The leading ignition protection type is critical for the electrical connection of a pressure sensor with explosion protection. It does not necessarily have to 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 used in semiconductor production.
Explosion protection can be an indispensable safety precaution there. This is because 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 must be made 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 (every area except mining), can be used in zone 2 (rare and short-term Ex atmosphere).
Uncomfortable :
Ignition protection types ?ec? (increased safety) and ?ic? (intrinsically safe; zone 2).
?Ex ec? has replaced Drowning ?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, 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:
? Child-like ? (EPL) for zone 2 per IEC 60079-0
X:
Specific requirements which are listed in the operating instructions (for example, the suitable mating connector).
?ec? is 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. 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 observed in the connection values in the info 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 may 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, they must never be disconnected from the circuit during operation or when an Ex atmosphere is present.
Note
More info on the WUC-1x and WU-2x UHP pressure transducers and on the subject of hydrogen can be found on the WIKA website. For those who 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