Pepperl+Fuchs KFD2-ST3-EX1.LB Switch Amplifier

Technical Overview

Isolated barrier for NAMUR/dry contact inputs, 1-channel, dual active transistor outputs, SIL 2, line fault detection, 19-30VDC.

Key Features

1-channel isolated barrier for intrinsic safety applications
24 V DC supply, compatible with Power Rail
Accepts dry contact or NAMUR inputs
Equipped with 2 active transistor outputs
Functions as a signal splitter (1 input to 2 outputs)
Reversible mode of operation
Integrated Line Fault Detection (LFD)
Certified up to Safety Integrity Level (SIL) 2 (SC 3) according to IEC/EN 61508
Degree of protection: IP20
Operating ambient temperature range: -20 to 60 °C (-4 to 140 °F)

Technical Specification Matrix

Parameter	Value
Signal Type	Digital Input
Safety Integrity Level (SIL)	SIL 2 (SC 3) acc. to IEC/EN 61508
Supply Connection	Power Rail or terminals 14+, 15-
Rated Voltage (Ur)	19 ... 30 V DC
Ripple	≤ 10 %
Rated Current (Ir)	15 ... 10 mA + Iout
Power Dissipation	≤ 800 mW including maximum power dissipation in the output
Input Open Circuit Voltage	approx. 10 V DC
Input Current	approx. 8 mA
Output Current	100 mA
Switching Frequency	≤ 5 kHz
Response Time	200 us
Galvanic Isolation	Reinforced insulation according to IEC/EN 61010-1, rated insulation voltage 300 Veff
Display Elements	LEDs
Ambient Temperature	-20 ... 60 °C
Degree of Protection	IP20
Number of Channels	1-channel
Field Device Compatibility	NAMUR sensor, volt-free contact
Housing Material	Polycarbonate
Physical Weight (kg)	0
Dimensions L x W x H (cm)	11.43 x 2 x 11.94

Industrial Applications

1. Monitoring Level Switches in Chemical Processing Tanks

This switch amplifier is ideal for connecting NAMUR level switches located in hazardous chemical processing tanks. It safely transmits digital ON/OFF signals from the hazardous zone to the control system in the safe area.

Problem Solved

Provides intrinsic safety isolation (SIL 2), preventing ignition in explosive atmospheres while ensuring reliable level monitoring. Line fault detection (LFD) immediately reports sensor cable breaks or shorts, enhancing operational safety.

Intrinsic SafetyNAMUR SensorHazardous AreaLevel DetectionSIL 2Line Fault DetectionChemical Processing

2. Valve Position Feedback in Oil & Gas Pipelines

The KFD2-ST3-EX1.LB is used for monitoring the open/closed status of critical valves in oil and gas pipelines, especially those operating in potentially explosive environments. It interfaces with dry contact or NAMUR proximity switches mounted on valve actuators.

Problem Solved

Offers safe, isolated transmission of valve position feedback to the plant's Distributed Control System (DCS) in the safe area. Its two active transistor outputs can provide independent signals for valve status indicators or safety interlocks, compliant with SIL 2 for safety-instrumented functions.

Valve Position MonitoringOil & GasHazardous LocationDry ContactNAMURTransistor OutputIsolated BarrierSIL 2

3. RPM Monitoring of Motors in Dust-Explosion-Hazardous Environments

In industries with dust explosion risks, such as grain silos or food processing, this switch amplifier can be used to monitor motor RPM. It processes digital input from NAMUR proximity sensors detecting rotating machinery components.

Problem Solved

Ensures intrinsic safety for the NAMUR sensor located in the dust-hazardous area, effectively preventing ignition. The high switching frequency (≤ 5 kHz) allows for accurate RPM measurement, with outputs capable of driving local indicators or sending signals to a PLC in the safe area.

Dust Explosion HazardRPM MonitoringNAMUR SensorFrequency InputIntrinsic SafetyMotor ControlIsolated BarrierSIL 2