The bearing temperature of a steam turbine is one of the most critical indicators in monitoring and controlling the safe operation of the unit. Excessively high temperatures can pose significant risks to equipment integrity and overall operational safety.
Case Study: Bearing Temperature Fluctuation in a Petrochemical Compressor
In July 2016, a propylene refrigeration compressor at a petrochemical company resumed operation following an overhaul. However, by December of the same year, the bearing temperature began to fluctuate and gradually increased. Lubricating oil samples were taken from the oil tank for analysis, revealing the presence of water. Although repeated oil replacements eventually removed the water, the issue of bearing temperature fluctuation persisted.
Investigative Approach and Findings
Recognizing the potential risks, the enterprise’s equipment department conducted a thorough investigation. They examined the reliability of temperature measurement points, verified the actual bearing temperature rise, and analyzed various factors such as oil pressure, oil temperature, oil quality, bearing bush installation, and possible effects from vibration and process parameters.
The investigation concluded that the root cause was likely the formation of varnish on the bearing surface, not mechanical damage or other conventional factors. This varnish interferes with effective heat dissipation and leads to higher operating temperatures.
Understanding Varnish Formation and Its Impact
Varnish is a soft contaminant formed from the degradation of lubricating oil. As the oil ages, oxidation and polymerization reactions produce soluble polar compounds, including degraded antioxidants and base oil residues. When these soft pollutants accumulate and reach saturation, they precipitate and adhere to metal surfaces—such as bearings and gears—forming a varnish film.
Once present, varnish significantly hinders heat transfer, causing further temperature increases. This, in turn, accelerates oil degradation and creates a self-reinforcing cycle of rising temperatures and worsening oil quality.
Effective Solution: WSD Varnish Removal System
Given the limitations of traditional filtration methods—which cannot remove particles smaller than 0.08 μm—more advanced techniques are required. Currently accepted technologies include ion exchange resin, balanced charge purification, and electrostatic adsorption.
To address the issue efficiently, the company deployed a WSD varnish removal and oil purification system in July 2017. This targeted approach aimed to eliminate the root cause of bearing temperature fluctuations. Within one month of operation, all key lubricating oil indicators returned to normal, and the varnish tendency index dropped from 13.7 to 3.6. In the following three months, the bearing temperature remained stable with no further abnormal fluctuations.
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