During the shutdown of a petrochemical plant, a large number of gasketed joints are dismantled in order to gain access to the equipment, and subsequently remade. In order to ensure the integrity of the plant systems, they are leak tested with high-pressure nitrogen prior to the introduction of hydrocarbons. If leaks from gasketed joints are discovered during this process, it becomes necessary to de-pressure the systems in order that the joints can be remade, involving considerable additional downtime. In preparation for the 2002 shutdown, engineers at the Wilton Olefins 6 plant were set a target of achieving zero remakes during leak testing after the shutdown. This was a great challenge, especially given that approximately 7000 joints were to be remade by 400 technicians. This case study is based on a paper presented at the 17th International Conference on Fluid Sealing in April 2003.
15-21%. This is the same order as that computed in the hydrodynamic analysis.
Conclusions
The results of both the hydrodynamic and elastohydrodynamic analyses demonstrate that shaft roughness, viz. fluctuations on the shaft surface, can produce significant effects on lip seal behavior, through hydrodynamic effects. The fluctuations in the film thickness, caused by the roughness pattern on the shaft surface, produce increases in the average film thickness, load support and reverse pumping rate. This may be one of the reasons why seals operating with very smooth shafts are unsuccessful.