Example of zoning for a silo facility
When storing grain as well as during the loading and unloading of transport vehicles for these products, it is possible for potentially explosive dust-air mixtures to be produced. Zoning allocations must be undertaken for the selection of the approved monitoring devices. A potentially explosive atmosphere is constantly present on the inside of silos filled with grain (zone 20). Outside of the silo and in the loading duct this condition occurs only occasionally, e.g. during filling and empty (zone 21). Zone 21 is enclosed by Zone 22, in which hazardous dust-air mixtures can be found only during breakdowns, which in this case is estimated to be very seldom.
Diagram of a possible zoning allocation for a grain operation
Sensors under ATEX for Ex dust
Airflow sensors STS 21..
The airflow sensors in series STS 21.. are conceived for use in extraction systems and conveyor systems. They belong to equipment category 1D and are therefore approved for use in zone 20, the most demanding.
Amplifiers for air flow monitors in series SZA are intended for installation on a mounting rail. The devices can be delivered as switches with adjustable limiting values or as an analog device with 4..20mA output as a trend display.
Inductive sensors IGEX and IDEX
Sensors for detecting metals in the Ex area zone 20 or zone 22. Devices can be delivered in the standard configurations M12, M18 and M30. For large switching distances there are configurations with diameters of 80mm to 160mm.
Capacitive sensors KGEX and KDEX
Sensors for almost all materials in the Ex area zone 20 or zone 22 can be delivered as proximity switches up to 80 mm diameter or as used as level monitor with G1 thread.
Amplifier SS 400...
The amplifiers for airflow sensors are installed directly in zone 21 and can be adjusted and read on site.
Amplifier EGE 90...
The amplifiers EGE 90... instruments for inductive and capacitive sensors are intended for rail mounting installation.
Housing for screw terminals GK...
These terminal boxes make it possible to set up terminal clamping points in intrinsically safe and in not intrinsically safe electric circuits within zone 21. The boxes are manufactured with type "e" (increased safety) or type "i" (intrinsic safety) protection.
Housing for amplifiers GAM...
The analysis devices are ready for mounting and use within zone 21 and serve to connect several optical or thermal level controllers.