for example, for the UHP pressure transducers of the WU series from WIKA. They are designed for use in semiconductor production.
Explosion protection is an indispensable safety precaution there. This is due to the substances required for manufacturing include highly flammable gases. Consequently, there is a risk of an explosive atmosphere forming.
Explosion protection concept
UHP pressure transducers for such processes should be designed with the corresponding safety. As well as their small design and specific process connections, the models WUC-1x and WU-2x have a comprehensive explosion protection concept. The marking of the instruments provides info on this:
II 3G Ex ec ic IIC T6/T5/T4 Gc X
The abbreviations listed inside them mean, in more detail:
II 3G:
Equipment group 2 (every area except mining), can be utilized in zone 2 (rare and short-term Ex atmosphere).
Ex ec ic:
Ignition protection types ?ec? (increased safety) and ?ic? (intrinsically safe; zone 2).
?Ex ec? has replaced the ignition protection type ?Ex nA? ( Uncomfortable -sparking) because the start of 2022. However, this does not affect the Ex concept of the instruments.
IIC:
Explosion group (here: gases, resistive ignition energy of 40 �J, suitable for hydrogen/acetylene).
T6/T5/T4:
Temperature classes. T6 as the highest requirement means a maximum permissible surface temperature in the Ex environment < 85 �C (max. surface temperature of the WUC-1x and WU-2x: 40 �C).
Gc:
?Equipment Protection Level? (EPL) for zone 2 per IEC 60079-0
X:
Specific requirements which are listed in the operating instructions (for example, the best mating connector).
?ec? may be the leading ignition protection type
It is noticeable that the marking contains two ignition protection types. However, only one is pertinent for the electrical connection: the best ignition protection type. In the case of the pressure transducers from the WU series, this is the Ex ec (Ex nA up to 2022) mentioned first and not the stricter Ex ic. This may also be seen in the connection values in the info sheet and operating instructions. Only the specification of the maximum supply voltage UN = 30 V, which is also stated in the IECEx certificate, is pertinent here.
What does the classification ?Ex ic? are a symbol of? It only pertains to the potentiometer of the transducer. The resistive component has an intrinsically safe circuit and will therefore be adjusted to improve zero drift during operation. Within their overall form, the WU models usually do not require an intrinsically safe circuit. However, they must never be disconnected from the circuit during operation or when an Ex atmosphere is present.
Note
Further information on the WUC-1x and WU-2x UHP pressure transducers and about hydrogen can be found on the WIKA website. In case you have any questions, your contact will gladly help you.
Also read our articles
Ex protection: The most common ignition protection types for sensors in gas hazardous areas
Ex protection: The difference between the zone and division model