330191-00-08-20-CN Bently Nevada 8 mm ETR Proximity Probe, 2.0 m

330191-00-08-20-CN: Engineered for Harsh Turbomachinery Environments

Machine protection systems in power generation, oil and gas, and heavy industry demand displacement measurements that remain stable under extreme thermal and mechanical stress. The Bently Nevada 330191-00-08-20-CN addresses this need as a 3300 XL 8 mm ETR (Extended Temperature Range) proximity probe. It is purpose-built for radial vibration, axial position, and eccentricity measurements where standard probes may degrade. This probe carries country-specific approval (CN) and ships as new original factory-packed material.

Key Specifications of the 330191-00-08-20-CN Probe

• Model: 330191 - 3300 XL 8 mm ETR Probe, 3/8-24 UNF thread, without armor
• Total Length: 2.0 meters (6.6 feet)
• Probe Tip Material: Polyphenylene sulfide (PPS)
• Case Material: AISI 303 or 304 stainless steel
• Nominal Probe DC Resistance: 7.88 ± 0.50 Ω at 2.0 m
• Output Resistance: 50 Ω
• Supply Sensitivity: Less than 2 mV change per volt input change
• Power Requirement: -17.5 Vdc to -26 Vdc (nonincendive, 12 mA max); -23 Vdc to -26 Vdc with barriers
• Maximum Connector Torque: 0.565 N·m (5 in·lbf)
• Tensile Strength: 330 N (75 lbf) probe case to lead; 270 N (60 lbf) lead to extension cable

The 8 mm probe body provides thicker coil encapsulation than smaller diameters, yielding a more rugged assembly. The patented TipLoc molding method creates a robust bond between tip and body, while the CableLoc design ensures high pull strength. For installations where oil leakage through the cable interior is a concern, an optional FluidLoc cable is available. Note that one-meter systems do not use an extension cable.

Addressing Installation and Environmental Challenges

Engineers frequently face limited mounting space and extreme temperatures. This probe meets both challenges. Its minimum unthreaded length is 0.0 in. and minimum case length is 0.8 in., allowing flush mounting in tight bores. The 3/8-24 UNF thread engages up to 0.563 in. The ETR cable, insulated with perfluoroalkoxy (PFA), supports ambient temperatures from -55°C to +232°C depending on the temperature classification. For EPL Ga and Gc, T1 allows -55°C to +232°C, while T4 limits to +80°C. For EPL Dc, T280°C @ Ta -55°C to +232°C applies. These ratings make the probe suitable for steam turbines, gas turbines, and compressors where thermal gradients are severe.

To ensure measurement accuracy, use only Bently Nevada extension cables and proximitors. The probe entity parameters are met when connected to BN Prox. Operation at a more positive voltage than -23.5 Vdc can reduce linear range, so verify supply voltage at the proximitor terminals.

Maintenance and Reliability

Inspect the probe tip and cable periodically for mechanical damage, oil ingress, or loose connectors. The Viton O-ring seals differential pressure between tip and case, but probes are not pressure-tested prior to shipment. Therefore, avoid exceeding rated pressure differentials. Because the probe case is stainless steel and the tip is PPS, it resists corrosive attack in most industrial atmospheres. However, always follow the manufacturer's safety manual for hazardous-area installations.