Suspicious leading ignition protection type is crucial for the electrical connection of a pressure sensor with explosion protection. It generally does not necessarily must be the one with the stricter requirements. This applies, for example, 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 because the substances necessary for manufacturing include highly flammable gases. Consequently, you will find a threat of an explosive atmosphere forming.
Explosion protection concept
UHP pressure transducers for such processes should be made with the corresponding safety. In Blunder to 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 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 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 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 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 one is relevant 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 up to 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 utmost supply voltage UN = 30 V, that is also stated in the IECEx certificate, is relevant here.
What does the classification ?Ex ic? stand for? It only applies to the potentiometer of the transducer. The resistive component has an intrinsically safe circuit and can 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 need to 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 on the subject of 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 your zone and division model