We are facing plugging of 350 distillate pump strainers in the VDU (lube oil refinery). The 350 distillate is the middle cut of the distillation column.
Since Sunday, the pump strainer has been cleaned more than 5 times due to coke deposition. All operating parameters have been compared to the PFD and no deviation has been observed except that the pumparound flow above the 350 distillate bed is less than the required.
Also this problem started after a revamp on our vacuum distillation column in 2013. Since then there has been severe coking in this pump and it requires monthly cleaning. But as of now the problem has become severe and the strainer is getting plugged in a matter of hours.
Your advice/insight on troubleshooting the problem will be appreciated.
We have sent the samples for analysis and are waiting for the results.
The heater skin temperatures were running high, and we adjusted it.
However, we are still seeing coke in the strainer. Although the frequency of plugging is reduced.
How can I increase the flow on the 1st pumpdown. The flow of the 2nd and 3rd pumpdown is above 50 m3/h but the 1st pumpdown is less than 35 m3/h.