3 replies to this topic

[prasad_kara]

hi,
can any one help me to solve my problem.
in our factory we r using water ringvauuum pump for conveying in which we r supplying water mixture of soft water and DM water.for overhaukling when we opened the pump we found it's impeller had gone severe corrosion.can any one tellme what is the reason for it

[edfarman]

Dear prasad_kara,

That pump needs to mixed the soft water and demineralized water.
If corrosion just assumed, can you describe it in detail of blade material? It shall be compatible for the service fluid. What kind of erosion there? Is it continues operating or temporarily? If any pitting, you must consider to MIC attack on specific blade material when the pump stand by.
Is it any solid material go throught your pump? it can be considered as erosion problem... when solid particle carried by water.
Did you check the in service pumping load to consider to pump design capability? Did the NPSHr covered by available NPSH? It also may be caused by cavitation/turbulence problem.

Hope it can help.

[Art Montemayor]

prasad_kara:

edfarman is asking you the right question: are you certain that what you are experiencing is corrosion and not cavitation? An LRP (Liquid Ring Pump) is a vacuum device that is very sensitive to the vapor pressure characteristics of the seal fluid being used. Because of this feature, it is very susceptible to cavitation effects. If you respond with your email address, I can send you an Adobe Acrobat file dealing with this specific problem. The file includes color fotos of the cavitation effect and perhaps it can help you identify what you have.

On the same issue, edfarman is erroneously confusing a centrifugal pump with an LRP. An LRP has no dependency on NPSHr or NPSHa whatsoever. It is a continuous-running vacuum device and it should be quite obvious to someone familiar with it. Unless you have operated an LRP and had the opportunity to dissasemble one on several occasions, you will have a difficult time understanding its principle of operation as well as its good and bad characteristics.

Let me know about the Cavitation file.

Art Montemayor