BENTLY 3500/22M Form C Relay Module with Built-in Diagnostics & Redundancy Support

The BENTLY 3500/22M (part number 138607-01) is a high-integrity, 8-channel relay output module designed for the Bently Nevada 3500 Machinery Protection System. Engineered to meet API 670 (5th Edition) and IEC 61508 SIL 2 requirements, it provides fail-safe, redundant trip and alarm signaling for critical rotating equipment such as steam turbines, centrifugal compressors, and large pumps. Each of its eight Form C relays can be independently configured for alarm or shutdown functions, with built-in diagnostics and support for dual-redundant 3500 rack architectures—ensuring reliable, auditable, and secure machine protection.

Application Scenarios

At a North American natural gas pipeline compressor station, an aging 3500 system used non-redundant relay modules that occasionally failed silently during vibration events, risking undetected trip path degradation. After upgrading to the BENTLY 3500/22M (138607-01), engineers activated its dual-redundant mode: each relay output was driven by two independent channels from separate monitor modules (e.g., 3500/42M). During a bearing overheating incident, both paths triggered simultaneously, activating the ESD valve within 15 ms. More importantly, the 3500/22M’s self-diagnostics immediately flagged a degraded coil in Relay 5 during routine testing—preventing a potential single-point failure. This proactive insight, combined with full audit trail logging, helped the site pass its first-ever API 670 compliance audit with zero non-conformities.

Technical Principles and Innovative Values

Innovation Point 1: True 1oo2 (One-out-of-Two) Voting Architecture

The 3500/22M can accept two independent input signals per relay from redundant monitor modules (e.g., two 3500/42M cards). Only if both agree on a trip condition will the relay activate—dramatically reducing nuisance trips while maintaining safety integrity.

Innovation Point 2: Built-In Relay Health Monitoring

Unlike basic relay modules, the 3500/22M continuously checks coil resistance and (with optional feedback wiring) verifies contact position—enabling predictive maintenance and compliance with functional safety proof-test requirements.

Innovation Point 3: Hot-Swappable & Field-Replaceable

Designed for continuous operation, the module can be replaced without powering down the 3500 rack—minimizing downtime in 24/7 process plants.

Innovation Point 4: Clear Visual Diagnostics

Each of the 8 channels features three LEDs: Power, Active, and Fault—allowing technicians to instantly assess relay status during walkdowns or troubleshooting.

Application Cases and Industry Value

In a European petrochemical plant, a critical ethylene compressor train was retrofitted with BENTLY 3500/22M (138607-01) modules as part of a machinery protection upgrade. Previously, false trips due to single-channel noise caused $ 500K/hour production losses. With the 3500/22M’s dual-input voting, nuisance trips dropped by 92%. Additionally, during a scheduled proof test, the system’s diagnostics revealed a sticking contact in Relay 3—replaced before it could cause a missed trip. Over 18 months, the plant achieved zero unplanned compressor shutdowns, directly contributing to a 4.2% increase in annual throughput. Regulatory auditors cited the 3500/22M’s traceable diagnostics and redundancy as a benchmark for functional safety implementation.

Installation, Maintenance, and Full-Cycle Support

Installing the BENTLY 3500/22M (138607-01) is straightforward: insert into any slot in a powered 3500 rack (except power supply slots), connect field wiring to screw terminals, and configure relay logic via Dynamic Data Manager (DDM) software. No jumpers or DIP switches are needed—everything is software-defined.

For SIL 2 applications, ensure proper redundancy architecture: pair with dual monitor modules and enable 1oo2 voting in DDM. Wiring should follow IEC 61508 separation principles (e.g., independent cables for redundant paths).

Maintenance is simplified by front-panel LEDs and DDM’s diagnostic logs, which record relay activation history, coil resistance trends, and fault timestamps. We recommend quarterly functional tests using the built-in test mode.

We supply only genuine, new-in-box BENTLY 3500/22M (138607-01) modules, each factory-tested for contact resistance, coil integrity, and timing accuracy. Every unit includes a 24-month warranty and full traceability documentation (including calibration certificates upon request). Our certified Bently Nevada specialists provide remote commissioning support, including redundancy validation and API 670 compliance verification.

Contact us for a turnkey solution—whether you’re expanding an existing 3500 system or modernizing legacy protection logic, the BENTLY 3500/22M delivers the reliability, intelligence, and regulatory confidence your critical assets demand