Wear ring flushing

[bharath1950]

For the coker heater charge pump,licensor document specifies, Wear ring flushing is required ( since coke fines are present in the pumping stream ). But the reputed vendors are not recommending wear ring flushing and states that this is giving detrimental effect to the performance of the pump after a long run. However vendors also say that the wear ring design, clearance are all taken care to avoid entrapment of coke fines and wear out of the wear rings. Can anybody share the experience of the wear ring flushing in such pumps? Is this wear ring flushing is mandatory to the pumps that handle coke fines. However these pumps are provided with coke crusher impeller on the first stage , double suction impeller. The pumps are BB2 pumps .Thanks to clarify

 

[JJPellin]

I have only ever seen wear ring flush used on streams with extremely abrasive catalyst fines. Coke fines are generally not abrasive enough to damage hardened wear rings. And, the pressure differential inherent in the wear ring design in an API pump would prevent any blockage from occurring. We have three coker units with two charge pumps per unit and none of these six pumps has wear ring flush. Our failures have generally never involved wear that could have been reduced with wear ring flush.

The second problem concerns what stream you would use. If you are flushing with heavy coker gas oil, it gets very expensive as a certain amount of this flush will coke off in the heater and be lost to the coke pile. Using HCGO as a seal flush can cost US$500,0000 per year or more for a single pair of pumps. Using it for wear ring flush could easily triple that cost.

Design the wear rings with appropriate hardness, but do not flush the rings.

Johnny Pellin

 

[bharath1950]

Thank a lot JJ for your reply.