english 
Abstract
Bearing lubrication systems are vital for the reliable operation of rotating machinery in power plants, including turbines, pumps, and generators. Undetected oil leakage in these systems can lead to catastrophic failures, unplanned downtime, and significant financial losses. This article presents a detailed case study of oil leakage in the bearing lubrication system of a 300-MW combined-cycle power plant unit. By integrating vibration analysis, oil quality monitoring, and thermographic inspections, the root causes of leakage—including seal degradation, thermal expansion mismatches, and pressure imbalances—were identified. The study highlights remediation strategies such as upgraded sealing materials, redesigned oil return pathways, and predictive maintenance protocols. Results demonstrate a 90% reduction in leakage incidents and a 30% improvement in bearing lifespan post-intervention.
1. Introduction
Power plants depend on bearing lubrication systems to minimize friction, dissipate heat, and prevent wear in high-speed rotating equipment. However, aging infrastructure, harsh operating conditions, and design flaws can cause persistent oil leaks, jeopardizing operational safety and efficiency. This article examines a real-world leakage incident in a gas turbine bearing lubrication system, offering insights into diagnostic methodologies, corrective actions, and preventive measures for industrial applications.
2. Background: Case Study Overview
The case study focuses on a combined-cycle power plant unit where recurrent oil leaks were observed in the #2 gas turbine’s journal bearing lubrication system. Initial symptoms included:
- Oil consumption spikes: A 25% increase in lubricant top-up frequency over six months.
- Contamination alarms: Particle counts in oil samples exceeded ISO 4406 cleanliness standards.
- Elevated bearing temperatures: Localized hotspots detected via infrared cameras.
3. Diagnostic Approach
3.1 Root Cause Analysis
- Seal Integrity Testing: Pressure decay tests revealed micro-cracks in elastomeric shaft seals due to thermal cycling and chemical degradation.
- Flow Dynamics Simulation: Computational fluid dynamics (CFD) identified turbulent flow patterns near drain ports, causing oil splashing and seepage.
- Vibration Spectral Analysis: High-frequency vibrations (8–12 kHz) correlated with bearing misalignment, exacerbating seal wear.
3.2 Oil Sample Analysis
- Viscosity and Additive Depletion: Oil viscosity dropped by 18% compared to baseline, indicating thermal breakdown.
- Metallic Wear Debris: Ferrography detected abnormal iron and copper particles, signaling bearing surface wear.
4. Identified Failure Mechanisms
- Seal Hardening: Prolonged exposure to temperatures above 90°C caused elastomer seals to lose elasticity.
- Pressure Differential Imbalance: Inadequate venting in the oil reservoir created negative pressure, drawing oil past seals.
- Thermal Expansion Mismatch: Differential expansion between the stainless-steel bearing housing and carbon steel piping induced joint gaps.
5. Remediation Strategies
5.1 Seal and Material Upgrades
- High-Temperature Seals: Fluorocarbon (FKM) seals replaced standard nitrile rubber, improving thermal resistance up to 200°C.
- Expansion Joints: Bellows-style flexible connectors were installed to accommodate thermal movement.
5.2 System Redesign
- Optimized Drain Geometry: Angled drain ports with anti-splash baffles reduced turbulence and redirected oil flow.
- Pressure Equalization: A vent valve was added to stabilize reservoir pressure, minimizing oil migration.
5.3 Predictive Maintenance Enhancements
- Real-Time Oil Condition Sensors: Inline sensors monitored viscosity, moisture, and particulate levels.
- Vibration Monitoring Network: Wireless accelerometers provided continuous bearing health data.
6. Results and Validation
Post-implementation metrics over 12 months showed:
- Leakage Reduction: Leak incidents decreased from 15/month to 1–2/month.
- Bearing Temperature Stability: Peak temperatures dropped from 95°C to 72°C.
- Oil Consumption Savings: Annual lubricant costs fell by $48,000.
7. Broader Implications for Industry
This case study underscores the importance of proactive leakage management in critical infrastructure. Key takeaways include:
- Multi-Disciplinary Diagnostics: Combining fluid dynamics, material science, and vibration analysis delivers comprehensive insights.
- Cost-Benefit of Upgrades: Sealing system retrofits yielded a 6-month ROI through reduced downtime and maintenance.
- Predictive Technologies: IoT-enabled sensors and machine learning algorithms can forecast leakage risks before failures occur.
8. Conclusion
Oil leakage in bearing lubrication systems is a multifaceted challenge requiring tailored engineering solutions. The strategies applied in this power plant case study—material upgrades, hydrodynamic optimization, and predictive monitoring—provide a replicable framework for enhancing reliability in energy, manufacturing, and transportation sectors. Future advancements in self-healing seals and digital twin simulations promise further improvements in leakage prevention.