Study On The Application And Improvement Of 28AT Dry-gas Seal Sets

JianFeng Fertilizer factory uses a 28AT spiral groove dry-gas seal, made by John Crane Inc., as a high pressure seal of the rotor shaft of a CO2 compressor, made by Nuovo Pignone Co. Up to now, the compressor has had to be shut down seven times for failure and thirteen seal sets have been replaced since August 1997. Every failure led to urea system shutdown, which resulted in money losses of at least several million yuans. It has seriously restricted the safely, stably full loading and long-term operation of the urea producing system.As new generation of seal products, 28AT dry-gas seals have found many applications in many imported chemical plants since the beginning of 1980s. But there were short time defects in the seals many times in other factories during these years. Therefore, JianFeng Chemicals Co. organized a group to investigate the reasons of defects and to improve the dry-gas seal system.This paper analyzed the influences of process parameters on operation of a dry-gas seal by means of CFD based on practical operation data. Many useful data were obtained and operating curves were plotted in order to predict the operation conditions of the dry-gas seals. The normal operation conditions of the seal of a CO2 compressor were discussed based on theoretical analysis. It provided the theoretical basis for the on-line evaluation, maintenance, and optimal operation of the dry-gas seals.By comparing the designed conditions, test parameters with actual operation conditions, the reasons for the short term defects of the dry-gas seals were analyzed and an improvement scheme and process adjustment measures were proposed. In terms of them, the problems of frequent seal damage on the CO2 compressor were solved and the reliable operation of the seal was insured.For the current development of domestic dry-seal technology, the feasibility of homemade spare parts of the dry-gas seals was also analyzed. Combining theoretic analysis with the experience, the detail requirements on the quality examination, installment and maintenance of dry-gas seals were suggested, which are helpful to other users.