Pepperl+Fuchs has introduced a new generation of F-LB surge protection devices for field instruments used in hazardous areas. The range comprises four screw-in modules and one pass-through module designed for installation in Ex Zones 1 and 2. The products provide surge protection for power, signal and fieldbus interfaces while allowing direct integration into field devices.
Simplied safe installation and reduced component count
The screw-in versions can be mounted directly into field instruments, eliminating the need for additional surge protection enclosures or junction boxes. Versions are available with M20x1.5 and 1/2-14 NPT thread connections to support different installation requirements. One module combines Ex i and Ex d protection technologies in a single device, enabling protection of two ungrounded signal circuits or one power circuit together with one signal circuit. This approach can reduce component count and simplify installation, spare-parts management and plant standardisation.
Another module is intended for field devices that use a 120/230 V power supply and a 24 V data interface. According to the manufacturer, a fault-safe Y-circuit helps increase installation safety and reduce the risk of incorrect wiring on the high-voltage side.
Compliant with NAMUR NE 21 requirements
The pass-through version incorporates an energy-coordinated two-stage surge arrester with a low-capacitance protection circuit. It is designed for intrinsically safe measuring loops and bus systems and supports distortion-free transmission of 4-20 mA and HART signals. The device meets FISCO requirements and can be used in PROFIBUS PA and FOUNDATION Fieldbus installations. A serial protection circuit compliant with NAMUR NE 21 requirements for intrinsically safe interfaces provides residual voltage limitation.
Target applications include measuring signal converters, positioners, intelligent valve controls, analysis and monitoring equipment, as well as pump and compressor skids. The protection concept can also be applied to HART transmitters, RTD circuits and thermocouple loops installed in hazardous environments.
