Valuable leading ignition protection type is critical for the electrical connection of a pressure sensor with explosion protection. It does not necessarily need to be the 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 is an indispensable safety precaution there. The reason being the substances necessary for manufacturing include highly flammable gases. Consequently, there is a threat 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 in them mean, in greater detail:
II 3G:
Equipment group 2 (every area except mining), can be utilized 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, 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 suitable mating connector).
?ec? may be the leading ignition protection type
It really is noticeable that the marking contains two ignition protection types. However, only Crisis 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 may also be seen in the bond values in the data 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? stand for? It only applies to the potentiometer of the transducer. The resistive component has an intrinsically safe circuit and will therefore be adjusted to correct zero drift during operation. Within their overall form, the WU models 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. 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 your zone and division model