How to maintain mixed flow pumps
When the bearing uses thin oil for lubricating, it is important to regularly inspect the oil level; and when it uses dry oil (lubricating grease), supplement a proper amount of oil in a periodic time by means of removing both front and rear covers.
Common Vertical Turbine Pumps repairs include replacement of the line shaft and pump bowl bearings. It is recommended for worn shafting to be replaced, while removing corrosion from submerged components. Furthermore, Impellers that have been corroded or have sustained damage as a result of cavitation should be repaired and coated, or potentially even replaced depending on the severity of damage.
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.
A key element of successful VTP maintenance is the replacement bearings to the proper shaft clearances. The intricacies of vertical bearings tend to vary when it comes to horizontal machines.
Fit & Alignment
Frequent maintenance should focus on the fit and alignment of line shaft and pump bowl bearings. This is due to the fact that they are the most common wear parts for such pumps. This is in addition to the replacement of worn bearings in order to restore proper running clearances.
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.
Operators using Mixed flow pumps should also pay attention to:
- The outer edge of the impeller and the impeller casing wear.
- Check the shafts, exhaust valve and external fastening. A partial adjustment of centre is usually: impeller clearance ( 0. 37 - 0. 78)
- Running time, as it is suggested that a total running time of 1000 hours or so should require minor repairs, whilst a total running time around 2000 hours should be overhauled.
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Keep a look out for both frictional and collided noises that may sound during a pumping cycle. In the event of friction between the pump cover and impeller, add a paper pad in between both pump cover and casing.
Adjust the packing properly to have the liquid intermittently leak in drops from the packing gland. Too tight packing will cause the shaft to heat and the power increase while too loose will cause an excessive liquid leak and a lowered efficiency.
In the case of the direct link between both pump and motor, have the axial lines of both on the same straight line.