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3. Key Technical Specifications
| Parameter | Value |
|---|---|
| Configuration Options | 02 = Two-channel system; 03 = Three-channel system (recommended for 2oo3) |
| Input Signal | Single transducer per module (proximity probe or magnetic pickup) |
| Input Range | +10.0 V to –24.0 V (internally limited) |
| Input Impedance | 20 kΩ |
| Power Consumption | 8.0 W typical per module |
| Compatible Transducers | 3300 8 mm / 16 mm HTPS, 7200 series, 3300 RAM Proximitor®, magnetic pickups |
| Speed Range | 1–255 events/rev; max full-scale 99,999 rpm; max input frequency 20 kHz |
| Relay Response | ≤30 ms from overspeed event to relay activation |
| Relay Contacts | 4 per I/O module (1 dedicated to Overspeed); selectable NDE/NE |
| Contact Ratings | 5 A max; 30 Vdc / 250 Vac; 120 W dc / 600 VA ac |
| Front-Panel LEDs | OK, TX/RX, Bypass |
| Environmental | Operating –30 °C to +65 °C typical |
| System Requirement | Redundant 3500 power supplies mandatory |
4. Product Introduction
The Bently Nevada 3500/53 is the Electronic Overspeed Detection System for the 3500 Series. It provides a highly reliable, fast-response redundant tachometer specifically for overspeed protection on turbines, compressors and other critical rotating equipment.
Each module accepts one proximity-probe or magnetic-pickup signal and can be combined into a 2-out-of-2 or (preferred) 2-out-of-3 voting arrangement. The system meets API 670 and API 612 requirements and is available in Functional Safety (SIL 3) configurations. Redundant power supplies in the 3500 rack are mandatory. This is the dedicated overspeed protection solution—distinct from the 3500/50M tachometer used for normal speed monitoring.
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No OK LED | Missing or out-of-range input signal | ✅ High | Measure transducer voltage at I/O terminals (+10 to –24 V) | Verify probe gap or magnetic pickup output first |
| False overspeed trip | Noise on speed signal or wrong events/rev setting | ✅ High | Scope the buffered output; confirm events-per-revolution value | Check shielding and set correct teeth/events count |
| Relay does not trip on overspeed | Relay configured NDE when NE required, or wiring error | ✅ High | Force test setpoint in software; measure contact state | Confirm relay polarity switch and field wiring |
| Voting disagreement between modules | Different Keyphasor sources or calibration mismatch | ✅ Medium | Compare instantaneous rpm readings across channels | Use identical transducers and identical configuration |
| Module will not communicate | Backplane contact or missing redundant power | ❌ Low (module side) | Verify both power supplies are online and OK LEDs lit | Redundant supplies are required—do not run simplex |
| High residual speed after trip | Mechanical coast-down normal; check if zero-speed needed | ❌ Low | Monitor rpm decay | Use 3500/50M if zero-speed or reverse-rotation detection is required |
If symptoms continue, capture front-panel LED status, a full diagnostic log from the 3500 Rack Configuration Software, and photos of the I/O module face, then contact technical support.
- 3500/53
- 3500/53
6. Frequently Asked Questions (FAQ)
Q: Is the 3500/53 the same as the 3500/50M Tachometer? A: No. The 3500/53 is dedicated overspeed protection with fast trip relays and voting. The 3500/50M is for normal speed, acceleration and zero-speed monitoring and is not intended for overspeed protection.
Q: Do I need one, two or three modules? A: A single module can be used, but API 670 recommends a 2-out-of-3 (three-module) voting system for critical machines. Two-module (2oo2) is also supported.
Q: Are redundant power supplies required? A: Yes. The Overspeed Detection System will not operate correctly without redundant 3500/15 power supplies in the rack.
Q: Can it accept magnetic pickups as well as proximity probes? A: Yes. Both proximity probes (3300/7200 series) and magnetic pickups are supported.
Q: What is the typical trip response time? A: Relay activation occurs in ≤30 ms from the overspeed event.
Q: Why is the price lower than a factory-new unit from Baker Hughes? A: This is New Original / New Surplus stock—genuine Bently Nevada parts that have never been installed in a running system. Units ship with a 1-year warranty after functional verification.
Q: What is the typical lead time and warranty? A: Units are normally in stock for same- or next-day shipment. All modules carry a 1-year warranty against defects in materials and workmanship.
