Bearing RTD Sensors for Machine Protection

Case Style Reference

Start with the case style shown on the drawing or existing bearing housing. Dimensions are case dimensions. Wire sizes are AWG.

Decision path

• Match case style to bore, depth, and exit clearance.
• Select single or dual Pt100 construction where the case allows it.
• Confirm 2-, 3-, or 4-wire circuit requirements.
• Choose stainless first, with copper or tin-plated copper where needed.
• Call out lead protection, oil, vibration, and hazardous-area requirements.

Bearing RTD Contact and Lead Protection

Bearing RTDs need a stable contact point, protected lead routing, and the right insertion depth for the monitoring system. Stainless contact construction should lead the specification, with copper only where the application calls for faster heat transfer.

Bearing RTD Configuration Options

Stainless Contact Bearing RTD

The standard bearing RTD starting point is a Pt100 element with a stainless contact style for rugged bearing housing measurement, corrosion resistance, and long-term stability in motors, generators, turbines, turbo machinery, pumps, and gearboxes.

For turbine bearings, generator bearings, and turbo machinery, BRTD assemblies are typically part of a machine-protection strategy. Stable contact, repeatable insertion depth, protected lead routing, and compatibility with RTD input cards help operators track bearing metal temperature trends and trigger alarm or shutdown logic before damage develops.

Copper Contact Bearing RTD

Copper contact styles can be specified as a secondary option when the application benefits from higher thermal conductivity at the bearing interface. Stainless should remain the first-position construction unless the installation calls for copper contact behavior.

Mounting and Retention Options

Bearing RTDs can be configured around housing bore detail, insertion depth, contact force, lead protection, and retention method. Spring-loaded or bayonet hardware may be appropriate for repeatable-contact installations, but those details should not define the entire bearing RTD category.

API 670 Bearing Temperature Monitoring

API 670 (Machinery Protection Systems) specifies requirements for bearing and winding temperature monitoring on critical rotating equipment. Pt100 RTD sensors are commonly preferred over thermocouples for bearing temperature measurement because of their higher accuracy and better long-term stability.

Intrinsically Safe Bearing RTDs for Hazardous Areas

For hazardous-area rotating equipment, Thermometrics can support RX26-style intrinsically safe bearing RTDs. These are different from a standard explosion-proof connection-head assembly: the sensor construction, case, lead wire, element count, and accessory selection all have to stay inside the approved configuration.

Typical Program Fits

• Large motors and generators with machine protection panels
• Steam turbine, gas turbine, and turbo machinery bearings where stable baseline tracking matters
• Gearboxes and reducers that benefit from stable contact and protected lead routing
• Pumps and driven equipment with stainless contact styles first and copper contact options where needed
• Rotating assets monitored through RTD input cards or protection systems

Information to Share for Quoting

• Bearing housing style, bore detail, and available insertion depth
• Retention method, spring travel if required, and tip contact requirements
• Pt100 element, wiring scheme, and lead length
• Environmental exposure around oil, vibration, splash, and ambient heat
• Monitoring system interface, including API 670 or plant DCS expectations
• Hazardous-area classification if the application requires an intrinsically safe bearing RTD build