Honeywell 8937-HN Ruggedized Fiber Optic Extender Module

Product Overview

Honeywell 8937-HN Ruggedized Fiber Optic Extender Module: Industrial Resilience for Harsh Environments

The Honeywell 8937-HN is a ruggedized Fiber Optic Extender Module engineered for the TDC 3000 Local Control Network (LCN) — one of the most widely deployed distributed control system architectures in continuous-process industries. Designed to extend fiber optic communication links across the LCN backbone, the 8937-HN delivers deterministic, high-integrity data transmission in environments where copper-based media would fail: high electromagnetic interference (EMI), wide temperature swings, corrosive atmospheres, and vibration-intensive plant floors.

In critical infrastructure applications — from offshore oil platforms and onshore gas processing terminals to coal-fired power stations, hydroelectric control rooms, and municipal water treatment facilities — the LCN must sustain millisecond-level response times without interruption. The 8937-HN fulfills this requirement by converting electrical signals to optical pulses, eliminating ground-loop noise and providing galvanic isolation between nodes. This makes it indispensable wherever long cable runs, high-voltage equipment, or electrically noisy machinery such as variable frequency drives (VFDs), large motor starters, and high-current bus bars are present in the same facility.

Rugged Specifications Table

Comprehensive Protection Solutions

The 8937-HN does not operate in isolation — it is a critical link in a layered control and protection architecture. In a typical TDC 3000 or TPS installation, the LCN connects high-level supervisory nodes such as the Honeywell AM (Application Module) and HM (History Module) to operator workstations running the GUS (Global User Station) interface. The 8937-HN extends these fiber segments reliably, ensuring that process data from field-level HPM (High-Performance Process Manager) controllers and UCN (Universal Control Network) gateways reaches the supervisory layer without signal degradation.

In the field, the HPM communicates with I/O subsystems through the UCN, where modules such as the Honeywell PM I/O Link and associated FTA (Field Termination Assembly) panels handle analog and digital signal conditioning. The integrity of this entire chain depends on a noise-free LCN backbone — precisely what the 8937-HN provides. When paired with a properly configured Honeywell NIM (Network Interface Module), the fiber extender enables multi-segment LCN topologies that span large plant footprints, such as those found in refinery complexes or integrated steel mills.

Beyond the LCN layer, the 8937-HN supports overall system resilience when used alongside complementary protection hardware. Honeywell 24 VDC redundant power supplies for the TDC 3000 card cages ensure that the extender module remains energized during utility fluctuations. Surge protection devices on incoming power rails and UPS (Uninterruptible Power Supply) systems at the control room level further shield the module from transient events. In safety-instrumented system (SIS) architectures, the LCN may also interface with Honeywell FSC (Fail-Safe Controller) safety PLCs, where the 8937-HN’s optical isolation is especially valuable in preventing fault propagation between the basic process control system (BPCS) and the safety layer.

For facilities running mixed-vendor environments, the 8937-HN’s role as a passive optical extender means it does not interfere with higher-level protocol gateways — including Modbus RTU/TCP bridges, PROFIBUS DP segment couplers, or OPC DA/UA servers — that may be integrated into the TDC 3000 architecture via third-party interface modules. This makes the 8937-HN a universally compatible backbone component in multi-protocol industrial networks.

Application in Critical Infrastructure

The Honeywell 8937-HN has proven its value across the most demanding sectors of critical infrastructure:

Oil & Gas: In upstream and midstream facilities — wellhead automation, gas compression stations, and pipeline SCADA nodes — the LCN must tolerate explosive atmospheres, wide ambient temperature ranges, and persistent RF interference from radio communication equipment. The 8937-HN’s optical medium is inherently immune to these conditions, making it a preferred choice for Zone 2 classified control rooms where the card cage is housed in a purged and pressurized enclosure.

Power Generation: Coal, gas, and nuclear power plants rely on TDC 3000 / TPS systems for boiler management, turbine control, and balance-of-plant automation. In these environments, high-voltage bus bars, large transformer banks, and generator excitation systems generate intense electromagnetic fields. The 8937-HN’s galvanic isolation prevents these fields from corrupting LCN data frames, maintaining the sub-second scan cycles that turbine protection logic demands.

Petrochemical & Refining: Continuous catalytic cracking units, distillation columns, and reactor control loops require 24/7 uptime. A failed LCN extender can cascade into a full DCS communication fault, triggering emergency shutdowns. Stocking the 8937-HN as a certified spare — tested, serialized, and ready for hot-swap — is standard practice in reliability-centered maintenance (RCM) programs at major refineries.

Water & Wastewater Treatment: Municipal utilities operating TDC 3000 systems for pump station control, chemical dosing, and SCADA integration benefit from the 8937-HN’s resistance to the high-humidity, chemically aggressive environments typical of treatment plant control buildings.

Mining & Metals: In smelters, concentrators, and rolling mills, vibration from crushers and mills, combined with airborne conductive dust, creates a hostile environment for electronic modules. The 8937-HN’s sealed module design and optical signal path make it significantly more resilient than copper-based alternatives in these conditions.

Security & Quality FAQ

Q1: What does the 12-month warranty cover, and how is it enforced?
The 12-month warranty covers all functional defects arising under normal operating conditions, including premature component failure, optical port degradation, and firmware-related communication faults. Each unit shipped by TOPNLMS is individually tested against Honeywell’s functional acceptance criteria before dispatch. If a defect is confirmed within the warranty period, TOPNLMS will arrange replacement or repair at no additional cost to the buyer. Warranty claims are processed via email at [email protected] with proof of purchase and a fault description.

Q2: How is each 8937-HN tested before shipment?
Every unit undergoes a multi-stage pre-shipment inspection: visual inspection for physical damage, optical port continuity verification, power-on functional test in a TDC 3000-compatible test bench, and firmware version confirmation. Units that do not pass all stages are quarantined and not offered for sale. A test report is available upon request for customers with strict incoming inspection requirements.

Q3: Is the 8937-HN compatible with both TDC 3000 and TPS (TotalPlant Solution) systems?
Yes. The 8937-HN is backward-compatible with the TDC 3000 LCN architecture and is also supported in TPS environments, which represent the evolutionary upgrade path from TDC 3000. Customers migrating from TDC 3000 to TPS can retain existing 8937-HN modules in their LCN infrastructure without hardware replacement, protecting their capital investment.

Q4: Can TOPNLMS support long-term or repeat procurement of the 8937-HN?
Yes. TOPNLMS maintains a dedicated inventory of TDC 3000 and TPS spare parts, including the 8937-HN, to support ongoing maintenance programs at facilities with multi-year operational commitments. Blanket purchase orders, scheduled delivery agreements, and priority reservation for critical spares are all available. Contact our team to discuss volume pricing and supply continuity arrangements.