Temperature fluctuations of steam turbine bearings and improvement measures

The bearing temperature of the steam turbine is one of the important indicators for unit operation control.

Excessive bearing temperature will seriously threaten the safe operation of the unit.

In a petrochemical company, the propylene refrigeration compressor was put into operation after overhaul in July 2016. In December 2016, the compressor bearing temperature fluctuated for the first time and gradually increased. Subsequently, the oil tank was sampled and analyzed, and the inspection found that the lubricating oil contained water. After multiple replacements, the water was eliminated, but the unit still had multiple bearing temperature fluctuations. fluctuation.

There are many reasons for high turbine bearing temperature. Only by investigating the potential causes one by one can we better formulate corresponding measures. The equipment department of the enterprise checked the authenticity of the temperature measurement points, the authenticity of the bearing temperature rise, the lubricating oil pressure, temperature and oil product analysis, the installation and maintenance of the bearing bush and the impact of vibration and process parameters on the bearing surface, and found that the bearing temperature fluctuation is the most important It may be related to the formation of varnish on the bearing surface, rather than mechanical damage to the bearing surface or other factors. The lubricating oil forms a “varnish” during use, which will seriously affect the heat dissipation on the bearing surface. The formation of the varnish is relatively complicated. There are currently many theoretical explanations, and the theory of soft pollutant deposition is widely recognized. When the quality of lubricating oil deteriorates, oxides will be produced and polymerization reactions will occur, gradually producing soluble and polar soft pollutants (antioxidants and base oil degradation products), which will be dissolved in the lubricating oil. Under certain working conditions, this soft pollutant will precipitate when its concentration reaches saturation, and will precipitate on metal surfaces, such as bearings and gears, forming a paint film. After the varnish is produced, it affects the heat dissipation of the metal surface, and the increase in temperature further accelerates the oxidation of the lubricating oil, forming a vicious cycle.

Since varnish seriously threatens the normal operation of equipment, it is urgent to find an effective measure to solve the problem of paint film. When the varnish is formed, it is a soft pollutant with a “particle” diameter less than 0.08 μm. It is difficult to remove by traditional mechanical filtration and is easily deposited on the surface of components. The mainstream solutions in the market include: ion exchange resin method, balanced charge purification technology and electrostatic adsorption technology.

In order to quickly restore the equipment to normal, the customer invested in WSD varnish removal and oil purifier in July 2017 to improve the problem of bearing temperature fluctuations that may be caused by the paint film. After one month of operation, all major indicators of the lubricating oil were within the normal range, and the film tendency index dropped from the original 13.7 to 3.6. In the following three months, the bearing temperature remained stable and no rebound occurred.