Bently Nevada 135613-02 | 3500/50 Tachometer Module | Obsolete Critical Spare for Machinery Protection
Bently Nevada 135613-02 | 3500/50 Tachometer Module | Obsolete Critical Spare for Machinery Protection - Image 2
Bently Nevada 135613-02 | 3500/50 Tachometer Module | Obsolete Critical Spare for Machinery Protection - Image 3

Bently Nevada 135613-02 | 3500/50 Tachometer Module | Obsolete Critical Spare for Machinery Protection

  • Model: 135613-02
  • Brand: Bently Nevada (a Baker Hughes company)
  • Core Function: 3500/50 Tachometer/Sensor Input Module for speed and zero-speed detection in the 3500 machinery protection system
  • Lifecycle Status: Discontinued (Obsolete)
  • Procurement Risk: High – no longer manufactured; limited to secondary market with testing, authenticity, and pricing volatility concerns
  • Critical Role: Provides primary speed reference for overspeed protection, vibration compensation, and trip logic; failure can disable critical shutdown functions
Category: SKU: Bently Nevada 135613-02

Description

Technical Specifications (For Spare Verification)

  • Product Model: 135613-02
  • Manufacturer: Bently Nevada
  • System Family: 3500 Machinery Protection System
  • Module Type: 3500/50 Tachometer Module (Single or Dual Channel configuration)
  • Input Channels: 2 (accepts proximity probe or magnetic pickup signals)
  • Output: Digital speed data to 3500 framework via backplane; supports zero-speed detection
  • Compatibility: Requires 3500/20 Rack Interface Module and 3500/22 or /25 Transient Data Interface for full functionality
  • Power Supply: +24 VDC via 3500 backplane
  • Form Factor: Standard 3500 4-slot module (approx. 80 mm wide)
  • Diagnostic Features: Front-panel LEDs for power, OK status, and channel activity
  • Firmware Dependency: Must match revision level of adjacent modules to avoid communication faults

Bently Nevada 135613-02

Bently Nevada 135613-02

 

System Role and Downtime Impact

The Bently Nevada 135613-02 is a foundational component in legacy 3500-based machinery protection systems, commonly deployed on steam turbines, compressors, and large pumps in power generation, oil & gas, and petrochemical facilities. It processes raw tachometer signals to generate accurate rotational speed data used by other modules—such as the 3500/42M or /45—for vibration analysis, overspeed trip logic, and runout compensation. If this module fails or provides erroneous speed data, the entire protection logic becomes unreliable. In many safety instrumented systems (SIS), loss of valid speed input will automatically trigger a trip or place the machine in a safe shutdown state. Recovery requires physical replacement, as the module cannot be repaired onsite. Given its role in preventing catastrophic mechanical failure, its unavailability directly increases operational risk.

 

Reliability Analysis and Common Failure Modes

Although designed for industrial environments, the 135613-02 is susceptible to several age-related and environmental failure mechanisms:

  • Degradation of internal signal conditioning circuitry due to prolonged exposure to electrical noise from variable frequency drives (VFDs) or ignition systems.
  • Failure of front-end protection components (e.g., transient voltage suppressors) after repeated surge events, leading to distorted waveform interpretation.
  • Corrosion or oxidation on the backplane connector pins, causing intermittent communication with the rack controller—often manifesting as “Module Fault” alarms.

A key design limitation is its reliance on analog signal integrity; unlike newer digital protocols (e.g., Bently’s 3500/15 Enhanced Keyphasor), it lacks built-in diagnostics for signal quality. Additionally, early revisions had marginal immunity to ground loops, which could cause speed jitter in poorly grounded installations.

Preventive maintenance recommendations include:

  • Periodic verification of tachometer signal waveform using an oscilloscope during outages.
  • Inspection of backplane contacts for discoloration or pitting.
  • Ensuring proper shielding and grounding of tachometer cables to minimize EMI coupling.
  • Maintaining spare units in static-dissipative, dry storage to prevent latent damage.

Bently Nevada 135613-02

Bently Nevada 135613-02

 

Lifecycle Status and Migration Strategy

Bently Nevada has officially discontinued the 135613-02 as part of the broader phase-out of the classic 3500/50 platform. While the 3500 system remains supported in general, this specific module is no longer available through authorized channels. Continued use poses significant operational risk: verified spares are scarce, and untested units from third-party brokers may fail immediately upon installation.

Short-term mitigation strategies include:

  • Securing at least one fully tested spare per critical machine train.
  • Engaging specialized vendors for board-level refurbishment, including reflow of solder joints and replacement of aging capacitors.
  • Implementing redundant tachometer inputs where the machine design allows, to provide backup speed reference.

For long-term reliability, Bently Nevada recommends upgrading to the 3500/53 Enhanced Speed Measurement Module (part number 135640-01), which offers improved noise immunity, digital diagnostics, and compatibility with modern 3500 frameworks. This upgrade typically requires:

  • Replacement of the 135613-02 with the 3500/53 module.
  • Minor rewiring if switching from magnetic pickups to proximity probes (or vice versa).
  • Configuration update via the 3500 Rack Configuration Software (RCS).

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