The leading ignition protection type is critical for the electrical connection of a pressure sensor with explosion protection. It generally does not necessarily have 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 necessary 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 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 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 pressure gauge 10 bar ).
?Ex ec? has replaced the ignition protection type ?Ex nA? (non-sparking) since the start of 2022. However, this does not affect the Ex idea of the instruments.
IIC:
Explosion group (here: gases, resistive ignition energy of 40 �J, ideal 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 instance, the best mating connector).
?ec? may be pressure gauge leading ignition protection type
It is noticeable that the marking contains two ignition protection types. However, only one is relevant for the electrical connection: the leading ignition protection type. In the case of the pressure transducers from the WU series, this can be 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 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 pertinent 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 can therefore be adjusted to correct 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 is present.
Note
Further information on the WUC-1x and WU-2x UHP pressure transducers and about hydrogen are available 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 typical ignition protection types for sensors in gas hazardous areas
Ex protection: The difference between your zone and division model