Sundyne Pump Impeller and Indecer damage

[Muhammad Abdul Rauf]

Hi Everyone!
We have a sundyne pump at Crude Distillation Unit to inject stripped water to desalters.. The pump was opened due to seal leakage issues. Internal Inspection revealed damage to impeller and Inducer.
Following are the process conditions
Serive : Stripped Water
pH : 10.5 to 11.0 on average
Rated Flow: 37 m3/h
Suction Presssure : ~ 0.5 kg/cm2.G
Discharge Pressure : 31 kg/cm2
Flow variation: 15 ~ 38 m3/h
Normal Flow : 32 m3/h
Design Minimum Flow : 7.2 m3/h
Stripped Water Temp : 65 ~ 70 C ( Temperature remained 80 ~ 85 C for 4 to 5 months as well)
Material of Impeller : ss316L
Pictures are attached for reference.
Can anyone help me sort out the root cause of the problem and remedial actions:

http://files.engineering.com/getfil...d30-4938-bc5e-d20b099009e7&file=Impeller3.jpg

Abdul Rauf

 

[Nicolas13]

problem of cavitation, NPSHa is too low

 

[EdStainless]

Is all of the damage at the eye?

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P.E. Metallurgy, Plymouth Tube

 

[Nicolas13]

It could be also a too low flow with inlet recirculation

 

[Muhammad Abdul Rauf]

Dear EdStainless,
Yes, all the damage is at eye. The edges of the inducer have some material loss as well.
I have checked the flow history of the pump. The flow varied from 17 to 38 m3/h with normally @ 27 ~ 30 m3/h. Average pH of the fluid ~10.8. This pump has a history of seal leakage.


Abdul Rauf

 

[1gibson]

NPSH curve with an inducer increases at high AND at low flows. Check the curve NPSHR against NPSHA at 17 m3/hr, could be insufficient NPSHA there. Obviously could be a problem at 38 m3/hr also.

 

[LittleInch]

What is "stripped water"?

Does it have a vapour pressure higher than normal water?

At the moment it looks like cavitation damage.

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