The leading ignition protection type is critical for the electrical connection of a pressure sensor with explosion protection. It does not necessarily need to 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 used in semiconductor production.
Explosion protection can be an indispensable safety precaution there. The reason being the substances required for manufacturing include highly flammable gases. Consequently, you will find a risk of an explosive atmosphere forming.
Explosion protection concept
UHP pressure transducers for such processes should be designed with the corresponding safety. In addition to 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 info on this:
II 3G Ex ec ic IIC T6/T5/T4 Gc X
The abbreviations listed in them mean, in more detail:
II 3G:
Equipment group 2 (every area 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, this 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 because 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 really is noticeable that the marking contains two ignition protection types. However, only one is pertinent for the electrical connection: the best ignition protection type. Regarding the pressure transducers from the WU series, this is the Ex ec (Ex nA around 2022) mentioned first and not the stricter Ex ic. This may also be observed in the connection values in the info 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 applies to the potentiometer of the transducer. The resistive component comes with an intrinsically safe circuit and will therefore be adjusted to improve zero drift during operation. In their overall form, the WU models usually do not require an intrinsically safe circuit. However, Delicious 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 on the subject of 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 common ignition protection types for sensors in gas hazardous areas
Ex protection: The difference between the zone and division model