Pepperl+Fuchs KFD2 Modules: KFD2-SR2-EX2.W

Technical Dossier

Product Details And Specifications

Pepperl+Fuchs KFD2 Series: Comprehensive Module Range and Technical Overview

The Pepperl+Fuchs KFD2 series is a family of DIN-rail-mounted signal conditioners and isolating switching amplifiers designed for intrinsically safe (Ex ia) field device interfacing in Zone 0/1/2 hazardous areas. Deployed across global heavy industry — including petrochemical refineries, offshore platforms, nuclear auxiliary systems, and large-scale chemical processing plants — the KFD2 range serves as the backbone of NAMUR-compliant field signal transmission between the hazardous area and the safe-side control system (DCS/PLC). The series is certified to ATEX, IECEx, and FM standards, and is compatible with major DCS platforms including Emerson DeltaV, Honeywell Experion, ABB 800xA, and Siemens PCS 7. Its 22.5 mm slim housing and K-System power rail bus architecture allow high-density marshalling cabinet installations with centralized power distribution, eliminating the need for individual module power supplies.

The Evolution of KFD2 Architecture

The KFD2 series was introduced as part of Pepperl+Fuchs' K-System platform, succeeding the earlier KFA and KFD (first generation) isolator families. The core architectural shift in the KFD2 generation was the adoption of the K-System power rail, which allows up to 40 modules to share a single 24 V DC bus via a backplane rail, eliminating individual terminal block wiring for power. Early KFD2 modules used discrete optocoupler-based isolation; later revisions incorporated transformer-based galvanic isolation for improved noise immunity in high-EMI environments such as motor control centers.

The KFD2 series spans multiple functional sub-families: SR (switching amplifier/repeater), SB (solenoid driver), UT (universal temperature transmitter), WAC (frequency converter), CD (current driver), and SOT (solenoid output). Compatibility across revisions is generally maintained at the terminal and rail level, though firmware-dependent variants (e.g., HART-transparent models) require attention when substituting. As of 2024, the KFD2 series is in a mature/sustained phase — Pepperl+Fuchs continues to manufacture and support the full range, but new installations increasingly specify the KFD3 platform. For existing KFD2 installations, long-term maintenance sourcing remains the primary procurement driver.

KFD2 Full Catalog & Functionalities (SKU List)

Switching Amplifiers / Repeaters (SR Sub-family)

• KFD2-SR2-EX2.W: 2-channel NAMUR/dry-contact switch amplifier, relay output, 24 V DC K-System bus powered, ATEX/IECEx Zone 0
• KFD2-SR2-EX1.W: 1-channel NAMUR switch amplifier, single relay output, slim 22.5 mm housing, K-System rail
• KFD2-SR2-EX2: 2-channel switch amplifier, relay output, standalone 24 V DC supply (non-bus), ATEX Zone 1
• KFD2-SR2-EX2-W-SM: 2-channel switch amplifier with status monitoring output, relay output, K-System bus
• KFD2-SR2-EX4.W: 4-channel switch amplifier, transistor output, K-System bus powered, high-density marshalling
• KFD2-SB-EX1.PA: 1-channel solenoid driver, PROFIBUS PA segment coupler compatible, Ex ia output

Solenoid Drivers (SB Sub-family)

• KFD2-SB-EX1.PA: Single-channel solenoid/valve driver, 24 V DC, ATEX Zone 0/1, PA-compatible
• KFD2-SB-EX2.PA: 2-channel solenoid driver, dual output, K-System bus, ATEX/IECEx
• KFD2-SB-EX2-R: 2-channel solenoid driver with relay feedback, used in ESD valve applications

Temperature Transmitters (UT Sub-family)

• KFD2-UT2-EX1: Universal temperature transmitter, TC/RTD input, 4–20 mA output, HART transparent, ATEX Zone 0
• KFD2-UT2-EX2: 2-channel universal temperature transmitter, dual 4–20 mA output, K-System bus
• KFD2-UT2-EX1.D: Temperature transmitter with HART device variable mapping, DCS-ready, Ex ia

Current Drivers / Analog Output (CD Sub-family)

• KFD2-CD-EX1.32: 1-channel current driver, 4–20 mA output to Ex field device, 24 V DC K-System bus
• KFD2-CD-EX1.32.300: Current driver with extended output range to 300 mA, for motorized valve positioners

Frequency / Pulse Converters (WAC Sub-family)

• KFD2-WAC-EX1.D: Frequency-to-analog converter, pulse input from Ex field device, 4–20 mA output, ATEX Zone 0
• KFD2-WAC-EX1.55: Frequency converter, 0–55 kHz input range, 4–20 mA / relay output, K-System bus

Solenoid Output Modules (SOT Sub-family)

• KFD2-SOT2-EX2: 2-channel solenoid output, transistor output, 24 V DC, ATEX Zone 1, used in burner management
• KFD2-SOT2-EX2.W: 2-channel solenoid output, K-System bus powered, relay output, ESD-rated applications

Sourcing Hard-to-Find & Obsolete KFD2 Parts

DriveKNMS maintains a dedicated inventory program for the KFD2 series, with particular focus on variants that have been discontinued or placed on extended lead time by Pepperl+Fuchs' standard distribution channels. Models such as the KFD2-SR2-EX2.W, KFD2-UT2-EX1.D, and early-revision KFD2-CD-EX1.32 are frequently required for like-for-like replacement in certified SIL-rated loops where substitution with a newer model would require re-validation. DriveKNMS sources these units from decommissioned plant inventories, certified refurbishers, and authorized surplus channels, with full traceability documentation provided. All units are supplied with original Pepperl+Fuchs datasheets, CE/ATEX certificates, and where applicable, calibration records. For plant operators running KFD2-based marshalling cabinets beyond the standard 15-year lifecycle, DriveKNMS offers bulk reservation agreements to secure multi-year spare parts supply.

Quality Control for the KFD2 Range

Each KFD2 module processed by DriveKNMS undergoes a structured verification protocol prior to dispatch. Functional testing is performed on a dedicated K-System test rack with a calibrated 24 V DC K-System power rail, replicating the operational bus environment. For switching amplifier variants (SR sub-family), NAMUR sensor simulation is applied to both channels using a precision resistor decade box, and relay output switching is verified against the specified switching threshold (typically 1.2 mA / 2.1 mA for NAMUR). For temperature transmitter variants (UT sub-family), RTD and thermocouple simulation is applied across the full input range, and 4–20 mA output linearity is verified against the factory calibration curve. HART communication integrity is verified using a HART communicator on HART-transparent models. Visual inspection covers terminal block condition, housing integrity, label legibility, and K-System bus connector pin condition. Units failing any parameter are quarantined and not dispatched.