I am an Operations Engineer from a refinery here in Asia. Our crude charge pumps were found to have deposits thrice in 7 months causing high amperage to the motor drivers. Consequently, this necessitated the decrease in our pipestill feedrate thus affecting our programmed crude run. We tested the deposits and found out that these were mainly composed of sodium salts. Please see attached file for the simplified process flow diagram of the crude charge pump system.
In order to address this, we recommended and applied caustic dilution to the system from 25 deg Be to 8-10 deg Be in order to avoid unreacted concentrated caustic freely moving in the system which later may react with freely moving ions from crude and water.
However, even after the implementation of caustic dilution, high motor current was still observed. Pump impeller was pulled out and deposits were found again on the impeller.
Sludge migration was one of the possible causes of the deposition however, during the time of the incident, crude was being fed at elevated suction from crude tanks. We are also suspecting asphaltene formation as a possible cause.
Have you had any experience similar to this? What are the possible causes that may bring this incident about?
Thanks and best regards.