Are you facing frequent bearing failures caused by stray electrical currents in your motors?
TFL provides a professional solution — TFL Electrically Insulated Bearings, engineered for motor repair, VFD (Variable Frequency Drive) systems, wind turbines, and rail traction applications. These bearings effectively eliminate shaft currents, prevent electrical erosion, and extend bearing service life.
Core Advantages of TFL Electrically Insulated Bearings
- Outstanding Insulation Performance: Stable resistance ≥100 MΩ under DC voltages up to 3000 V.
- High-Precision Manufacturing: Made from high-purity GCr15 bearing steel with ISO 492 Class P6 geometric accuracy.
- Wide Model Compatibility: Includes 6322 C3VL0241, 6316 C3VL0241, 6319 C3VL0241, NU318 ECM/C3VL0241, and more.
- Custom Options Available: Existing standard bearings can be upgraded to insulated types with coatings like J20AA, VL0241, or VL2071.
Why Electrically Insulated Bearings?
If your motor bearings show signs of increased noise, premature grease degradation, and the raceways exhibit a washboard-like pattern (similar to the image shown), your bearings are likely suffering from electrical corrosion (also known as electrical erosion).
What Causes Shaft Currents and Electrical Erosion?
Simply put, during the operation of a motor or generator, factors such as magnetic field asymmetry, electrostatic charge buildup, and the use of frequency converters (VFDs) generate shaft currents.
Under normal conditions, a lubricating oil film exists between the shaft and the bearing, acting as an insulator. For low shaft voltages, this oil film maintains its insulating properties, preventing current flow.
However, when the shaft voltage increases, especially during motor startup before a stable oil film forms, the voltage can break down the oil film and discharge, creating a circuit that leads to various hazards.
- Shaft currents cause minute electric arcs at the metal contact points between the rolling elements and raceways.
- This process erodes the oil film, leading to a rise in bearing temperature and carbonization of the lubricant.
- As the current flows through the rolling element/raceway contact area, spark discharge melts the local metal, which is then re-pressed by the high-speed rotating inner ring and rolling elements, forming the distinctive “washboard” or fluting pattern.
The passage of shaft current dramatically shortens the service life of motor bearings—from thousands of hours in mild cases down to only a few hours in severe situations, significantly impacting site safety and continuous production.
How to Protect Bearings from Electrical Corrosion
It is virtually unavoidable for large AC motors to generate some level of shaft voltage.
- Traditional Method 1: Insulation Barrier: One method is to install an insulation board at the non-drive end bearing housing to break the shaft current circuit.
- Traditional Method 2: Grounding Brush: For static charge-induced voltages, a grounding carbon brush can be applied to the motor shaft on the load side. This diverts the static charge to the ground, preventing the formation of shaft voltage and instantaneous discharge currents.
Limitations of Grounding Brushes: Grounding brushes work by shunting the current away from the bearing. However, their diversion effectiveness is limited. They may not handle all frequencies and current types well, especially at high speeds and high frequencies, potentially allowing some current to pass through the bearing. Furthermore, grounding brushes are subject to wear, pressure, contamination, temperature, vibration, and humidity, requiring regular maintenance to prevent failure. They are also external components requiring extra space and mounting brackets, which is not ideal for space-constrained motors.
Insulated bearings offer a set-and-forget solution, requiring no external components or routine inspections. This is crucial for large or critical motors operating long-term in difficult-to-maintain environments.
TFL Electrically Insulated Bearings Solve Bearing Failure
A major seawater desalination and wastewater treatment plant in the Middle East operates multiple advanced pump systems, driven by hundreds of high-power VFD motors. Continuous, high-efficiency operation is essential to meet the massive demand for local residential and industrial water. This client has long been a loyal partner, routinely purchasing high-quality standard bearings from TFL.
TFL’s Observation and the Client’s Complaint:
Over the past year, TFL noticed an unusual spike in the client’s procurement of 6322 bearings, far exceeding normal spare parts consumption. When inquired about this, Mr. Fahad, the facility’s Equipment Maintenance Supervisor, expressed his frustration:
“Bella, your TFL bearings are top-notch—we’ve always been satisfied. But recently, the failure rate on a few of our critical pump motor bearings has been ridiculously high. Our motor grounding brushes keep failing, leading to bearing electrical breakdown. We’ve tried the best brushes on the market, but they can’t solve the problem entirely.”
After a thorough analysis of the client’s operating conditions, motor types, and bearing failure reports, TFL’s technical team confirmed that shaft current electrical corrosion was the root cause of the premature bearing failure.
TFL experts recommended the 6322 C3VL0241 Electrically Insulated Bearing, explaining how its advanced ceramic coating fundamentally blocks the shaft current path.
Mr. Fahad was initially concerned about potential assembly issues or incompatibility. TFL provided detailed size comparisons and technical drawings, clarifying that the VL0241 insulation coating does not alter the bearing’s mounting dimensions or tolerance class, making it a 100% direct replacement for the original model.
TFL also emphasized that while the unit price of an insulated bearing is slightly higher, its service life can be extended by 3 to 5 times, and the elimination of brush maintenance drastically reduces the Total Cost of Ownership (TCO).
Results: Success Beyond Expectation
Mr. Fahad’s team piloted the installation of TFL Electrically Insulated Bearings—models 6322 C3VL0241 and NU318 ECM/C3VL0241—on their two most critical, high-failure-rate pump motors.
After eighteen months of continuous operation, the results surpassed all expectations:
- Bearing Life Returns to Normal: Bearings installed with TFL Insulated Bearings run smoothly without abnormal noise, the grease remains clean, and there is zero evidence of electrical erosion. Bearing life has returned to and even exceeded design expectations.
- Procurement Shift: The client officially and permanently adopted TFL Insulated Bearings as the standard configuration for all their cooling tower motors and VFD-driven pump equipment, placing bulk orders for models like 6319 C3VL0241, 6220 C3VL0241, and 6316 C3VL0241 as their new standard spare parts for all VFD motors.
- Significant Cost Savings: The client entirely eliminated the need for purchasing, installing, and maintaining grounding brushes, substantially reduced bearing spare parts inventory, and avoided the enormous production losses caused by unscheduled bearing replacement downtime.
Mr. Fahad later shared his delight:
“TFL not only delivered a quality product, but more importantly, you solved a major problem we’ve faced for years! Our engineers can now focus on optimizing production processes instead of constantly scrambling to change bearings. Insulated bearings are truly a permanent solution!”
TFL Core Insulated Bearing Model Recommendations
TFL’s electrically insulated bearings cover deep groove ball, cylindrical roller, and tapered roller types to meet various load and speed requirements. TFL’s electrically insulated series can completely replace products from multiple brands such as SKF, FAG, NKE, NSK, and NTN.
For example, in the 6322 series, TFL’s 6322M/C3VL0241 can replace SKF’s 6322M/C3VL0241, FAG’s 6322-M-J20AA-C3, NKE’s 6322-M-C3-SQ77, NSK’s 6322HDY2C3, and NTN’s 7MC3-6322L1BC3.
Insulated Deep Groove Ball Bearings (VL0241/VL2071 Series)
These bearings are suitable for radial and light axial loads. The suffix VL0241 indicates the insulation coating is on the outer ring, while VL2071 indicates the coating is on the inner ring.
| Popular Model (VL0241) | Bearing Type | Primary Application Scenarios |
| 6322 C3VL0241 | DGBB | Medium-to-large high-voltage motors, generators, compressor drives |
| 6316 C3VL0241 | DGBB | VFD-driven medium industrial motors, water pumps, fans |
| 6319 C3VL0241 | DGBB | Industrial gearboxes, high-speed spindle systems |
| 6220 C3VL0241 | DGBB | Rail transport traction motor auxiliary systems |
Insulated Cylindrical Roller Bearings (VL0241 Series)
Cylindrical roller bearings offer higher radial load capacity and rigidity, suitable for heavy-duty and shock-load environments.
- NU318 ECM/C3VL0241: Typically used at the non-drive end to accommodate axial displacement, allowing for motor shaft thermal expansion.
- NU228 ECM/C3VL0241: Applied in heavy-duty equipment like rolling mills and hoists.
TFL Customization Service: For Non-Standard and Urgent Needs
If you need to quickly replace or upgrade existing bearings to an insulated type, but standard models are not a perfect match, TFL’s customization service is the ideal solution.
| Service Project | Advantages & Commitment | Applicable Scenarios |
| Non-Standard Coating Processing | Rapid conversion of existing bearings (including tapered roller, angular contact, etc.) to VL0241 or VL2071 standard. | Urgent maintenance, non-standard sizes, bulk conversion/upgrade projects. |
| High-Voltage Customization | Provides ultra-high-voltage insulation coatings of ≥5000V. | High-voltage wind turbine converters, specialized laboratory equipment. |
| Specific Clearance/Precision | Guarantees custom bearings meet P5 class precision and C4/C5 clearance. | High-speed operation, large temperature difference environments. |
Don’t let shaft currents hinder your motor’s performance! Choosing TFL Electrically Insulated Bearings means opting for a high-performance, cost-effective motor solution.
Contact us immediately! Send your model requirements or customization needs to any of the contacts below, and we will respond as quickly as possible:
- Email: info@sdtflbearing.com
- Phone: +86 15806631151
- Form: Contact Us
Our sidebar chat box is also always open for your inquiries.
Frequently Asked Questions
Q1: How much voltage can TFL bearings withstand?
A1: Our standard VL0241 coated models can withstand over 3000V DC; customized types can reach 5000V.
Q2: Will the TFL insulating coating peel off due to thermal expansion and contraction?
A2: No. TFL’s plasma spray technology ensures an extremely high bond strength of ≥15 MPa between the coating and the substrate, and the Al2O3 coating can withstand temperature shocks of 300℃, far exceeding the normal operating temperatures of motor bearings.
Q3: Can existing bearings be processed into insulated bearings?
A3: Yes. TFL supports processing customer-supplied samples or coating modifications for specified models.
Q4: Will the coating affect the load capacity?
A4: No. The coating thickness is only 100–300 μm and does not affect mounting dimensions or load capacity.
Q5: What fields are electrically insulated bearings suitable for?
A5: Variable frequency drive motors, wind turbine generators, rail transit traction systems, new energy vehicle electric drives, electric pumps, and compressors, among others.
