BENTLY 125720-01 | 3500/15 Dual Redundant Power Supply | Obsolete Spare Parts & Risk Assessment
BENTLY 125720-01 | 3500/15 Dual Redundant Power Supply | Obsolete Spare Parts & Risk Assessment - Image 2
BENTLY 125720-01 | 3500/15 Dual Redundant Power Supply | Obsolete Spare Parts & Risk Assessment - Image 3
BENTLY 125720-01 | 3500/15 Dual Redundant Power Supply | Obsolete Spare Parts & Risk Assessment - Image 4

BENTLY 125720-01 | 3500/15 Dual Redundant Power Supply | Obsolete Spare Parts & Risk Assessment

  • Model: 125720-01
  • Brand: BENTLY NEVADA (a Baker Hughes company)
  • Core Function: Dual-redundant 24 VDC power supply module for Bently Nevada 3500 machinery protection racks
  • Lifecycle Status: Obsolete (End-of-Life declared by manufacturer)
  • Procurement Risk: High – genuine new-old-stock exhausted; secondary market units vary in condition and usage history
  • Critical Role: Provides primary and backup power to all modules in a 3500 rack; failure of both supplies results in complete loss of machinery protection
Category: SKU: BENTLY 125720-01​

Description

Key Technical Specifications (For Spare Parts Verification)

  • Product Model: 125720-01
  • Manufacturer: BENTLY NEVADA
  • System Family: 3500 Machinery Protection System
  • Module Type: 3500/15 Dual Redundant Power Supply
  • Output Voltage: +24 VDC nominal (regulated)
  • Output Current: Up to 6 A per supply (12 A total in redundant mode)
  • Input Voltage: 88–132 VAC or 100–150 VDC (auto-ranging)
  • Redundancy: Active/standby configuration with automatic switchover on fault
  • Status Indicators: LED indicators for AC OK, DC OK, Fault, and Redundancy status
  • Physical Slot: Occupies one full-height slot in 3500 rack
  • Connector Type: Rear-panel screw-terminal block for AC/DC input and alarm relay output
  • Firmware Dependency: None (hardware-only module), but must be paired with compatible 3500 rack backplane
  • Physical Identifier: Label includes “125720-01” and revision code (e.g., REV A); critical for mechanical and electrical compatibility

System Role and Downtime Impact

The BENTLY 125720-01 is a foundational component of the 3500 machinery protection system. Installed in every 3500 rack, it delivers regulated 24 VDC power to all I/O, monitor, and communication modules via the backplane. The dual-supply design ensures that if one unit fails, the other seamlessly assumes full load—maintaining continuous protection for critical rotating equipment such as compressors, turbines, and pumps. However, if a single remaining supply fails—or if a spare is unavailable during a failure—the entire 3500 rack loses power. This results in immediate de-energization of all trip relays, disabling the safety function and potentially triggering an uncontrolled machine shutdown or, worse, allowing unsafe operation without protection. In high-consequence applications (e.g., offshore platforms, ethylene crackers), this represents a high-risk single point of failure when redundancy is compromised.

Reliability Analysis and Common Failure Modes

Although designed for industrial reliability, the 125720-01 is vulnerable to long-term wear due to its continuous operation under thermal and electrical stress. The most common failure modes include:

  • Degradation of internal electrolytic capacitors, leading to output voltage ripple, instability, or complete dropout
  • Failure of switching transistors or rectifier diodes due to thermal cycling, especially in poorly ventilated cabinets
  • Corrosion or loosening of input terminal blocks, causing intermittent power or overheating
  • Burnout of the internal fuse or surge suppression components after repeated line transients

A key design limitation is the lack of remote health monitoring—the only diagnostics are local LEDs. Many failures occur without prior warning, and the “Fault” LED may not activate until the unit is already non-functional. Additionally, older units often lack modern overvoltage protection, making them susceptible to damage from upstream power anomalies.

Preventive maintenance recommendations include:

  • Quarterly inspection of terminal tightness and signs of overheating (discoloration, odor)
  • Annual measurement of output voltage under load using a calibrated multimeter
  • Verification of redundancy switchover by manually disabling one supply during scheduled outages
  • Storage of spares in dry, temperature-controlled environments to minimize capacitor aging
BENTLY 125720-01

BENTLY 125720-01

Lifecycle Status and Migration Strategy

BENTLY NEVADA has officially discontinued the 125720-01. No new units are available from the OEM, and technical documentation updates have ceased. Continued reliance on this module introduces operational risk: secondary market parts may have unknown service life, and failure during operation can cascade to total rack outage.

As a short-term mitigation, facilities should secure at least one fully tested spare per critical rack and implement rigorous preventive checks. Third-party refurbishment services can replace aging capacitors and semiconductors, restoring near-original reliability.

The recommended migration path is to replace the 125720-01 with the current 3500/15R Enhanced Redundant Power Supply (part number 146944-01). This modern equivalent offers:

  • Higher efficiency and improved thermal performance
  • Enhanced surge and overvoltage protection
  • Compatibility with existing 3500 racks (same form, fit, and function)
  • Support under current Bently Nevada service programs

Replacement requires no rack modification or reconfiguration—only physical swap and functional validation. For organizations planning full system modernization, upgrading to the Orbit 60 platform includes integrated, digitally monitored power management, but the 3500/15R provides a low-risk, drop-in solution to extend the life of legacy 3500 installations while maintaining safety integrity.

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