replica
Materials
- Apr 22, 2016
- 146
Hi all,
I am new to this forum and would like to ask whether anyone had experience on worn nitronic 50 pump shaft used in VS6 pump. The length of the shaft is 4.35m and pump is 19 stage pump used to transfer crude oil offshore. It was observed that all 19 locations where the bowl bush bearings were placed on the shaft shown the severe wear on the shaft surface and not on the bronze bush. The length and locations of the worn shaft region has similar length as the length of the bush. The clearance between bush and the shaft was self lubricated with the transferred crude oil. The worn shaft at the first and second stage shows severe wear with smooth and shiny surface (mirror finish) where else the worn shaft in contact with bowl bearing at other stages have rough surface. The shaft which is in contact with the line shaft bearing also showed a rough surface and some are not concentric (uneven wear). The diameter of the shaft is 1.5 inches. The bush bearings are made of C836 bronze and the shaft is made of Nitronic 50. The hardness of the shaft is 44HRC and the hardness of the bush is 90HRB. All the bush bearings observed have either no sign of wear or minimum wear and tear. This problem happened about a year ago and kept on reoccurring even though the shaft and bush bearing were replaced during maintenance using the same new spare parts. The longest the pump in operation after maintenance was for two months and the shortest was two weeks before the same failure happened. The shaft and bush bearings can normally last for a year. The main issue is why the shaft worn out and not the bush bearing. Normally from what I understand, the bronze bush should wear out and not the shaft. Any suggestions for possible causes of the worn shaft are highly appreciated. Is it possible for softer bush to abrade the harder shaft and under what condition?
Attached herewith are the photographs of a portion of 4.35m pump shaft showing worn shaft region and the unaffected bush bearing.
Regards,
I am new to this forum and would like to ask whether anyone had experience on worn nitronic 50 pump shaft used in VS6 pump. The length of the shaft is 4.35m and pump is 19 stage pump used to transfer crude oil offshore. It was observed that all 19 locations where the bowl bush bearings were placed on the shaft shown the severe wear on the shaft surface and not on the bronze bush. The length and locations of the worn shaft region has similar length as the length of the bush. The clearance between bush and the shaft was self lubricated with the transferred crude oil. The worn shaft at the first and second stage shows severe wear with smooth and shiny surface (mirror finish) where else the worn shaft in contact with bowl bearing at other stages have rough surface. The shaft which is in contact with the line shaft bearing also showed a rough surface and some are not concentric (uneven wear). The diameter of the shaft is 1.5 inches. The bush bearings are made of C836 bronze and the shaft is made of Nitronic 50. The hardness of the shaft is 44HRC and the hardness of the bush is 90HRB. All the bush bearings observed have either no sign of wear or minimum wear and tear. This problem happened about a year ago and kept on reoccurring even though the shaft and bush bearing were replaced during maintenance using the same new spare parts. The longest the pump in operation after maintenance was for two months and the shortest was two weeks before the same failure happened. The shaft and bush bearings can normally last for a year. The main issue is why the shaft worn out and not the bush bearing. Normally from what I understand, the bronze bush should wear out and not the shaft. Any suggestions for possible causes of the worn shaft are highly appreciated. Is it possible for softer bush to abrade the harder shaft and under what condition?
Attached herewith are the photographs of a portion of 4.35m pump shaft showing worn shaft region and the unaffected bush bearing.
Regards,
