Material for pump

[maintennance]

For one of the refinery plant , the MOC of the Fractionator bottom pump is Carbon steel. The Hydrocarbon pumping temperature is around 340 Degc. The above MOC is specified in the process licensor document. Is Carbon steel material suitable for such high temperature services? Thanks to clarify.

 

[JJPellin]

It is impossible to answer your question with the information provided. You did not specify the service. Based on the temperature, I assume you mean crude tower bottoms. Or, you could be referring to vacuum tower bottoms. You did not make any statement about the composition of the crude that you run. The selection of material may have as much to do with process chemistry as it does with pressure or temperature. In crude tower bottoms service in our refinery, we would require CA6NM (11-14% chrome) for a new pump. We have older pumps that are CA-15 (12% chrome). We have carbon steel cases in crude tower charge, but not crude tower bottoms. But, we run very sour, very heavy, high TAN crudes and synthetic crudes. Our crude tower bottoms would be much nastier than a refinery running light, sweet WTI crude.

Johnny Pellin

 

[maintennance]

Thank U JJ. This is for the VGO unit fractionator column.The service indicated in the data sheet says " Hydrocarbon'. Details of the crude is not available at present . I will get and come back.One of the point here is that the lines connecting the pump is of P11 material. This is where I got the thread to analyse for the proper selection of MOC.Thanks to clarify.

 

[JJPellin]

I am not familiar with the material specification you mentioned for the piping (P11). Our pump selection standard requires that the pump is at least as corrosion resistant as the piping on the discharge. However, since most of our crude piping has been ungraded to Incolloy (spelling?), this is not practical. We use CA6NM with the knowledge that it will not last as long as the piping. We purchased one set of pumps in 317 SS to resist the Naphthenic Acid corrosion, but there were problems getting good castings. And because of our high Chloride levels, most stainless steel is prone to cracking.

We have three crude units. None of them has a Gas Oil distillation tower. We take the Gas Oil from our vacuum tower directly with no further distillation. With our crude slate, the gas oil from the vacuum tower has the greatest problem with Naphthenic Acid. I would not consider carbon steel for these streams. But, this is because of our crude.


Johnny Pellin