Bently Nevada 136719-01 | 3500/20 Relay Module | Obsolete Machinery Protection Spare Parts
Bently Nevada 136719-01 | 3500/20 Relay Module | Obsolete Machinery Protection Spare Parts - Image 2
Bently Nevada 136719-01 | 3500/20 Relay Module | Obsolete Machinery Protection Spare Parts - Image 3
Bently Nevada 136719-01 | 3500/20 Relay Module | Obsolete Machinery Protection Spare Parts - Image 4

Bently Nevada 136719-01 | 3500/20 Relay Module | Obsolete Machinery Protection Spare Parts

  • Model: 136719-01
  • Brand: Bently Nevada (a Baker Hughes company)
  • Core Function: 3500/20 Relay Module – provides configurable alarm and shutdown relay outputs for the Bently Nevada 3500 Machinery Protection System, used to interface vibration, position, or speed alarms to plant DCS, ESD, or motor control centers
  • Lifecycle Status: Obsolete (End-of-Life declared by Bently Nevada)
  • Procurement Risk: Very High – no longer manufactured; extremely limited availability on secondary markets; units often lack functional test reports or certification documentation
  • Critical Role: Serves as the final output interface between machinery protection logic and external safety or control systems; failure can prevent a required trip signal from reaching a shutdown valve, turbine stop valve, or breaker—posing direct process safety risk
Category: SKU: Bently Nevada 136719-01

Description

Key Technical Specifications (For Spare Parts Verification)

  • Product Model: 3500/20 Relay Module
  • Bently Part Number: 136719-01
  • System Family: 3500 Machinery Protection System
  • Relay Configuration: 8 independent electromechanical relays (Form C contacts: SPDT)
  • Contact Ratings:
    • 2 A @ 30 VDC (resistive)
    • 1 A @ 125 VAC
    • Max switching voltage: 250 VAC / 125 VDC
  • Input Source: Receives alarm status from 3500 monitor modules (e.g., 3500/42M, /44M, /32) via backplane
  • Configuration: Relays assignable to specific alarm conditions (Alert, Danger, OK-to-Run, etc.) via 3500 Rack Configuration Software (RCS)
  • Diagnostics: LED indicators per channel (energized/de-energized); module fault detection via backplane
  • Redundancy: Not redundant at module level, but critical trips often use dual relays from separate modules
  • Form Factor: Half-height module (occupies one slot in 3500 rack)
  • Certification: Designed for compliance with API 670, IEC 61508 (SIL 2) when used in approved redundant architectures
  • Operating Temperature: 0°C to +65°C

System Role and Safety Impact

The 136719-01 is a critical safety interface in machinery protection systems. It converts internal digital alarm states from vibration or position monitors into dry contact closures that can:

  • De-energize a motor starter
  • Trigger an emergency shutdown (ESD) solenoid
  • Block a compressor restart via “OK-to-Run” interlock
  • Signal high vibration to a plant DCS or fire & gas system

Unlike data-acquisition modules, the 3500/20 directly participates in safety actions. A failed relay—especially one that is welded closed or fails to operate on demand—can result in:

  • Fail-dangerous: Machine continues to run during a hazardous condition (e.g., bearing wipe, rub, overspeed)
  • Fail-safe: Spurious trip causing unplanned downtime (less severe but still costly)

Because it often interfaces with hardwired safety systems, its reliability is subject to regulatory scrutiny under OSHA PSM, EPA RMP, and facility-specific LOPA studies.

Reliability Analysis and Common Failure Modes

Despite robust industrial construction, aging 136719-01 modules are susceptible to:

  • Contact welding: Repeated switching of inductive loads (e.g., solenoid coils) causes arcing, leading to welded contacts that cannot open—creating a dangerous failure mode.
  • Coil burnout: Relay drive transistors or coil circuits degrade due to overcurrent or thermal stress, resulting in open circuits.
  • Mechanical fatigue: After thousands of operations, spring tension weakens, increasing contact bounce or causing incomplete closure.
  • Backplane communication loss: Corrosion or vibration loosens the module, masking actual relay state from the controller.
  • Configuration corruption: Rare, but possible if EEPROM degrades, causing relays to map to wrong alarm conditions.

Design limitations include finite mechanical life (~100,000 operations) and no built-in contact supervision. For preventive maintenance, technicians should:

  • Perform annual proof tests that verify both electrical continuity and mechanical operation under load
  • Use external contact supervision relays (where safety integrity demands it)
  • Install flyback diodes or RC snubbers on inductive field devices to reduce arcing
  • Monitor RCS logs for “Relay Mismatch” or “Output Fault” warnings
Bently Nevada 136719-01

Bently Nevada 136719-01

Lifecycle Status and Migration Strategy

Bently Nevada has discontinued the 136719-01 as part of its evolution toward the 3500/53 Dual Relay Module (with enhanced diagnostics) and integration with the 3500/94 Enhanced Gateway. The 3500/20 is no longer produced, and official repair services are unavailable outside rare legacy contracts. Continued reliance introduces significant risk:

  • No access to new, certified spares
  • Inability to validate post-failure performance
  • Growing difficulty meeting IEC 61511 audit requirements for spare parts availability

As an interim mitigation, facilities may:

  • Source units exclusively from Bently-authorized service centers that provide full operational and contact resistance testing
  • Maintain at least two tested spares per critical safety loop
  • Implement external relay monitoring circuits (subject to SIL revalidation)

For long-term resolution, Bently recommends upgrading to the 3500/53 module, which offers:

  • Dual-channel voting for higher diagnostic coverage
  • Built-in contact feedback for weld detection
  • Better compatibility with modern gateway and APM platforms

Given its role as the final actuation point in machinery protection sequences, the obsolescence of the 136719-01 represents a high-severity safety risk. Proactive management through formal sparing, proof testing, or system modernization is essential to ensure ongoing process safety, regulatory compliance, and asset integrity.

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