Description Key Technical Specifications Parameter Specification Model Number 125720-01 Probe Diameter 11 mm System Type 3300 XL 11mm Proximitor Cable Length 5.0 meters (integral) Sensitivity 200 mV/mil (7.87 V/mm) typical Linear Range 0.25 to 2.3 mm (10 to 90 mils) Input Voltage -17.5 to -26V DC (from Proximitor) Temperature Range -35°C to 177°C (probe tip) Tip Material PPS (polyphenylene sulfide) Thread Size M14 x 1.5 Unthreaded Length 0 mm (full thread) Case Material AISI 303 stainless steel Approvals ATEX, IECEx, CSA (when used with approved Proximitor)   Product Introduction Larger shafts need larger probes. The BENTLY 125720-01 is the 11mm version of the 3300 XL proximity probe—built for turbines, compressors, and generators with shaft diameters that make the 8mm probes impractical. Same 200 mV/mil sensitivity, same -24V DC system, but the bigger tip diameter gives you better linear range on larger targets. You’ll find these on main turbine bearings, boiler feed pump turbines, and centrifugal compressors in the 10 MW class. The 5-meter integral cable means no splice boxes near the bearing housing—cleaner installation, fewer failure points. The probe tip is PPS, not Delrin like the 8mm version. Handles higher temperatures and is chemically resistant. If you’re working around steam seals or process gas compressors with aggressive carryover, that matters. The 11mm body also means more robust threads—M14 x 1.5 instead of 3/8-24. Less prone to cross-threading in aluminum bearing housings. The 125720-01 uses the same Proximitor as the 8mm probes (3300 XL 11mm Proximitor), so your spares inventory stays simple. One Proximitor type covers both.   Installation & Configuration Guide Phase 1: Pre-Installation Confirm machine shutdown and shaft static. Lock out driver. Bearing housing may be hot—check temperature before starting. Gather tools: 14mm open-end wrench, M14 x 1.5 thread gauge, DC voltmeter. You’ll need the Bently probe installation tool if clearance is tight. Have threadlocker (Loctite 242) ready. Phase 2: Removal Unscrew old probe counter-clockwise. Count turns to removal—note approximate depth. If the probe broke off inside the housing (common if over-tightened), you’ll need an easy-out. Remove the Proximitor in the junction box separately—it’s not part of the 125720-01 assembly. Inspect mounting hole. Clean threads thoroughly. Old threadlocker residue changes the probe’s effective depth. Phase 3: Installation Apply a small amount of threadlocker to the BENTLY 125720-01 threads—just the first 3-4 threads. Hand-thread until finger tight. Now calculate final position: 11mm probes require about 1.27 mm (50 mils) nominal gap, which gives -9 to -11V DC. One full turn of an M14 x 1.5 thread moves the probe 1.5 mm axially. So from finger-tight contact, back out approximately 0.8 turns to achieve 1.2 mm gap. Tighten locknut to 20-25 ft-lb. Route cable away from heat sources and sharp edges. Secure with Ty-wraps every 300 mm, but not tight enough to deform the cable. Phase 4: Power-On & Testing Connect the 125720-01 to the Proximitor. Apply -24V DC. Measure DC gap voltage at the Proximitor output. Target is -9 to -11V. If outside that range, adjust probe position—but that requires shutdown. At nominal gap, slowly rotate shaft manually (if possible). Voltage should change smoothly without dropouts. Then run at operating speed. Check vibration amplitude and phase. Clean 1X component? Good. Distorted? Check for mechanical runout or electrical runout—the latter often requires shaft runout compensation in the monitor.   Frequently Asked Questions (FAQ) Q: What’s the difference between 125720-01 and 125760-01? The -01 suffix indicates cable length. 125720-01 is 5.0 meters. 125760-01 is 7.0 meters. The 11mm probes also use different part numbers for reverse-mount configurations. Verify your existing part number before ordering. If you need 5m, this is correct. If 7m, look for 125760-01. Q: Can I use this probe with a 3500/40 monitor? Yes. The BENTLY 125720-01 works with any 3300 XL Proximitor, which connects to 3500 series monitors via the appropriate I/O module. Just confirm your Proximitor model is compatible with 3500 rack input cards. Most are. The 11mm probe itself is just the sensing element; the Proximitor does the signal conditioning. Q: The gap voltage reads -3V with the shaft at rest. What’s wrong? -3V means the probe tip is too far from the shaft—beyond the linear range. Either the probe wasn’t installed deep enough, or the shaft has moved axially (thrust bearing wear). Shut down, adjust probe inward. If voltage reads -18V, it’s too close—risk of rubbing. Adjust outward. Do not run with voltage outside -1 to -15V range; you’ll get clipped or non-linear vibration data. Q: How do I test the probe without removing it? Disconnect the probe from the Proximitor at the junction box. Measure resistance between probe tip and ground. Should be open circuit (megaohms). If low resistance, tip is shorted to case—replace probe. Then measure probe inductance across the two probe wires. Should be a few millihenries. If open circuit, the coil is broken—replace. Then reconnect and check DC gap voltage. Q: What’s the maximum temperature at the probe tip? The 125720-01 is rated to 177°C continuous at the tip. The cable is rated to 120°C. If your bearing housing runs hotter (steam turbines often do near the inlet), you need high-temperature extensions or a different probe. Check your application temps before installation. Q: Can I install this probe in a Division 2 hazardous area? Yes, when used with an appropriately certified Proximitor and barrier. The probe itself is passive and simple construction. But the system certification requires the entire loop—probe, cable, Proximitor, and barrier—to match. Verify the Proximitor model has the necessary ATEX/IECEx/CSA markings for your zone. The 125720-01 alone is not certified; it’s part of a system. Q: The vibration reading is noisy. Probe or something else? Disconnect at the Proximitor input. If noise disappears, it’s the probe/cable. If noise remains, it’s the Proximitor or monitor. Common noise sources: cable abraded and shorting to ground, or the probe tip picking up electrical runout from the shaft surface. Electrical runout appears as once-per-rev noise that changes with shaft position but not with actual vibration. Requires shaft demagnetization or runout compensation. 1C31204G03 PLC EMERSON 1C31205G01 EMERSON 1C31206G01 EMERSON EMERSON 1C31224G02 1C31227G02 PLC EMERSON Email: [email protected] Phone: 86 15340683922 Sales:Wu Jiedong Our products are guaranteed for 1 year, with new and original production stopped and imported spare parts. All prices listed on the official website are subject to confirmation by contact: Wu Jiedong (manager). Our product: brand new original packaging Our warranty: All new or repaired parts have a 12 month warranty period beginning Our payment: 100% telegraphic transfer of inventory items before shipment, conditions can be proposed! If you have any downtime spare parts that you cannot find, please feel free to call or use email to contact me. If there are issues that the product cannot solve, please contact me. Product prices can be negotiated. Please do not consider contacting me!