BENTLY 3500/93 135785-02C

Description

Product Description

The BENTLY 3500/93 135785-02C is a sophisticated Steam Turbine Control Interface Module within the Bently Nevada 3500 Machinery Health Monitoring System. This specialized module serves as a critical bridge between the 3500 monitoring rack and the electro-hydraulic control (EHC) system of a steam turbine. The primary function of the BENTLY 3500/93 135785-02C is to process and convert signals related to turbine control and protection, specifically managing speed/load control and overspeed protection. It accepts inputs such as speed probe signals and control system commands, and provides outputs to govern turbine speed via the EHC system. The module plays a dual role: it enables the integration of turbine control functions within the trusted 3500 monitoring framework and acts as a dedicated, reliable channel for executing an emergency overspeed trip, which is a fundamental safety requirement for any steam turbine. The suffix “02C” denotes a specific hardware and firmware revision.

Technical Parameters and Specifications

• System Compatibility: Bently Nevada 3500 System.
• Module Type: Steam Turbine Control Interface (Overspeed Protection & Control).
• Key Functions:
  • Overspeed Detection and Trip: Continuously monitors turbine speed (typically from two independent magnetic pickups or proximity probes). Executes a voting logic (e.g., 2-out-of-2 or 2-out-of-3) and initiates a relay trip output if a dangerous overspeed condition is detected.
  • Speed Control Interface: Provides analog (4-20 mA) or discrete outputs to interface with the turbine’s governor or EHC system for normal speed/load control.
• Inputs: Accepts signals from speed sensors (magnetic pickups, proximity probes). Also accepts control signals from a separate control system (DCS/PLC).
• Outputs:
  • Trip Relay Outputs: Redundant, fail-safe relay contacts to trip the turbine emergency stop valves (ESVs).
  • Control Outputs: Analog or discrete outputs for speed reference or governor control.
• Configuration: Programmed using the Bently Nevada 3500 Configuration Software. Key parameters include overspeed trip setpoints, speed scaling, time delays, and voting logic.
• Diagnostics: Comprehensive self-diagnostics for module health, sensor input validity, and output circuit verification. Faults are annunciated on the module’s LED display and communicated to the monitoring system.
• Safety Integrity: Designed to support high Safety Integrity Level (SIL) applications (e.g., SIL 2 or SIL 3 as part of a certified system) for overspeed protection, following rigorous design and testing standards (e.g., IEC 61508).
• Redundancy Support: Often deployed in triplicated (TMR) or dual-channel configurations within the 3500 rack to create a fault-tolerant protection system.

Advantages and Key Features

• Integrated Protection and Control: The BENTLY 3500/93 135785-02C unifies critical overspeed protection and control interface functions into a single module within the established 3500 platform, simplifying system architecture and leveraging the rack’s power, communication, and diagnostics.
• High Reliability and Safety-Certifiable Design: Engineered for the most critical protection function on a steam turbine. Its design principles—including redundancy support, diagnostic coverage, and fail-safe behavior—make it suitable for SIL-rated safety applications.
• Advanced Voting Logic for Fault Tolerance: The module can implement sophisticated voting algorithms (e.g., 2oo3) on speed inputs, ensuring that a single sensor or channel failure does not cause a nuisance trip nor prevent a legitimate trip, maximizing both availability and safety.
• Seamless Integration with 3500 Ecosystem: As a native 3500 module, it shares a common engineering tool, rack infrastructure, and operator display environment with vibration, temperature, and other monitoring modules, providing a unified view of turbine health and control.
• Comprehensive Diagnostics and Testing: Supports online and offline testing of the overspeed protection loop. Technicians can simulate speed signals to verify trip setpoints and output relay functionality without causing an actual turbine trip, a crucial feature for periodic safety validation.

Application Cases in Various Fields

• Utility Steam Turbine Generator Protection: The BENTLY 3500/93 135785-02C is the core of the overspeed protection system for a 600 MW coal-fired or nuclear steam turbine. Triplicated modules process signals from three speed probes, and their voted output directly trips the ESVs to prevent catastrophic rotor failure.
• Industrial Cogeneration Turbines: In a paper mill or refinery cogeneration plant, this module provides the overspeed trip function and interfaces the plant’s DCS with the turbine’s mechanical-hydraulic governor for integrated plant load control.
• Geothermal Steam Turbines: Used in harsh geothermal plant environments to provide reliable speed control and protection, where its robust design withstands challenging conditions.
• Marine Propulsion Turbines: Employed in naval or commercial ships for primary turbine overspeed protection, where space is limited and reliability is paramount.

Comparison with Competing Products

Competing solutions come from turbine control OEMs and specialized safety system vendors:

• Vs. Turbine OEM Control Systems (GE, Siemens, Mitsubishi): These OEMs offer integrated turbine control systems (e.g., GE’s Mark VIe, Siemens’ T3000) that include overspeed protection. The 3500/93 offers a best-in-class, specialized protection system that can be integrated with any OEM’s turbine, often specified by end-users for its independent, focused safety philosophy and proven track record.
• Vs. Other Safety PLCs (Triconex, HIMA): While Triconex or HIMA safety PLCs can be programmed for overspeed protection, the BENTLY 3500/93 135785-02C is a pre-engineered, application-specific solution. It comes with built-in speed processing algorithms, dedicated sensor interfaces, and is supported by Bently Nevada’s deep turbine expertise, potentially reducing engineering and validation time.
• Key Differentiator: The 3500/93‘s deep integration with vibration and condition monitoring data within the same rack is unique. It allows for a more holistic protection strategy (e.g., considering vibration levels during startup before releasing overspeed protection).

Selection Suggestions and Precautions

1. Safety Lifecycle Compliance: Implementing the BENTLY 3500/93 135785-02C for overspeed protection is a safety instrumented function (SIF). Its selection and configuration must be part of a formal safety lifecycle process per IEC 61511, including a Hazard and Risk Assessment (HARA) and SIL determination.
2. Mandatory Redundant Architecture: For overspeed protection, never use a single module. Always implement a redundant or triple modular redundant (TMR) architecture using multiple 3500/93 modules and independent speed sensors as defined in the safety requirements specification (SRS).
3. Independent and Qualified Speed Sensors: Use high-quality, magnetically isolated speed sensors (pickups) as recommended by Bently Nevada. Ensure they are installed correctly and on separate power supplies or isolators to ensure true signal independence for the voting logic.
4. Rigorous Configuration Management: The configuration (trip setpoints, time delays, voting logic) is critical. It must be documented, password-protected, and any changes must follow a strict management of change (MOC) procedure. Always keep secure backups of the configuration.
5. Regular Proof Testing: Plan and execute periodic functional proof tests of the entire overspeed protection loop, including sensors, the 135785-02C module, and trip solenoids/valves. This is a legal and safety requirement for maintaining the SIL rating. Use the module’s testing features where possible.
6. Expert Integration and Support: The integration of this module with the turbine’s EHC system and the broader control system is complex. Engage with Bently Nevada or a highly qualified system integrator with specific experience in turbine protection systems. Always source the module and its associated components through authorized channels to guarantee authenticity and support.

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