How to maintain vertical turbine pumps

Vertical turbine pumps (VTPs) are mostly used in power generation and manufacturing industries. Generally, they will be found in municipal water applications that handle the primary intake load.

This is owing to the pump’s ability to develop high head with multiple impeller bowls, also coupled with the availability of standard vertical motors that can support heavy pump shaft loads. In as much as the pumps are built for resilience, abrasive sediments in the pump cavity tend to take a toll. This happens particularly on line shaft and pump bowl bearings.

As such, routine maintenance is often necessary. Moreover, instead of replacing the bearings, one should ensure that the routine maintenance addresses the issues that are hindering maximum pump operating life.

Common Repairs
Common Vertical Turbine Pumps repairs include replacing line shaft and pump bowl bearings. Worn shafting should also be replaced, while removing corrosion from submerged components. The latter should also get corrosion-resistant coatings. Furthermore, corroded or cavitation-damaged impellers may be repaired and coated. On the other hand, it can also be replaced if badly damaged.

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Parts such as the pump bowls, suction bells and discharge casings are heavy castings that can be reconditioned and fitted with replacement wear rings as necessary. The same treatment can also be given to affected column sections.

Fit & Alignment
Routine maintenance should focus on the fit and alignment of line shaft and pump bowl bearings. This is because the two are the most common wear parts for such pumps.  Distorted discharge elbows as well as column sections’ faces and rabbits of the mating components must be re machined to restore dimensional integrity. This is in addition to the replacement of worn bearings in order to restore proper running clearances.

Bearing-to-Shaft Clearances
A key element of successful VTP maintenance is the machining of replacement bearings to the proper shaft clearances. The intricacies of vertical bearings vary when it comes to horizontal machines. Moreover, clearance specifications highly differ among pump manufacturers.

Tighter clearances reduce shaft whip and resulting wear but require the shafting and couplings to be free of excessive run out.  The bearings should also be concentric up and down the column and bowls. Thus, the machine work to true up the flanges and rabbits allows tighter bearing clearances, improving the longevity of the bearings.