The leading ignition protection type is crucial for the electrical connection of a pressure sensor with explosion protection. It 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 used in semiconductor production.
Explosion protection is an indispensable safety precaution there. Simply because the substances required 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 must 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 information on this:
II 3G Ex ec ic IIC T6/T5/T4 Gc X
The abbreviations listed in them mean, in greater detail:
II 3G:
Equipment group 2 (all areas except mining), may 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 Kickstart ?Ex nA? (non-sparking) since the start of 2022. However, this will not affect the Ex idea 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 leading 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 rather than the stricter Ex ic. This may also be observed in the connection values in the data sheet and operating instructions. Only the specification of the utmost supply voltage UN = 30 V, which is also stated in the IECEx certificate, is pertinent here.
What does the classification ?Ex ic? stand for? It only pertains to the potentiometer of the transducer. The resistive component comes with an intrinsically safe circuit and will therefore be adjusted to correct zero drift during operation. In their overall form, the WU models usually do not require an intrinsically safe circuit. However, Battle 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 typical ignition protection types for sensors in gas hazardous areas
Ex protection: The difference between the zone and division model