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Salt Cake Slurry Gear Pump Failures

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eybersen

Mechanical
Aug 14, 2001
1
Hi there;

I am fighting a chronic problem with a mag driven gear pump pumping a sodium sulphate (salt cake) slurry. Required flow is ~ 32 GPM against ~ 100 PSI, temps of 60+ Degrees C. The pump is process lubricated and uses tungsten carbide main bushings with a chromium oxide coated shaft, 316 SS wetted parts.

We have had repeated failures of the pump (pump seizes). When dissasembled the coating on the shaft is worn/damaged, opening up the bearing clearance and the pump. The locknut/threads/key connecting the drive magnet to the shaft is often loose/damaged. The wetted parts (main and idler gear) usually appear "as new" with little damage or wear visible.

At least one previous failure has been blaimed on severe cavitation when the pump suction was blocked, but this does not seem to be a root cause of the majority of failures; the manufacturer believes the metalurgy of the pump is right for the material we are pumping.

Any thoughts on possible causes of the failure, areas to investigate would be welcome!

Thx,

Brad
 
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Maybe solids settling out of the pumpage in the bushings/insufficient flow through the bushings leading to wear, and subsequent vibration slackening off the coupling and locknut. I am not really keen on using gear pumps on suspended solids applications.
John
 
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