Pump failure

[migueldiaz]

All,

Is anybody familiar with the failure shown in teh attachment. The pump is a Sulzer, model CAP8, pumping sour water to 345 gpm @ 265°F (max). The casing material is C.S, impeller and wear rings 316SS and Nitronic 50 for the shaft. I am loking for some posible causes and posibles repair procedure.

Regards,
M.D

 

[JJPellin]

This looks like simple corrosion damage to me. The damage is deeper in high velocity areas and in the heat affected zone along the tack welds that hold the wear ring into the case. I would not normally allow carbon steel in sour water service. Depending on the particular water stream, our sour water pumps are normally 316 SS or Duplex SS construction. The damage can be repaired by welding and grinding. The repairs will last longer if the case is stress-relieved following welding. It will last longer if you apply hard coating over the high velocity areas. I am not a coatings expert and am not in a position to recommend a particular coating for your application. But, ultimately, you would be better off to order an upgraded case and head in a different material.

Johnny Pellin

 

[SlurryPumps01]

for me, it is not corrosion. corrosion will damage the whole case, not localized. i suggest to check the capacity and pressure, compare it with Performance Curve, check also NPSHa and NPSHr. Under capacity operation also should be consider.
how old is the pump?

 

[JJPellin]

Some corrosion mechanisms will attack all wetted surfaces equally. But, there are other corrosion mechanisms that are highly dependant on velocity. The corrosion of 316 SS in concentrated sulfuric acid would be one example. Naphthenic acid corrosion of CA-15 (12% Chrome) is another example where the damage may be localized to the high velocity areas. The damage shown in the pictures seems to me to fit this same category. If the problem was off design operation, I would expect to see cavitation damage highly localized in the impeller or volute. I am not aware of any cavitation mechanism that would result in the sort of damage shown.

Johnny Pellin

 

[DLite30]

Just don't do the same repair you did before!

Call Sulzer.