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Phone: +86 16626708626Description
3. Key Technical Specifications
- Channels: 4 (programmed in pairs)
- Power Consumption: 7.7 Watts nominal
- Input Types: Proximity transducers
- Input Impedance: 10 kΩ
- Scale Factors: 0.79 mV/μm (20 mV/mil), 3.94 mV/μm (100 mV/mil), or 7.87 mV/μm (200 mV/mil)
- Measurements: Rod position, rod drop, hyper-compressor, gap, 1X/2X amplitude
- Frequency Response: Peak-Peak filter 1 Hz to 600 Hz
- Accuracy: ±0.33% of full-scale typical (position/gap)
- Front Panel LEDs: OK, TX/RX, Bypass
- Buffered Outputs: One per channel, short-circuit protected
- Operating Temperature: -30°C to +65°C
- Dimensions (Module): 241.3 mm x 24.4 mm x 241.8 mm
4. Product Introduction
The Bently Nevada 3500-72M is a 4-channel Recip Rod Position Monitor for reciprocating compressors. It accepts proximity transducer signals, conditions them for rod position, rod drop, and related parameters, and drives alarms based on configured setpoints.
It meets API 618 requirements for critical reciprocating machinery protection. In compressor applications, it tracks piston rod movement to detect drop, wear, and abnormal positioning before failures occur. Channels program in pairs for flexible monitoring of multiple rods or combined measurements.
- 3500-72M
- 3500-72M
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| No OK LED | Power/backplane issue | ❌ Low | Measure supply voltage at module | Confirm rack power supplies |
| High rod drop readings | Probe misalignment or wear | ✅ High | Check probe gap voltage | Verify installation per drawing |
| No dynamic signal | Transducer failure or gap out of range | ✅ High | Measure DC gap at buffered output | Adjust probe or replace transducer |
| Alarms not matching machine state | Configuration error | ✅ High | Review setpoints in software | Reload and verify configuration |
| Intermittent position data | Keyphasor or speed reference loss | ✅ Medium | Check Keyphasor status | Validate speed input signal |
| Bypass LED on | Manual bypass active | ✅ Medium | Check software status | Clear bypass after maintenance |
Provide event logs, probe gap readings, and crank angle data for faster support.
6. Frequently Asked Questions (FAQ)
What measurements does the 3500-72M provide? Rod position (magnitude, angle, crank angle), rod drop (average piston position, gap), hyper-compressor parameters, plus dynamic data like 1X/2X and gap.
Is the module hot-swappable? No. Properly bypass protection functions and follow shutdown procedures. Reciprocating machines often require careful coordination to avoid process upsets.
What condition is this unit? New Original / New Surplus. Units receive full inbound checks, power-on testing, and functional verification in a 3500 rack setup.
How critical is probe placement for rod drop? Extremely. Incorrect gap or alignment causes false readings or missed faults. Document existing probe positions and gaps before any swap. Use manufacturer installation drawings.
Does it require a Keyphasor for all functions? Yes for crank angle and certain position calculations. Ensure reliable Keyphasor input to the rack.
What about firmware and software compatibility? Requires specific 3500 Rack Configuration Software versions (3.20 or higher, with later releases for advanced functions). Match to your existing rack to avoid configuration issues.
How do I avoid common installation mistakes? Take clear photos of probe mounting and wiring before removal. Mirror the setup exactly. Improper probe orientation on the rod is a frequent cause of immediate post-installation alarms. Test thoroughly at low speed first.
