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 instance, for the UHP pressure transducers of the WU series from WIKA. They are designed for use in semiconductor production.
Discount can be an indispensable safety precaution there. This is due to the substances necessary 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 must be made with the corresponding safety. As well as their small design and specific process connections, the models WUC-1x and WU-2x have a thorough explosion protection concept. The marking of the instruments provides home elevators 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) because the start of 2022. However, this will 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 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 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 1 is pertinent for the electrical connection: the leading ignition protection type. Regarding the pressure transducers from the WU series, this is actually the Ex ec (Ex nA around 2022) mentioned first rather than the stricter Ex ic. This may also be seen in the bond values in the data sheet and operating instructions. Only the specification of the maximum supply voltage UN = 30 V, that is also stated in the IECEx certificate, is relevant here.
What does the classification ?Ex ic? are a symbol of? It only pertains to the potentiometer of the transducer. The resistive component comes with an intrinsically safe circuit and may therefore be adjusted to improve zero drift during operation. In their overall form, the WU models do not require an intrinsically safe circuit. However, they must 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. If you have any questions, your contact will gladly help you.
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