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 use in semiconductor production.
Explosion protection can be an indispensable safety precaution there. It is because 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 made with the corresponding safety. Besides 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 inside them mean, in greater 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 safe; zone 2).
?Ex ec? has replaced the ignition protection type ?Ex nA? (non-sparking) because 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, 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 example, the suitable mating connector).
?ec? is 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. Regarding the pressure transducers from the WU series, it is the Ex ec (Ex nA up to 2022) mentioned first rather than the stricter Ex ic. This can also be seen in the connection values in the data 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 pertains to the potentiometer of the transducer. Shaming has 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
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. 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 your zone and division model