Below is a structured, field-practical 100-question framework for Journal Bearing Failure Analysis, aligned with how a senior reliability engineer (MLE/RCM mindset) would approach root cause determination—not just symptom identification.
I’ve grouped the questions into 10 critical domains so you can use this as:
- A failure investigation checklist
- A training/assessment tool
- A standardized RCA template for turbomachinery
🔴 1. Failure Definition & Context (10 Questions)
- What is the exact failure mode observed (wipe, scoring, fatigue, seizure, overheating, etc.)?
- When was the failure first detected?
- Was the failure sudden or progressive?
- What were the operating conditions at the time of failure?
- Was the machine running, starting, or stopping?
- What alarms were triggered (temperature, vibration, pressure)?
- What is the criticality of this machine in the process?
- Has this failure occurred before on the same bearing?
- What is the total operating time since last overhaul?
- What is the bearing design type (tilting pad, sleeve, fixed geometry)?
🔴 2. Bearing Design & Geometry (10 Questions)
- What is the bearing clearance (design vs actual)?
- Is the clearance within OEM specification?
- What is the bearing load direction and magnitude?
- Is the bearing correctly oriented relative to load zone?
- What is the bearing material (Babbitt composition)?
- Are there signs of fatigue cracking in the lining?
- Is there any geometric distortion in the bearing shell?
- Are oil grooves correctly positioned?
- Is there evidence of edge loading?
- Was the bearing properly installed and aligned?
🔴 3. Lubrication Regime & Film Formation (10 Questions)
- Was full hydrodynamic lubrication achieved?
- What is the minimum oil film thickness (calculated vs actual)?
- Is the bearing operating in mixed lubrication regime?
- What is the Sommerfeld number for this bearing?
- Is viscosity sufficient for load and speed?
- Was there any loss of oil film during transient conditions?
- Are there signs of metal-to-metal contact?
- Was start-up lubrication adequate?
- Is there any evidence of oil starvation?
- Are there pressure fluctuations in the oil supply?
🔴 4. Lubricant Properties & Chemistry (10 Questions)
- What is the oil type (mineral, synthetic, Group II/III)?
- What is the ISO viscosity grade?
- Has viscosity changed from new oil baseline?
- What is the oil temperature at bearing inlet and outlet?
- What is the TAN (ASTM D664) trend?
- What is the antioxidant health (RULER)?
- What is the MPC value (varnish potential)?
- Is there evidence of varnish formation in the system?
- Are additives depleted or chemically altered?
- Is the oil compatible with bearing metallurgy?
🔴 5. Contamination Control (10 Questions)
- What is the ISO cleanliness code?
- What types of particles are present (silica, wear metals)?
- Is there evidence of abrasive wear?
- What is the water content (ppm)?
- Is water dissolved, emulsified, or free?
- Are there signs of corrosion on bearing surfaces?
- Is there ingress of process contaminants (gas, chemicals)?
- Are filters functioning correctly?
- What is the filter rating and efficiency (β ratio)?
- Is there any bypassing in the filtration system?
🔴 6. Thermal Behavior (10 Questions)
- What was the bearing metal temperature trend?
- Was there a sudden temperature spike?
- Is heat removal (cooling) sufficient?
- Is oil flow adequate for heat dissipation?
- Are there hot spots on the bearing surface?
- Is there evidence of thermal degradation of oil?
- Is viscosity dropping due to high temperature?
- Is there uneven temperature distribution?
- Is cooling water system functioning properly?
- Is thermal expansion affecting clearance?
🔴 7. Mechanical & Dynamic Conditions (10 Questions)
- What are the vibration trends (overall and spectrum)?
- Is there misalignment between shaft and bearing?
- Is there shaft deflection under load?
- Is rotor balance within acceptable limits?
- Are there signs of rotor instability (whirl/whip)?
- Is there excessive axial movement?
- Are coupling forces affecting the bearing?
- Is there structural looseness?
- Are there transient dynamic events (trip/start cycles)?
- Is there resonance near operating speed?
🔴 8. Electrical & External Influences (10 Questions)
- Is there evidence of electrical erosion?
- Are there shaft grounding systems installed?
- Is the machine VFD-driven?
- Are there stray currents passing through the shaft?
- Is there evidence of fluting or pitting?
- Are external vibrations affecting the system?
- Is there process upset affecting load?
- Is there gas ingestion into the oil?
- Are seal systems functioning correctly?
- Are environmental conditions contributing (humidity, dust)?
🔴 9. Maintenance & Operational Practices (10 Questions)
- Was proper lubrication procedure followed?
- Were oil changes performed correctly?
- Was flushing done before startup?
- Are sampling practices correct (location, temperature)?
- Are operators trained in lubrication best practices?
- Were alarms ignored or delayed?
- Is there a preventive maintenance program?
- Are spare bearings stored properly?
- Was installation done using correct tools and methods?
- Are maintenance records complete and accurate?
🔴 10. Root Cause & Systemic Factors (10 Questions)
- What is the primary root cause (not symptom)?
- What are contributing secondary causes?
- Is this a design issue or operational issue?
- Could this failure have been predicted earlier?
- What indicators were missed (MPC, RULER, vibration)?
- What is the remaining useful life trend before failure?
- Is this a single event or systemic issue across fleet?
- What corrective actions are required?
- What preventive measures will eliminate recurrence?
- What changes are needed in lubrication strategy (TOR approach)?
⚙️ How to Use This (Important)
This is not just a checklist — it’s a failure thinking model:
- Questions 1–20 → Design & setup validation
- Questions 21–40 → Lubrication physics + chemistry
- Questions 41–60 → Contamination + thermal stress
- Questions 61–80 → Dynamic & external influences
- Questions 81–100 → Human + system reliability
🔥 Final Insight (Very Important)
Most journal bearing failures are NOT mechanical failures.
They are:
👉 Lubrication failures
👉 Chemistry failures (varnish, oxidation, depletion)
👉 System failures (cooling, contamination, operation)
If you answer these 100 questions properly, you move from:
❌ “Bearing failed”
to
✅ “System allowed the bearing to fail”
Discover more from Turbine Oil Reliability
Subscribe to get the latest posts sent to your email.