The Industry Standard: 8mm & 11mm Vibration Sensors
The workhorses of any condition monitoring program are the 8mm and 11mm proximity probes. The 3300 XL 8mm system is a true industry benchmark, fully compliant with API 670 standards for performance, accuracy, and temperature stability. Its key advantage is complete component interchangeability—probes, cables, and proximitors can be swapped without needing time-consuming bench calibration.
When you need a bit more reach, the 3300 XL 11mm system is the answer. It offers a wider linear sensing range (4 mm / 160 mil), making it perfect for applications where the standard 8mm probe can't quite bridge the gap. Crucially, it also carries certifications for installation in hazardous areas, providing flexibility and safety in challenging environments.
Measuring Massive Movement: Large-Range 25mm & 50mm Sensors
For large steam turbines, measuring differential expansion (DE)—the difference in thermal growth between the rotor and stator—is critical to avoiding catastrophic rubbing. This requires sensors with a much larger measurement range.
The 3300 XL 25mm system provides a 12.7 mm (500 mil) range and is specifically designed for mid-to-large steam turbine DE applications. Its robust design is built to survive the harsh steam turbine environment.
For the largest machines, the 3300 XL 50mm system offers an impressive 27.9 mm (1100 mil) sensing range. Both the 25mm and 50mm systems feature excellent RFI/EMI immunity, earning them European CE approvals without special mounting requirements.
Surviving the Extreme: High-Temperature & Specialty Sensors
Not all machinery environments are created equal. Some applications demand sensors built for extreme conditions.
The 3300 XL 16mm High-Temperature System (HTPS) is engineered to withstand intense heat up to +350°C (+662°F), making it ideal for direct installation inside gas and steam turbines to measure vibration, thrust position, and seal clearance.
Other specialty sensors include:
Ceramic Capped Probes: Designed for corrosive or high-pressure environments like anhydrous ammonia, featuring a rugged alumina ceramic cap.
NSv (Narrow Side View) Probes: The solution for tight spaces, perfect for compressors with small counterbore clearances or tiny target surfaces.
Underwater Probes: Sealed to withstand constant immersion in liquids or gases, rated for pressures up to 500 psi, and essential for hydroelectric plants.
Simplified Installation: The PROXPAC XL Integrated Assembly
Simplifying installation and enhancing durability is the 3300 PROXPAC XL Transducer Assembly. This innovative product integrates the proximitor sensor directly into a rugged, molded PPS thermoplastic housing. It eliminates the need for a separate extension cable and connector, creating a compact, self-contained unit. With its IP66 and Type 4X rating, it offers superior protection against moisture and dust in severe environments.
Choosing the Right Sensor and Proximity Probe for Your Application
3300 5mm Proximity Probe. Sensor and Transducer System
3300 5mm probe
3300 XL 5mm extension cable
3300 XL 5mm proximity sensor
3300 XL 8mm Proximity Probe, Sensor and Transducer System
3300 XL 8mm proximity probe
3300 XL 8mm extension cable
3300 XL 8mm proximity sensor
3300 XL 11mm Proximity Probe, Sensor and Transducer System
3300 XL 11mm probe
3300 XL 11 mm extension cable
3300 XL 11mm proximity sensor
Conclusion
From monitoring simple vibration on a pump to safeguarding a multi-million dollar steam turbine, Bently Nevada’s 3300 XL series of proximity sensors provides a tailored, reliable solution. Understanding the strengths and specific applications of each sensor type—from the standard 8mm to the specialized underwater probes—is key to building an effective predictive maintenance program. By choosing the right sensor for the environment and measurement need, plant operators can achieve unparalleled machine health insight, maximize reliability, and prevent costly unplanned downtime.
