Erosion of Pump Casing and Impeller

Not sure about your acidity, but if you have excessive cavitation in your pump it will cause damage that may look similar to acidic pitting. The cavitation causes small voids of vacuum which collapse and damage the trailing side of the impeller. Check your pump for periods of low or no flow with the pump running, this would be a source of cavitation.

Drew

Thanks for prompt reply, we have provided required NPSH as mentioned by supplier but we have observed reduction in impleller diameter due to forien particale attack

Not sure why this was marked off topic Kaisan, I would also like to know wtf FTA lined means.

Apart from that the question is unanswerable without knowing ALL the pumping conditions. Some of the conjecture will undoubtably prove correct, but with this information it is just that - conjecture.

At this temperature, the liquid may be nearly as hot as its boiling point. This would be another possible source of cavitation (low NPSH_a). Or running too far to the right on the pump curve.

It sounds as though the liquid temperature is around its boiling point. Reducing the temperature may help.

But wouldn't boiling reduce vacuum cavitation because the voids would be filled with vapor and not collapse with the same force? I am not as experienced with pumping fluids other than fuel...and we like to keep that as cool as possible!

Drew

If the liquid is close to boiling temperature, stuffing it into the inlet connection of a centrifugal pump runs the risk of the impeller creating small pockets of vapour as low-pressure areas are created by its movement within the pump casing. When these pockets of vapour reach a high pressure area, the higher pressure makes them collapse. The effect is to make the pump very noisy, and the collapsing pockets can cause mechanical damage, including impeller and casing scour. "Cavitation" is the label that describes this phenomenon.

Lowering the temperature of the fluid, so that it works well away from its boiling point, will certainly help avoid cavitation, as will due consideration to pipeline design upstream of the pump.

It is for this reason that a steam condensate return pump, as found in process industries that are large users of steam as a heat transfer fluid, is a specially-designed beast. By requirement, it has to push condensate around close to, or at, its boiling temperature. Less-conservatively designed pumps will not last long in condensate service for this very reason.

GA Alexander. OP did not give suction head See the link below for explanation of vapour pressure and suction head and cavatation OP.

http://www.pipeflow.co.uk/public/articles/Net_Positive_Suction_Head_Or_NPSH.pdf

Quite likely you are cavitating and the high temperature mixed with acidity is not helping either. how viscous is the solution and what flow rate and pressure is at the outlet and does that conform with the pump's designed performance on the Data Plate, are there any pipe bends near the pump inlet. Is there a restriction or half closed valve in the suction line feeding the pump You may have to look at a different type a pump, possibly a rubber lined slurry pump or diaphram pump as they use in the mining industry. Contact your local pump supplier for available pump alternatives.

Send that question to the Belzona Corp. I had similar problems with a pump that went from acid to alkali (Ph 2-10.7) @ 180deg F and their pump kote product did it for me.