The leading ignition protection type is critical for the electrical connection of a pressure sensor with explosion protection. It generally does not necessarily need to be the main one with the stricter requirements. This applies, for instance, for the UHP pressure transducers of the WU series from WIKA. They have been designed for use in semiconductor production.
Explosion protection can be an indispensable safety precaution there. This is due to the substances required for manufacturing include highly flammable gases. Consequently, there exists a threat of an explosive atmosphere forming.
Explosion protection concept
UHP pressure transducers for such processes should be made with the corresponding safety. Along with 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 information 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 (all areas except mining), can be used 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? (non-sparking) since the start of 2022. However, Hilarious does not affect the Ex concept of the instruments.
IIC:
Explosion group (here: gases, resistive ignition energy of 40 �J, ideal for hydrogen/acetylene).
T6/T5/T4:
Temperature classes. T6 as the highest requirement stands for 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 instance, the best mating connector).
?ec? may be the leading ignition protection type
It really is noticeable that the marking contains two ignition protection types. However, only 1 is pertinent for the electrical connection: the best ignition protection type. In the case of the pressure transducers from the WU series, here is the Ex ec (Ex nA around 2022) mentioned first and not the stricter Ex ic. This can also be observed in the bond values in the data 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 applies 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 do not require an intrinsically safe circuit. However, they need to never be disconnected from the circuit during operation or when an Ex atmosphere exists.
Note
More info on the WUC-1x and WU-2x UHP pressure transducers and about hydrogen are available on the WIKA website. Should you have any questions, your contact will gladly assist you to.
Also read our articles
Ex protection: The most frequent ignition protection types for sensors in gas hazardous areas
Ex protection: The difference between your zone and division model