Quick answer
If the measured temperature at the drive‑end bearing exceeds the non‑drive‑end bearing by more than the OEM‑specified differential, the press is operating outside its normal thermal envelope. Begin with a lockout/tagout (LOTO) isolation, verify lubrication, inspect for mis‑alignment, and compare vibration signatures. Correct the root cause before the differential returns to the OEM‑approved range.
Problem / job
During routine monitoring of a vertical roller press, the temperature sensor on the drive‑end bearing reports a value noticeably higher than the sensor on the non‑drive end. The differential may indicate bearing wear, lubrication failure, load imbalance, or excessive heat from the drive motor. The goal is to diagnose the source of the temperature difference, apply corrective action, and verify that the press returns to normal operating conditions.
Evidence
- Drive‑end bearing temperature: value recorded
- Non‑drive‑end bearing temperature: value recorded
- Vibration spectra from the bearing housings (if available)
- Lubrication level and oil condition reports
- Recent maintenance history (bearing replacement, alignment checks, motor service)
- Ambient temperature and cooling‑system performance data
Decision
When the temperature differential exceeds the OEM‑specified limit, the press must be taken out of production for a systematic investigation. The decision tree follows a seven‑step workflow that isolates the equipment, gathers data, and narrows the cause to one of the common failure modes. Only after the root cause is corrected should the press be re‑energized and the temperature differential re‑checked for compliance.
Practical 7‑step workflow
- Secure isolation and LOTO. Verify that the press is fully de‑energized, the drive motor is locked out, and all stored‑energy devices (flywheels, hydraulic accumulators) are depressurized. Follow the plant’s LOTO procedure and post isolation tags before any bearing access.
- Collect baseline temperature data. Using calibrated handheld infrared thermometers or the plant’s process historian, record the temperature at both bearing housings, the motor housing, and ambient conditions. Document the time of measurement and operating load at the moment of shutdown.
- Compare against OEM / site limits. Reference the equipment manual or site‑specific engineering data for the maximum allowable bearing temperature and the permissible differential between drive and non‑drive ends. If the measured differential exceeds that limit, proceed to the next steps; otherwise, monitor for a trend.
- Inspect lubrication system. With the press still isolated, remove the bearing oil sight‑glass or dip‑stick. Check oil level, clarity, and presence of metal particles. Replace oil if it is contaminated, low, or does not meet the OEM viscosity grade. Verify that the oil pump, filters, and heat exchangers are operating correctly.
- Examine bearing condition. Remove the bearing caps according to the manufacturer’s disassembly sequence. Visually inspect raceways, rollers, and cages for scoring, discoloration, or pitting. Measure axial and radial clearances with a feeler gauge or dial indicator. Record any deviation from the OEM tolerance range.
- Check alignment and load distribution. Use a laser alignment tool or dial‑indicator method to confirm that the drive‑end shaft is parallel to the non‑drive‑end shaft within the specified tolerance. Verify that the roller press’s load‑bearing plates are evenly seated and that the feed rollers are not imposing an uneven radial load on one bearing.
- Assess drive‑end motor heat contribution. Measure motor winding temperature and compare it to the motor’s rated hot‑spot temperature. Confirm that the motor’s cooling fans, external water jackets, or air‑flow ducts are free of obstruction. If motor heat is excessive, service the cooling system before re‑installing the bearing.
After completing the steps, re‑assemble the bearing housing, restore oil flow, remove LOTO, and conduct a controlled start‑up. Record temperature and vibration data during the first 30 minutes of operation to confirm that the differential has returned to an acceptable range.
Diagnostic matrix
| Evidence | Likely direction | Next check |
|---|---|---|
| Drive‑end temperature > non‑drive by > OEM limit, oil level normal | Excess heat from drive motor or localized bearing wear | Motor winding temperature, bearing visual inspection |
| Both bearings hot, differential small, oil dark and gritty | Lubrication degradation | Oil sampling, filter condition, oil pump flow test |
| Drive‑end temperature high, vibration amplitude ↑ on drive side | Roller‑bearing wear or cage damage on drive side | Disassemble drive‑end bearing, measure clearance, inspect rollers |
| Drive‑end temperature high, alignment reading out of tolerance | Mis‑alignment causing uneven load | Realign shafts, verify bearing preload |
| Non‑drive temperature higher than drive, oil level low | Oil starvation at non‑drive end (possible seal leak) | Inspect seals, verify oil circuit balance |
| Temperature differential within limit but trending upward over shifts | Gradual bearing wear or cooling‑system fouling | Schedule predictive maintenance, clean cooling passages |
Verification and acceptance criteria
- Temperature differential. After corrective action, the measured temperature difference between drive‑end and non‑drive‑end bearings must be equal to or less than the OEM‑specified maximum differential for the current load and ambient conditions.
- Vibration levels. Bearing‑housing vibration (RMS) at the drive and non‑drive locations must be within the limits defined in the equipment vibration baseline. Any increase above the baseline must be investigated.
- Lubrication quality. Oil analysis must show particle counts and viscosity within the OEM‑approved range. Oil level must be at the recommended sight‑glass mark.
- Clearance and runout. Measured axial and radial clearances of both bearings must be within the tolerance band specified by the bearing manufacturer. Shaft runout must not exceed the allowable limit.
- Alignment. Shaft alignment must be within the angular tolerance (typically a few mils or mm per meter) indicated in the press installation manual.
- Motor cooling. Motor winding temperature must remain below the hot‑spot rating defined by the motor OEM under the same load conditions.
- Operational test. Run the press for at least one full production cycle while recording temperature, vibration, and load data. All parameters must remain stable and within the acceptance limits throughout the test.
Document each verification step in the maintenance log and obtain sign‑off from the reliability engineer before returning the press to normal production.
Common mistakes and repeat‑failure traps
- Skipping LOTO. Performing bearing inspection or oil changes while the press is still energized can lead to accidental start‑up, causing injury and further damage to the bearing.
- Relying on a single temperature reading. Temperature sensors can drift; always compare multiple data points and verify sensor accuracy before concluding.
- Adjusting preload without checking clearance. Over‑tightening bearing caps can increase internal heat generation and mask the real cause of the temperature rise.
- Replacing oil without analyzing the cause of contamination. New oil will hide the symptom but not correct a leaking seal, blocked filter, or excessive wear that continues to generate heat.
- Ignoring motor cooling performance. A clogged fan or fouled water jacket will raise drive‑end temperature even when bearings are healthy.
- Failing to re‑measure after corrective action. Returning to production without a post‑repair temperature and vibration check can allow a hidden issue to progress to catastrophic failure.
- Documenting only the symptom. Maintenance records that note “high bearing temperature” without root‑cause details make future troubleshooting longer and increase repeat‑failure risk.
By adhering to the workflow, confirming each acceptance criterion, and avoiding the pitfalls listed above, reliability teams can reliably diagnose and correct bearing temperature differentials in roller presses, extending equipment life and maintaining safe operation.
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