Pepperl+Fuchs K-System Isolation Barrier Complete Guide

Pepperl+Fuchs K-System Barrier: Modular Solution for Intrinsic Safety Explosion proof Interface

Product Overview and System Positioning

In the field of process automation, field instruments (such as transmitters, solenoid valves, proximity switches) used in hazardous areas (such as chemical plants, refineries, pharmaceutical workshops) must exchange signals with the control system of the safe area, while ensuring that no energy sufficient to ignite explosive environments is generated. The K-System isolation barrier launched by Pepperl+Fuchs is the essential safety interface product series designed for this purpose. It is located between the danger zone (site side) and the safety zone (control side), providing not only limitations on current, voltage, and power, but also achieving galvanic isolation between the site circuit and the controller, thereby cutting off potential grounding circuits and surge paths.

The K-System is suitable for installation on 35mm DIN rails and includes over 150 different functions of equipment, including switch amplifiers, transmitter power supplies, temperature converters, frequency converters, solenoid valve drivers, HART multiplexers, and more. Its modular design makes the system easy to select, integrate, and expand. This manual systematically explains the mechanical structure, electrical connections, installation specifications, configuration methods, fault monitoring, and technical parameters of K-System, providing complete guidance for engineers in equipment selection and engineering implementation in hazardous areas.

Core functions and isolation principles

2.1 Intrinsic Safety Interface

The core task of K-System isolation barriers is to limit the energy transmitted to hazardous areas. According to the IEC 60079-11 standard, the electric sparks or thermal effects generated by intrinsically safe circuits under normal operation and specified fault conditions cannot ignite specific explosive gas environments. The isolation gate clamps the voltage and current output to the field side within safe values through Zener diodes, current limiting resistors, or more complex electronic circuits. At the same time, electrical isolation (usually using transformers or optocouplers) ensures that there is no direct electrical connection between the hazardous area circuit and the safe area circuit, and even if a high-voltage fault occurs in the safe area, it will not be transmitted to the site.

2.2 Signal Conversion and Conditioning

In addition to security restrictions, K-System devices also perform signal conditioning functions:

Convert 0/4-20mA analog signals from hazardous areas into standard signals for safe areas (also 0/4-20mA, or 0-10V, 1-5V, etc.).

Convert signals from NAMUR (EN 60947-5-6) proximity switches or mechanical switches into relay, transistor, or logic level outputs.

Provide isolated power supply (usually around 17V DC) for two-wire transmitters in hazardous areas.

Process sensor signals such as thermocouples, thermistors (Pt100), resistors, potentiometers, etc., and linearize the output.

Supports HART communication, allowing smart instruments to transmit analog signals while superimposing digital signals for easy configuration and diagnosis.

2.3 Fault Monitoring and Self Diagnosis

K-System equipment continuously monitors on-site line faults (disconnection, short circuit) and internal equipment failures. When a malfunction occurs, it can be reported through the following methods:

The red LED flashes or stays on (according to NAMUR NE44 standard).

Independent fault output (FAULT terminal, normally closed principle).

The aggregated error message is transmitted to the power feed module through the Power Rail, and then output by its relay contacts.

Shell design and modular system

K-System offers three housing widths based on functionality and power consumption, and all devices are compatible with 35mm DIN rail mounting (compliant with EN 60715).

3.1 KC Series -12.5mm Width

The KC device is the most compact version, suitable for simple signal conditioning or switch isolation. Its width is only 12.5 mm, making it suitable for high-density installation in cabinets. The terminal adopts removable terminal blocks, allowing users to pre wire the device without disassembling it. Terminal types available: screw terminals or spring terminals (model suffix. SP). In addition, the KC device is equipped with a transparent front cover to protect the operating components from contamination, and integrates a label rack for identification.

3.2 KF Series -20mm or 40mm Width

KF equipment offers two widths: 20mm for medium functional density (such as ordinary transmitter power supply, switch amplifier), and 40mm for more terminal requirements or higher power (such as solenoid valve drivers, HART multiplexers). It also uses pluggable terminals and can be equipped with test sockets for online signal measurement without interrupting the circuit. KF devices also have a transparent front cover, while some models do not have a front cover but are equipped with a label holder.

3.3 KH series -40mm width

The terminals of KH equipment (without pluggable terminals) are directly fixed on the housing and cannot be disassembled. Suitable for applications that do not require frequent replacement of wiring. Its width is also 40mm.