Ethylene Unit Compression System E-GT501 turbine is the driving machine of condensate pump (E-GA501A), which is responsible for the prompt discharge of the condensate of the propylene refrigeration compressor turbine (E-GBT501) to ensure The normal operation of the unit, June 1998 E-GT501 turbine worm failure, despite repeated maintenance results are very unsatisfactory, the new worm gear life is very short, the longest no more than 20 hours, resulting in the turbine can not work properly, so that Another motor-driven condensate pump (E-GA501B) has been operating without a backup pump in a single run. If the E-GA501B pump suddenly fails, it will inevitably cause the compressor to stop the propylene unit. The entire ethylene plant The steady production poses a great threat. We analyzed and found the root cause of turbine worm failure, successfully solved the problem by changing the worm gear material.

Analysis of the first failure of worm gear

After the first failure of the worm gear in June 1998, we found in the inspection of the turbine that the turbine lubricating oil tank contains more free water. Due to the meshing of the worm gear and the tooth surface, the friction surface must be established with an extreme pressure lubrication film. It is a lubricating film formed by the reaction between the extreme pressure agent in the lubricating oil and the metal surface. It has high strength and can withstand Worm gear meshing load. Lubricant with water will cause the extreme pressure agent inactivation, the meshing surface can not form a lubricating film, resulting in direct contact with the worm gear surface, resulting in surface wear. As the worm gear made of tin bronze (code ZQSn10-1), the allowable contact stress of 220MN / m2, and the worm is made of alloy steel (steel: 35CrMo), the allowable contact stress of 850MN / m2, the worm relative worm Soft, so the failure of the performance of the worm gear tooth wear.

We conducted a comprehensive analysis of the lubricating oil system and concluded that the water in the oil system came from the condensate formed by the leakage of steam from the turbine seal. As the turbine insulation is airtight very good, some of the leakage of steam will inevitably enter the oil through the bearing seal system.

In view of the failure of the worm gear caused by the water brought by the lubricating oil, we sampled and analyzed the moisture content of the lubricating oil on a monthly basis according to the random operating manual of the turbine. We regularly drained water from the bottom of the tank and formulated the relevant management system.

After the above improvement measures, the E-GT501 turbine was put into operation in October 2000 and has been operating normally for more than two years. So far, no signs of damage have been found, providing a powerful guarantee for the stable operation of the turbine. The turbine can be balanced every year Medium-pressure steam more than 8,000 tons, saving 15Kw × 8000h = 120000 degrees per year, 0.6 yuan per degree basis, the annual savings of 72,000 yuan electricity, the economic benefits are obvious.

Due to the condensate pump turbo-worm gear design contactlessness without margin, resulting in its frequent failure, by changing the worm gear, and in accordance with the requirements of the development of the relevant management system to solve the problem. With the increase of foreign equipment imported from China, the original design conditions are checked according to the differences of national conditions and should be given priority in the localization of spare parts. Condensate pump turbine worm failure problem solving process has some reference value.

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